HK1172313B - Wastewater treatment system and process including irradiation of primary solids - Google Patents

Description

Wastewater treatment system and method including radiation of primarily solids

RELATED APPLICATIONS

This application claims the benefit of U.S. provisional patent application No. 61/224,016, filed on 7/8/2009, the entire contents of which are incorporated herein by reference.

Technical Field

The present invention relates to a system and method for wastewater treatment.

Background

The effective treatment of domestic and industrial wastewater is an extremely important aspect of improving quality of life and maintaining clean water. Up to about half a century ago, the problems of simply discharging wastewater to water sources such as rivers, lakes, and oceans were evident, and biological and chemical wastes endangered all life forms, including the spread of infectious diseases and exposure to carcinogenic chemicals. Thus, wastewater treatment processes have emerged from ubiquitous municipal wastewater treatment facilities, cleaning sanitary wastewater from populations, to specialized industrial wastewater treatment processes, where specific pollutants from various industrial applications must be addressed.

Wastewater treatment plants typically employ multiple treatment stages, including primary, secondary, and tertiary treatment. Biological oxidation is a well-known secondary treatment step for removing most wastewater contaminants. Typically, effluents from biological oxidation and/or other secondary treatment processes still contain levels of further treatment (e.g., tertiary treatment) for their removal of the desired contaminants.

Biologically refractory and biologically inhibitory organic and inorganic compounds are present in certain industrial and sanitary wastewater streams to be treated. Various attempts have been made to address the treatment of these biologically intractable and biologically inhibitory compounds. Certain types of known treatments include the use of powdered activated carbon to adsorb and subsequently remove biologically refractory and biologically inhibitory organic compounds.

Part of certain wastewater treatment processes that are operationally cost intensive include the removal of relatively low concentrations of contaminants from wastewater that has been treated by aeration or other secondary processes. While various systems have been used for tertiary treatment, such as adsorption and filtration, there is a need for more efficient and less costly tertiary treatment without the limitations and disadvantages associated with conventional methods.

Summary of The Invention

In accordance with one or more embodiments, the present invention relates to systems and methods for treating wastewater.

The present invention provides systems and methods for treating wastewater in which a majority of solids and biological oxygen demand compounds are separated from the wastewater material using a primary separation process to produce a solid phase and an aqueous phase. The solid phase is irradiated to reduce pathogen levels so that it is safe to use as a soil substitute and/or additive so that the solid can thus be discarded in an environmentally friendly manner. In further embodiments, the solids that have been sterilized by radiation are mixed with a suitable inert filler material to produce a soil substitute, fertilizer, compost, or other soil additive. The liquid phase is treated in a substantially smaller system than is required for treating full-strength wastewater, which may include a suspended media biological regeneration reactor system. A liquid treatment system according to the present invention includes a high flux adsorbent material treatment system integrated with a low flux adsorbent material biological regeneration reactor.

In accordance with one or more embodiments, the present invention is directed to a method of treating wastewater containing solids and biological oxygen demand compounds. The method comprises the following steps:

separating a majority of the solids and biological oxygen demand compounds from the wastewater material using a primary separation process to provide a solids phase containing an initial level of pathogens and an aqueous phase comprising wastewater (and in certain embodiments, low concentration wastewater);

irradiating the solid phase to reduce pathogen levels;

mixing the wastewater and adsorbent material in a mixing zone for a sufficient time to adsorb contaminants from the wastewater onto the adsorbent material;

separating and removing a majority of the wastewater from a mixture of the wastewater and adsorbent material;

passing adsorbent material having contaminants adsorbed thereon and a minor portion of the wastewater to a biological regeneration reactor;

suspending the adsorbent material and wastewater in the biological regeneration reactor for a time sufficient to allow microorganisms in the biological regeneration reactor to biologically act on at least a portion of the adsorbed contaminants;

discharging a biologically treated water effluent from the biological regeneration reactor; and

recycling the regenerated adsorbent material to the mixing zone.

In accordance with one or more embodiments, the present invention is directed to a wastewater treatment system. The system comprises: a radiation treatment section having: a radiation source; an inlet for receiving a primary solid; a solids outlet for discharging primarily solids of the radiation; and a waste water outlet. The system also includes a mixing section having: a wastewater inlet connected to the wastewater outlet of the radiation treatment section; an adsorbent material inlet; and a drain outlet. The system also includes an adsorbent material deposition and liquid separation section having: a slurry inlet connected to the discharge outlet of the mixing section, a treated water outlet and a contaminated adsorbent material outlet. The system also includes an adsorbent material biological regeneration reactor system having: a biological regeneration reactor comprising a contaminated adsorbent material inlet in communication with the contaminated adsorbent material outlet of the adsorbent material deposition and liquid separation zone, a biologically treated water outlet, and a regenerated adsorbent material outlet in communication with the adsorbent material inlet of the mixing zone.

In accordance with one or more embodiments, the present invention is directed to a wastewater treatment system. The system comprises: a radiation treatment section having: a radiation source; an inlet for receiving a primary solid; a solids outlet for discharging primarily solids of the radiation; and a waste water outlet. The system also includes a high flux adsorption system and a low flux adsorption system. The high-throughput adsorption system comprises: an inlet connected to the wastewater outlet of the radiation treatment section, a source of adsorbent material for contacting the wastewater and adsorbing contaminants from the wastewater, a liquid outlet for discharging a majority of the received wastewater that has contacted the adsorbent material, and an adsorbent material outlet for discharging the adsorbent material having adsorbed contaminants and a minority of the received wastewater. The low flux adsorbent material biological regeneration reactor system is used to maintain adsorbent material with adsorbed contaminants in suspension for a time sufficient to allow microorganisms to digest the adsorbed organic contaminants. The low flux adsorbent material biological regeneration reactor system comprises: a biorenewation reactor having: an inlet for receiving adsorbent material having adsorbed contaminants from an adsorbent material outlet of the high flux adsorption system, a mixed liquor outlet, and an adsorbent material outlet in communication with a source of adsorbent material of the high flux adsorption system.

Brief Description of Drawings

The present invention will be described with additional specificity and detail through the use of accompanying drawings in which apparatus, systems and methods are described and/or illustrated. In the drawings, which are not necessarily to scale, like elements are illustrated by like reference numerals throughout the several views. In the drawings:

FIG. 1 is a schematic view of a membrane bioreactor system using bioreactors containing one or more sections with suspended adsorbent material;

FIG. 2 is a schematic of an embodiment of a wastewater treatment system using an adsorbent material in the bioreactor upstream of the membrane operating system used in the present invention to regenerate and/or reactivate the adsorbent material;

FIG. 3 is a schematic diagram of a wastewater treatment system including an embodiment of a high flux adsorbent material treatment system including a mixing section and an adsorbent material deposition and liquid dumping section (integrated with a low flux adsorbent material biological regeneration reactor having a biological regeneration reactor and a membrane operating system);

FIG. 4 is a schematic view of a wastewater treatment system including a high flux adsorbent material treatment system including another embodiment of a mixing section and an adsorbent material deposition and liquid separation section (integrated with a low flux adsorbent material membrane biological regeneration reactor);

FIG. 5 is a schematic view of a wastewater treatment system including a high flux adsorbent material treatment system (integrated with another embodiment of a low flux adsorbent material biological regeneration reactor);

FIG. 6 is a schematic view of a wastewater treatment system including a further embodiment of a high flux adsorbent material treatment system (integrated with a low flux adsorbent material biological regeneration reactor);

FIG. 7 is a schematic diagram of a process for treating wastewater including irradiation of primary solids according to one embodiment of the present invention; and

FIG. 8 is a schematic diagram of a process for treating wastewater including irradiation of primary solids according to another embodiment of the present invention.

Detailed Description

As used herein, "biologically refractory compounds" refer to those classes of chemical oxygen demand ("COD") compounds (organic and/or inorganic) in wastewater that are difficult to biodegrade when contacted by microorganisms. "biologically intractable compounds" can have a variety of intractable degree properties ranging from mild to highly intractable.

"biostatic compounds" means those compounds (organic and/or inorganic) in wastewater that inhibit the biological decomposition process.

"Biolability" refers to simple organic matter such as human and animal excreta, food waste, and inorganic matter such as ammonia and phosphorus-based compounds that are readily digestible.

"COD" or "chemical oxygen demand" refers to a measure of the ability of a waste to consume oxygen during a chemical reaction that results in the oxidation of organic matter and the oxidation of inorganic chemicals such as ammonia and nitrite. COD measurements include biologically unstable, biologically inhibitory and biologically refractory compounds.

“BOD₅"means a biological aerobic compound that is biodegradable over a period of 5 days.

"mixed liquor suspended solids" or "MLSS" refers to dissolved and suspended microorganisms and other substances present in the wastewater being treated; "mixed liquor volatile suspended solids" or "MLVSS" refers to the active microorganisms in MLSS; and "mixed liquor" means a combined mixture of wastewater, MLSS and MLVSS.

As used herein, "adsorbent" or "adsorbent material" means that the granular activated carbon includes materials that have been treated to provide an affinity for a predetermined chemical species, metal, or other compound present in the wastewater to be treated; a compound based on granular iron such as an iron oxide complex; a synthetic resin; and a particulate aluminum silicate compound.

In the context of the presence of adsorbent material described in the effluent from one section of the system to another, e.g., from a bioreactor containing suspended adsorbent material to a membrane operating system, the term "substantially free of or" substantially free of "refers to an amount that limits the amount of adsorbent material sent to the membrane operating system from an amount that does not adversely affect the efficiency required by the membrane filtration procedure therein. For example, in certain embodiments, "substantially free of" or "substantially free of" refers to a predetermined amount of adsorbent material used within a given system within a bioreactor or one or more biological reaction zones, up to at least about 80 volume percent; in additional embodiments at least about 90 vol%, and in yet other embodiments at least about 95 vol%, and in still other embodiments at least about 99 vol%. It will be appreciated by those skilled in the art based on the teachings herein that these percentages are for illustration purposes only and may vary depending on factors including, but not limited to, the type of membrane used and its corrosion resistance, the desired effluent quality, the predetermined amount of adsorbent material used in a given system, and other factors.

The invention relates to a wastewater treatment system and a method. As used herein, "wastewater" (e.g., influent stream 101, 201, 301, 401, 501, 601, or 701) defines any water to be treated that flows into a wastewater treatment system, such as surface water, ground water, and wastewater streams from industrial, agricultural, and municipal sources, having biodegradable material contaminants, inorganic substances that can be decomposed by bacteria, labile organic compounds, biologically refractory compounds, and/or biostatic compounds.

Wastewater from industrial and municipal sources typically contains biosolids, as well as inerts and organics, including biostatic and biologically refractory organics. Examples of biostatic and biocompatable organic compounds include synthetic organic chemicals, such as polyelectrolyte treatment chemicals. Other biologically inhibitory and intractable organic materials include polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans. Endocrine disrupting compounds also belong to a class of biostatic and biologically intractable organisms that may affect the hormonal system of the organism and are present in the environment. Endocrine disrupting compounds include: alkylphenol compounds, such as nonylphenol for removing fats and oils, and natural hormones and synthetic steroids found in contraceptives, such as 17-b-estradiol, estrone, testosterone, ethinyl estradiol.

Other examples of wastewater to be treated include: high-strength wastewater; low-strength wastewater; and leachate from the landfill. The water may also be treated to remove viruses. Other examples of contaminants in wastewater include: flame retardants, solvents, stabilizers, polychlorinated biphenyls (PCBs); dioxins; furans; polynuclear aromatic compounds (PNA); drugs, petroleum; a petrochemical product; petrochemical by-products; cellulose; waste products from the pulp and paper industry; phosphorus; phosphorus compounds and derivatives; and agricultural chemicals such as those derived from or used in the manufacture of fertilizers, pesticides, and herbicides.

Wastewater from industrial and municipal sources also contains trace amounts of constituent compounds that originate from the water treatment process and are subsequently difficult to remove. Examples of minor ingredients introduced during water treatment include nitrosamines, such as N-Nitrosodimethylamine (NDMA), which may be released from proprietary cationic and anionic resins.

As used herein, "low concentration wastewater" refers to wastewater having a low concentration of biologically labile (i.e., readily digestible) organic compounds that is lower than the influent feed concentration that typically supports biological treatment systems in conventional secondary treatment systems (e.g., activated sludge aeration processes or membrane bioreactors). In addition, as used herein, "low concentration wastewater" includes influent that is not readily bio-oxidized in conventional treatment biological systems because the wastewater is too low in strength or contains certain compounds that are not readily biodegradable. They may also contain compounds that are completely resistant to biodegradation, biostatic compounds and/or biologically intractable compounds, or combinations of these compounds, that are not biooxidizable, or require longer residence times than would be the case if a typical biooxidative system were available.

Additionally, as used herein, "effluent undergoing upstream wastewater treatment" generally refers to effluent from one or more conventional or any later-developed wastewater treatment systems. "effluent undergoing upstream wastewater treatment" may be derived from wastewater undergoing primary and/or primary treatment processes and secondary treatment processes (e.g., activated sludge aeration processes or membrane bioreactors) and generally have low concentrations of biologically labile (i.e., readily digestible) organic compounds that typically will not be sufficient to support biological reactions in most conventional secondary treatment systems (e.g., activated sludge aeration processes or membrane bioreactors). Additionally, it is also contemplated in certain embodiments of the present invention that an "effluent undergoing upstream wastewater treatment" is an effluent that has also undergone one or more conventional or later-developed tertiary treatments, e.g., in certain wastewater treatment plants, the effluent from a tertiary treatment system may contain pollutant levels in excess of the approved emission levels, and such effluent may be treated by the systems and methods of the present invention. In further embodiments, the "effluent undergoing upstream wastewater treatment" may be derived from a primary separation system in which substantially all of the solids have been removed, such as one or more of a settler, clarifier, or other solids separation device. In even further embodiments, the "effluent undergoing upstream wastewater treatment" may include wastewater that has been subjected to a primary separation system and later irradiated.

Generally, wastewater treatment facilities use multiple treatment stages to clean water so that it can be safely released into bodies of water such as lakes, rivers, and streams. Currently, many sanitary sewage treatment plants include a preliminary treatment stage in which mechanical devices are used to remove large objects (e.g., bar screens) and sand or gravel channels are used to deposit sand, gravel and stones. Some treatment systems also include a first stage where some fats, greases and oils float to the surface for skimming and heavier solids settle to the bottom and are then treated in either an aerobic or anaerobic digestion tank to digest biomass and reduce the biosolids content.

After primary and/or primary treatment, the wastewater is sent to a secondary biological activated sludge treatment stage. Biological treatment of wastewater is widely practiced. Wastewater is often treated with waste activated sludge in which biological solids are acted upon by bacteria in a treatment tank. The activated sludge procedure involves aerobic biological treatment in an aeration tank, typically followed by a clarifier/settling tank. The settled sludge is recycled back to the aeration tank to obtain a sufficient mixed liquor suspended solids concentration to digest the contaminants. Some alternative routes that may be used to dispose of excess biosolids, such as sludge, include, but are not limited to, incineration, disposal in landfills, or as fertilizer if free of toxic components. The wastewater is then sent to a secondary biologically activated sludge treatment stage. Biological treatment of wastewater is widely implemented. Wastewater is typically treated using waste activated sludge in which biosolids are acted upon by bacteria in a treatment tank. The activated sludge process involves aerobic biological treatment in an aeration tank, typically in a clarifier/settling tank. The settled sludge is recycled back to the aeration tank to maintain a sufficient mixed liquor suspended solids concentration to digest the contaminants. Some alternative means of disposing of excess biosolids (e.g., sludge) include, but are not limited to, incineration, disposal in landfills, or use as fertilizer (if not toxic components).

In the aeration tank, oxygen-containing gas such as air or pure oxygen is added to the mixed liquor. Oxygen is typically used by bacteria to biologically oxidize suspensions dissolved or carried in wastewater feeds. Biological oxidation is typically the lowest cost oxidation process that can be used to remove organic pollutants and other inorganic compounds such as ammonia and phosphorus compounds from wastewater; and is the most widely used wastewater treatment system for treating wastewater contaminated with biologically treatable organic compounds. Wastewater containing chemicals that resist biological decomposition, biostatic compounds, and/or biologically refractory compounds may not be adequately treated by conventional simple biological wastewater treatment systems. These compounds can be acted upon by bacteria for the residence time that the water remains in the particular treatment tank. Since water retention times are often insufficient for biological oxidation of sufficient quantities of biostatic and/or biologically refractory compounds, it is possible that some portions of these recalcitrant compounds are not adequately treated or destroyed and pass through the treatment process unaltered or are only partially treated before being discharged into the effluent or excess residual sludge.

The mixed liquor effluent from the aeration tank typically enters a clarifier/settling tank where the sludge includes concentrated mixed liquor suspended solids that settle by gravity. The settled biomass waste gas is either disposed off-site (i.e., discharged) or recycled back to the aeration tank. However, some biological oxidation systems use different treatment methods to remove solids from wastewater effluents based on wastewater and economic needs. The clarifier/settling tank may be replaced with a membrane operating system or other unit operation, such as a dissolved/induced gas flotation device. The liquid effluent from the clarifier/settling tank, operating system or dissolved/induced gas flotation device is discharged or subjected to further treatment prior to discharge. The solids removed from the clarification/separation device are returned to the aeration tank as a return activated sludge to maintain a sufficient concentration of bacteria in the system. Some portion of this returned activated sludge (also referred to as waste activated sludge) is periodically removed from this recycle line to control the concentration of bacteria in the mixed liquor. The waste activated sludge is then disposed of in a predetermined manner.

A recent development in conventional industrial biological wastewater treatment plant technology involves the addition of powdered activated carbon particles to the mixed liquor. In biological processes utilizing powdered activated carbon, organic matter may be adsorbed onto the activated carbon and retained in the treatment tank for a water retention time similar to the sludge retention time, thus performing adsorption processes and extended biological processes resulting in increased removal of certain biologically inhibitory or biologically refractory compounds. In these procedures, certain organic and inorganic compounds are physically adsorbed onto the surface of powdered activated carbon particles. At least some of these compounds are then biodegraded (e.g., oxidized in an aerobic process) for an extended period of time during their presence in the system, and the remainder is adsorbed and discharged by the activated carbon as it is exhausted from the system.

Powdered activated carbon has been used in conventional biological treatment plants by providing an effluent containing lower concentrations of these contaminants due to the adsorption of bio-inhibitory or bio-refractory compounds. The mixed liquid contains powdered activated carbon to provide multiple operation effects. Carbon provides the advantages of suspension media biological treatment systems, including increased contaminant removal and increased resistance to turbulent conditions. In addition, carbon allows for the adsorption of biostatic or biocompatable compounds onto the carbon surface and exposure to biological treatment over significantly longer periods of time than conventional biological treatment systems, by providing an effect similar to that of fixed film systems. Carbon also allows the evolution of certain bacterial products to be more digestible over biologically inhibitory organic matter. The continuous circulation of the carbon back to the aeration tank containing the returned activated sludge, i.e. the sludge residence time, means that bacteria can act on the digestion of the biostatic organic compounds adsorbed on the carbon surface for a longer time than the water residence time of the biological treatment system. This method also results in the biological regeneration of carbon and allows carbon to remove significantly greater amounts of bio-inhibitory or bio-refractory compounds than simple packed bed carbon filtration systems, simple packed bed carbonsThe filtration system also requires frequent carbon replacement or expensive physical regeneration of the carbon once the carbon's adsorption capacity is exhausted. The carbon in the mixed liquor also adsorbs certain compounds, thereby providing an effluent that is free of, or substantially contains, lower concentrations of compounds that cannot be treated by conventional biological oxidation or that are entirely resistant to biological decomposition. One example of a known powdered activated carbon system is sold under the trademark "PACT" by Siemens Water Technologies, Inc. (Siemens Water Technologies)"supply.

But because both biological growth and adsorption of organic and inorganic compounds occur on activated carbon in powder form, excess solids are wasted. In addition, the discharge of powdered activated carbon from the treatment process is accompanied by the removal of biosolids and therefore must be continuously replenished. PACTThe primary mode of contaminant removal in the system is adsorption, which is a second order function of the biological regeneration of the organic matter adsorbed onto the powdered activated carbon, which does not remain in the system for a sufficient time to undergo biological regeneration (which will be the primary treatment mechanism).

Increasingly, sanitary wastewater is treated using membrane bioreactor technology, which provides improved effluent quality, a smaller physical footprint (more wastewater can be treated per unit area), increased tolerance to turbulence, improved ability to treat difficult-to-treat wastewater, and a number of other operational advantages. For example, wastewater containing high total dissolved solids can encounter sedimentation problems in conventional clarifiers/settling tanks, requiring solids separation devices such as dissolved/induced gas flotation devices or other solids removal systems that are significantly more difficult to operate. Although membrane bioreactors can remove the sedimentation problems encountered with clarifier/settling tank systems, there are often membrane fouling and foaming problems that do not occur with conventional clarifier system. The fouling may be a result of extracellular polymeric compounds resulting from the decomposition of biological life forms in the mixed liquor suspended solids, the accumulation of organic substances such as oils, or exfoliation via inorganic substances.

Furthermore, membrane bioreactors have not been commercially used to date for the addition of powdered activated carbon. Powdered activated carbon has been used in surface water treatment systems that utilize membranes for filtration. However, these surface water treatment systems utilizing membrane and powdered activated carbon have been reported to suffer from carbon erosion films and carbon persistent plugging and/or fouling films.

Industrial waste water that is treated prior to discharge or reuse often includes oily waste water, which may contain emulsified hydrocarbons. Oily wastewater may come from a variety of industries including the steel and aluminum industries, chemical processing industries, automotive industries, laundry industries, and crude oil manufacturing and petroleum refining industries. As discussed above, some amount of un-emulsified oil and other hydrocarbons may be removed in the primary treatment procedure, where floating oil is skimmed off the top. Biological secondary wastewater programs are generally employed to remove residual oil, typically dissolved and emulsified oil, from the wastewater, but some free oil may be present. Typical hydrocarbons remaining after primary treatment include lubricants, cutting fluids, tars, crude oil, diesel, gasoline, kerosene, jet fuel, and the like. These hydrocarbons are typically removed before the water is discharged to the environment or the water is reused in an industrial process. In addition to governmental regulations and ecological considerations, effective removal of residual hydrocarbons is also advantageous because properly treated wastewater can be used in a variety of industrial processes, and eliminates raw water treatment costs, and reduces regulatory discharge problems.

Other types of wastewater to be treated include contaminated process water from other industrial products such as pharmaceuticals, various goods, the manufacture of agricultural products (e.g., fertilizers, pesticides, herbicides) and paper and medical wastewater.

The commercial deployment of membrane bioreactors for the treatment of oily/industrial wastewater is slow, mainly due to maintenance issues associated with oil and chemical fouling membranes. The industrial/oily wastewater treated in the membrane bioreactor (where powdered activated carbon is added to the mixed liquor) tested indicates the same treatment advantages observed in conventional biological wastewater treatment systems including powdered activated carbon. It has also been found that the advantages of using a membrane bioreactor can also be achieved. The membrane bioreactors with and without the added powdered activated carbon are compared side by side to verify that the membrane bioreactor with the added powdered activated carbon provides treatment advantages compared with the membrane bioreactor without the added powdered activated carbon. Furthermore, membrane bioreactors without added powdered activated carbon are extremely difficult to operate due to dissolved organic matter and additional extracellular polymeric compounds fouling the membrane. However, the test further verified: while the addition of powdered activated carbon provides a very useful biological wastewater treatment system, carbon has the adverse effect of producing a significant amount of abrasion and irreversible fouling of the membrane. Such abrasion and irreversible fouling are significant enough to render the operation of such systems extremely expensive due to the significantly shortened life expectancy of the membranes and the frequent cleaning of the membranes.

Conventional biological oxidation of wastewater is generally a secondary treatment step for removing most of the wastewater contaminants because it is typically the most expensive oxidation process available to treat organic compounds in wastewater. In addition, to a lesser extent, biological systems may also remove some of the organic compounds, such as some of the organic compounds that may be oxidized (e.g., ammonia, phosphate), adhere to the biomass, or may be adsorbed by the biomass. If it is adsorbed by the biomass, it is eventually discharged together with the waste activated sludge.

Despite the advances and developments in biological oxidation processes and other secondary treatments, many secondary treatment systems are not capable of adequately treating wastewater feeds by biological oxidation alone. Wastewater effluent that has undergone secondary treatment sometimes does not have sufficiently low levels of organic and/or inorganic contaminants to allow for discharge or reuse in compliance with regulatory limits. Therefore, three stages of processing steps are typically required.

Conventional tertiary treatment steps typically include the passage of effluent that has undergone secondary treatment through one or more adsorption columns, including adsorbent materials (e.g., activated carbon), commonly referred to as "polishing". Other tertiary treatment methods may include passing the secondary treatment effluent through one or more filters, coalescing agents, UV oxidation, chemical oxidation, other tertiary treatment systems, or a combination of these systems. However, these tertiary treatment systems are typically large and/or expensive to operate. The primary reason for the cumbersome size and fertilizer problems of conventional tertiary treatment systems is that the entire secondary treatment effluent, which has a relatively low concentration of contaminants or a substantial portion thereof, undergoes these treatments.

The systems and methods of the present invention overcome the deficiencies of existing tertiary treatment systems and in certain embodiments provide systems that can be used as secondary or tertiary treatment systems, particularly when the wastewater to be treated is low-strength wastewater.

The present invention relates to an improved wastewater treatment method and system for treating a wastewater stream having a flow rate similar to the influent flow rate in a biological treatment system having a low throughput (i.e., high throughput). This is achieved by: the high flux stream of contaminants is adsorbed onto the adsorbent material, which is then biologically regenerated and/or reactivated in a suspended media membrane biological regeneration reactor system. The system is particularly useful for processing low concentration wastewater that is not particularly suited for conventional biological wastewater treatment because of low levels of biologically labile compounds.

In certain embodiments, wastewater treatment methods and systems for low contaminant concentration wastewater can be used as a tertiary treatment system in which a substantial portion of the effluent that has undergone secondary treatment and/or other treatment is exposed to a high flux adsorbent material treatment and a small portion having a relatively high level of contaminants adsorbed onto the adsorbent material is subjected to a low flux adsorbent biological regeneration treatment system to regenerate the adsorbent material.

The system and method of treating wastewater of the present invention encompasses a treatment system comprising a high flux adsorbent material treatment system integrated with a low flux adsorbent material biological regeneration reactor. Generally, a high flux adsorbent material treatment system includes one or more unit operations for mixing low concentration wastewater or other wastewater (containing compounds that are completely resistant to biodegradation, biostatic compounds, and/or biologically refractory compounds, or combinations of these compounds) with adsorbent materials and decanting a liquid effluent having a reduced concentration of contaminants.

The adsorbent material having contaminants from the low concentration wastewater (adsorbed onto the surfaces thereof and/or the surfaces of the walls of the pores) is sent to a low flux adsorbent material biological regeneration reactor where the biological microorganisms degrade organic and certain inorganic contaminants and provide an adsorbent material having a lower concentration of these compounds so that it can be reused as a fresh adsorbent. In certain embodiments where the bioreactor is a bioreactor having a source of oxygen to support aerobic microorganisms, the biological reaction includes biological oxidation, where organic contaminants in the wastewater are typically metabolized to carbon dioxide and water. Excess biomass is removed from the adsorbent material and the regenerated adsorbent material is recycled to the high flux adsorbent material treatment system. Alternatively, the low flux adsorbent material bioreactor can be an anaerobic biological regeneration reactor system, for example in embodiments where the compounds to be adsorbed onto the adsorbent material are more susceptible to degradation in the anaerobic reactor.

In accordance with one or more embodiments, the present invention employs a system comprising a suspended media membrane bioreactor system, such as a granular activated carbon aeration reactor, followed by a membrane operating system wherein the adsorbent material is substantially prevented from entering the membrane operating system, as described in PCT publication No. WO/09085252, which is incorporated herein by reference.

In a preferred embodiment, the present invention provides a three stage treatment process comprising the steps of: mixing an adsorbent material with low-concentration wastewater; depositing an adsorbent material; pouring or removing water with which the adsorbent material is in contact; treating the adsorbent material with adsorbed contaminants in a biological regeneration reactor; treating mixed liquor from the bioreactor in a membrane operating system, including mixed liquor suspended solids and mixed volatile liquid suspended solids (i.e., substantially free of adsorbent material); removing excess biomass from the adsorbent material; and recycling the adsorbent material to the step of mixing it with the low concentration wastewater in the high flux adsorbent material treatment system. Advantageously, the decanted supernatant comprises a substantial portion of the low concentration wastewater. Thus, the biological regeneration reactor and membrane operating system are used to treat only a small portion of the volume of the total low concentration wastewater effluent that has previously undergone other treatments of the prior art. Thus providing a cost effective treatment for low concentration wastewater, particularly as compared to conventional tertiary treatment systems such as granular activated carbon adsorption columns typically used for polishing wastewater discharged from secondary treatment sections. These systems typically use energy intensive regeneration processes to regenerate the adsorbent material, such as hot air regeneration or air flow regeneration.

The low concentration wastewater treatment system of the present invention includes an adsorbent material, which in certain preferred embodiments is granular activated carbon, arranged in one or more vessels to adsorb low concentrations of organic compounds. The adsorbed organics are then exposed to biological microorganisms in a low flux adsorbent material bioreactor for a time longer than the typical hydraulic residence time in a granular activated carbon filter. The low-concentration wastewater treatment system and method of the present invention concentrates these organic compounds from the effluent that has undergone upstream wastewater treatment. Thus, when used as a tertiary treatment system, the low concentration wastewater treatment system and method of the present invention allows exposure of organic contaminants to bacteria for times longer than what can be nominally achieved in conventional secondary treatment systems based on the throughput of upstream wastewater treatment. Thus, the time for a biological reaction (e.g., biological oxidation in embodiments where the microorganism is an aerobic bacterium) is substantially reduced. Using biological regeneration rather than an energy intensive system, which is typically used to polish regenerated granular activated carbon in a filter, is a more cost effective regeneration system.

In accordance with one or more embodiments, the low-concentration wastewater treatment system of the present invention includes an adsorbent material, in certain preferred embodiments granular activated carbon, disposed in one or more vessels to adsorb low-concentration organic compounds. The low-concentration wastewater treatment system and method of the present invention concentrates these organic compounds from the effluent that has undergone upstream wastewater treatment. Thus, when used as a tertiary treatment system, the low concentration wastewater treatment system and method of the present invention allows exposure of organic contaminants to bacteria for longer periods of time than can be nominally achieved in conventional tertiary treatment systems (e.g., carbon polishing systems) based on the throughput of upstream wastewater treatment. Thus, the time for biological reactions (e.g., biological oxidation in embodiments where the microorganisms are aerobic bacteria) is substantially longer than can be achieved in a bioreactor that treats the entire influent flow.

In addition, according to one or more embodiments, the low concentration wastewater treatment systems and methods of the present invention use adsorbent material (e.g., granular activated carbon) to adsorb contaminants from low concentration wastewater (e.g., a full flow low concentration wastewater stream from a secondary treatment system) and transfer the adsorbent material with the adsorbed contaminants to a relatively smaller membrane bioreactor system, the arrangement of which is similar to the membrane bioreactor system described in co-pending and co-owned PCT application number PCT/US10/38644, which is incorporated herein by reference, and PCT publication number WO/09085252, which is also incorporated herein by reference. The organic compounds adsorbed onto the adsorbent material are biologically treated in a suspended media membrane bioreactor system and, therefore, the following needs are overcome: treating the full wastewater flow and organic load from the upstream wastewater treatment system. In embodiments where the suspended media membrane bioreactor system is an aerobic system, the biomass is supplied with oxygen required for biological oxidation by using air or oxygen from air diffusers and/or other sources. In embodiments where the suspended media membrane bioreactor system is an anaerobic bioreactor, the system is operated under conditions required to anaerobically degrade the compounds. Thus a relatively small membrane bioreactor system can treat organic compounds that are present in low concentrations in a high flux stream of effluent undergoing upstream wastewater treatment.

Additionally, while certain embodiments of the present invention are described as a three-stage system and method for treating effluent from one or more upstream wastewater treatment processes (including primary and/or secondary processes), those skilled in the art will appreciate that the system and method of the present invention may be used to treat wastewater effluent directly from processes having low concentrations of organics, e.g., will not effectively support biological processes in conventional bioreactors.

Figures 1 and 2 show a suspended media membrane bioreactor system suitable for integration with the system of the present invention for treating low concentration wastewater, in particular, for regenerating and/or reactivating adsorbent materials having contaminants adsorbed thereon in a high throughput adsorption step. These systems, described in PCT application Nos. PCT/US10/38644 and PCT publication No. WO/09085252, provide for the use of adsorbent materials such as granular activated carbon in a bioreactor system upstream of a membrane operating system. Specifically, the system includes a separation subsystem that substantially prevents adsorbent material from being sent to the membrane operating system, thereby abrading, fouling, or damaging the membranes therein.

Referring now to fig. 1, a wastewater treatment system 100 is schematically shown to include a bioreactor system 102 upstream of a membrane operating system 104. In certain embodiments, bioreactor system 102 comprises a single bioreactor vessel. In further embodiments, bioreactor system 102 comprises a plurality of bioreactor vessels, a bioreactor vessel divided into separate sections, or a plurality of bioreactor vessels wherein some or all are divided into separate sections. The individual reactor vessels or divided sections are generally referred to herein as bioreaction sections. During wastewater treatment operations using a suspended media membrane bioreactor system, the adsorbent material is maintained in suspension along with the microorganisms throughout the biological reaction zone or a subset of the total number of biological reaction zones. The membrane operating system 104 is maintained substantially free of adsorbent material using one or more of the separation subsystems described herein. The influent wastewater stream 106 is directed in series flow from a primary treatment system, a primary screening system, or as previously untreated wastewater. In further embodiments, the influent wastewater stream 106 may be previously treated wastewater, such as effluent from one or more upstream bioreactors, including but not limited to aerobic bioreactors, anoxic bioreactors, continuous flow reactors, sequencing batch reactors, or other types of biological treatment systems of any number of biodegradable organics and in certain embodiments certain inorganic compounds.

The bioreactor and/or certain bioreactor sections may be various types of bioreactors including, but not limited to, aerobic bioreactors, anoxic bioreactors, anaerobic bioreactors, continuous flow reactors, sequencing batch reactors, trickling filters, or other types of biological treatment systems that can biodegrade organic and, in certain embodiments, certain inorganic compounds.

Further, the bioreactor and/or certain bioreactor sections used herein may be of any size or shape suitable for suspending adsorbent materials in conjunction with a suspension system. For example, the container may have a cross-sectional area of any shape, such as circular, oval, square, rectangular, or any other irregular shape. In certain embodiments, the container may be constructed or modified to facilitate proper suspension of the adsorbent material.

FIG. 2 schematically shows a process flow diagram of a wastewater treatment system 200 for producing treated effluent having reduced concentrations of biologically unstable, biologically intractable, biologically inhibitory and/or organic and inorganic compounds that are all resistant to biological decomposition. System 200 generally includes a bioreactor 202 and a membrane operating system 204. Bioreactor 202 includes an inlet 206 for receiving wastewater and an outlet 208 for discharging biologically treated effluent, including mixed liquor volatile suspended solids and/or mixed liquor, to membrane operating system 204.

Bioreactor 202 includes a dispersed mass of adsorbent material 234 having pores 236 and an effective amount of one or more microorganisms 238, both attached to the adsorbent material and free floating apart from the adsorbent material in the mixed liquor for acting on biologically unstable and certain biologically refractory, biologically inhibitory compounds in the mixed liquor. The adsorbent material adsorption sites, including the adsorbent particles or the outer surface of the particles and the walls of the pores 236, initially serve as adsorption sites for biologically labile, biologically refractory, biologically inhibitory and/or organic and inorganic compounds that are entirely resistant to biological decomposition. In addition, microorganisms 238 may be adsorbed to the adsorption sites of the adsorbent material. This allows for a preferred degree of digestion of certain biologically refractory and/or biostatic compounds without a proportionately longer water residence time and sludge residence time, since in practice some biologically refractory and/or biostatic compounds remain on the adsorbent material that is sequestered or retained in the bioreactor for a longer period of time.

Often the biological instability and certain inorganic substances will be digested relatively rapidly, mainly by microorganisms that are not adsorbed to the adsorbent material, i.e., free-floating microorganisms in the mixed liquor. Some components, including organic and inorganic substances that are all resistant to biological decomposition and biologically refractory and biologically inhibitory compounds that are extremely recalcitrant, will remain adsorbed on the adsorbent material or may be adsorbed and/or absorbed by the biological material that floats freely within the reactor. Finally, these indigestible compounds will concentrate on the adsorbent to the point where the adsorbent needs to be removed or washed and replaced to maintain the effluent quality at an acceptable level. While the adsorbent material remains in the suspended media membrane bioreactor system, microorganisms grow and are retained on the adsorbent material, typically for a time sufficient to break down at least a portion of certain biologically refractory and/or biostatic compounds in the particular influent wastewater that have concentrated on the adsorbent material. While not wishing to be bound by theory, it is believed that the microorganisms eventually evolve into mature strains with the special acclimation required to break down at least a portion of certain intractable compounds in the particular influent wastewater. Over additional time, e.g., days to weeks, as the system becomes acclimated, wherein the adsorbent material containing certain biologically refractory and/or biostatic compounds remains in the system, the highly specific microorganisms become second, third and higher generations by increasing their effectiveness in biodegrading at least a portion of certain specific biologically refractory and/or biostatic compounds present in that particular influent wastewater.

Each influent wastewater may be deficient in certain nutrients that are biologically beneficial to be present in bioreactor 202. In addition, some influent wastewater may have a pH of peracid or overbase. Thus, as will be apparent to those skilled in the art, phosphorus, nitrogen, and pH adjusting materials, supplemental simple carbon or chemicals may be added to maintain optimal nutrient ratios and pH values within bioreactor 202 for biological life and related activities, including biological oxidation.

Effluent from bioreactor 202 is directed through separation subsystem 222 to membrane operating system 204 inlet 210. Such transferred mixed liquor that has been treated in bioreactor 202 is substantially free of adsorbent material. In the membrane operating system 204, the wastewater is passed through one or more microfiltration or ultrafiltration membranes, by removing or reducing the need for clarification and/or tertiary filtration. The membrane permeate, i.e., the liquid that passes through membrane 240, is discharged from membrane operating system 204 via outlet 212. Membrane retentate, i.e., solids from the bioreactor 202 effluent, comprising activated sludge, is returned to the bioreactor 202 via return activated sludge line 214.

Spent adsorbent material, such as granular activated carbon, from the bioreactor 202, which is no longer effective at adsorbing contaminants, such as certain compounds that are all resistant to biological decomposition, biologically refractory compounds, and biologically inhibitory compounds, can be removed through the mixed liquor waste discharge port 216 of the bioreactor 202. A waste outlet 218 may also be coupled to the activated sludge line 214 to dispose of some or all of the returned activated sludge, such as to control mixed liquor and/or culture concentration. Sludge is discharged from the unit with waste activated sludge when it has risen to a point where the mixed liquor solids concentration is too high and thus disrupts the operation of a particular membrane bioreactor system. In addition, the mixed liquor waste discharge port 216 can be used to remove portions of the adsorbent material, resulting in lower concentrations of certain biologically refractory compounds, biostatic compounds, and/or organic and inorganic compounds that are all resistant to biological decomposition in the effluent, and more stable biomass within the membrane bioreactor, by removing some portions of the biologically refractory compounds, biostatic compounds, and/or organic and inorganic compounds that are all resistant to biological decomposition, rather than from the return activated sludge line with the waste activated sludge. An equivalent amount of fresh or regenerated adsorbent material may then be added to replace the adsorbent so removed.

Primary screening and/or separation system 220 may be disposed upstream of inlet 206 of bioreactor 202. This primary screening and/or separation system may include a dissolved oxygen flotation system, a coarse mesh screen, or these and/or other primary treatment devices of the type known in the art for separating suspended matter. Optionally, the primary screening and/or separation system 220 may be eliminated, or other types of primary treatment devices may be included, depending on the particular wastewater being treated.

To prevent at least a majority of the adsorbent material 234 from entering the membrane operating system 204 and causing undesirable abrasion and/or fouling of the membrane 240, a separation subsystem 222 is provided. As shown, in FIG. 2, separation subsystem 222 is located proximal to the outlet of bioreactor 202. In certain embodiments, however, separation subsystem 222 may be located in a separate vessel downstream of bioreactor 202. In either case, the separation subsystem 222 includes devices and/or structures to prevent contact between at least a majority of the adsorbent 234 and the membrane 240 handling system 204. Separation subsystem 222 may include one or more of a screening device, a deposition section, and/or other suitable separation device.

Suitable types of mesh screens or screening devices for certain embodiments of the suspended media membrane bioreactor system include wedge wire mesh screens, metal or plastic orifice plates, or woven fabrics, in cylindrical or flat configurations and arranged at various angles, including vertically oriented, horizontally oriented, or any angle therebetween. In additional embodiments, an active screening device, such as a rotary drum screen, a shaker screen, or other mobile screening device may be employed. In general, the other separation subsystems 222 used are screening device systems with a mesh size less than the lower limit of the effective particle size of the adsorbent material used.

Other types of separation subsystems may be used in place of or in combination with the screening apparatus. For example, as described in more detail below, a deposition zone may be provided in which the adsorbent material is deposited by gravity.

In other embodiments, or in combination with the preceding embodiments, the separation subsystem may include a centrifugal system (e.g., hydrocyclones, centrifuges, etc.), an aerated grit chamber, a floatation system (such as to induce gas floatation or dissolved air), or other known devices.

Optionally, or in combination with a separation subsystem 222 at the proximal outlet end of bioreactor 202, the separation subsystem may be disposed between bioreactor 202 and membrane operating system 204 (not shown). Such alternative or additional separation subsystems may be the same as or different from separation subsystem 222 in terms of type and/or size. For example, in certain embodiments, a settling section, a clarifier, a hydrocyclone separator, a centrifuge, or a combination thereof may be provided to operate as a separate unit between the bioreactor 202 and the membrane operating system 204.

Note that the separation subsystem 222 is highly effective for preventing passage of its original size adsorbent material to the membrane operating system. In certain preferred embodiments, the separation subsystem 222 prevents substantially all of the adsorbent material 234 from passing to the membrane operating system 204. However, during operation of the system 200, various causes of attrition of the adsorbent material, including inter-particle collisions, shearing, circulation, or particle impingement within stationary or moving equipment, may result in particle formation that is too small to be effectively retained in the separation subsystem 222. To reduce damage to the membrane and waste from adsorbent material consumption, certain embodiments include a separation subsystem 222, which separation subsystem 222 prevents passage of substantially all of the adsorbent material 234 in the range of about 70% to about 80% of its original size. The percentage reduction of the initial size that is acceptable can be determined by one skilled in the art, for example, based on economic evaluation. If the reduction in size results in an increase in particle throughput to the screening system, the film will exhibit increased erosion. As such, a cost-benefit analysis can be used to determine which is an acceptable percentage reduction of adsorbent material based on the cost of abrasion versus the final replacement of the membrane, the cost associated with reducing damaged adsorbent material, and the processing and operating costs associated with the separation subsystem that can prevent particles that are much smaller than the original adsorbent material particles or particles from passing through. Furthermore, in certain embodiments, it is desirable that some degree of inter-particle collisions, or particle impact inside the stationary or moving equipment, strip off excess biomass from the outer surface of the adsorbent material.

The mixed liquor effluent from bioreactor 202 that has been screened or separated may be pumped or otherwise moved by motive flow (depending on the design of the particular system) into membrane operating system 204. In systems using an external separation subsystem (not shown), the apparatus is preferably configured to allow the adsorbent material from the mixed liquor separation to fall back into bioreactor 202 by gravity through an external fine mesh screen or separation subsystem.

Adsorbent material, such as granular activated carbon, for example, suitably pre-wetted to form an adsorbent material slurry, may be added to the wastewater at various points of the system 200, for example, from an adsorbent material source 229. As shown in fig. 2, the adsorbent material may be introduced into one or more locations 230a, 230b, 230c and 230 d. For example, the adsorbent material may be added to the feed stream downstream of the preliminary screening system 220 (e.g., location 230 a). Optionally, or in combination, the adsorbent material may be added directly to bioreactor 202 (i.e., location 230 b). In certain embodiments, the adsorbent material can be introduced through the return activated sludge line 214 (e.g., location 230 c). In additional embodiments, it may be desirable to add adsorbent material upstream of the preliminary screening system 220 (e.g., location 230d), where the preliminary screening system 220 is specifically designed for this application, by including screening to allow passage of adsorbent material through and into the bioreactor 202. The mixed liquor passes through the separation subsystem 222 and the adsorbent material is substantially prevented from entering the membrane operating system 204 with mixed liquor suspended solids.

When the adsorbent material is left in the system and exposed to wastewater constituents, including biologically refractory compounds, biologically inhibitory compounds, and/or organic and inorganic compounds that are all resistant to biological decomposition, some or all of the adsorbent material becomes ineffective for treating the wastewater constituents, i.e., the adsorption capacity decreases. This results in a higher concentration of these components entering membrane operating system 204 where they pass through the membrane and are discharged with membrane effluent 212. Furthermore, the adsorbent material is rendered ineffective by being coated with bacteria, polysaccharides and/or extracellular polymeric substances. This coating may be to the extent of blocking the location of the orifice, thereby preventing access to biologically intractable compounds, biologically inhibitory compounds, and/or organic and inorganic compounds that are all resistant to biological decomposition, and as a result, preventing adsorption and inhibiting biological decomposition. In certain embodiments of a suspended media membrane bioreactor system, this coating may be removed by shear action generated by one or more mechanisms in the system, such as collisions between adsorbent material particles suspended in the mixed liquor or shear forces associated with the suspension and/or movement of the adsorbent material.

When the adsorbent material has lost all or part of its effectiveness in reducing biologically refractory compounds, biologically inhibitory compounds, and/or organic and inorganic compounds that are all resistant to biological decomposition, a portion of the adsorbent material can be discarded through the waste port 216, such as by discharging a portion of the mixed liquor containing the adsorbent material dispersed therein.

As previously described, additional fresh or regenerated adsorbent material may be introduced into the system interior through the adsorbent material introduction device 229 and/or at one or more suitable addition locations. The influent and effluent wastewater COD compound concentrations and/or inorganic compound concentrations can be monitored to determine when the adsorbent material and its attendant biomass within the system has suffered a reduction in effectiveness. A plot of the difference between influent COD and effluent COD divided by influent COD concentration will show the diminishing loss of effectiveness of the adsorbent material in the mixed liquor. The same type of mapping can be used to monitor the inorganic removal capacity of the system or the removal of specific organic materials. The COD removal amount from the feed stream may provide the relative amount of biologically refractory compounds and/or biostatic compounds removed from the wastewater feed. When the system operator has experience with treating a particular wastewater, it will be possible to determine when this ratio indicates a point in time at which it is desired to remove a portion of the adsorbent material within the bioreactor and replace it with fresh adsorbent material. Thus, the desired efficacy of the system for biologically intractable compounds, biologically inhibitory compounds, and/or organic and inorganic compounds that are entirely resistant to biological decomposition will be regained, for example, by producing effluent that meets regulatory requirements. Sampling and analyzing the effluent for specific organic and inorganic compound concentrations can also be used to determine when the adsorbent material and its attendant biomass within the mixed liquor has suffered from a decrease in effectiveness and must begin partial replacement.

The operator of the suspended media membrane bioreactor system 200 can begin replacing portions of the adsorbent material as certain organic or inorganic compounds of the effluent begin to approach the discharge concentration of the facility-permitted compounds. The allowable emission concentrations are typically limited by the facility's license, such as determined by the national pollutant emission removal system (NPDES) license program as set forth by the united states environmental protection agency, or by similar governing bodies in a particular state or country. As the operator gains experience in operating such a system with their particular wastewater, it will be expected when replacement of the adsorbent material should begin. When the operator determines that the efficacy of the adsorbent material and its accompanying biomass approaches the contaminant concentration of the effluent that is not meeting the requirements, normal wasting of excess biomass performed by wasting the returned activated sludge from the line 218 may be stopped, with the excess biomass and accompanying adsorbent material being wasted from the bioreactor 202 through the waste port 216. The amount of waste material is determined by the requirement to maintain mixed liquor suspended solids within the optimum operating range for the particular membrane bioreactor system. After replacement of a portion of the adsorbent material, the effluent is monitored by an operator to determine whether the desired contaminant removal efficiency has been restored. Additional changes may be made as needed based on operational experience.

In certain implementations, the system and/or individual devices of the system can include a controller to monitor and adjust the system, if desired. The controller may direct any parameters within the system in accordance with desired operating conditions, such as based on government regulations regarding effluent flow. The controller may associate each potential flow adjustment or regulation valve, feeder, or pump based on one or more signals generated by sensors or timers located within the system or individual devices. The controller may also associate each potential flow adjustment or regulation valve, feeder, or pump based on one or more signals generated by sensors or timers located within the system or individual devices that indicate a particular trend, such as an upward or downward trend in the characteristics or properties of the system over a predetermined period of time. For example, a sensor in the effluent stream may generate a signal indicating that a contaminant concentration, such as biologically refractory compounds, biologically inhibitory compounds, and/or organic and inorganic compounds that are entirely resistant to biological decomposition, has reached a predetermined value or trend, or that the COD level has reached a predetermined value or trend, thereby triggering a controller to perform certain actions from or downstream of the sensor. This action may include any one or more of removing adsorbent material from the bioreactor, adding new or regenerated adsorbent material to the bioreactor, adding different types of adsorbent material, adjusting the flow of wastewater at the feed inlet or the inlet of any device within the system, diverting the flow of liquid at the feed inlet or the inlet of any device within the system to a storage tank, adjusting the flow of gas within the bioreactor, adjusting the residence time within the bioreactor or other device, and adjusting the temperature and/or pH within the bioreactor or other device. One or more sensors may be used with one or more devices or flows of the system to provide an indication or characteristic of the status or condition of any one or more processes performed at the system.

The system and controller of one or more embodiments of the suspended media membrane bioreactor system provide a diversified unit with multiple modes of operation that can increase the efficiency of a wastewater treatment system in response to multiple input signals. The controller may be implemented using one or more computer systems, which may be, for example, a general purpose computer. In addition, the computer system may include specially-programmed special-purpose hardware, such as an application-specific integrated circuit (ASIC) or a controller intended for use in a water treatment system.

The computer system may include one or more processors, typically coupled to one or more storage elements, which may include, for example, any one or more of hard disk memory, flash memory elements, RAM memory elements, or other components to store data. Memory is typically used for storing programs and data during system operation. For example, the memory may be used to store historical data relating to the parameters over a period of time and operational data. Software, including program code that implements embodiments of the invention, can be stored on a computer-readable and/or writable non-volatile recording medium and then typically copied into memory where it can then be executed by one or more processors. Such program code may be written in any one or combination of a variety of program languages.

The components of the computer system may be coupled to one or more interconnection mechanisms, which may include one or more buses between the components, e.g., integrated within the same device, and/or a network of components, e.g., residing in separate discrete devices. The interconnection mechanism typically allows communication, for example, data and commands to be exchanged between components of the system.

The computer system also includes one or more input devices, such as a keyboard, mouse, trackball, microphone, touch panel, and other human interface devices, and an output device, such as a printing device, display screen, or speaker. In addition, a computer system may contain one or more interfaces that may connect the computer system to a communications network, either in addition to or in place of a network that may be formed by one or more components of the system.

According to one or more embodiments of the suspended media membrane bioreactor system, the one or more input devices may include sensors to measure any one or more parameters of the system and/or components thereof. Additionally, one or more of the sensors, pumps, or other components of the system, including metering valves or dosers, may be connected to a communication network operatively coupled to the computer system. Any one or more of the foregoing may be coupled to another computer system or component to communicate with the computer system via one or more communication networks. This configuration allows any sensor or signal-generating device to be located at a significant distance from the computer system and/or any sensor to be located at a significant distance from any subsystem and/or controller while still providing data therebetween. Such communication mechanism may be performed by utilizing any suitable technique including, but not limited to, utilizing a wireless communication protocol.

While the computer system is illustrated as one type of computer system that can implement the suspended media membrane bioreactor system and aspects of the present invention, it should be understood that the present invention is not limited to implementation on software or the computer system illustrated. Indeed, rather than being implemented on a general purpose computer system, for example, the controller or components thereof or subsections thereof may alternatively be implemented as a dedicated system or dedicated Programmable Logic Controller (PLC) or implemented in a distributed control system. In addition, it should be understood that one or more suspended media membrane bioreactor systems and features or aspects of the present invention may be implemented in software, hardware, or firmware, or any combination thereof. For example, one or more segments of the algorithm executable by the controller may be executed on separate computers, which in turn may communicate over one or more networks.

In certain embodiments, one or more sensors may be included at locations throughout the system 200 that communicate with a human operator or an automated control system to implement appropriate process modifications in a programmable edit control membrane bioreactor system. In one embodiment, the system 200 includes a controller 205, which may be any suitably programmed or dedicated computer system, PLC, or distributed control system. The concentration of certain organic and/or inorganic compounds may be determined from membrane operating system effluent 212 or the effluent from outlet 208 of bioreactor 202, as indicated by the dashed connection between controller 205 and both effluent line 212 and the intermediate effluent line between outlet 208 and inlet 210. In another embodiment, the concentration of volatile organic compounds or other properties or characteristics of the system may be determined at one or more of the inlets 201, 206, or 210. Methods sensors known to those skilled in the art of control devices include laser-induced fluorescence based sensors or any other sensor suitable for in situ real-time monitoring of the concentration of organic or inorganic compounds in effluents or system characteristics. Sensors that can be used include immersion Sensors for oil-in-water measurements that use UV fluorescence for detection, such as the environment-friendly fluorescence (enviroFlu) -HC sensor from sister-in-law oes Optical Sensors (TriOS Optical Sensors, orlamb, germany). The sensor may include a lens that is coated or otherwise treated to prevent or limit the amount of fouling or filming that occurs on the lens. When one or more sensors in the system generate a signal that the concentration of one or more organic and/or inorganic compounds exceeds a predetermined concentration, the control system can perform a responsive action, such as an appropriate feedback action or a forwarding action, including but not limited to the removal of the adsorbent material through the waste discharge port 216 (as indicated by the dashed link between the controller 205 and the waste discharge port 216); adding new or regenerated adsorbent material through the adsorbent material introduction device 229 or at one of the other locations (as indicated by the dashed connection between the controller 205 and the adsorbent material introduction device 229); adding different types of adsorptive materials; modifying the water retention time; modifying biological characteristics such as simple carbon food for microorganisms or adding phosphorus, nitrogen, and/or pH adjusting chemicals; and/or other modifications as previously described or apparent to those skilled in the art.

Note that although the controller 205 and the adsorbent material introduction device 229 are shown only with respect to fig. 2, it is contemplated that these features and multiple feedback and forwarding capabilities may be incorporated into any of the systems described herein. In addition, the controller 205 may be electrically coupled to other components, such as a wastewater feed pump and suspension system 232.

After the mixed liquor is aerated and treated by the adsorbent material in bioreactor 202, the treated mixed liquor is transported to membrane operating system 204 through separation subsystem 222, and substantially free of adsorbent material. The separation subsystem 222 prevents adsorbent material from entering the membrane operating system 204. By maintaining the adsorbent material in bioreactor 202, or upstream of membrane operating system 204, the suspended media membrane bioreactor system reduces or eliminates the chance of fouling and/or abrasion of the membrane operating system tank membrane by the adsorbent material.

Membrane operating system 204 contains filtration membrane 240 from biomass and any other solids in the mixed liquor in effluent filtration membrane operating system tank 204 from bioreactor 212. As known to those skilled in the art, these membranes 240 may be hollow fiber membranes or other suitably configured configurations, typically very expensive and highly desirable to protect the membrane from damage to maximize its useful life. In the suspended media membrane bioreactor system 200, the membrane life of the operating system tank is extended because the separation subsystem 222 substantially reduces or eliminates the entry of adsorbent materials such as granular activated carbon and/or any other solid particles and particulates into the membrane operating system 204.

The outlet 212 transports the filtered effluent from the membrane operating system tank 204. A return activated sludge line 214 transports the return activated sludge from the membrane operating system tank 204 to the bioreactor 202 for further treatment of the wastewater feed stream. Excess sludge is dumped from the system using waste line 218 as in conventional membrane bioreactor systems.

The suspension system 232 utilizes one or more of jet suspension, mechanical mixing, coarse bubble aeration, gas lift suspension systems such as draft tubes and draft slots, and other types of mechanical or air suspension systems to maintain the adsorbent material 234 in suspension while reducing abrasion of the adsorbent material 234.

In certain embodiments, after an initial period in which the adsorbent material 234 is broken within the bioreactor 202 and a portion of the particles, a portion of the rough and/or protruding surface of the adsorbent material 234 breaks down to become a powder, fines, needles, or other small particles, the adsorbent material 234 is maintained in suspension by the suspension system 232 with little or no further breakage or size degradation occurring.

The concentration of adsorbent material in the mixed liquor is generally dependent upon the particular system parameters and the particular combination of wastewater, biologically refractory and/or biologically inhibitory organic or inorganic compounds to be treated to meet the discharge requirements of the plant. Tests have indicated that operating a membrane bioreactor with a typical industrial mixed liquor suspended solids concentration (in the normal range for the particular membrane bioreactor configuration employed) and an adsorbent material concentration such as granular activated carbon of about 20% of the total mixed liquor suspended solids concentration is sufficient to remove biologically refractory and/or biostatic compounds present in the wastewater feed without fouling the screening system used. Higher concentrations of adsorbent materials may be added to provide additional margin of safety against process perturbations that may result in higher than normal effluent concentrations of biologically intractable compounds, biostatic compounds, and/or organic and inorganic compounds that are all resistant to biological decomposition. Note that such additional adsorbent material would result in increased screening and/or deposition requirements. Based on experience or otherwise based on the safety margin expected against process upset, the minimum concentration of adsorbent material available to still achieve the desired effluent quality can be determined experimentally, based on the safety margin deemed appropriate for the particular system and process.

Suspended media membrane bioreactor systems use adsorbent materials upstream of the membrane operating system tank to adsorb organic and inorganic materials (biologically refractory, biostatic, or otherwise), as well as provide for the application of suspended media membrane bioreactors in a variety of different configuration configurations. In addition, various separation devices may also be used to maintain the adsorbent material in the bioreactor. It will be apparent to those skilled in the art that different systems will have different economic benefits based on the individual characteristics of the wastewater and the area in which the facility is to be erected.

Factors that are controlled to produce optimal processing conditions include the type of adsorbent material, including its size, shape, hardness, specific gravity, deposition rate, desired air flow rate, or other suspension requirements for the suspension of the particles in the mixed liquor, i.e., maintaining the granular activated carbon in a suspension medium, spacing or opening size and pore configuration of the bar screens, concentration of adsorbent material in the mixed liquor, mixing, and mixingThe combined liquor volatile suspended solids concentration, the total mixed liquor suspended solids concentration, the ratio of the flow rate of the returned activated sludge divided by the flow rate of the mixed liquor entering the membrane operating system tank, the water retention time, and the sludge retention time. Such optimization provides biologically refractory compounds, readily decomposable biological oxygen demand compounds (BOD)₅) Some of the bio-inhibitory compounds, organic or inorganic compounds that are all resistant to biological decomposition, and extracellular polymeric substances are adsorbed by an adsorbent material such as granular activated carbon suspended in the mixed liquor.

Another effect of the suspended media membrane bioreactor system provides a site to which microorganisms in the mixed liquor suspended solids can adhere. This aspect of the method produces a mixed liquor volatile suspended solids stream that is more stable and more resilient to disturbance conditions than membrane bioreactors operated with similar water and sludge residence times but without granular activated carbon reinforcement, and allows for the promotion of the biodegradation of organic matter present in the wastewater. Where the upstream process perturbation results in the depletion of some viable microorganisms that auto-float in the mixed liquor, the microbial source inside or on the surface of the adsorbent material pore space is used as an inoculum source. In the case of thermal shock or toxic chemical impact systems, some bacteria will die in conventional systems, while some microorganisms inside or on the surface of the pore space may survive, thus requiring only a partial recovery time compared to conventional systems that do not contain an adsorbent. For example, in systems where the bacteria are mesophilic, the adsorbent may allow some of the bacteria inside the pore sites to survive thermal shock caused by the temperature rise. Similarly, in systems where the bacteria are thermophilic, the adsorbent may allow some of the bacteria inside the pore locations to survive thermal shock due to the temperature drop. In both cases, the time required for the culture to re-acclimate is greatly reduced. Furthermore, in the case of a system-impact-destroying all or part of the microorganism population, the presence of the adsorbent material allows for sustained operation in which unstable, intractable, and inhibitory contaminants can be adsorbed and simultaneously modulate the microorganism population.

It has been shown that various effects result in a mixed liquor that acclimates more rapidly to wastewater feed, reduces fouling of the membrane, improves tolerance to feed concentration and flow rate, produces a faster dewatering sludge, is easier to handle with less oil properties, and has a lower concentration of organic and inorganic impurities than can be achieved with conventional membrane bioreactor devices.

The use of adsorbents such as granular activated carbon instead of powdered activated carbon may allow for the elimination of membrane fouling and/or erosion problems that have been identified in powdered activated carbon membrane bioreactor testing.

Although the use of granular activated carbon instead of powdered activated carbon does not use carbon equally effectively on a weight basis, the suspended media membrane bioreactor system and separation subsystem substantially prevents the granular activated carbon from entering the membrane operating system, thereby reducing or eliminating the chance of membrane erosion and fouling. But the impact on the decrease of the adsorption efficiency caused by the use of granular activated carbon instead of powdered activated carbon does not significantly affect the overall efficiency of the membrane bioreactor device reinforced by activated carbon.

Tests have indicated that the primary mechanism for removing certain bio-inhibitory and/or bio-refractory compounds involves the extension of the residence time of the bio-refractory and/or bio-inhibitory compounds exposed to microorganisms in a powdered activated carbon enhanced device. Microorganisms in the mixed liquor volatile suspended solids adsorbed on the adsorbent material, such as granular activated carbon, have a longer time to digest these certain biologically refractory and biostatic compounds. The extension of residence time for biological decomposition has been shown to be a major factor in reducing the concentration of certain biologically refractory and biostatic compounds in the membrane bioreactor effluent, and the need for higher adsorption efficiency of powdered activated carbon to achieve the desired results.

Granular activated carbon functions equally well or better than powdered activated carbon reinforced membrane bioreactors by allowing substantial regeneration of the granular activated carbon in terms of enhancing the removal of biologically refractory compounds, biostatic compounds, organic and inorganic compounds that are totally resistant to biological decomposition, and extracellular polymeric compounds. In addition, due to the large size of the granular activated carbon, it can be effectively filtered or otherwise separated from the mixed liquor entering the membrane operating system tank. By using granular activated carbon in a suspended media membrane bioreactor system, the erosion that occurs when powdered activated carbon is used can be eliminated or significantly reduced.

While the use of powdered activated carbon particles in membrane bioreactors has shown some of the same advantages previously described for granular activated carbon systems, membrane erosion from powdered activated carbon in membrane operating system tanks is unacceptable because the life expectancy of the membranes can be shortened to unacceptable levels, e.g., significantly shorter than the warranty period for typical membranes. Since the membrane cost represents a significant portion of the total membrane bioreactor system cost, extending its useful life is an important factor in the operating cost of the membrane operating system.

Figures 3-6 illustrate certain embodiments of the wastewater treatment system of the present invention. As described above, the wastewater treatment system of the present invention may employ a suspended media membrane bioreactor system as described with reference to FIGS. 1 and 2 and also described in PCT application No. PCT/US10/38644 and publication No. WO/09085252. While certain preferred embodiments are described in connection with the treatment of low concentration wastewater (e.g., derived from effluent undergoing upstream wastewater treatment), those skilled in the art will recognize with the benefit of this disclosure: the wastewater treatment system of the present invention may be advantageously used to treat wastewater having some level of biologically labile compounds as well as compounds that are fully resistant to biodegradation, biologically inhibitory compounds and/or biologically refractory compounds, or a combination of these compounds.

Referring to fig. 3, a treatment system 354, generally referred to as a wastewater treatment system 350, is schematically illustrated that treats effluent 351 from one or more upstream wastewater treatment stages. The wastewater treatment system 350 typically treats the influent 301 and discharges an excess activated sludge 352 and a liquid treated effluent 351, referred to herein as "low strength wastewater" or "effluent undergoing upstream wastewater treatment," as is conventionally known. Although the following description refers to the effluent 351 as being derived from one or more upstream wastewater treatment stages, such as primary and/or secondary treatment stages, one of ordinary skill in the art will appreciate that the systems and methods of the present invention are also effective for treating low concentration wastewater from other sources, such as directly from processes having low levels of suspended solids and relatively low levels of dissolved organics. In addition, the wastewater treatment system of the present invention may be advantageously used to treat wastewater having some level of biologically labile compounds as well as compounds that are completely resistant to biodegradation, biologically inhibitory compounds and/or biologically refractory compounds, or a combination of these compounds. In these embodiments, stream 351 may be a direct influent, or undergo minimal upstream processing, such as a primary separation system in which substantially all solids have been removed.

As discussed above, tertiary treatment of the effluent from the secondary treatment section typically involves passing the complete secondary effluent through one or more granular activated carbon columns or other tertiary systems for additional treatment, such as polishing, to achieve the desired water quality standards. In contrast, the treatment system 354 of the present invention, which may be used as a tertiary treatment system, uses a combination of high flux adsorbent material systems 359 to adsorb a large amount of contaminants, and uses an additional system 399 to biologically treat the adsorbed contaminants, i.e., by biologically regenerating and/or reactivating the contaminants adsorbed onto the adsorbent material.

In general terms, the treatment system 354 of the present invention encompasses a high flux adsorbent material treatment system 359 and a low flux adsorbent material biological regeneration reactor system 399. The high flux adsorbent material treatment system 359 includes a mixing section 360 for receiving fresh and/or recycled adsorbent material from a source 393 of adsorbent material. Mixing section 360 is fluidly connected to a source of low-concentration wastewater 351, such as an effluent undergoing upstream wastewater treatment or other low-concentration wastewater. The mixing section 360 intimately mixes the adsorbent material and the wastewater and passes a mixture of low concentration wastewater and adsorbent material 361 to the adsorbent material deposition and liquid separation section 370. The majority of the total liquid volume/flux is dumped or discharged from the adsorbent material deposition and liquid separation section 370 as effluent 371, which may optionally be subjected to further tertiary treatment 390. The adsorbent material is removed from the adsorbent material deposition and liquid separation section 370 as an adsorbent material effluent discharge 372, which is sent to a low flux adsorbent material biological regeneration reactor system 399, including the biological regeneration reactor 302, the membrane operating system 304, the adsorbent material shearing section 386, and the adsorbent material/biomass separation section 387. In an aerobic system, biological regeneration reactor 302 also includes a source of oxygen, and the microorganisms biologically oxidize organic and some inorganic matter adsorbed onto the adsorbent material in biological regeneration reactor 302, and the mixed liquor including mixed liquor volatile suspended solids passes through adsorbent solids separation device 322 and as a discharge outlet of biological regeneration reactor mixed liquor effluent 308 to a solids separation device to remove biomass and any other solids in the mixed liquor. For example, in certain embodiments of the present invention, the solids separation apparatus comprises a membrane operating system 304, wherein the biological regeneration reactor effluent 308 passes through an inlet 310 of the membrane operating system 304 to remove the biomass and any other solids in the mixed liquor. The membrane treated effluent 312 is discharged as permeate and the activated sludge 314 is returned as residue to the biological regeneration reactor 302. A portion of the activated sludge may be discharged from the system through a waste line 318. The adsorbent material from the biological regeneration reactor 302 is sent to an adsorbent material shearing section 386 where excess biomass is sheared from the particles or granules of adsorbent material. The biomass is separated from the adsorbent material in the adsorbent material/biomass separation section 387. The separated adsorbent material (which has been regenerated by biological regeneration reactor 302 and subsequently sheared and separated in sections 386 and 387) is recycled to mixing section 360 via recycle line 389, and biomass is returned to biological regeneration reactor 302 via 388. Spent adsorbent material may be removed from the biological regeneration reactor 302 via line 316 or from the adsorbent material/biomass separation section 387 via line 392.

In certain embodiments, the functions of the adsorbent material shearing section 386 and the adsorbent material/biomass separation section 387 can be integrated into a single unit operation. Examples of equipment that can perform shearing and biomass separation include continuous backwash filters and/or walnut shell filters. In further embodiments, some or all of the functions of the adsorbent material shearing section 386 and the adsorbent material/biomass separation section 387 can be accomplished in the biological regeneration reactor 302, for example if the biological regeneration reactor 302 is suitably equipped with sufficient swirl to facilitate the necessary shearing. In these embodiments, biomass may remain in the biorenewable reactor 302 and regenerated, sheared, and separated adsorbent material may pass directly through the mixing section 360.

In addition, the adsorbent material can be introduced at multiple locations in the system. For example, source 393 can be used to introduce fresh or regenerated adsorbent material, e.g., adsorbent material of the mixing cycle (back to mixing section 360), via line 389. Other suitable locations may be used to introduce adsorbent material, such as discussed in relation to fig. 2, directly to the mixing section 360 or directly to the liquid separation section 370.

In certain embodiments, the adsorbent material effluent stream 372 lacks sufficient nutrients to support the bioprocess within the biological regeneration reactor 302. Thus, a portion of the raw wastewater from influent 301 may be introduced into biological regeneration reactor 302, for example, via bypass stream 303. This stream 303 may be intermittent or continuous depending on the type of wastewater, its composition, and whether the wastewater composition changes over time. The addition of this raw wastewater or some other simple carbon source can enhance bacterial growth, which is required for optimal degradation of refractory organics (removed from the low concentration wastewater stream 351 by the adsorbent material). The raw wastewater initially provides bacteria that become accustomed to the raw wastewater feed composition, and these bacteria then provide a starting point for bacteria that can biodegrade intractable organic matter. The initial bacteria can evolve over time into substances that can digest intractable organic matter. Feeding an untreated wastewater stream into biological regeneration reactor 302 will result in a bacterial population that is capable of digesting more complex organic compounds than are present in sanitary wastewater treatment systems, which are typically the most common starting point for bacteria in wastewater treatment systems. Alternatively, in a combined manner, the inoculation medium may be added to biorenewable reactor 302. Periodically, additional inoculation media of the same or different type may be added, for example if the bacterial population is reduced due to upstream time or thermal shock, or if wastewater contamination changes.

The influent low-concentration wastewater may be deficient in certain nutrients that are beneficial to the biological processes occurring in biological regeneration reactor 302. In addition, some influent wastewater may have a pH of peracid or overbase. Thus, as will be apparent to those skilled in the art, phosphorus, nitrogen, and pH adjusting materials may be added to maintain optimal nutrient ratios and pH values within biological regeneration reactor 302 for biological life and related activities, including biological oxidation. Additionally, in certain embodiments, a simple carbon compound stream may be added to increase the rate of biodegradation of the adsorbed contaminants.

Specifically, the low concentration wastewater is introduced into a mixing section 360, which supplies an adsorbent material such as granular activated carbon. The adsorbent material can include fresh adsorbent material and/or adsorbent material circulating from within the system, i.e., from the adsorbent material/biomass separation section 387. The low concentration wastewater and the adsorbent material are intimately mixed in the mixing zone 360 and at least a portion of the organic and/or inorganic species of the solvent present in the effluent 351 adsorb onto the adsorbent material, i.e., on the exterior surface, on the pore wall surface, or both.

The mixed system 361 from the mixing zone 360, including the adsorbent material that adsorbs at least a portion of the organic and/or inorganic species from the effluent 351, is then sent to the adsorbent material deposition and liquid separation zone 370, for example in the form of a slurry. If organic and/or inorganic species remain in the liquid portion of the mixture 361, adsorption may continue in the adsorbent material deposition and liquid separation zone 370, depending on the flow rate, deposition rate, adsorption capacity of the adsorbent material, and other factors. Preferably, a substantial amount of the contaminants are removed such that the remaining liquid portion, poured or removed as high flux adsorbent material effluent stream 371, at least meets the requirements of the relevant regulatory agency, and can be recycled or discharged in an environmentally friendly manner. Stream 371 can be sent to tertiary treatment section 390 for final polishing if desired and the polished effluent 391 discharged. Advantageously, the organic and/or inorganic species removed from stream 371 (i.e., as compared to effluent 351 from wastewater treatment system 350) are adsorbed onto the adsorbent material, and stream 371 represents the majority of the liquid volume of the initial low-concentration wastewater stream presented to system 354, e.g., stream 351. In certain embodiments, the flux of stream 371 is at least 90% of the flux of stream 351; in other embodiments, the flux of stream 371 is at least 95% of the flux of stream 351; in further embodiments, the flux of stream 371 is at least 99% of the flux of stream 351; in further embodiments, the flux of stream 371 is at least 99.9% of the flux of stream 351; and in even further embodiments, the flux of stream 371 is at least 99.99% of the flux of stream 351. The ratio of the flow 371 to the flow 351 may depend on a variety of factors, including the initial contamination level, the level of mixing in the mixing section 360, the configuration and residence time within the adsorbent material deposition and liquid separation section 370, the adsorption capacity of the adsorbent material, and/or other factors.

In one embodiment, the adsorbent material deposition and liquid separation section 370 comprises a vessel configured with an inverted conical or frustoconical bottom 385. Thus, the adsorbent material is removed by gravity settling through a drain in the bottom of the vessel along with a small portion of the water from influent stream 351. Additionally, in embodiments where the organic and/or inorganic species are not sufficiently adsorbed into the mixing zone 360, the adsorbent material deposition and liquid separation zone 370 may be sized to provide additional contact time between the wastewater effluent so treated and the adsorbent material. In certain embodiments of the adsorbent material deposition and liquid separation zone 370, this can be accomplished within a vessel, providing a low concentration wastewater residence time of greater than about 5 minutes, and in certain embodiments greater than about 15 minutes. Of course, those skilled in the art, given the benefit of the teachings herein, will appreciate that the time required to separate the sorbent from the effluent will depend on a variety of factors, including but not limited to the density of the adsorbent material, the density of the wastewater, and the geometry of the tank.

The adsorbent material deposition and liquid separation zone 370 may preferably comprise: a separation subsystem for preventing the adsorbent material from leaving the adsorbent material deposit; and a liquid pour section having a high velocity liquid effluent 371. In certain embodiments, the separation subsystem may include a stationary section 384, e.g., formed by baffles 381 and 382. This allows a substantial amount of the adsorbent material present in the adsorbent material deposition and liquid separation section 370 to be directed toward the inverted cone or frustoconical bottom 385. In further embodiments, the separation subsystem may include a screening apparatus 383 proximate the outlet of the adsorbent material deposition and liquid separation section 370. The screening apparatus 383 may be a stationary screen, a moving screen, a wedge wire screen, a rotary drum screen, or other suitable screen type. In further embodiments, the separation subsystem may include a stationary section 384 and a screening apparatus 383. In even further embodiments, the separation subsystem may include a stationary section and a weir for the liquid effluent 371 at the outlet of the adsorbent material deposition and liquid separation section 370. Note that the separation subsystem used in the adsorbent material deposition and liquid decanting section 370 can be the same as or different from the separation subsystem used in the biological regeneration reactor 302 (including one or more of a screening system, a deposition section, or a combination thereof). Additionally, if further solids removal from the effluent 371 is desired, a clarifier, filter or other separation device can be fluidly connected downstream of the effluent 371 from the adsorbent material deposition and liquid separation section 370 outlet.

For example, the separation subsystem within the adsorbent material deposition and liquid separation zone 370 can be eliminated in embodiments where the adsorbent material has a relatively high specific gravity (e.g., a specific gravity greater than about 1.10 in 20 ℃ water, in certain embodiments a specific gravity greater than about 1.40 in 20 ℃ water, and in further embodiments a specific gravity up to about 2.65 in 20 ℃ water), such that a high deposition rate, combined with suitable dimensions and configurations of the adsorbent material deposition and liquid decantation zone 370 (including the geometry of the bottom 385 and the location of the effluent 371 outlet). In these embodiments, a clarifier, filter, or other separation device may be disposed downstream of the adsorbent material deposition and liquid separation section 370. Alternatively, a clarifier, filter, or other separation device may also be eliminated, wherein the effluent 371 is subjected to the final polishing apparatus 390. In certain embodiments, if the final polishing apparatus 390 is a fixed bed granular activated carbon adsorption column, any excess adsorbent material from the adsorbent material deposition and liquid decanting section 370 through which the effluent 371 may pass will not affect the final effluent as it will be captured in the polishing apparatus 390.

From the adsorbent material deposition and liquid separation section 370, the adsorbent material is sent to a biological regeneration reactor where microorganisms biodegrade the organic and certain inorganic species adsorbed onto the adsorbent material.

In certain embodiments, biological regeneration reactor 302 is an aerobic system in which microorganisms are aerobic, and biological regeneration reactor 302 is an aerated tank, including a source of oxygen (not shown), such as one or more of a diffuser, a jet suspension device, or a gas lift suspension system, as described in PCT application No. PCT/US10/38644, and biodegradation includes biological oxidation. Biological processes within a biorenewable reactor are discussed in detail in PCT application No. PCT/US10/38644 and PCT publication No. WO/09085252.

In further embodiments, the biological regeneration reactor 302 is an anaerobic system, wherein the microorganisms are anaerobic.

Mixed liquor, including mixed liquor volatile suspended solids, is discharged through a separation subsystem 322 in or downstream of bioreactor 302 and is sent from outlet 308 of bioreactor 302 to membrane operating system 304 through inlet 310. The membrane operating system 304 contains one or more membranes 340. The membrane treated effluent 312 is discharged as permeate and the activated sludge 314 is returned as residue to the biological regeneration reactor 302. Optionally, the activated sludge waste may be discharged from the return activated sludge line 314 through a waste line 318. In addition, an optional adsorbent material waste line 316 (shown in long dashed lines) may remove used adsorbent material that has lost its effectiveness, or for periodic removal of adsorbent material, as described in connection with FIG. 2 and PCT publication No. WO/09085252 and PCT application No. PCT/US 10/38644. Preferably, the removed spent adsorbent material is replenished with an equal amount of fresh or regenerated adsorbent material. In another preferred embodiment, all or a portion of the membrane treated effluent 312 can be sent to the tertiary treatment section 390 via optional line 313 (shown as long dashed line) for final polishing.

Adsorbent material such as granular activated carbon, and any captured liquid in stream 372 sent to the biological regeneration reactor 302, is treated in a similar manner to the membrane bioreactor system described in PCT application No. PCT/US10/38644 and PCT publication No. WO/09085252. However, the flux of stream 372 is relatively low. For example, the flux of stream 372 may be less than about 10%, 5%, 1%, 0.1%, or even less than about 0.001% of the flux of stream 351. In certain embodiments, the flux is the minimum flow that can pass through the membrane operating system 304 without affecting the activity of the microorganisms in the biological regeneration reactor 302. Alternatively, the system may be operated as a sequential batch reactor, wherein the effluent is discharged when the wastewater is sufficiently treated. Additionally, in certain embodiments, biological regeneration reactor 302 may be an aeration tank that incorporates a combination of jet suspension or gas lift suspension, a static section, and a wedge wire screen, as described in PCT application No. PCT/US 10/38644. The membrane operating system 304 in the low-concentration wastewater treatment system 354 of the present invention operates in a similar manner to the membrane bioreactor described in PCT application No. PCT/US10/38644 and PCT publication No. WO/09085252, however, operates at a very low flow rate. Because biomass accumulates in the system, it can be discarded in a manner similar to conventional membrane bioreactor systems (e.g., by returning activated sludge waste line 318). An adsorbent material waste line 316 is also provided. For example, the adsorbent material may lose its adsorption capacity under conditions in which the effluent undergoing upstream wastewater treatment contains inorganic or bio-inhibitory compounds that do not oxidize at substantially increased residence times even with the low concentration wastewater treatment system of the present invention. The adsorbent material may be supplemented in the system, for example, using one or more adsorbent material input locations as described in PCT publication No. WO/09085252 or at another location or source 393.

On a continuous or batch basis, a sidestream comprising adsorbent material and optionally a mixed liquor to provide a liquid carrier (e.g., in the form of a slurry) of adsorbent material to facilitate transfer is removed from biological regeneration reactor 302 and sent to shear zone 386. In the shearing section 386, excess biomass is sheared from the outer surface of the adsorbent material such that the adsorptive capacity of the adsorbent material in the mixing section 360 and/or the adsorbent material deposition and liquid separation section 370 is maximized. Shear section 386 may include one or more of pumps, jet nozzles, aerated grit chambers, mechanical agitators, centrifuges such as hydrocyclones or centrifuges, or other devices that facilitate impingement to complete shear and, in certain embodiments, facilitate separation of biomass from adsorbent material. The swirling of the shear zone, collisions between particles and collisions with other solid objects (stationary or moving), piping between the shear zone and the biological regeneration reactor 302 in certain embodiments, can cause excess biomass to shear from the outer surface of the adsorbent material and become free floating mixed liquor suspended solids including mixed liquor volatile suspended solids.

In addition, the effect of fluid circulation, including high velocity liquid and/or gas contacting the surface of the adsorbent material with excess biomass, contributes to the desired shear.

In certain embodiments, the adsorbent material shearing section 386 may comprise a continuous regeneration system, such as a configuration with a walnut shell filter or other similar unit operation, for example without walnut shell media, such as one type available from Siemens Water Technologies. For example, when the adsorbent material is passed through a continuous regeneration system, such as a continuous backwash filter or walnut shell filter, collisions between particles and collisions with other solid objects and/or surfaces in the continuous regeneration system cause the excess biomass to shear from the particles of the adsorbent material.

The slurry (including sheared adsorbent material, sheared free biomass from adsorbent material, and any mixed liquor) is sent to adsorbent material/biomass separation section 387 to separate the mixed liquor sheared from adsorbent material from denser adsorbent material from the suspended solid biomass. The adsorbent material/biomass separation section 387 can include one or more of a hydrocyclone separator, a centrifuge, a side stream of a continuous regeneration system, or other suitable means for separating adsorbent material from biomass.

Note that in certain embodiments where biorenewation reactor 302 includes jet nozzles or other devices that effect shearing at biorenewation reactor 302 as described in PCT application number PCT/US10/38644, shearing section 386 may be eliminated or bypassed such that a side stream from biorenewation reactor 302 is sent directly to adsorption/biomass separation section 387.

The adsorbent material separated from the adsorbent material/biomass separation section 387 is sent to the mixing section 360 via line 389. The adsorbent material returned to the mixing section 360 contains a reduced concentration of microorganisms and thus organics in the low concentration wastewater can be adsorbed and exposed to the desired biological process in the mixing section 360 and the adsorbent material deposition and liquid separation section 370 before being sent to the biological regeneration reactor 302.

Sheared biomass, which may include mixed liquor with mixed liquor suspended solids and mixed liquor volatile suspended solids from adsorptive material/biomass separation section 387, is sent to biological regeneration reactor 302 via line 388.

In alternative embodiments, the mixed liquor from the adsorbent material/biomass separation section 387 can be transferred downstream from the separation subsystem 322, e.g., biological regeneration reactor 302, in conjunction with effluent 308, or sent directly to a membrane operating system. Clearly, the separation requirements of the separation subsystem 322 may be reduced or eliminated in this alternative embodiment, as the mixed liquor may be diverted without further separation. In certain embodiments, the source of mixed liquor for the membrane operating system 304 (or clarifier/settling tank 395 when described in connection with fig. 3) can be a liquid effluent from the adsorbent material/biomass separation section 387.

In certain preferred embodiments, to facilitate the deposition of the adsorbent material in the adsorbent material deposition and liquid separation zone 370, a granular activated carbon having a relatively high specific gravity level is used. For example, granular activated carbon having a specific gravity of greater than 1.10 may be used. In a further embodiment, granular activated carbon having a specific gravity greater than 1.40 may be used. Because the flow rate of the mixture containing granular activated carbon is relatively low, the biological regeneration reactor 302 and membrane operating system 304 are relatively small, requiring higher energy to keep the denser adsorbent material in suspension for a time sufficient to cause a desired level of biological processes within the biological regeneration reactor 302, which is not a significant factor in the overall energy requirements of the operating system.

Some low-concentration wastewater influent may include inorganic compounds that are not biodegradable by microorganisms. The level of these inorganics must typically be reduced to within allowable regulatory requirements. The adsorbent material may be modified with treatment methods and/or substances to provide affinity for metals in chemicals and/or wastewater, for example, by impregnation with suitable compounds, as further described in PCT application No. PCT/US 10/38644. Microorganisms in the low concentration wastewater treatment systems of the present invention are not effective in removing these inorganic compounds because they can remove organic compounds, and systems that use adsorbent materials to adsorb inorganic contaminants typically require more frequent replacement of the adsorbent materials than systems that only treat organic compounds. The spent adsorbent material is removed from the system as it reaches the adsorption limit of the compounds to be removed from the low concentration wastewater. For example, sampling and analysis or on-line monitoring may be performed periodically or continuously to determine the concentration of organic or inorganic species of the low-concentration wastewater treatment system of the present invention, as the adsorption capacity of the granular activated carbon of various compounds is inversely related to the waste concentration of the effluent 371.

In further embodiments in which a tertiary treatment system 390 is used and includes a conventional adsorbent material filtration system, contaminated adsorbent material from the system 390 may be regenerated and/or reactivated using an adsorbent material biological regeneration reactor system 399, as shown by line 394 between the tertiary treatment system 390 and the biological regeneration reactor 302. Some existing granular activated carbon adsorbent filter systems use staged adsorption, wherein fresh granular activated carbon is added in the final downstream filter and partially loaded granular activated carbon is used in the upstream filter. In embodiments of the invention in which contaminated adsorbent material from system 390 is regenerated and/or reactivated during adsorbent material biological regeneration reactor system 399, the partially loaded granular activated carbon is transferred to biological regeneration reactor 302 for regeneration and reuse as all or a portion of the adsorbent material in mixing zone 360. Although line 394 represents the transfer of the partially loaded adsorbent material directly to the biological regeneration reactor 302, one skilled in the art, given the benefit of the teachings herein, will appreciate that the partially loaded adsorbent material can be introduced into the adsorbent material shear section 386, the adsorbent material/biomass separation section 387, the source of adsorbent material 393, the mixing section 360, or the liquid separation section 370.

In some embodiments, one or more sensors may be included at locations throughout the system 350, including within the high flux adsorbent material treatment system 359 and the low flux adsorbent material biological regeneration reactor system 399. These sensors can be used in manually controlled and operated systems or in automated control systems to implement appropriate program modifications in programmable logic controlled wastewater treatment systems. In one embodiment, the system 350 (or the high flux adsorbent material treatment system 359 and the low flux adsorbent material biological regeneration reactor system 399) includes a controller 305, which may be any suitable programmed or dedicated computer system, PLC, or distributed control system. The concentration of certain organic and/or inorganic compounds may be monitored and measured by one or more sensors fluidly connected to the effluent 312 or the effluent of the outlet 308 of the biological regeneration reactor 302, as represented by the dash-dot-line connection between the controller 305 and the effluent line 312 and the intermediate effluent line between the outlet 308 and the inlet 310. In further embodiments, the concentration or other property or characteristic of the volatile organic compounds of the system may be measured at one or more of the inlets 301, 351, or 310. In further embodiments, the concentration of certain organic and/or inorganic compounds may be monitored and measured by one or more sensors in fluid communication with the effluent 371 of the adsorbent material deposition and liquid separation zone 370, as indicated by the dash-dot-line connection between the controller 305 and the effluent line 371. Sensors known to those skilled in the art of programmed devices may include those based on laser-induced fluorescence or any other device suitable for in situ real-time monitoring of the concentration or other properties or characteristics of organic or inorganic compounds in the effluent of a system. Sensors that may be used include submersible Sensors used in oil-in-water measurements that use UV fluorescence for detection, such as the enviroFlu-HC sensor available from TriOS Optical Sensors (Oldenburg, Germany). The sensor may include a lens that is coated or treated to prevent or limit the amount of contamination or filming that occurs on the lens. When one or more sensors in the system generate a signal that the concentration of the one or more organic and/or inorganic compounds exceeds a predetermined concentration, the control system can perform a reactive action, such as a suitable feed return action or feed advance action, including but not limited to removing adsorbent material through a waste drain 316 (as represented by the dashed connection between the controller 305 and a valve associated with the waste drain 316); removing the return activated sludge through a waste line 318 (as represented by the dashed connection between the controller 305 and the associated valve of the waste drain 318); adding new or regenerated adsorbent material through the adsorbent material source 393 or at one of the other locations (as represented by the dashed connection between the controller 305 and the valve associated with the adsorbent material source 393); adding different types of adsorbent materials; improving hydraulic retention time (hydraulic retention time); improving biological properties such as simple carbon food for microorganisms or adding phosphorus, nitrogen and/or pH adjusting chemicals; and/or other modifications as described above or as will be appreciated by those skilled in the art.

In further embodiments, the condition of the slurry containing the adsorbent material may be by one or more sensors (represented by shaded circles in fig. 3), such as an optical sensor and/or a UV fluorescence sensor. For example, one or more sensors can be associated with the adsorbent material effluent stream 372, as represented by the dash-dot-dash connection between the controller 305 and the stream 372, to measure the concentration of one or more compounds in the stream and/or to determine the mass of adsorbent material in the slurry. Additionally, one or more sensors can be associated with the adsorbent material effluent stream from the biological regeneration reactor, as represented by the dash-dot-dash connection between the controller 305 and the line between the biological regeneration reactor and the adsorbent material shearing section 386, and/or one or more sensors can be associated with the adsorbent material recycle line 389, as represented by the dash-dot connection between the controller 305 and the recycle line 389. In the case of an assay, an adsorbent material having a reduced adsorption capacity, suitable feed return or feed advance action may function based on information or information sources from one or more of these sensors and/or other sensors.

Referring now to FIG. 4, a low strength wastewater treatment system 454 similar to the system 354 of FIG. 3 is schematically illustrated. In the system 454, an adsorbent material deposition and liquid separation section 470 is provided, which may be one or more of a centrifuge, hydrocyclone, clarifier, various types of filters, or other suitable separation device. The adsorbent material deposition and liquid separation section 470 separates liquid from the mixed system 461 containing the low concentration wastewater of adsorbent material from the mixing section 460.

In certain embodiments of system 454, the flow rate within the high flux adsorbent material system 459 is controlled to provide sufficient residence time to allow for the desired level of contaminants from stream 451 to adsorb onto the adsorbent material, such as granular activated carbon, and drain stream 471 to meet the allowable quality level of effluent discharge, or the contaminant level is low enough to be conveniently treated in the supplemental tertiary treatment system 490. Other aspects of the low-strength wastewater treatment system 454 are substantially identical to those described in system 354, and similar or identical components are designated with similar reference numerals in fig. 4.

Referring now to fig. 5, a low concentration wastewater treatment system 554 similar to system 454 in fig. 4 is schematically illustrated, wherein a low flux adsorbent material biological regeneration reactor system 599 comprises a bioreactor system other than a membrane operating system. In particular, the low flux adsorbent material biological regeneration reactor regeneration system 599 includes the biological regeneration reactor 502, the adsorbent material shearing section 86, the adsorbent material/biomass separation section 587, and the clarifier/settling apparatus 595 which is a solids separation apparatus. The clarifier/settling apparatus 595 may be a clarifier apparatus, a settling apparatus, or an apparatus that performs clarification and settling. The system operates in a manner similar to system 354, but without membrane operating system 304. Instead, to remove the biomass and any other solids in the mixed liquor, a clarifier/settling device 595 is used. Specifically, the clarifier/settling apparatus 595 allows the activated sludge to settle and it is returned to the bioreactor 502 through the return activated sludge line 514. The clarified liquid passes as effluent 512. The clarifier/settling tank 595 may be replaced in any of the systems described in relation to fig. 3, 4 and/or 6. Other aspects of the low-strength wastewater treatment system 554 are substantially identical to those described in relation to system 354, and like reference numerals are used in fig. 5 to identify like or equivalent components.

Referring now to fig. 6, a low concentration wastewater treatment system 654 similar to the system 354 of fig. 3 is schematically illustrated wherein the high flux adsorbent material system 659 is an integrated mixing/deposition unit operation. For example, in certain embodiments, the high flux adsorbent material system 659 may comprise a continuous backwash filter or continuous regeneration filtration system similar to a continuous regeneration walnut shell filter (without walnut shell media), such as the type available from Siemens Water Technologies. The adsorbent material is removed as effluent 672, and effluent 671 is the wastewater from which the contaminants have been adsorbed. In certain embodiments, the continuous regeneration system may also perform an exfoliation function, in conjunction with or in place of the adsorbent material shearing section 686 and the adsorbent material/biomass separation section 687. Note that in such embodiments, the adsorbent material/biomass separation section is disposed downstream from the continuous countercurrent high flux adsorbent material system 659. In further embodiments, the high flux adsorbent material system 659 comprises an adsorbent material filtration apparatus, such as a conventional three-stage carbon filter, wherein the treated water is discharged as stream 671 and the partially loaded adsorbent material 672 is treated instead of being regenerated with conventional hot air or gas streams (e.g., regeneration of the system 699 using biological treatment of adsorbed contaminants), which operates in a similar manner as described in relation to fig. 3, and the regenerated adsorbent material 688 is introduced into the three-stage carbon filter included in the high flux adsorbent material system 659. Other aspects of the low-strength wastewater treatment system 654 are substantially identical to those described in relation to the system 354 and like reference numerals are used in fig. 6 to designate like or identical components.

In further embodiments of the invention, the source of wastewater treated by the high flux adsorbent material treatment system of the integrated low flux adsorbent material biological regeneration reactor according to the invention may be from a system that treats primary solids including a portion of BOD by radiation₅A compound is provided. Specifically and with reference to fig. 7, a system 700 is shown to treat an influent wastewater stream 701 containing suspended organic solids, dissolved organic solids, and optionally other contaminants such as inorganics. The influent wastewater stream 701 is introduced into a primary separation system 753, such as a settling section that allows for the settling of biosolids, a clarifier, a centrifuge, a filter, a mesh screen, a belt press, a vortex separator, a floatation device, or other solids removal system. In the main separation system 753, biological oxygen demand compounds (BOD) are readily degraded₅) Solids and portions of the material are separated from the wastewater stream.

A typical primary processing system is generally capable of BOD₅The concentration is reduced by about 40% to about 50%, and the total suspended solids concentration is reduced by aboutFrom 60% to about 70%. The solids removed in this step are generally larger, slowly biodegradable suspended solids, and the effluent is typically a mixture of more volatile, readily disposed of compounds present in sanitary wastewater. Additional unit operations may also be used to provide greater removal efficiency of undissolved contaminants in the raw wastewater. For example, one or more centrifuge devices, sedimentation devices, or floatation devices (e.g., dissolved air, induced air floatation) may be used. In further embodiments, additional unit operations may include the addition of suitable compounds to be treated to remove at least a portion of the less dense solids present in the original wastewater.

In certain embodiments, the aqueous phase, typically including dissolved contaminants and most of the suspended solids, may be discharged as a wastewater effluent containing some level of biologically labile compounds or a low concentration wastewater effluent 751, and then processed downstream through a wastewater treatment system 754, which operates in a manner similar to, for example, one or more of the previously described systems 354, 454, 554, or 654. Effluent 712 is discharged, which is typically suitable for recycling as industrial water, irrigation, or environmentally friendly discharge. Untreated biosolids are separated from main treatment system 753 as solids effluent stream 774, typically containing entrained liquid, and passed through, for example, using a sewage sludge pump or progressive screw pump (not shown) adapted to handle solids-laden liquid and slurry to homogenization section 775, where the solids are homogenized by suitable mechanical equipment, such as one or more grinders and/or shredders. Homogenization section 775 ensures that a solid, dense mass with no solids is introduced downstream of radiation/sterilization section 777, thereby ensuring maximum level of sterilization.

Untreated homogenized solids 776, typically in the form of a slurry, is pumped to a radiation/disinfection section 777 where the solids are disinfected using beta-ray, gamma-ray, x-ray, or electron beam radiation, for example to meet United States Environmental Protection Agency Class A or B biosolids disinfection requirements or other jurisdictionally allowed sludge disinfection requirements. The sterilized solid 778 can be disposed of in an environmentally friendly manner.

FIG. 8 illustrates another embodiment of a wastewater treatment system that includes radiation mixing of the primary solids of inert material to allow its reuse as a soil substitute or for other uses. Specifically, the system 800 is similar to the system 700 with the additional operation of a mixing section 763 in which the sanitized solids 778 are mixed with an inert filler material 762, such as sand, clay, and/or another suitable filler material, to produce a product 764, which may be used as soil, compost, or fertilizer. The system 800 including providing the product 764 is particularly desirable for treating wastewater having solids without toxic organic or inorganic compounds.

Optionally, a dewatering section can be provided in the system 700 or 800. However, in the system 800, the excess water may be adsorbed by sand or other inert material mixed with the disinfected primary solids.

In certain embodiments, influent wastewater 701 includes high concentrations of metals, other inorganic or toxic organics. Thus, even when sterilized to a suitable level, the mixture of sterilized biosolids and filler material is not suitable as a soil, compost, or fertilizer product. However, most of the capital cost, energy and size benefits can be gained even when the sterilized material is disposed of in a landfill, for example after drying and/or mixing of suitable inert materials.

In certain embodiments of the invention, the system is configured as a portable system, for example mounted on skids, truck bodies, trailers, and the like. The portability allows the tertiary treatment system to be produced and delivered as a contract (turn) system. A portable or skid mounted system would also facilitate the tertiary system being set up as needed, for example, in situations where other tertiary treatment systems are in service, under repair, or under construction. In addition, certain plants process chemicals for relatively short periods of time and produce particularly difficult waste water streams, which can benefit from a portable or skid-mounted system according to the present invention. A piping arrangement may be provided which is adapted to match the standard arrangement and ports in existing wastewater treatment plants to easily and quickly install the system of the present invention.

The system and method of the present invention avoids the problems of the prior art and involves treating low concentration wastewater by: wastewater that has undergone secondary treatment, such as effluent from a secondary system, is passed through an adsorbent material mixing zone, where the adsorbent material and secondary effluent are intimately mixed. Note that the secondary effluent, at the point of delivery to the adsorbent material mixing zone, has substantially all solids, and therefore a high majority of the BOD₅The components are removed. Thus, the secondary effluent is not readily bio-oxidized by conventional treatment biological systems because the wastewater is too low in strength, contains biologically intractable compounds, contains bio-inhibitory compounds, contains inorganic compounds, or contains a combination of these that are not bio-oxidizable or require a longer residence time than is typically suitable for bio-oxidation. Typically, a more energy intensive three stage system such as a granular activated carbon adsorption filter or another three stage treatment system is used to polish the stream, which is no longer treated by normal biological oxidation.

The low concentration wastewater treatment system of the present invention allows for the concentration of contaminants on the carbon and provides for the treatment of low strength wastewater or wastewater having biologically refractory compounds, including biologically inhibitory and/or biologically refractory compounds. In addition, inorganic compounds present in the low-concentration wastewater may be adsorbed.

The low-concentration wastewater treatment system of the present invention is a lower cost alternative to the currently used methods (as it utilizes biological oxidation) -typically lower cost removal techniques suitable for treating wastewater. Activated carbon adsorption columns are typically very expensive to operate and require very energy intensive methods to regenerate the carbon, typically based on incineration to regenerate the granular activated carbon. The development of the three stage treatment system of the present invention as a replacement or supplement to the activated carbon column can result in considerable energy savings. As a result, a carbon trading (carbon trade) of carbon dioxide reduction associated with the reduction of energy consumption can be obtained.

The volume requirements for various operations within the low concentration wastewater treatment system of the present invention can be significantly less than conventional membrane bioreactors for treating the same volume of wastewater and significantly less than conventional wastewater treatment systems that do not use membranes.

The use of the low-concentration wastewater treatment system of the present invention allows for the treatment of relatively low-strength wastewater, particularly wastewater having only dissolved contaminants and small amounts of entrained solids, and still results in an effluent having a very low concentration of intractable (intractable compounds) or simple organic compounds that were originally present in the wastewater. It is noted that certain preferred embodiments are described in connection with the treatment of low concentration wastewater and are referred to as "low concentration wastewater treatment systems". However, one of ordinary skill in the art having had the benefit of this disclosure will appreciate that the wastewater treatment system of the present invention may be advantageously used to treat wastewater having some level of biologically labile compounds as well as compounds that are completely resistant to biodegradation, biologically inhibitory compounds and/or biologically refractory compounds, or combinations of these compounds. For example, the solvent biolabile compound may be adsorbed onto the adsorbent material together with: completely resistant to biodegradation compounds, biostatic compounds, and/or biologically refractory compounds, or combinations of these compounds, and sent to the adsorbent material biorenewable reactor system described herein. The biologically labile compounds may be used alone or in combination with a secondary nutrient source as a food to support the microorganisms.

Adsorbent materials useful in the present invention include various types of carbon, such as activated carbon. In particular, granular activated carbon is extremely effective because the size range and density of the granules can be selected to allow them to remain in predetermined portions of the system by preventing fouling and/or abrading the membranes.

In systems where the granular activated carbon is not subjected to significant shear forces and/or inter-particle collisions, the granular activated carbon may be manufactured from wood, coconut, bagasse, sawdust, peat, pulp mill waste, or other cellulose-based materials. One suitable example is a mesh having a nominal mesh size of 14x35MeadWestvaco Nuchar (based on American Standard Sieve series)WV-B。

In additional embodiments, particularly where the shear force is provided by turbulence and/or inter-particle collisions within the pump and/or spray nozzle, it is desirable to use adsorbent materials having higher hardness values. For example, granular activated carbon derived from pitch or coal-based materials is effective. In a particular embodiment, the granular activated carbon is derived from lignite.

Carbon materials may also be provided which are modified and/or the species of which provide affinity for certain chemical classes and/or metals in wastewater. For example, in wastewater having a relatively high concentration of mercury, at least a portion of the adsorbent material preferably comprises granular activated carbon impregnated with potassium iodide or sulfur. Other treatment and/or impregnation species may be provided to target specific metals, other inorganic compounds, and/or organic compounds.

Further, the adsorbent may be a material other than activated carbon. For example, iron-based compounds or synthetic resins can be used as adsorbent materials, alone or in combination with other adsorbent materials, such as granular activated carbon. Still further, treated adsorbent materials other than activated carbon targeting certain metals, other inorganic compounds, and/or organic compounds may be used. For example, in wastewater containing relatively high concentrations of iron and/or manganese, at least a portion of the adsorbent may comprise a particulate manganese dioxide filter media. In the arsenic-containing wastewater, at least a portion of the sorbent can comprise a particulate iron oxide composite. In wastewater containing lead or heavy metals, at least a portion of the adsorbent may comprise a particulate aluminosilicate complex.

In one embodiment, the adsorbent material may be selected based on a desired specific gravity range. To maintain the adsorbent material in suspension within an acceptable energy expenditure/cost range, it is desirable that the specific gravity range be relatively close to the wastewater specific gravity. On the other hand, in embodiments where the separation is at least partially based on rapid deposition of material, a higher specific gravity is more suitable. Generally, the specific gravity in water at 20 ℃ is preferably greater than about 1.05. In certain embodiments, the specific gravity is greater than about 1.10 in water at 20 ℃. In certain embodiments, a suitable upper limit for specific gravity is about 2.65 in 20 ℃ water.

Thus, adsorbent materials are selected having a range of specific gravities that provide adequate suspension and thus adequate contact with wastewater and its contaminants. Further, in certain embodiments, the specific gravity range provides sufficient sedimentation characteristics for subsequent removal of the adsorbent material from the wastewater. In additional embodiments, the selection of the specific gravity of the adsorbent material is minimized based on the energy required to maintain the adsorbent material in suspension.

In addition, desirable adsorbent materials such as granular activated carbon have a hardness level that minimizes the formation of fines and other particulates due to inter-particle collisions and other process effects.

The separation subsystem is designed to maintain a reduced amount of adsorbent material and fines entering the membrane operating system by optimizing the size of the adsorbent material that prevents it from entering the membrane operating system. Thus, in embodiments where the solids separation apparatus is a membrane operating system, erosion and fouling due to impingement of carbon particles or other particulate materials on the membrane is minimized while still providing the operational advantages associated with the use of adsorbent materials, including activated carbon.

The appropriate particle size of the adsorbent material is selected to compensate for the screening/separation method selected and the particular wastewater being treated. In certain preferred embodiments, the effective lower particle size limit of the adsorbent material is selected such that it is easily separable from the mixed liquor stream entering the membrane operating system tank in which the membranes are located. Generally, the effective particle size of the adsorbent material has a lower limit of about 0.3 millimeters, where greater than about 99.5 weight percent adsorbent material is above the lower limit; preferably having a lower limit of about 0.3 mm to an upper limit of about 2.4 mm (corresponding to a screen size of 50 to 8 based on U.S. standard sieve series), where greater than 99.5 wt.% of the adsorbent material falls between the lower and upper limits; and in certain preferred embodiments from about 0.3 mm to about 1.4 mm (corresponding to screen No. 50 to screen No. 14 based on U.S. standard screen rows), where greater than 99.5 wt.% of the adsorbent material falls between a lower limit and an upper limit. Granular activated carbon having a minimum effective particle size of about 0.5 mm to about 0.6 mm has proven to be easily and efficiently screened from the mixed liquor using a suitable separation system, and such effective size is also effective in maintaining suspension in granular activated carbon having a suitable density.

The use of adsorbent materials to adsorb compounds that are fully resistant to biodegradation, biostatic compounds, and/or biologically refractory compounds, or combinations of these compounds, would allow the process to treat higher flow rates of wastewater than conventional systems, as the organics of the biodegradable organic compounds would not be limited by the hydraulic retention time of the conventional systems. The bio-inhibitory compounds and/or certain bio-refractory compounds remain on the adsorbent material for an extended period of time and thus the microorganisms have several times the hydraulic residence time to break them apart. This allows a significantly smaller unit to treat the wastewater stream than would be required if the adsorbent material were not added.

The use of the low concentration wastewater treatment system of the present invention rather than the conventional system or the conventional system with the addition of powdered activated carbon eliminates the problems associated with solids deposition that would occur in high flow rate conventional systems that do not use membranes for separating solids from the effluent.

The low concentration wastewater treatment system of the present invention can be modified to treat a particular contaminant (which may be present in any particular wastewater) by using adsorbent materials that have been specially treated to selectively adsorb the particular contaminant of interest. For example, granular activated carbon or other adsorbent materials that have been specially treated to adsorb metals may be used for wastewater having a high concentration of metals. The dissolved metals may preferably be adsorbed onto the treated granular activated carbon and then removed from the effluent. Periodic replacement of the adsorbent material allows metal to be removed from the system and the adsorption capacity to be maintained at a desired level.

The present invention provides a low cost alternative to the permanent installation of a high cost activated carbon adsorption column or any number of other tertiary treatment systems that are expensive to operate. In addition, the present invention provides a simpler, smaller footprint, lower operating cost wastewater treatment system that can be installed and operated in a shorter time, and if desired, can be constructed as a portable system/device. Which may be configured during upset conditions or when the wastewater treatment plant requires the treatment of waste that is not normally treated.

The system and method of the present invention avoids the need to treat the entire effluent stream in an expensive tertiary treatment system. Which adsorbs contaminants from low concentration wastewater and treats them in a high flux adsorbent material treatment system integrated with a low flux adsorbent material biological regeneration reactor.

Previously developed tertiary systems have attempted to treat the effluent from existing wastewater treatment plants having low concentrations of contaminants, which plants have expensive activated carbon adsorption systems or some other expensive tertiary treatment system. In all of these cases, the entire wastewater stream is treated with a three-stage treatment process. The system and method of the present invention removes contaminants from the entire wastewater stream by adsorption and then treats the adsorbent material in a low flux biological regeneration system (which is relatively inexpensive to operate).

The method and system of the present invention have been described above and in the accompanying drawings; modifications thereof will be apparent to those skilled in the art and the scope of the invention is defined by the appended claims.

Claims (22)

1. A method of treating wastewater containing solids, biological aerobic compounds and biologically refractory and/or biostatic compounds, comprising:

separating a majority of the solids and biological oxygen demand compounds from the wastewater material using a primary separation process to provide a solid phase and an aqueous phase, the solid phase containing an initial level of pathogens;

irradiating the solid phase to reduce pathogen levels;

mixing an aqueous phase of wastewater containing biologically refractory compounds and/or biologically inhibitory compounds and an adsorbent material in a mixing section for a time sufficient to cause biologically refractory compounds and/or biologically inhibitory compounds from the aqueous phase of the wastewater to adsorb onto the adsorbent material to produce a mixture of treated wastewater and adsorbent material having biologically refractory compounds and/or biologically inhibitory compounds adsorbed thereon;

separating and removing a majority of the treated wastewater from a mixture of the treated wastewater and an adsorbent material having adsorbed thereon biologically refractory compounds and/or biologically inhibitory compounds;

passing an adsorbent material having adsorbed thereon biologically refractory and/or biologically inhibitory compounds and a minor portion of said treated wastewater to a biological regeneration reactor containing microorganisms;

suspending the adsorbent material having adsorbed thereon the biologically refractory and/or biostatic compounds and a minor portion of the treated wastewater in the biological regeneration reactor for a time sufficient to allow the microorganisms in the biological regeneration reactor to bioaffect at least a portion of the biologically refractory and/or biostatic compounds on the adsorbent material to produce regenerated adsorbent material and a biologically treated water effluent;

recycling the regenerated adsorbent material to the mixing zone; and

passing the biological regeneration reactor water effluent through a separation subsystem located within or downstream of the biological regeneration reactor to direct the biological regeneration reactor water effluent substantially free of adsorbent material to a solids separation device that is one or more of a membrane operating system, a clarifier, or a depositor.

2. The method of claim 1, further comprising homogenizing the separated solid phase prior to said irradiating.

3. The method of claim 1, wherein said irradiating comprises exposing said solid phase to one or more of beta-ray, gamma-ray, x-ray, or electron beam radiation.

4. The method of claim 1, wherein the step of separating the solids and biological oxygen demand compounds from the wastewater material produces a low concentration wastewater.

5. The method of claim 1 further including passing at least a portion of the activated sludge from the solids separation device to the biological regeneration reactor.

6. The method of claim 1, further comprising shearing accumulated biomass from the regenerated adsorbent material prior to circulating the regenerated adsorbent material to the mixing zone.

7. The method of claim 6, further comprising separating the accumulated biomass from the regenerated adsorbent material prior to circulating the regenerated adsorbent material to the mixing zone.

8. The method of claim 1 further including mixing the irradiated solid phase with a filler material to produce a soil, compost or fertilizer product.

9. A wastewater treatment system comprising:

a radiation treatment section comprising:

a radiation source;

an inlet for receiving a primary solid;

a solids outlet for discharging primarily solids of the radiation; and

a waste water outlet;

a source of fresh or recycled porous adsorbent material;

a mixing section comprising:

a wastewater inlet connected to the wastewater outlet of the radiation treatment section;

an adsorbent material inlet; and

an exhaust outlet;

an adsorbent material deposition and liquid separation zone comprising:

a slurry inlet connected to the discharge outlet of the mixing section,

a treated water outlet, and

a contaminated adsorbent material outlet; and

an adsorbent material biological regeneration reactor system comprising:

a biological regeneration reactor comprising a contaminated adsorbent material inlet in communication with a contaminated adsorbent material outlet of the adsorbent material deposition and liquid separation zone,

a water outlet of the biological treatment is provided,

a regenerated adsorbent material outlet in communication with the adsorbent material inlet of the mixing zone,

a solids separation device connected to the biologically treated water outlet, the solids separation device being a membrane operating system, a clarifier, a settler, or a combination of a clarifier and a settler, and

a separation subsystem located within or downstream of the biological regeneration reactor and between the biological regeneration reactor and the solids separation apparatus to direct the biological regeneration reactor water effluent substantially free of adsorbent material to the solids separation apparatus.

10. The system of claim 9, further comprising a homogenization apparatus upstream of the radiation treatment section.

11. The system of claim 9, further comprising a shear zone comprising an inlet in communication with the regenerated adsorbent material outlet and an outlet in communication with the adsorbent material inlet of the mixing zone.

12. The system of claim 11, further comprising an adsorbent material/biomass separation zone comprising an inlet coupled to the outlet of the shearing zone and an outlet coupled to the adsorbent material inlet of the mixing zone.

13. The system of claim 9, further comprising an apparatus for shearing and separating biomass from adsorbent material, the apparatus comprising an inlet connected to the regenerated adsorbent material outlet and an outlet connected to the adsorbent material inlet of the mixing section.

14. The system of claim 9, wherein the radiation source comprises one or more of a beta-ray source, a gamma-ray source, an x-ray source, or an electron beam radiation source.

15. A wastewater treatment system comprising:

a radiation treatment section comprising:

a radiation source;

an inlet for receiving a primary solid;

a solids outlet for discharging primarily solids of the radiation; and

a waste water outlet;

a source of fresh or recycled porous adsorbent material;

a high throughput adsorption system comprising:

an inlet connected to the wastewater outlet of the radiation treatment section for receiving wastewater containing biologically refractory compounds and/or biologically inhibitory compounds,

a source of adsorbent material for contacting the wastewater and adsorbing the biologically refractory compounds and/or biologically inhibitory compounds from the wastewater to produce an adsorbent material and treated wastewater having biologically refractory compounds and/or biologically inhibitory compounds adsorbed thereon,

a liquid outlet for discharging a substantial portion of the treated wastewater, an

An adsorbent material outlet for discharging an adsorbent material having adsorbed thereon biologically refractory compounds and/or biologically inhibitory compounds and a minor portion of the treated wastewater; and

a low flux adsorbent material biological regeneration reactor system for maintaining an adsorbent material having adsorbed thereon biologically refractory and/or biostatic compounds in suspension for a time sufficient to allow microorganisms to biologically affect at least a portion of the biologically refractory and/or biostatic compounds adsorbed thereon, the low flux adsorbent material biological regeneration reactor system comprising:

a biorenewation reactor comprising:

an inlet for receiving from an adsorbent material outlet of the high throughput adsorption system an adsorbent material having adsorbed thereon biologically refractory compounds and/or biologically inhibitory compounds,

an outlet of the mixed liquid is provided,

an adsorbent material outlet in communication with the source of adsorbent material of the high flux adsorption system,

a solids separation device connected to the biologically treated water outlet, said solids separation device being a membrane operating system, a clarifier, a settler, or a combination of a clarifier and a settler, and

a separation subsystem located within or downstream of the biological regeneration reactor and between the biological regeneration reactor and the solids separation apparatus to direct the biological regeneration reactor water effluent substantially free of adsorbent material to the solids separation apparatus.

16. The system of claim 15, wherein the low flux adsorbent material biological regeneration reactor system further comprises:

a shearing apparatus for shearing accumulated biomass from adsorbent material to produce a mixture of sheared adsorbent material and free biomass, the shearing apparatus being located at least one location selected from the group consisting of:

in the biological regeneration reactor, and

separating from the biological regeneration reactor and connecting the adsorbent material outlet to receive regenerated adsorbent material from the biological regeneration reactor;

an adsorbent material/biomass separation section for separating free biomass from a mixture of sheared adsorbent material and free biomass to produce separated sheared adsorbent material and free biomass;

an adsorbent material conduit for passing the separated sheared adsorbent material from the adsorbent material/biomass separation section to the high-throughput adsorption system; and

a biomass conduit for passing free biomass from the adsorbent material/biomass separation zone to at least one of the biological regeneration reactor and a location downstream of the biological regeneration reactor.

17. The system of claim 15, wherein the low flux adsorbent material biological regeneration reactor system further comprises:

a combining apparatus for shearing and separating accumulated biomass from the regenerated adsorbent material, the combining apparatus being located at least one location selected from the group consisting of:

in the biological regeneration reactor, and

a regenerated adsorbent material outlet separated from the biological regeneration reactor and connected to receive regenerated adsorbent material from the biological regeneration reactor and having an outlet for discharging separated sheared adsorbent material and an outlet for discharging free biomass;

an adsorbent material conduit connected to the regenerated adsorbent material outlet of the combining apparatus for returning regenerated adsorbent material to the high-throughput adsorption system; and

a biomass conduit connected to the outlet of the combining device for discharging free biomass for sending free biomass to at least one of the biorenewable reactor and a location downstream of the biorenewable reactor.

18. The system of claim 15, wherein the high throughput adsorption system comprises a mixing zone and a deposition zone.

19. The system of claim 15, wherein the high flux adsorption system comprises an adsorbent material filtration apparatus.

20. The system of claim 15, wherein the high flux adsorption system comprises a continuous backwash filter.

21. The system of claim 15, wherein the high flux adsorption system comprises a continuous regeneration filtration system.

22. The system of claim 15, wherein the radiation source comprises one or more of a beta-ray source, a gamma-ray source, an x-ray source, or an electron beam radiation source.