HK1188431A - Methods and systems for treating wastewater - Google Patents

Description

Wastewater treatment system and method

Cross Reference of Related Applications

The priority of the U.S. provisional application serial No. 61/326,428 entitled "biosorption process", filed on 21/4/2010, the contents of which are incorporated herein by reference, is claimed for all purposes.

Background

1. Field of the invention

The present invention relates to systems and processes for wastewater treatment, and in particular, to systems and methods for wastewater treatment employing biological sorption, biofilm, anoxic treatment, aerobic treatment, and anaerobic sludge digestion.

2. Description of the related Art

The contents of U.S. patent No.6,383,389, incorporated herein by reference, are used for all purposes. Pilgram et al, in U.S. Pat. No.6,383,389, disclose a wastewater treatment system and method of controlling the treatment system, including but not limited to sequences or stages that can be used in batch or continuous reactors. A control system can sequence and monitor the processing steps in either batch flow mode operation or continuous flow mode.

Sutton, U.S. patent application No.2008/0223783, discloses a wastewater treatment system and a method of treating wastewater. The system includes an aerobic membrane bioreactor (aerobic membrane bioreactor) and an anaerobic digestion system coupled to the aerobic membrane bioreactor and continuously receiving waste solids from the aerobic membrane bioreactor. The system also continuously returns effluent from the anaerobic digestion system to the aerobic membrane bioreactor.

Disclosure of Invention

One or more aspects of the present disclosure relate to embodiments of a wastewater treatment process. The method includes providing wastewater to be treated and denitrifying the wastewater in a first bioreactor to produce a denitrification mixture. The method may further comprise nitrifying the denitrification mixed liquor with a nitrifying biofilm on a support and biosorpting undesirable constituents from the denitrification mixed liquor with suspended biomass in a second bioreactor. The method may also include separating a first portion of the nitrified mixed liquor in a separator to produce a solids-rich sludge and a treated effluent having a total nitrogen concentration of less than about 10 milligrams elemental nitrogen per liter, and mixing a second portion of the nitrified mixed liquor with the wastewater to be treated.

One or more further aspects of the present disclosure relate to a wastewater treatment system. The wastewater treatment system includes a source of wastewater to be treated and a first bioreactor having an inlet fluidly connected downstream from the source of wastewater. The wastewater treatment system may further include a biological sorption tank including a biofilm carrier and having an inlet fluidly connected to the first bioreactor, the biological sorption tank being constructed and arranged to retain an effluent having a total nitrogen concentration of less than about 10 milligrams of elemental nitrogen per liter and a hydraulic retention time of less than about 3 hours. The wastewater treatment system may also include a separator having a sludge outlet, an effluent outlet, and an inlet fluidly connected downstream of the biological sorption tank, and a sludge recycle line fluidly connecting the outlet of the separator with the source of wastewater.

One or more further aspects of the present disclosure relate to a method of facilitating (treating) wastewater in a wastewater treatment system to reduce a concentration of nitrogen-containing compounds in the wastewater. The system has a wastewater source, an anoxic reactor, an aerobic reactor, a mixed liquor recycle stream fluidly connecting an outlet of the aerobic reactor with the anoxic reactor, a separator, and a sludge recycle stream fluidly connecting an outlet of the separator with the anoxic reactor. The method of promoting includes introducing a biofilm carrier into an aerobic reactor and fluidly connecting a solids-rich outlet of a separator with an anaerobic digester.

One or more further aspects of the present disclosure relate to a wastewater treatment process. The wastewater treatment method includes providing wastewater to be treated and facilitating a denitrification treatment of the wastewater in a first bioreactor to produce a first biologically treated mixed liquor. The wastewater treatment method may further include promoting bio-sorption and biofilm growth of the first biologically treated mixed liquor in a second bioreactor. The wastewater treatment process may also include separating the effluent of the second bioreactor to produce a solids-rich sludge and a treated effluent having a total nitrogen concentration of less than about 10 milligrams elemental nitrogen per liter, and treating the solids-rich sludge in a third bioreactor to produce a biologically treated sludge.

Brief description of the drawings

The figures are not intended to be drawn to scale. The same or equivalent components or features are denoted by like numerals in many different figures. For purposes of clarity, not every component may be labeled in every drawing, nor may every component of every embodiment of the invention be shown, the description of which is not necessary to enable a person of ordinary skill in the art to understand the invention. In the drawings, there is shown in the drawings,

FIG. 1 is a flow diagram illustrating a representative processing system in connection with one or more aspects of the present invention;

FIG. 2 is a graph of ammonia-nitrogen concentration versus time, which may be related to one or more aspects of the present invention;

FIG. 3 is a graph of ammonia-nitrogen concentration versus time in a wastewater treatment process;

FIG. 4 is a graph of ammonia-nitrogen concentration versus time in a wastewater treatment process;

FIG. 5 is a plot of Chemical Oxygen Demand (COD) concentration versus time, which may be related to one or more aspects of the present invention;

FIG. 6 is a graph of COD concentration versus time in a wastewater treatment process; and

FIG. 7 is a graph of COD concentration versus time in a wastewater treatment process.

Detailed description of the invention

Aspects and embodiments of the present invention relate to systems and methods for water, wastewater, or sludge treatment to achieve, for example, a reduction in oxygen demand, such as Biological Oxygen Demand (BOD), and make the water suitable for reuse or suitable for discharge into the environment. Further, aspects of the present invention relate to reducing the content of nitrogen compounds, such as ammonia, in wastewater. One or more aspects of the present invention relate to wastewater treatment systems and methods of operation and facilitating the methods of operation.

The invention is not limited in its application to the details of construction and the arrangement of components, systems or subsystems set forth in the present application, which may be embodied and carried out in various ways. In particular, the wastewater to be treated, such as a wastewater or wastewater stream containing waste, may, in some cases, contain solid, soluble or insoluble organic or inorganic materials. These wastewater streams may require purification prior to discharge into the environment or to at least partially render the wastewater streams environmentally benign or at least meet the discharge requirements of regulatory requirements or guidelines. For example, water treatment may be used to reduce its Chemical Oxygen Demand (COD), BOD, nitrogen content, and/or other characteristics such as Giardia (Giardia) content to within acceptable limits.

Certain aspects of the present invention relate to biological treatment of wastewater by promoting bacterial digestion of at least a portion of biodegradable matter in at least one of the wastewater. Further, other aspects of the invention relate to influencing or at least facilitating the separation of the converted, biodegraded digested solid material from the mixed liquor. Further, still further aspects of the invention relate to influencing or at least facilitating a reduction in the amount of solids in wastewater or water to be treated.

Some aspects of the invention relate to the removal, conversion, and/or recovery of one or more desired minerals or compounds, such as nitrogen and/or phosphorus-containing compounds, from wastewater.

The terms "water", "wastewater stream" and "wastewater stream" in this context refer to water to be treated, for example water streams or bodies of water originating from residential, commercial or urban areas, industrial and agricultural areas, and mixtures thereof, which water to be treated usually contains at least one undesirable substance or pollutant, which comprises biodegradable, inorganic or organic substances which can be degraded or converted by biological processes to form environmentally friendly or at least less harmful compounds. The water to be treated may also contain biosolids, inerts, organic compounds, including recalcitrant (recalcitrant) compounds or classes of compounds that are less biodegradable than other organic compounds, and components introduced by auxiliary treatment operations; ingredients introduced by the secondary treatment operations, such as, but not limited to, nitrosamines and endocrine disruptors.

A "solids-lean" or "sludge-lean" slurry (slurry), portion (fraction), stream (stream), or fluid, typically a liquid, such as at least partially treated water, that has undergone one or more settling or separation operations and contains less suspended solids than the initial mixed liquid or sludge. In contrast, a "solids-rich" or "sludge-rich" slurry, fraction, stream, or fluid is typically a liquid, such as at least partially treated water, that has a higher solids concentration after one or more settling or separation operations than the initial mixed liquid or sludge. For example, a mixed liquor containing suspended solids may allow for the promotion of precipitation of at least a portion of the suspended solids therein; the water body portion (water body) thus obtained, under the influence of artificial induction or natural gravity, generally forms a lower water layer (lower water layer) and an upper water layer (upper water layer), wherein the lower water layer has a higher concentration of solids than the initial mixed liquid and the solids-depleted upper water layer. Further, the solids-depleted aqueous layer typically has a lower concentration of suspended solids than the initial mixed liquor. Separation operations that can be utilized to affect or facilitate certain aspects of the present invention can utilize the effects of gravity to produce any solids-rich, solids-lean, sludge-rich, sludge-lean fraction or stream. Other separation operations may include filtration.

The "treated" fraction, after one or more treatment stages (such as one or more biological or separation operations), typically contains fewer undesirable or contaminating materials than the initial "solids-lean" fraction. The "solids-lean" fraction containing undesirable substances, such as soluble inorganic or organic compounds, may be introduced to one or more separation operations, such as a membrane filtration device or membrane bioreactor that may retain the inorganic or organic compounds as a "second mixed liquid" on the first side of the filter, while allowing the "treated" fraction to pass through the filter.

In certain embodiments, the treated portion may have a characteristic or characteristic related to the concentration of the particular component therein. For example, the treated portion may have a concentration of nitrogen-containing components or a BOD or COD content below a particular value. In certain embodiments, the treated product or effluent may have an ammonia concentration of less than about 5 milligrams elemental nitrogen per liter. The treated product or effluent may have a COD concentration of less than about 80 mg/l.

One or more inventive systems disclosed herein include one or more biologically-based or non-biologically-based manipulation devices. The systems or techniques of this disclosure may be implemented, or at least partially implemented, as a purification or processing system, which typically includes one or more pre-processing, primary processing, secondary processing, and post-processing or finishing operations. A processing facility utilizing one or more aspects of the present invention may include at least one of pre-processing, primary processing, secondary processing, and post-processing or finishing operations.

The pretreatment systems and operations may remove sand (grit), sand (sand), and gravel (gravel). The primary treatment operation or system may include at least partial equalization (equalization), neutralization (neutralization), and/or removal of large insoluble materials such as, but not limited to, fats (fats), oils (oils), and greases (grease) of the water to be treated. The pre-treatment and primary treatment operations may be combined to remove materials like precipitable solids and floating bodies, and insoluble objects like rags and sticks. For example, a primary clarifier may be utilized to separate solids.

The secondary treatment operation device or system may include a biological treatment; biological treatments such as those typically using a consortium of biomass and bacteria or microorganisms to at least partially hydrolyze or convert biodegradable materials; such biodegradable substances, for example, but not limited to, sugars, fats, organic molecules and compounds that make oxygen requirements in water. Indeed, some preferred aspects of the present invention utilize biological processes and systems to remove or convert at least a portion of the organic matter in the water to be treated.

Post-processing or modification operations or systems may include biological processes, chemical processes, and separation systems. The post-treatment operations may include nitrification/denitrification and/or phosphorus removal processes involving biological means. Chemical treatments that may be employed include chemical oxidation and chemical precipitation. The separation system may include removal of dissolved inorganic solids by means of ion exchange, ultrafiltration, reverse osmosis or electrodialysis. Further processing includes sterilization (inactivation), decontamination (inactivation), inactivation (inactivation) of at least a portion of any residual microorganisms by chemical or physical means. For example, sterilization may be achieved by exposure to one or more oxidizing agents or actinic radiation (actinic radiation). Commercially available separation systems employed in some embodiments of the invention include those employing CMF-S^TMThe system of continuous membrane filtration modules may also be available from Siemens Industry Inc. (Siemens Industry Inc.)CMF (pressurized) XP, CP and XS membrane filtration systems. Other separators including filter presses and centrifuges may also be used.

Some embodiments of the treatment system of the present invention may include a source of wastewater to be treated and a first bioreactor having an inlet fluidly connected downstream from the source of wastewater. The wastewater treatment system may further include a biological sorption tank including a biofilm carrier and having an inlet fluidly connected to the first bioreactor, the biological sorption tank being constructed and arranged to retain an effluent having a total nitrogen concentration of less than about 10 milligrams of elemental nitrogen per liter and a hydraulic retention time of less than about 3 hours. The wastewater treatment system may further include a separator having a sludge outlet, an effluent outlet, and an inlet fluidly connected downstream of the biological sorption tank, and a sludge recycling line fluidly connecting the outlet of the separator with the source of wastewater.

Some embodiments of a wastewater treatment process may include providing wastewater to be treated and denitrifying the wastewater in a first bioreactor to produce a denitrification mixture. The method may further comprise nitrifying the denitrification mixed liquor with a nitrifying biofilm on a support and biosorpting undesirable constituents from the denitrification mixed liquor with suspended biomass in a second bioreactor. The method may also further include separating a first portion of the nitrified mixed liquor in a separator to produce a solids-rich sludge and a treated effluent having a total nitrogen concentration of less than about 10 milligrams elemental nitrogen per liter, and mixing a second portion of the nitrified mixed liquor with the wastewater to be treated.

Other embodiments of a wastewater treatment process may include providing wastewater to be treated and facilitating a denitrification process of the wastewater in a first bioreactor to produce a first biologically treated mixed liquor. The wastewater treatment method may further include promoting bio-sorption and biofilm growth of the first biologically treated mixed liquor in a second bioreactor. The wastewater treatment process may also further include separating the effluent of the second bioreactor to produce a solids-rich sludge and a treated effluent having a total nitrogen concentration of less than about 10 milligrams elemental nitrogen per liter; and treating the solids-rich sludge in a third bioreactor to produce a biologically treated sludge.

One or more further embodiments relate to a method of facilitating treatment of wastewater to reduce a concentration of nitrogen-containing compounds in the wastewater in a wastewater treatment system. The system has a wastewater source, an anoxic reactor, an aerobic reactor, a mixed liquor recycle stream fluidly connecting an outlet of the aerobic reactor with the anoxic reactor, a separator, and a sludge recycle stream fluidly connecting an outlet of the separator with the anoxic reactor. The promotion method includes introducing the biofilm carriers into the aerobic reactor, and fluidly connecting the solids-rich outlet of the separator with the anaerobic digester.

Non-limiting examples of clarifiers or components thereof that may be used in one or more configurations of the treatment system of the present invention include, but are not limited to, clarifiers available from Siemens industries, IncFloc-clarifier system, SPIRACONE^TMAn upflow sludge blanket (upflow sludgblanket) clarifier,A loop clarifier anda clarifier.

Membrane Bioreactor (MBR) systems that may be used in accordance with one or more configurations disclosed herein include, but are not limited to, MEMPLULSE available from Siemens industries, Inc^TMMembrane bioreactor system, PETRO^TMMembrane bioreactor system, submerged membrane bioreactor system and XPRESS^TMMBR packaging Wastewater System (Packaged Water System)

Non-limiting examples of components or portions of anaerobic systems that may be used in one or more configurations of a wastewater system include, but are not limited to, those available from siemens industry, llcA digester gas (digester gas) reservoir (holder system),A disruption system,A gas mixing system of the digester,A helical guided digester gas holder,Vertical guided digester gas holder, DUO-DECK^TMFloating digester cover anda heater and a heat exchange system.

The system and assembly of the present invention provides a cost advantage over other wastewater treatment systems by utilizing a biological process that incorporates anaerobic digestion. The wastewater treatment process of the present invention can reduce sludge production by utilizing various operating devices including biological processes and recycle streams (recycle streams). The wastewater treatment process also overcomes some of the technical difficulties associated with the use of anaerobic wastewater treatment processes by, for example, concentrating, consolidating the sludge introduced into the anaerobic digester. Many processes also produce methane as a product of the anaerobic digestion process, which can be used as an energy source. In some embodiments, the use of an anaerobic digester can reduce a substantial portion of the COD and BOD. This can reduce the aeration requirements and oxygen requirements, thus reducing operating costs, and increasing the methane production that can be used as an energy source. In addition, since anaerobic digestion can be used to reduce COD and BOD in the sludge, sludge yield can also be reduced.

The wastewater treatment process of the present invention can also reduce the concentration of nitrogen compounds in the treated effluent, as well as the concentration of COD and/or BOD in the treated effluent. In some embodiments of the invention, the operating conditions and parameters of the system may be selected to achieve a desired hydraulic retention time of the bioreactor. The hydraulic retention time of one or more bioreactors in the system may be selected to reduce, minimize, or optimize hydraulic retention time. The hydraulic retention time of the bioreactor may be selected to reduce, minimize or optimize the hydraulic retention time to facilitate wastewater treatment and provide a treated effluent stream of particularly desirable quality. In some embodiments, the hydraulic retention time of the aerobic bioreactor may be selected to reduce, minimize, or optimize the hydraulic retention time to promote at least one of the biological sorption and nitrification reactions. At least part of the nitrification reaction may be accomplished by a combination of nitrifying bacteria. In some embodiments, the nitrifying bacteria may be in the form of a biofilm or a nitrifying biofilm.

The biofilm may be grown on any suitable carrier or vehicle to promote attachment of microorganisms (attachment) and growth of microorganisms and biofilms. The biofilm carrier may comprise a plurality of similarly shaped modules of suitable size and configuration and having a suitable surface area to promote growth of microorganisms and biofilm thereon. The biofilm carrier may be a unit or several units providing sufficient surface to promote attachment of microorganisms and growth of a biofilm. The biofilm carrier may be composed of any material suitable for these intended uses. In certain embodiments, the biofilm carrier can be an inert material, such as a polymeric material or a ceramic material. The biofilm carrier in certain embodiments of the invention can be activated carbon, such as granular activated carbon or powdered activated carbon.

The biofilm carrier may occupy any volume in the tank in which it is placed, so long as it provides sufficient surface area to promote the growth of microorganisms and biofilm on its surface. In certain embodiments, the biofilm carriers can occupy from about 20% to about 75% of the volume of the tank. For example, the biofilm carriers may occupy about 66% of the volume of the tank.

In contrast to conventional anoxic-aerobic processes, wherein nitrification and denitrification reactions are carried out at hydraulic retention times of between about 4-12 hours of an aerobic bioreactor, one or more of the treatment systems of the present invention may utilize an aerobic bioreactor that promotes assimilation (or biological adsorption) of suspended and/or dissolved species and nitrification reactions at hydraulic retention times of less than 3 hours.

Some other embodiments of the treatment system of the present invention may include collecting and/or converting a plurality of substances to produce a sludge material. For example, a biological sorption process may be used to facilitate the absorption and adsorption processes that promote the conversion of at least a portion of the dissolved and suspended solids in the water or wastewater. In adsorption processes, particulate ions and molecules are physically attached or linked to the surface of another molecule or compound. For example, the adsorption process may involve the attachment of compounds or molecules to the surface of soluble or insoluble particles in the wastewater to cause their precipitation in a downstream clarifier. During absorption, chemical and biochemical reactions occur during the transformation of a compound or substance in one state to another compound or substance in another state. For example, a compound in the wastewater may be converted to another compound, or may be incorporated by or integrated into the bacteria to grow new bacteria. Aeration may be employed in the biological sorption process to mix and provide an aerobic environment. The retention time in the biological sorption tank may be between a few minutes to several hours, for example, between about 15 minutes and 3 hours, more preferably between 30 minutes and 2 hours. Aeration is achieved here to provide mixing and to maintain an aerobic environment that promotes biological sorption, flocculation, and nitrification. Further flocculation or aggregation is achieved in systems utilizing aerobic treatment tanks. In certain embodiments, however, the aerobic treatment tank provides substantially all of the dissolved oxygen into the biological sorption tank.

In certain embodiments, the treatment system may involve an operating device having a plurality of microbial consortia (consortia) that may facilitate rapid return of the system to a steady state environment following a chaotic state. For example, the treatment system may circulate microorganisms that may provide or promote anaerobic digestion activities, such as methanogenic activity.

It has previously been believed that methanogens are absolutely anaerobic bacteria that rapidly die in an aerobic environment. However, many aspects of the invention, relating to processing systems and subsystems, operating devices and components thereof, may modulate or increase the viability of methanogenic organisms. One preferred feature of the treatment system of the present application relates to the provision of large quantities of methanogenic organisms by anaerobic circulation to an anoxic-aerobic process through a unique internal anaerobic sludge circulation path. At least a portion of the methanogenic bacteria is returned to the anaerobic digester, whereby the anaerobic digester is inoculated with methanogenic bacteria to increase the number of viable methanogenic organisms present in the anaerobic digester. This reduces the need for anaerobic digesters to be of scale and produce hydraulic or solids retention times to maintain a stable methanogenic bacterial count in the absence of inoculated bacteria, as in previously known processes.

The concentration of the inoculated methanogenic bacteria, based on the amount of microorganisms provided at the inlet of the anaerobic digester, in some embodiments, can be at least a target percentage, for example, about 10% or more of the concentration of methanogenic bacteria present in the anaerobically digested sludge stream exiting the anaerobic digester. In some embodiments, the percentage may be, for example, 25% or more, 33% or more, 50% or more, or 75% or more. In some embodiments, the concentration of methanogenic bacteria provided at the inlet of the anaerobic digester is a significant fraction of the concentration of methanogenic bacteria present in the anaerobically digested sludge stream exiting the anaerobic digester, for example, about 10% or more, about 30% or more, about 40% or more, or about 50% or more.

The scale of the anaerobic digester of the system according to the invention can be smaller than that of previously known systems. Inoculation of methanogenic bacteria in the anaerobic digester can provide a safety factor against disruption of the anaerobic digestion process. In the event of a disruption or failure of the anaerobic digestion process, the anaerobic digester of the disclosed system can recover faster than the anaerobic digester of previously disclosed systems because the seeding of the anaerobic digester with methanogenic bacteria can increase the replenishment rate of methanogenic bacteria in the anoxic reactor, based on the growth of these bacteria in the anoxic reactor, while reducing the time required for the anoxic reactor to reach the desired methanogenic bacteria concentration.

The benefit of methane recycle can be evaluated as follows:

wherein the content of the first and second substances,

θ_x= solid retention time in anaerobic digester (day)

Xa = concentration of methanogenic organisms

Q = flow rate of influent and effluent

X_a ⁰= concentration of methanogenic organisms in the inlet stream, normally considered zero for standard activated sludge processes;

if about 50% of the methanogens survive the anoxic-aerobic process and are recycled back to the anaerobic digester, the solids retention time of the anaerobic digester may be doubled, or the size of the anaerobic digester may be halved. For example, in prior known systems, hydraulic retention times in anaerobic digesters in many instances were set at about 20 and about 30 days. Treatment systems operating according to some embodiments of the present invention may have hydraulic retention times reduced by about 50% to between about 10 and about 15 days.

In other embodiments, inoculating the anaerobic digester with circulating methanogenic bacteria may result in a reduction in hydraulic retention time of the sludge being treated in the digester. This may result in a reduction in cycle time and thus an increase in processing capacity of the processing system. By increasing the number of methanogenic organisms recycled to the anaerobic digester, for example, by increasing the number of methanogenic organisms containing sludge introduced to the digester, the potential for reducing hydraulic retention time in the digester and increasing the treatment capacity of the system may be increased.

In some embodiments, the biological sorption tank is continuously seeded with nitrifying bacteria that can survive in the anaerobic digester and can be recycled back to the aerobic environment (e.g., ammonia and nitrite oxidized biomass). For example, nitrification and denitrification may occur in the biological sorption tank. Nitrification can be accomplished by two groups of autotrophs that are growth retarded: ammonium-oxidizing bacteria (AOB, which can convert ammonia into nitrite) and nitrite-oxidizing bacteria (NOB, which can convert nitrite into nitrate). Both groups of autotrophs are slow growing and strictly aerobic bacteria. In certain embodiments of the treatment systems disclosed herein, nitrifying bacteria are introduced into and/or grown in a biological sorption tank where they may be captured by floe (floc). Some nitrifying bacteria will be distributed out of the biological sorption tank and sent to the anaerobic digester.

It was previously thought that the strictly anaerobic environment of an anaerobic digester may kill nitrifying bacteria. Many aspects of the invention, however, relate to processing systems and subsystems, operating devices and components thereof that can modulate or increase the viability of nitrifying organisms in anaerobic and anoxic environments that may occur during some biological nutrient removal processes. Nitrifying bacteria that survive in the anaerobic digester and are returned to the aerobic portion of the treatment process can improve the performance of the nitrification process in a cost-effective manner, for example, by providing a reduced aerobic treatment vessel size and/or a reduced aerobic treatment hydraulic retention time and/or a safety-increasing factor that can make the nitrification process more stable against disruption of the treatment process. Disruption of the process includes deviations in expected operating parameters that may result from, for example, a disruption in the flow of material in the processing system or a loss of temperature control at one or more of the operating devices. The survival rate of nitrifying bacteria in an anaerobic digester can be increased by reducing the hydraulic retention time in the anaerobic digester, which can be achieved if the anaerobic digester is inoculated with recycled methanogens, as described above.

In certain embodiments of the invention, the sludge treated by the anaerobic digester may enter the anoxic tank and/or the biological sorption tank as a recycle stream to support the biological sorption and/or nitrification/denitrification processes. Other treated streams, such as a solids-lean fraction or a sludge-lean fraction exiting a thickener or clarifier, or a mixed liquor produced from a polishing unit (polishing unit) may also be introduced as a recycle stream to the anoxic tank and/or the biological sorption tank to support the treatment process.

In other embodiments, some configurations involve chemically promoted adsorption mechanisms (chemical adsorbed adsorption mechanisms).

Some embodiments of the treatment process of the present invention may include biologically treating at least a portion of the sludge from the wastewater to be treated. Biological treatment processes are employed to remove and/or biodegrade undesirable materials, such as organic contaminants, from wastewater to be treated. In some embodiments, the biological treatment process may be an aerobic biological treatment process. Depending on the operating environment, at least a portion of the organic matter in the wastewater or sludge to be treated may be biologically oxidized and converted to carbon dioxide and water. In certain embodiments, the reduction in oxygen demand may be up to about 80% to 90%. In some embodiments, a portion of the organic matter in the wastewater or sludge to be treated may be reduced only in part by utilizing an insufficient aeration rate or an insufficient retention time. For example, the reduction in oxygen demand may be less than 70%, less than 50%, less than 30%, or less than 10%. The wastewater or sludge to be treated may be aerated and mixed for a period of time, for example, in an open pond employing an air diffusion device or aeration device. Aerobic biological treatment processes may be performed to provide a dissolved oxygen content of from about 0.2mg/L to about 5mg/L, or in some embodiments, from about 1.5mg/L to about 2.5 mg/L. The retention time in the biological treatment tank may be several weeks, or in some embodiments, between about 1 and about 6 hours, or in some embodiments, between about 1 and about 2 hours.

Some embodiments of the treatment systems of the present invention may include systems that can decompose and/or convert various substances into other, more useful end products. In this system, the microorganisms can degrade biodegradable substances in an anoxic environment. In the anaerobic digestion process, a number of organic materials may be treated, such as waste paper, grass clippings, food, sewage, and animal waste. This process has the advantage of a reduction in the volume and mass of sludge to be introduced into the system. The process can produce biogas rich in methane and carbon dioxide at a suitable yield. The anaerobic digestion process may include bacterial hydrolysis of the sludge introduced into the digester, which is capable of breaking down insoluble organic polymers, such as carbohydrates to sugars, amino acids and fatty acids. In certain anaerobic digesters, acidifying bacteria can convert these intermediates into carbonic acid (carbonic acids), alcohols, hydrogen, carbon dioxide, ammonia, and organic acids. These compounds converted by the acidifying bacteria can be further digested by acetogenic microorganisms to produce acetic acid, carbon dioxide and hydrogen. The methanogenic bacteria or organisms may then convert the carbon dioxide, hydrogen, ammonia and organic acids to methane and carbon dioxide. Methane produced from anaerobic digestion processes can be used as an energy source. In some embodiments, a higher concentration of methanogenic bacteria present in the anaerobic digester, or a greater amount of methanogenic bacteria recycled to the anoxic reactor, may produce a greater amount of methane.

In certain embodiments, the anaerobic digester is continuously inoculated with a methanogenic combination of organisms present in the sludge of the treatment process. Certain slow-growing anaerobic bacteria, such as acetolytic methanogens (acetogenic methanogens) and methanogenic organisms with hydrogen as a nutrient source (hydrogengenic methanogens), may survive the aerobic environment of the present invention and will return to the anaerobic digester while allowing the anaerobic digester to be continuously inoculated with non-ineffective levels of methanogenic organisms. This makes the treatment process more reliable and enables a more smooth transition to steady state if problems occur in the system, such as a disruption in the flow of material. The inoculation of the anaerobic digester may also, as described above, increase methane production in the anaerobic digester.

The anaerobic digestion process may be operated at temperatures between 20 degrees celsius and 75 degrees celsius depending on the type of bacteria employed in the digestion process. For example, the use of mesophilic bacteria (thermophilia) generally requires an operating temperature of about 20 to 45 degrees celsius, while thermophilic bacteria (thermophilia) generally require an operating temperature of about 50 to 75 degrees celsius. In particular embodiments, the operating temperature may be between about 25 degrees celsius and about 35 degrees celsius to promote mesophilic activity but not thermophilic activity of the bacteria. The retention time in the anaerobic digester, depending on other operating parameters, may be between about 7 to about 50 days, in some embodiments, between about 15 to about 30 days. In particular embodiments, the oxygen demand may be reduced by about 50%.

In particular embodiments, the sludge treated by the anaerobic digester may be recycled back to the wastewater to be treated or to a biological treatment reactor, such as to an inlet of an anoxic tank or a biological sorption and nitrification tank. Anaerobic sludge may be treated by aerobic conditioning tanks (aerobic conditioning tanks) to alter the characteristics of the anaerobically digested sludge before it is recycled to the wastewater to be treated or to the biological treatment reactor.

Some other embodiments of the treatment system may comprise one or more systems with separate processes. The separation process may separate a specific portion of the wastewater or sludge to be treated. The separation process can remove bulky materials such as fine stones (grit), sand (sand), and gravel (gravel) from the wastewater. Other separation processes may remove large insoluble materials in the wastewater to be treated, such as, but not limited to, fats (fats), oils (oils), and ointments (grease). Other separation systems may take advantage of the precipitation properties of materials, such as precipitable solids and floating bodies (floating bodies). Various separation processes may employ operating devices such as settling tanks, clarifiers, thickeners, and filtration systems.

Some other embodiments of the treatment system may comprise one or more recycle streams that may be passed from an outlet of a first operating device to an inlet of a second operating device located upstream of the first operating device. In certain embodiments, the outlet of the anaerobic digester, aerobic digester, sludge thickener, or aerobic polishing apparatus may be recycled back to the inlet of the primary clarifier or biological sorption tank. In other embodiments, the outlet of the anaerobic digester may be recycled back to the inlet of the anoxic bioreactor.

Some other embodiments of the treatment system may comprise a sequencing batch reactor (sequencing batch reactor) fluidly connected or connected (connectable) to a source of wastewater to be treated. Sequencing batch bioreactors may biologically treat wastewater by promoting biosorption, degradation, or conversion of biodegradable materials, followed by settling and/or decanting of the mixed liquor containing the materials. The sequencing batch reactor may be fluidly connected or connected to an anaerobic digester located downstream of the reactor.

FIG. 1 illustrates an exemplary implementation according to some aspects of the invention. The treatment system 10 may be fluidly connected or communicated to a source of water 110 to be treated. According to any of the above aspects of the invention, the treatment system 10 may include one or more treatment device operations (treatment units) that may include one or more biological treatment processes and one or more systems or processes for reducing and collecting solids.

The source 110 of wastewater or water to be treated may be a water collection system from any one or more of a city, residential area, and industrial or commercial facility, and an upstream pretreatment system or combination thereof. For example, the source 110 may be a settling or sedimentation tank that receives water from a sewer piping system.

The treatment system 10 may include one or more biological treatment reactors or tanks, such as an anoxic tank 112 that facilitates denitrification of at least a portion of the dissolved and suspended solids contained therein. The anoxic tank 112 may contain or be configured to contain a microbial biomass that may metabolize biodegradable materials in the wastewater to be treated. For example, the anoxic tank 112 may contain or be configured to contain a microbial biomass that may treat biodegradable materials in the wastewater to be treated by a denitrification process that converts nitrogen-containing species, such as nitrates, to nitrogen (N2). The anoxic tank may be maintained in an environment that promotes the maintenance and growth of the biomass of microorganisms involved in the denitrification process.

The anoxic tank 112 produces a mixed liquid 212 that is subjected to denitrification treatment, and the mixed liquid 212 may be introduced into one or more biological treatment reactors or tanks, such as the biological treatment tank 114, that promote aggregation of at least a portion of the dissolved or suspended solids contained therein. Biological treatment tank 114 may contain or be configured to contain a microbial biomass that can biologically sorb biodegradable materials in the wastewater to be treated. Biological treatment tank 114 may contain or be configured to contain biofilm carriers that may promote the growth of a biofilm on the carriers. For example, biological treatment basin 114 may contain or be configured to contain microbial biomass that treats biodegradable material in wastewater to be treated by absorbing the biodegradable material. Biological treatment basin 114 may contain or be configured to contain substances or compounds that promote soluble and insoluble materials, such as organic compounds, in the wastewater or water to be treated. The biological treatment tank 114 may also contain or be configured to contain a nitrification biofilm to promote the conversion of nitrogen compounds, such as ammonia, into nitrites and nitrates. The biological sorption and nitrification process may include aeration and mixing operations to help maintain an aerobic environment in the biological treatment tank 114.

Biological treatment tank 114 produces a nitrified mixed liquor 214, which nitrified mixed liquor 214 may be introduced to a separator, such as clarifier 116, to produce a solids-depleted stream 218 and a solids-enriched sludge 219. A portion of nitrified mixed liquor 214 may be recycled to wastewater to be treated or biological treatment tank 112 via recycle line 216. The solids-lean stream 218 may be further treated, for example, by subjecting the at least partially treated water to suitable discharge or feeding to a water polishing unit (not shown) to produce a treated product or effluent 120 suitable for other uses.

Solids-rich sludge 219 may be separated such that at least a portion of solids-rich sludge 220 may be recycled back to, combined with, or introduced into one or more biological treatment ponds or other operating devices of the treatment system to be treated wastewater source 110.

At least a portion of the solids-rich sludge 219 may be introduced to a bioreactor, such as anaerobic digester 122, to produce a biologically treated sludge or anaerobically digested sludge 226. A portion of the biologically treated sludge or anaerobically digested sludge 226 may be disposed of as waste sludge 130. A portion of the anaerobically digested sludge 226 may also be recycled back to the wastewater source 110, combined therewith, or introduced into one or more biological treatment tanks or other operating devices of the treatment system. The portion of biologically treated sludge or anaerobically digested sludge 226 that is recycled may be any portion that is satisfactory depending on the operating parameters of the system and/or the expected characteristics or features of the effluent. For example, a portion of the biologically treated sludge or anaerobically digested sludge that is circulated is selected based on a preset flow rate. The portion being circulated may be based on a preset flow rate, or a fraction or percentage of a preset flow rate. For example, in certain embodiments, the portion being circulated may be at a preset flow rate of about 50%.

Optionally, at least a portion of the solids-rich sludge 219 may be introduced to the thickener 118 via line 222 to produce a thickened sludge 228 and a sludge-depleted fraction 224 prior to introducing the at least a portion of the solids-rich sludge 219 to the anaerobic digester 122. The thickened sludge 228 may then be introduced to the bioreactor or anaerobic digester 122, and the sludge-depleted portion 224 may be recycled back to the wastewater source 110, combined therewith, or introduced to one or more biological treatment tanks or other operating devices of the treatment system.

Anywhere between zero and one hundred percent of the solids-rich sludge 219 may be recycled back to the wastewater source 110 to be treated, combined therewith, or introduced into one or more biological treatment tanks or other operating devices of the treatment system, with the remainder being directed to the anaerobic digester. In particular embodiments, the portion introduced into the thickener 118 or anaerobic digester 122 may be between about two percent and about twenty percent solids-rich sludge 219. In other embodiments, the portion of the solids-enriched sludge 219 that is introduced into the thickener 118 or the anaerobic digester 122 may be between about four percent and about eight percent solids-enriched sludge 219.

Anywhere between zero and one hundred percent of the anaerobically digested sludge 226 may also be recycled back to the wastewater source 110, combined therewith, or introduced into one or more biological treatment tanks or other operating devices of the treatment system, with the remainder being disposed of as waste sludge 130. In certain embodiments, the portion that is recycled to the wastewater source, combined therewith, or introduced to one or more biological treatment tanks or other operating devices of the treatment system, may be between about zero to about twenty percent anaerobically digested sludge 226. In other embodiments, the portion that is recycled may be between about four percent to about eight percent anaerobically digested sludge 226.

In particular embodiments, the treated product 120 may be monitored for dissolved solids content, COD/BOD, total nitrogen, particularly nitrogen-containing compounds such as ammonia, nitrites, nitrates, or other determined characteristics. If the level of any of the determined characteristics is not within the expected range or is not at the expected level, adjustments may be made to the processing system. For example, if the COD of the treated product is different than the expected level or acceptable range, a greater or lesser portion of anaerobically treated sludge 226 may be disposed of as waste sludge 130.

In particular embodiments, the treated portion has a characteristic or characteristic related to the concentration of a particular component therein. For example, the treated portion has a nitrogen-containing component concentration or BOD or COD content below a particular value. In particular embodiments, the ammonia concentration of the treated product or effluent is less than about 5 milligrams elemental nitrogen per liter. The COD concentration of the treated product or effluent is less than about 80 mg/l.

The system 10 may have one or more primary separators. For example, a primary clarifier (not shown) fluidly connected to the water source or wastewater source to be treated 110 may be employed to allow at least a portion of the components of the water source to be treated 110 to precipitate to produce solids-depleted wastewater and introduce it to the biological treatment basin 112. The primary clarifier may also produce a solids-rich wastewater stream that may be combined with solids-rich sludge 220 or 222 or thickened sludge 228 for introduction to the anaerobic digester 122, as described in more detail below. The separator of the system may be employed, including but not limited to a primary separator, including a filter and a suspension type unit(s) of dissolved air, with or without the removal of fine stones.

One or more configurations of the treatment systems disclosed herein may include one or more polishing devices employing treatment processes including, but not limited to, biological nitrification/denitrification and phosphorus removal, chemical oxidation, chemical precipitation and separation systems comprising removal of dissolved inorganic solids by ion exchange, ultrafiltration, reverse osmosis, ultraviolet radiation or electrodialysis. The treated product 120 obtained from one or more finishing units may be transported to storage, secondary use, or discharged to the environment.

One or more nitrification means may be employed. For example, the biofilm nitrification apparatus, which may be, for example, a moving bed bioreactor (moving bed bioreactor), may be configured to receive at least a portion of the solids-lean stream from the separator. The effluent from the nitrification apparatus may be mixed with sludge from the clarifier to affect at least partial denitrification. Then re-aeration is performed to remove at least a portion of the nitrogen, which is removed in gaseous form. These changes may reduce or eliminate the use of external carbon sources.

One or more target characteristics may be utilized during operation of the processing system to adjust one or more operating parameters of any one of the operating devices of the system.

A precipitation reactor may be included in any of the systems disclosed herein to precipitate out one or more desired compounds, such as phosphorus and/or nitrogen from one or more streams of the system.

The precipitation reactor may be employed to precipitate phosphorus and/or nitrogen depleted compounds, such as struvite (MgNH)₄PO₄·6H₂O), by adding a precipitant, such as a magnesium salt (e.g., magnesium chloride), in the precipitation reactor, according to the following reaction:

Mg²⁺+NH₄ ⁺+PO₄ ^3-+6H₂O→MgNH₄PO₄·6H₂O

in some applications it is advantageous to use a precipitant, such as a magnesium salt, to precipitate phosphorus and nitrogen in the precipitation reactor instead of removing, for example, aluminium or iron. Struvite can be used as a fertilizer and thus as an agriculturally useful precipitate.

Precipitation of phosphorus in a precipitation vessel with aluminum can produce an aluminum phosphate precipitate that is not suitable for use as a fertilizer and therefore is not as agriculturally valuable as struvite. Similarly, the use of iron to precipitate phosphorus can produce iron phosphate, which is also unsuitable for use as a fertilizer. In other embodiments, one or both of the aluminum phosphate and/or iron phosphate may be precipitated from the solids-depleted outlet stream from the separator for use in other applications.

A pH adjusting agent, such as ammonium hydroxide, magnesium hydroxide, other caustic, or acid, may also be added to the solids-depleted outlet stream in the precipitation reactor to control the concentration of Mg2+ and/or the pH within a desired range.

In some embodiments, the precipitation reaction may occur at a temperature ranging from about 20 degrees celsius to about 40 degrees celsius, or in some embodiments, from about 25 degrees celsius to about 35 degrees celsius, a pH between about 6 and about 12, in some embodiments, a pH between about 7.5 and about 11, and in some embodiments, between about 8.5 and about 10. In some embodiments, after struvite is precipitated, the phosphorus-depleted liquid may be recycled back to the activated sludge treatment system. In some embodiments, the pH of the phosphorus-depleted liquid may be adjusted, for example, to about 7, by introducing a pH adjusting agent, such as an acid or base derived from a source of the pH adjusting agent, before being recycled back to the activated sludge treatment system. In other embodiments, the phosphorus-depleted liquid recycled back to the activated sludge treatment system may be allowed to maintain an alkaline pH, or adjusted to an alkaline pH. In some embodiments, the alkaline environment may assist in performing the nitrification process in an activated sludge treatment system.

The amount of precipitant (e.g., magnesium chloride) can be determined based on an analysis of the phosphorus and/or nitrogen concentration in the solids-depleted stream introduced into the precipitation reactor. In some embodiments, the precipitating agent may be added to the phosphorus or nitrogen-containing solids-lean stream in a stoichiometric ratio, for example, one molecule of magnesium per molecule of phosphorus or nitrogen in the solids-lean stream. In other embodiments, a slightly higher, e.g., about 10% higher, stoichiometric ratio of precipitant to phosphorus or nitrogen can be added to the solids-lean stream. In other embodiments, a less than stoichiometric ratio of precipitating agent may be added.

The various systems and techniques disclosed herein may significantly reduce energy consumption or even provide energy, and may reduce the yield of sludge in a wastewater treatment process.

Further, the controller may facilitate or adjust an operating parameter of the processing system. For example, the controller may be configured to adjust the circulation rate of one or more streams, the duration of one or more retention times, the temperature, and/or the concentration of dissolved oxygen of the fluid in any of the operating devices of the treatment system.

The controller may be responsive to signals from a timer (not shown) and/or a sensor (not shown) located at any particular location within the processing system. For example, a sensor positioned within the anoxic reactor may indicate when conditions therein are less than optimal. Further, the one or more sensors may monitor one or more operating parameters such as pressure, temperature, one or more characteristics of the liquid, and/or one or more characteristics of any effluent or waste streams. Similarly, being arranged in or at other locations with any of the recirculation flows may indicate whether the flow rate therein is equal to, lower than, or higher than the expected or target rate. The controller then responds by generating a control signal to cause an increase or decrease in the circulation flow rate. The target circulation flow rate of the mixed liquid from the polishing sub-train may depend on the operating parameters of the treatment system. For example, the target circulation flow rate may be several times, e.g., at least two or four times, the flow rate of the influent of influent water to be treated. In some cases, the solids discharge rate may be adjusted to achieve one or more target characteristics of the treated water. Other control strategies may involve proportionally changing the relative flow rates between the anaerobic digester and the aerobic treatment tank based at least in part on the oxygen demand of the water or influent to be treated.

The system and controller of one or more embodiments of the present invention provide a multi-function device having multiple modes of operation that can respond to multiple inputs to increase the efficiency of a wastewater treatment system.

The controller is implemented using one or more computer systems, which may be, for example, general purpose computers, such as those based on the Intel Pentium processor (Intel)Typeprocessor), Motorola power chip processor (Motorola)processor）、Hewlett-PackardProcessor, SunA processor or any other type of processor and combinations thereof. Alternatively, the computer system may include specially programmed, special purpose hardware, such as an application-specific integrated circuit (ASIC) or a controller for a water treatment system.

The computer system may include one or more processors typically connected to one or more memory devices, which may include, for example, any one or more of a disk drive memory (disk drive memory), a flash memory device (flash memory device), a RAM storage device, or other data storage device. The memory may be used to store programs and data during operation of the system. For example, the memory may be used to store historical data relating to the parameter over a period of time, as well as operational data. Software, including program code that implements embodiments of the invention, may be stored on a computer-readable and/or writable recording medium that does not lose data and then copied into memory where it may then be executed by one or more processors. These program codes may be written in a variety of programming languages, such as Java, Visual Basic, C, C #, or C + +, Fortran, Pascal, Eiffel, Basic, or any of a variety of combinations thereof.

Components of a computer system may be coupled by one or more interconnection mechanisms including one or more information transfer pathways (busses) between components such as those incorporated in the same device and/or a network of components such as those found in separate discrete devices. The interconnection mechanism may enable communications, such as data and/or instructions, to be exchanged between the components of the system.

The computer system may also include one or more input devices such as a keyboard, mouse, trackball (trackball), microphone, touch screen, and other human interface devices and one or more output devices such as a printing device, display screen, or speaker. Additionally, the computer system may include one or more interfaces that may connect the computer system to a communications network in addition to, or in the alternative to, a network that may be formed by one or more components of the system.

According to one or more embodiments of the present invention, the one or more input devices may include sensors that measure any one or more parameters of any of the systems and/or components therein disclosed herein. Alternatively, the sensors, measurement valves and/or pumps or all of these components may be connected to a communications network that is operatively coupled to a computer system. Any one or more of the above can be coupled to another computer system or component to communicate with the computer system via one or more communication networks. Such a configuration allows any sensor or signal generating device to be positioned a significant distance from the computer system and/or any sensor to be positioned a significant distance from any subsystem and/or controller while still providing data therebetween. Such communication mechanisms may be effected using any suitable technique including, but not limited to, those utilizing wireless protocols.

The controller may include one or more computer storage media such as a readable and/or writable recording medium that does not lose data and in which signals may be stored, the signals defining programs that are executed by one or more processors. The medium may be, for example, a magnetic disk or a flash memory. In general operation, one or more processors may generate data, such as code that executes one or more embodiments of the present invention, to read from a storage medium to a memory that allows information to be retrieved by the one or more processors more quickly than the medium.

While the computer system has been illustrated by way of example as one type of computer system on which aspects of the invention may be implemented, it will be understood that the invention is not limited to implementation in software or on a computer system as illustrated by the example. Indeed, rather than being implemented on a computer system, for example, a general purpose computer system, the controller or component or parts thereof may also be implemented as a dedicated system (dedicated system) or as a dedicated Programmable Logic Controller (PLC) or in a distributed control system (decentralized system). Further, it will be appreciated that one or more features or aspects of the invention may be implemented in software, hardware or firmware (firmware), or any combination thereof. For example, one or more portions of the algorithm executed by the controller may be executed in separate computers, which may communicate with each other over one or more networks.

In some particular embodiments, the controller may be configured to generate a number of output signals that initiate or terminate one or more cycles or phases of the sequencing batch reactor. For example, the controller may generate output signals that open one or more inlet valves that fluidly connect one or more basins of at least one sequencing batch reactor to a source of wastewater to be treated. The controller then generates a second output signal, preferably but not necessarily, to close the valve and open the aeration system of at least one sequencing batch reactor to provide a source of oxygen to achieve or maintain a target dissolved oxygen level, for example, between about 0.5 and about 2 mg/L. Thus, the controller may be configured to facilitate biosorption phenomena and/or nitrification that accumulates at least a portion of the dissolved and suspended solids. The controller may then generate a third output signal that facilitates a static environment (quiesce conditions) in at least one settling basin (basins) for at least a portion of the precipitable component to settle. In some cases, the static environment may be affected by the termination output signal, and a third output signal may be generated by the controller to facilitate recovery of any supernatant (e.g., by decantation) or solids-rich portion of the settling basin after settling. Then, another output signal, such as a fifth output signal, is generated to restart the aeration system. The controller may further generate a sixth output signal that activates and a seventh output signal that deactivates the aeration system of the at least one aerobic treatment tank to provide the source of oxygen to achieve or maintain a target dissolved oxygen level, such as between about 0.5 and about 2 mg/L.

The daily inflow of many municipal wastewater treatment projects varies. In some embodiments, the biological sorption operation or nitrification-denitrification of the wastewater treatment system may become less stable, e.g., capture more or less COD in the wastewater of the influent or remove less nitrogen compounds in the wastewater of the influent, as the loading conditions become more dynamic. If biological sorption or nitrification-denitrification fails to capture or remove a sufficient amount of COD or nitrogen compounds, this may exceed the capacity that can be carried by downstream anaerobic digesters to effectively treat COD or downstream polishing processes. To facilitate an increase in the reliability of the implementation of the biological sorption process or nitrification-denitrification process, a control system using an on-line meter for controlling the biological sorption and nitrification-denitrification may be utilized.

Feedback control may be employed in some control system embodiments. An on-line COD (online COD) or Total Organic Carbon (TOC) meter or nitrogen content calculator may be employed to measure the COD or TOC or nitrogen content of the solids-lean effluent flowing from the separator downstream of the nitrification-denitrification system. The flow rate of at least one of the influent wastewater streams and any one or more of the recycle streams, or the ratio of any one stream to another, may be adjusted when the COD or TOC or nitrogen content of the effluent is at or above a threshold level at which the treatment system can effectively treat the influent wastewater. This may be facilitated, for example, by employing a controller that actuates one or more valves to regulate the output of at least one bioreactor or operating device in the system. The flow rates of either of the wastewater streams and the recycle stream may be adjusted when the COD or TOC or nitrogen of the effluent is at a level such that the treatment system can effectively treat wastewater having a high level of COD or TOC or nitrogen content.

Further aspects of the invention may relate to or be associated with computer-readable media or computer-readable media providing various features that facilitate the processing methods described herein.

For example, the computer readable medium may include instructions that are executed on a computer system or controller that is a controller in a wastewater treatment system that implements a method of treating wastewater that includes one or more steps of providing wastewater to be treated and denitrifying the wastewater in a first bioreactor to produce a denitrification mixture. The method may further comprise nitrifying the denitrification mixed liquor with a nitrifying biofilm on the support and biosorpting the undesirable constituents from the denitrification mixed liquor with the suspended biomass in a second bioreactor. The method may further include separating a first portion of the nitrified mixed liquor in the separator to produce a solids-rich sludge and a treated effluent having a total nitrogen concentration of less than about 10 milligrams elemental nitrogen per liter, and combining a second portion of the nitrified mixed liquor with the wastewater to be treated.

In other configurations, a computer-readable medium may include instructions executed on a computer system or controller that is a controller in a wastewater treatment system implementing a method of treating wastewater including one or more steps of treating wastewater, the method including providing wastewater to be treated and facilitating denitrification in a first bioreactor to produce a mixed liquor that is first biologically treated. The method of treating wastewater may further include promoting bio-sorption and biofilm growth of the first biologically treated mixed liquor in a second bioreactor. The method of treating wastewater may also further include separating the effluent of the second bioreactor to produce a solids-rich sludge and a treated effluent having a total nitrogen concentration of less than about 10 milligrams elemental nitrogen per liter, and treating the solids-rich sludge in a third bioreactor to produce a biologically treated sludge.

The functions and advantages of these and other embodiments of the systems and techniques disclosed herein may be more fully understood through the following examples. The following examples are intended to illustrate the benefits of the treatment methods disclosed herein, but do not exemplify their full scope.

Example 1

As shown in FIG. 1, a processing system 10 is employed to measure deamination (Ammonia removal)

The treatment system 10 includes a source of wastewater 110 to be treated. The wastewater source 110 is fluidly connected to a primary clarifier (not shown) to precipitate at least a portion of the components of the wastewater source to be treated. The solids-depleted wastewater is then introduced to the anoxic tank 112 to produce a denitrification mixed liquor 212 that may be introduced to the biological treatment tank 114. The biological treatment tank 114 promotes biological sorption of the biodegradable material in the denitrification mixed liquid, and also promotes growth of a biofilm and nitrification of the denitrification mixed liquid. The biological treatment tank 114 produces a nitrified mixed liquor 214, which nitrified mixed liquor 214 is introduced into the clarifier 116 to produce a solids-depleted stream 218 and a solids-enriched sludge 219. A portion of the nitrified mixed liquor 214 is recycled to the wastewater to be treated to be directed to the anoxic tank 112 via recycle line 216. The solids-lean stream 218 is directed to one or more downstream water refineries 120.

The solids-rich sludge 219 is divided such that a portion of the solids-rich sludge 220 is recycled back to the source of wastewater to be treated 110 that is introduced to the anoxic tank 112.

A portion of the solids-rich sludge 219 may be introduced to the anaerobic digester 122 to produce anaerobically digested sludge 226. A portion of the anaerobically digested sludge 226 is disposed of as waste sludge 130. A portion of the anaerobically digested sludge 226 may also be recycled back to the wastewater source 110 introduced into the anoxic tank 112.

Prior to introducing at least a portion of the solids-rich sludge 219 to the anaerobic digester 122, a portion of the solids-rich sludge 219 is introduced to the thickener 118 via line 222 to produce a thickened sludge 228 and a sludge-depleted fraction 224. Thickened sludge 228 is introduced to the anaerobic digester 122 and the sludge-depleted fraction 224 is recycled back to the wastewater source 110, the wastewater source 110 being introduced to the anoxic tank 112.

In this process, the hydraulic retention time in the anoxic tank 112 is between about 1-3 hours, and the hydraulic retention time in the bioreactor 114 is between about 3 hours.

When the system is started up, biofilm carriers are added to the bioreactor 114. The biofilm carrier is made of a polymeric material and occupies about 66% of the volume of the tank, or about 32 square meters of surface area for biofilm growth. Zero percent of the anaerobically digested sludge is recycled back to the wastewater source 110 to be introduced to the anoxic reactor 112. During start-up, anaerobically digested sludge is disposed of as waste sludge 130. Without wishing to be bound by theory, it is believed that operating the system without circulating anaerobically digested sludge may allow biofilm to grow on biofilm carriers in bioreactor 214. After about 1 month, about 4.1% of the anaerobically digested sludge is recycled back to the wastewater source 110 and introduced into the anoxic reactor 112. After 18 days, circulation was 4.1%, and the circulation rate was increased to 8.1% of anaerobically digested sludge.

Figure 2 shows an improved nitrogen removal process in effluent stream 218, compared to nitrogen removal achieved in the biological treatment process shown in figure 3, in which the hydraulic retention time for aerobic treatment is in the range of about 4-12 hours, and compared to another process shown in figure 4 employing biosorption, contact stabilization, and anaerobic digestion, the hydraulic retention time of which combined biosorption and contact stabilization processes is about 2.5 hours. In fig. 2, the ammonia-nitrogen level is constantly reduced to below 5ppm, however such low levels cannot be achieved in fig. 3 and 4, which illustrate other processes. It can be seen that ammonia-nitrogen levels are continually reduced below 5ppm for more than three months.

As shown in FIG. 5, it can also be concluded that in addition to reducing the ammonia-nitrogen level below 5ppm, the COD level in the effluent stream 218 is constantly reduced below 80 mg/L. This level remained consistent in each wastewater treatment process tested, as shown in figures 6 and 7. The process of the present invention can continuously reduce the COD level in the effluent stream to below 80mg/L for more than three months while reducing the nitrogen level.

This example demonstrates that the above-described process is effective in maintaining nitrogen and COD levels in the effluent stream at levels below specific target values, and at lower hydraulic retention times compared to conventional anoxic-aerobic processes. This shortened hydraulic retention time reduces operating costs by providing more efficient and effective wastewater treatment compared to conventional anoxic-aerobic processes.

Those skilled in the art will readily appreciate that the various parameters and configurations described herein are exemplary and that the actual parameters and configurations will depend upon the specific application for which the method and system of the present invention is used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments described herein. For example, those skilled in the art will recognize that a system and its components in accordance with the present invention may further comprise a component of a network or processing system of the system. It is therefore to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the disclosed processing system and techniques may be practiced otherwise than as specifically described. For example, although the term "solids-depleted sludge" is used herein to refer to separation products, this term is used for illustrative purposes only and the use of this term does not limit the scope of the claims to a particular separation technique. The processing systems and techniques of the present invention are directed to each individual feature, system, or method described herein. In addition, any combination of two or more such features, systems or methods, if such features, systems or methods are not mutually inconsistent, is included within the scope of the present invention.

Further, it is to be appreciated various alterations, modifications, and improvements of the present invention will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. For example, the solids-rich stream or sludge stream may be introduced to an upstream operating device, such as a primary clarifier, or a biological sorption tank, or both. In other cases, the solids-depleted fraction or the sludge-depleted fraction may be directed to another separator and/or to a polishing plant. In other examples, existing processing equipment may be modified to utilize or incorporate any one or more aspects of the present invention. Thus, in some cases, the treatment system may involve connecting or configuring existing equipment to include anoxic reactors, bioreactors capable of promoting biological sorption and biofilm growth, and anaerobic digesters. Accordingly, the foregoing description and drawings are by way of example only. Further, the description of the drawings does not limit the invention to the specific illustrative description. For example, one or more bioreactors may be employed in one or more lines of the treatment system.

Use of ordinal terms such as "first," "second," "third," and the like in the specification and claims to modify an element does not by itself connote any priority, precedence, or order of one element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one element having a certain name from another element having a same name, and use of the ordinal term to distinguish the elements.

Claims (27)

1. A method of treating wastewater comprising:

providing wastewater to be treated;

performing denitrification treatment on the wastewater in a first bioreactor to produce a denitrification mixed liquor;

nitrifying the denitrification mixed liquor by adopting a nitrifying biomembrane on a carrier in a second bioreactor and biologically adsorbing undesirable components from the denitrification mixed liquor by adopting suspended biomass;

separating a first portion of the nitrified mixed liquor in a separator to produce a solids-rich sludge and a treated effluent having a total nitrogen content of less than about 10 milligrams elemental nitrogen per liter; and

mixing a second part of the nitrifying mixed liquor with the wastewater to be treated.

2. The method of claim 1, wherein the hydraulic retention time in the second bioreactor is less than about 3 hours.

3. The method of claim 2, further comprising:

treating at least a portion of the solids-rich sludge in a third bioreactor to produce a biologically treated sludge.

4. The method of claim 3, further comprising: thickening the at least a portion of the solids-rich sludge to produce a thickened sludge and a sludge-poor portion, wherein treating the solids-rich sludge in the third bioreactor comprises treating the thickened sludge to produce at least a portion of a biologically treated sludge.

5. The method of claim 3, further comprising: mixing a portion of the biologically treated sludge with at least one selected from the group consisting of wastewater to be treated, the first bioreactor and the second bioreactor at a preset flow rate.

6. The method of claim 5, wherein the portion of biologically treated sludge is mixed with at least one selected from the group consisting of wastewater to be treated, the first bioreactor and the second bioreactor at about 50% of a predetermined flow rate.

7. The method of claim 1, further comprising: treating the wastewater to be treated in a clarifier located upstream of the first bioreactor.

8. The method of claim 1, wherein the ammonia concentration of the treated effluent is less than about 5 milligrams elemental nitrogen per liter.

9. The method of claim 8, wherein the treated effluent has a chemical oxygen demand concentration of less than about 80 mg/l.

10. A wastewater treatment system, comprising:

a source of wastewater to be treated;

a first bioreactor having an inlet fluidly connected downstream from the source of wastewater;

a biological sorption tank including a biofilm carrier and having an inlet fluidly connected to the first bioreactor, the biological sorption tank being constructed and arranged to retain an effluent having a total nitrogen concentration of less than about 10 milligrams elemental nitrogen per liter and a hydraulic retention time of less than about 3 hours;

a separator having a sludge outlet, an effluent outlet and an inlet fluidly connected downstream of the biological sorption tank; and

a sludge recycle line fluidly connecting an outlet of the separator to the source of wastewater.

11. The wastewater treatment system of claim 10, further comprising an anaerobic digester having an anaerobically digested sludge outlet and an inlet fluidly connected to the sludge outlet.

12. The wastewater treatment system of claim 11, further comprising a sludge thickening processor having an inlet fluidly connected downstream from the sludge outlet of the separator, a thickened sludge outlet fluidly connected to an anaerobic digester, and a solids-lean outlet.

13. The wastewater treatment system of claim 11, further comprising a mixed liquid recycle line fluidly connecting an outlet of the biological sorption tank with the source of wastewater.

14. The wastewater treatment system of claim 13, further comprising an anaerobically digested sludge recycle line fluidly connecting the anaerobically digested sludge outlet with the source of wastewater.

15. The wastewater treatment system of claim 10, further comprising a clarifier located upstream of the first bioreactor.

16. A method of facilitating treatment of wastewater to reduce the concentration of nitrogen-containing compounds in the wastewater in a wastewater treatment system having a source of wastewater, an anoxic reactor, an aerobic reactor, a mixed liquor recycle stream fluidly connecting an outlet of the aerobic reactor with the anoxic reactor, a separator, and a sludge recycle stream fluidly connecting an outlet of the separator with the anoxic reactor, the method comprising:

introducing a biofilm carrier into an aerobic reactor; and

fluidly connecting the solids-enriched sludge outlet of the separator to an anaerobic digester.

17. The method of claim 16, further comprising fluidly connecting an outlet of the anaerobic digester to at least one selected from the group consisting of a wastewater source, an anoxic reactor, an aerobic reactor, a mixed liquor recycle stream, and a sludge recycle stream.

18. The method of claim 17, further comprising fluidly connecting the solids-rich outlet of the separator to a sludge thickener and fluidly connecting the outlet of thickened sludge from the sludge thickener to an anaerobic digester.

19. A method of treating wastewater comprising:

providing wastewater to be treated;

facilitating denitrification treatment of the wastewater in a first bioreactor to produce a first biologically treated mixed liquor;

promoting biosorption and biofilm growth of the first biologically treated mixed liquor in a second bioreactor;

separating the effluent of the second bioreactor to produce a solids-rich sludge and a treated effluent having a total nitrogen concentration of less than about 10 milligrams elemental nitrogen per liter; and

treating the solids-rich sludge in a third bioreactor to produce a biologically treated sludge.

20. The method of claim 19, wherein the hydraulic retention time in the second bioreactor is less than about 3 hours.

21. The method of claim 20, further comprising thickening the solids-rich sludge to produce a thickened sludge and a sludge-depleted fraction, wherein treating the solids-rich sludge in the third bioreactor comprises treating the thickened sludge to produce at least a portion of the biologically treated sludge.

22. The method of claim 21 wherein the promoting bio-sorption of the first biologically treated mixed liquor and growth of a biofilm comprises introducing a biofilm carrier into the second bioreactor.

23. The method of claim 19, further comprising treating the wastewater to be treated in a clarifier located upstream of the first bioreactor.

24. The method of claim 19, further comprising introducing a portion of the biologically treated sludge at a predetermined flow rate into at least one selected from the group consisting of the wastewater to be treated, the first bioreactor, the second bioreactor, and the clarifier.

25. The method of claim 24, wherein the portion of biologically treated sludge is introduced to at least one selected from the group consisting of wastewater to be treated, the first bioreactor, the second bioreactor, and the clarifier at about 50% of a predetermined flow rate.

26. The method of claim 19, wherein the ammonia content of the treated effluent is less than about 5 milligrams elemental nitrogen per liter.

27. A process as claimed in claim 26, wherein the chemical oxygen demand concentration of the treated effluent is less than 80 mg/l.