HK1124035B - Apparatus and method for the non-chemical stabilization of bio-solids - Google Patents

Description

Apparatus and method for non-chemically stabilizing biosolids

Cross-referencing

This patent application claims priority from U.S. provisional patent application 60/681,465 filed on 17.5.2005.

Technical Field

The present invention relates generally to apparatus and methods for treating aqueous media such as water and wastewater, and/or sludge treatment systems and methods for improving the operation of bioreactors, and more particularly to such apparatus and methods using non-chemical technology means.

Background

Modern municipal sewage and industrial waste treatment plants utilize traditional mechanical and biological methods to recycle wastewater. The traditional approach is to convert the water pollution problem into a solid waste disposal problem. The disposal of microbial sludge solids (e.g., of microbial or biological nature) produced by conventional municipal sewage treatment has long been an expensive task because of the extremely large volumes of sludge produced and other problems caused by the inherent toxicity and potentially biohazardous nature of this waste sludge to the environment. This is particularly evident in biohazard "hot" areas such as the region of mexico, the region located in south america, and other areas. In these areas, human parasites will be incubated in biological systems and then spread to other areas via land-based transmission, irrigation and other methods of contaminated microbial activated sludge treatment. The extraction and disposal of this microbial activated sludge is expensive and uneconomical.

Waste sludges, particularly those comprised of and/or predominantly composed of biological sludges (microbially contaminated materials), have long been the most significant problem associated with activated sludge and other aerobic and/or anaerobic wastewater treatment plants. These sludges are difficult and expensive to dry, and are difficult and expensive to sterilize/stabilize. These sludges may contain a high proportion of volatiles. The unavailability of landfills and the lower acceptance of these sludges as fertilizer/land spreads for agricultural use have led to significant increases in disposal costs. In some areas, microbial activated sludge is completely banned from landfills because of high contamination potential, presence of active microbial catalysts and solids (VS), and large amounts of water left (70% or more before drying).

The unavailability of landfills and the lower acceptance of these sludges as fertilizer/land spreads for agricultural use have led to significant increases in disposal costs. In some areas, microbial activated sludge is fundamentally banned from landfills and as a land spread fertilizer because of the high potential for contamination and the presence of active microbial catalysts, and the potential for these sludges to have vectors for the spread of pathogenic organisms and diseases.

For the purpose of disinfecting, stabilizing or decontaminating aqueous media containing microorganisms, such as biological sludges and waste materials, various different techniques have been developed, including:

u.v. sterilizer;

pressure/pressure cycling sterilization (using a gas cap or no gas cap in the pressure vessel but in the pressure vessel);

sterilization by exposing the material or solution to a supercritical solution;

gamma radiation or similar radiation methods;

exposure to vacuum;

exposure to strong electromagnetic fields;

·sonofication

sterilization by chemical exposure to strong acids (lowering the pH of the total solution to near or below 2 for a period of time) or strong bases (raising the pH of the total solution to near or above 12 for a period of time);

sterilization by high ionic strength solutions;

thermal sterilization;

physical mincing and cutting;

cycling between high and low pressure, no air cap or other air initiation;

increasing pressure on the chemical sterilization mixture to increase sterilization speed;

flash evaporation of high solids waste with heat and/or steam to cause explosive decompression followed by shearing; and

ozone, peroxides and other strong oxidants.

The above techniques are too expensive to be commercially applied, require additional treatment steps, cause additional pollution loads, or are not effective in treating aqueous media containing microorganisms (e.g., cause sterilization of sludge). It would therefore be desirable to provide an improved method for treating such aqueous media containing microorganisms.

Summary of The Invention

Accordingly, an object of the present invention is to solve the problems associated with the prior art.

Thus, according to the present invention, there is provided an apparatus for treating an aqueous medium containing microorganisms, comprising: an intake for receiving an aqueous medium containing microorganisms; a differential pressure inducer coupled to the intake to receive the aqueous medium containing the microorganisms and having the desired level of gas saturation, the differential pressure inducer being actuatable to accelerate the aqueous medium containing the microorganisms having the desired level of gas saturation to cause cell wall rupture of the microorganisms; and an outlet coupled to the differential pressure initiator for outputting the treated aqueous medium containing the disrupted microbial cells and contents; whereby the treated aqueous medium containing disrupted cell walls of the microorganisms is subjected to at least one of disposal or recovery.

Also, the present invention provides a method for treating an aqueous medium containing microorganisms with a desired level of gas saturation, comprising the steps of: i) feeding an aqueous medium containing microorganisms to a differential pressure inducer; ii) actuating a differential pressure inducer to accelerate the aqueous medium containing the microorganisms with a desired level of gas saturation to cause cell wall rupture of the microorganisms; and iii) outputting from the differential pressure inducer the treated aqueous medium containing disrupted cell walls of the microorganisms; whereby the treated aqueous medium containing ruptured cell walls of the microorganisms is subjected to at least one of disposal and recovery.

Drawings

Having generally described the nature of the present invention, reference will now be made to the preferred embodiments of the present invention by way of example, with reference to the accompanying drawings in which:

FIG. 1 shows a block diagram of an apparatus for treating an aqueous medium containing microorganisms in one embodiment of the present invention.

Detailed description of the preferred embodiments

The features of this embodiment that characterize the method of operation, as well as further objects and advantages thereof, will be better understood from the following description taken in conjunction with the accompanying drawings. These and other objects attained, and advantages offered, by the present invention will become more fully apparent from the following description.

Provided herein are novel apparatuses and methods for treating aqueous media containing microorganisms.

It has been found that, in one aspect, the apparatus described herein provides an efficient and economical new method for treating such aqueous media, thereby reducing and substantially eliminating disposal conditions for microorganism-containing aqueous media, such as biosolids sludge.

Another unique aspect of the present device is: the apparatus also improves bioreactor operation and reduces micronutrient costs while reducing or substantially eliminating the need to dispose of biosolid sludge. In particular, if desired, at least a portion of the treated aqueous medium may be recovered in the bioreactor to provide the necessary micronutrients. The direct economic benefit of the present invention is foreseeable due to lower operating costs resulting from lower shipping and disposal costs, lower sludge thickening polymer costs, lower odor control chemical costs, and other factors including higher value and greater choice of disposal/screening sludge for the primary clarifier. The device 10 described below is relatively simple in construction and therefore operates at relatively low energy levels. This improves the economy of the apparatus 10.

The terms "treat" or "treated" are meant to include sterilizing, disinfecting and/or stabilizing and/or the like.

"aqueous medium" is meant to include aqueous solutions or suspensions, municipal wastewater, agricultural and industrial wastewater, storm run-off from agricultural, suburban and urban development, primary, secondary or tertiary sludge containing microorganisms.

The term "recovering" includes the act of collecting and further processing the treated aqueous medium or for use as a feedstock or nutrient or other use. Non-limiting examples include recycling to a bioreactor.

"nutrient" as used herein refers to any substance that can be used by a cell, microorganism, or microorganism to multiply or grow. It can be minerals such as calcium, potassium, and molecules such as amino acids, proteins, sugars, polysaccharides, or the like that can be used, as well as cell wall material.

In one embodiment, the bioreactor utilizes a treated microbial activated sludge containing the desired nutrients that can serve as a food source for the bioreactor.

In another embodiment, the method for treating an aqueous medium containing microorganisms results in exposure of the microorganisms or nutrients contained in the cytoplasm of the cells of the microorganisms. When the cell wall structure is properly disrupted, the cell wall itself can become a useful food source. Since the biological reactants tend to be unique to each other in their specific microorganism and micro-fauna configurations, and the specific configurations of viable microorganisms and micro-fauna of any particular bioreactor may even vary over time and season, satisfactory nutrient and micronutrient sources for any particular bioreactor are those available within the treated aqueous medium, such as microbial activated sludge.

Without being limited by theory, it is believed that passing the treated aqueous medium to the bioreactor has beneficial effects on reactor operation, such as improved aerobic, anaerobic and sequencing/cyclic bioreactor efficiency, improved bioreactor stability, reduced bioreactor nutrient supply requirements and reduced bioreactor operating costs or a combination of any of the above.

In one embodiment, the aqueous medium is primary, secondary, tertiary sludge.

In other embodiments:

sludge produced in water and/or wastewater treatment processes;

primary sludge is produced by a primary sludge separation plant;

secondary sludge is produced by an aerobic or anaerobic reactor;

tertiary sludge is produced by tertiary treatment plants.

In one embodiment, the aqueous medium is subjected to forces generated by the action of mechanical components such as impellers, including centripetal forces (so-called "g" forces and others), which cause the cell walls of the microorganisms to rupture.

In one embodiment, the aqueous medium is repeatedly subjected to forces generated by the action of mechanical components, such as impellers, causing the cell walls of the microorganisms to rupture.

In a further embodiment:

the method further comprises adding a gas to the aqueous medium;

the method further comprises adding a gas to the aqueous medium containing the microorganisms prior to applying the pressure differential to the aqueous medium;

the aqueous medium is substantially saturated with gas; the gas may be air, oxygen or nitrogen, among other gases;

in a further embodiment, the method for treating an aqueous medium containing microorganisms further comprises purifying the aqueous medium containing microorganisms in a purifier prior to the pressure treatment, thereby separating the fluid from the aqueous medium to increase the concentration of biosolids.

In a further embodiment, the method for treating an aqueous medium containing microorganisms further comprises directing the treated aqueous medium containing disrupted cell walls of microorganisms to a bioreactor after the pressure treatment.

In one embodiment, the centrifugal pump is a submersible pump. However, those skilled in the art will appreciate that mechanical components capable of operating centrifugal pumps (e.g., motor drives, windmills, or other mechanical drives) may alternatively be used.

In one embodiment, the centrifugal pump is a submersible multistage pump.

In one embodiment, the centrifugal pump has a plurality of impellers.

In a further embodiment, the centrifugal pump has at least two impellers.

Those skilled in the art will appreciate that alternative pumps, such as piston or diaphragm pumps, may be used with appropriate configurations to accomplish the pressure-inducing effect on the aqueous medium to be treated.

Reference will now be made in detail to the specific preferred embodiments of the present invention, with the understanding that the examples are exemplary only and are not intended to limit the invention thereto.

Referring to fig. 1, an apparatus for treating an aqueous medium according to a preferred embodiment is shown generally at 10. The device 10 generally has an intake section 12, a treatment section 14, and an outlet section 16.

The intake portion 12 is provided for receiving an aqueous medium containing microorganisms. The aqueous medium is then led to the treatment section 14, where the aqueous medium containing the microorganisms will be subjected to a pressure treatment, causing the cell walls of the microorganisms to rupture within the aqueous medium.

The outlet section 16 is coupled to the treatment section 14 to output the treated aqueous medium.

The various sections of the apparatus 10 are connected by appropriate piping to allow the aqueous medium to flow between the sections. One of the lines is shown as line a and correlates the various components of the intake section 12 with the treatment section 14.

Line B bypasses the processing section 14.

Line C enables the aqueous medium to be recycled in the treatment section 14.

Line D is optionally provided to enable aqueous medium to be fed from bioreactor 64 to intake section 12 for treatment within apparatus 10.

The intake portion 12 has an intake 20. The intake 20 is typically an opening in a tube or a line in which the aqueous medium is received in the device 10. The aqueous medium is provided, for example, from a source 11 or recovered from the apparatus 10. The intake 20 is optionally provided with a filter. Depending on the source of the aqueous medium, it may be desirable to filter out coarse solids from the aqueous medium, whereby the task is performed in the intake section 12 (e.g., at the intake 20 or the purifier 22).

A purifier 22 connected to the intake 20 is optionally provided to convert unwanted liquids (e.g., purified water) from the aqueous medium into an effluent from the aqueous medium. As shown in fig. 1, line a enables the purifier 22 to be bypassed.

A gas injector 24 is provided to optionally add gas to the aqueous medium. As discussed below, the aqueous medium needs to have a certain level of gas saturation to cause cell wall rupture. Thus, it may be necessary to inject a portion of the gas into the aqueous medium in the intake section 12 to achieve this level of gas saturation. On the other hand, the aqueous medium may already have a suitable saturation level, whereby line a may bypass the gas injector 24. According to experiments, the addition of gas to an aqueous medium enhances the cell wall rupture of a part of the microorganisms contained in the aqueous medium.

The treatment section 14 comprises equipment for subjecting the aqueous medium to a pressure treatment. More specifically, the aqueous medium is fed to the treatment station 14 at a suitable level of gas saturation. Saturation involves gas absorption by microorganisms of the aqueous medium. The pressure treatment comprises subjecting the gas-filled microorganisms to multiple accelerations which will cause the cell walls of the microorganisms to rupture.

To some extent, increased saturation (e.g., supersaturation) of the aqueous medium will enhance the effectiveness of the pressure treatment in rupturing cell walls and killing microorganisms. Thus, a saturation level adjuster 40 is optionally provided to increase the gas saturation level of the aqueous medium.

The saturation level adjuster 40 is typically a tank adapted to maintain a pressure drop. The gas-saturated aqueous medium is isolated in the tank and the pressure in the tank is reduced to cause some level of supersaturation for the aqueous medium. Increased saturation will increase the compressibility of the aqueous medium. The subsequent multiple accelerations generated in the differential pressure inducer 42 will be more effective in rupturing the cell walls due to the increased compressibility.

Regulator 40 is optional and may be bypassed by way of line B.

The differential pressure inducer 42 typically comprises mechanical components that act on a gas-saturated aqueous medium. As an example, the pump is provided in the treatment section 14 and is typically of the centrifugal type exhibiting multistage centrifugation. Thus, the saturated aqueous medium from the intake section 20 is exposed to the impellers of the various pumps, which will cause cell wall rupture. Multiple accelerations (e.g., centrifugal, tangential, capillary acceleration, and/or acceleration/deceleration) are caused by the mechanical environment of the initiator 42, such as the impeller, pump housing structure, tube walls (e.g., disposed in coils adjacent to a mechanical pressure initiator such as a pump), etc. Since liquid and gas are present in a saturated aqueous medium, multiple accelerations will occur at different rates for liquid and gas. As the solution compresses and then separates, this rate difference will cause the cell walls of the microorganisms that have absorbed the gas to rupture.

As shown in fig. 1, line C can repeatedly use the saturation level adjuster 40 and/or the differential pressure adjuster 42 in any suitable order. A number of cycles may be performed in the treatment section 40 to optimize process efficacy. Multiple stages generally enhance the performance of the device 10.

In addition, if the differential pressure initiator 42 includes a pump, it is observed that cavitation caused by the pump will increase the effectiveness of the device 10 in disrupting microorganisms.

The outlet 60 is typically a plumbing outlet of the device 10. A gas injector 62 coupled to the outlet is provided to optionally add gas to the treated aqueous medium. Without being bound by theory, it is believed that injecting air, particularly oxygen, into the feed stream used to return the treated aqueous medium, which inherently contains nutrients and micronutrients released from the microorganisms and/or sludge of the microorganisms, will further enhance aerobic and sequencing/cyclic bioreactor efficiency and/or stability, and further reduce bioreactor operating costs, particularly costs associated with the bioreactor aeration components (often referred to as "blowers"). Upon output of the treated aqueous medium, the aqueous medium may be recovered, for example, in bioreactor 64, or disposed of as shown in disposal section 66.

If bioreactor 64 provides the aqueous medium to be treated, line D is provided to allow the aqueous medium to be transported from bioreactor 64 to intake 20 for treatment at apparatus 10. In this case, the aqueous medium may have a high content of liquids, which may be removed using the purifier 22. It has been noted that all components of the apparatus 10 are provided with appropriate controls to ensure proper treatment of the aqueous medium in the apparatus 10.

As a practical example, centrifugal pumps are well known to those skilled in the art for the differential pressure inducer 42. Centrifugal pumps have two main components: (1) a rotating component comprising an impeller and a shaft, and (2) a static component comprising a housing, a housing cover, and a bearing.

Centrifugal pumps may include manual or automatic pressure and/or flow control valves at the outlet of the centrifugal pump, and/or multiple valves at multiple locations, or may additionally utilize specific tubing sizes and/or diameters and lengths to control pump pressure and flow, as desired.

For the gas injector 24, an air inducing means such as a venturi may provide the dual functions of (1) a pressure and/or flow control valve and (2) adding gas to the aqueous medium using energy obtained from the action of the centrifugal pump.

The impeller is the primary rotating component used to provide acceleration to the fluid. The above embodiments are not limited to a particular shape or type of impeller.

Water enters the impeller inlet and is thrown out by the forces generated by the rotation. The pressure that a centrifugal pump will produce can be viewed as a direct relationship between impeller diameter, impeller count, inlet or inlet opening size, and the magnitude of the velocity produced from the rotational speed of the shaft. The capacity is determined by the exit width of the impeller and can be easily adjusted according to specific needs. All of these factors affect the amount of horsepower used in a motor; the more water is pumped or generates more pressure, the more energy is required.

Once the aqueous medium is subjected to forces (i.e. acceleration) resulting from the action of the first impeller, it may be directed to another impeller stage or to another centrifugal pump for further processing of the medium. Alternatively, the treated medium may be directed to a system of pipes back to the bioreactor (e.g., outlet 16) so that nutrients are now available to enhance the operation of the aerobic bioreactor due to the release of intracellular components and other fluids.

As previously mentioned, it is believed that the force is generated as the liquid flows past the impeller rotating at high speed on the shaft. The liquid velocity is converted into pressure, centripetal and shear forces, cavitation and other forces. The forces generated by these actions cause the microorganisms and cells of the microorganisms to rupture at sufficiently high RPM to stabilize the solution.

As for the actuation speed of the mechanical components of the pressure-difference initiator 42, it is preferable to operate at a higher speed to increase the rupturing effect on the microorganisms. By having the speed within the pump/tubing exceed the sound speed of the solution, enhanced effectiveness and high energy bubbles will be achieved.

Example 1

As an illustration of an embodiment, in operation, water, wastewater and/or sludge near or above gas saturation enters a multistage submersible centrifugal pump at about 3450 RPM. The resulting treated aqueous medium is directed to a piping system for recycling to a bioreactor or disposal, or to another centrifugal pump for further treatment, or the medium is directed to another treatment operation, as desired.

Example 2

The sludge is passed through a gas injector 24, which is a venturi, into a compression tank (to near or above gas saturation) to which gas has previously been added. The tank 40 and the contents were pressurized to 5atm for 172 seconds. Once the desired internal pressure is achieved, the cell is decompressed substantially instantaneously. The pressurization and depressurization cycle is repeated a second time. The resulting treated sludge is then directed to a piping system for further processing operations, i.e., a differential pressure inducer 42.

The treated sludge obtained from the previous step enters a multistage submersible centrifugal pump (40) with 6 impellers and operating at 3450 RPM.

The resulting treated sludge is directed to outlet section 16 for recycle to bioreactor 64 or disposal 66, or to another centrifugal pump for further treatment using line C, or the media to another treatment operation, as desired.

While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications without departing from the spirit of the invention, and this application is intended to cover any variations, uses, or adaptations of the invention following, for example, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth and as follows in the scope of the appended claims.

Claims (16)

1. An apparatus for treating an aqueous medium containing microorganisms, comprising:

an intake for receiving an aqueous medium containing microorganisms;

a gas injector and a saturation level adjuster to increase the gas saturation level of the aqueous medium to a desired gas saturation level;

a differential pressure inducer coupled to the intake to receive an aqueous medium containing microorganisms having a desired level of gas saturation, the differential pressure inducer having: at least one pump having an impeller, said at least one pump being operated such that an aqueous medium containing microorganisms having a desired level of gas saturation is accelerated by the action of the pump impeller, thereby causing rupture of the cell walls of the microorganisms due to the action of the pump impeller; and

an outlet coupled to the differential pressure inducer to output the treated aqueous medium containing disrupted microbial cells and contents;

whereby the treated aqueous medium containing disrupted cell walls of the microorganisms is subjected to at least one of disposal and recovery,

wherein the differential pressure inducer causes the velocity of a portion of the aqueous medium to be at or above the sonic velocity of the aqueous medium.

2. The apparatus of claim 1, wherein the differential pressure inducer has a plurality of pumps in a multi-stage centrifuge.

3. The apparatus of claim 1, wherein the saturation level adjuster has a tank coupled to a pressure source to receive a pressurization and depressurization cycle, the tank receiving the aqueous medium containing the microorganisms to thereby subject the aqueous medium containing the microorganisms to the pressurization and depressurization cycle to increase the gas saturation level of the aqueous medium.

4. The apparatus of claim 1, wherein said gas injector is coupled to an intake to achieve a desired level of gas saturation in the aqueous medium for subsequent microbial cell wall disruption.

5. The apparatus of claim 1, further comprising a gas injector coupled to the outlet to increase the gas content in the treated aqueous medium.

6. The apparatus of claim 1, further comprising a bioreactor coupled to the outlet, whereby at least a portion of the treated aqueous medium containing disrupted microbial cells is directed into the bioreactor.

7. The device of claim 1, further comprising a bioreactor coupled to the intake to feed the aqueous medium containing the microorganisms to the differential pressure inducer for treatment.

8. The device of claim 1, further comprising a purifier coupled to the intake to separate a portion of the relative liquid in the aqueous medium containing the microorganisms from a portion of the relative solids in the aqueous medium containing the microorganisms, whereby the purifier in turn feeds the portion of the relative solids in the aqueous medium containing the microorganisms to the pressure differential inducer.

9. A method for treating an aqueous medium containing microorganisms having a desired level of gas saturation, the method comprising the steps of:

i) saturating an aqueous medium containing microorganisms with a gas to a desired gas saturation level;

ii) feeding the aqueous medium containing the microorganisms to a differential pressure inducer having at least one pump with an impeller;

iii) actuating the differential pressure inducer to cause the microorganism-containing aqueous medium having the desired level of gas saturation to be accelerated by the impeller action of the pump to cause cell wall rupture of the microorganisms; and

iv) outputting from the differential pressure inducer a treated aqueous medium containing disrupted cell walls of the microorganisms,

whereby the treated aqueous medium containing disrupted cell walls of the microorganisms is subjected to at least one of disposal and recovery,

wherein step iii) comprises bringing the velocity of a portion of the aqueous medium at or above the sonic velocity of the aqueous medium.

10. The method of claim 9, wherein the step of saturating the aqueous medium containing the microorganisms with a gas results in the production of a gas-saturated aqueous medium containing the microorganisms.

11. The method of claim 9, further comprising the step of adjusting the gas saturation level of the aqueous medium containing the microorganisms to supersaturate the aqueous medium prior to step iii).

12. The method of claim 11, wherein the step of adjusting the gas saturation level is accomplished by pressurizing and depressurizing the aqueous medium containing the microorganisms.

13. The method of claim 9, wherein the step iii) comprises repeatedly subjecting the aqueous medium containing the microorganisms to forces resulting from impeller action.

14. The method of claim 9, further comprising the step of decontaminating an aqueous medium containing microorganisms prior to step iii).

15. The method of claim 9, further comprising directing the treated aqueous medium containing ruptured cell walls of the microorganisms to a bioreactor.

16. The method of claim 9, further comprising adding a gas to the treated aqueous medium after step iii).