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Suspended media membrane biological reactor system and process including multiple biological reactor zones

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20120279920 patent thumbnailZoom

Suspended media membrane biological reactor system and process including multiple biological reactor zones


A wastewater treatment system is provided comprising a first biological reaction zone, a second biological reaction zone and a membrane operating system. The first biological reaction zone is constructed and arranged to receive and treat the wastewater. The second biological reaction zone includes a separation subsystem and is constructed and arranged to receive effluent from the first biological reaction zone. A suspension system for adsorbent material is provided in the second biological reaction zone. The membrane operating system is located downstream of the second biological reaction zone and is constructed and arranged to receive treated wastewater from the second biological reaction zone and discharge a membrane permeate.

Inventors: William G. Conner, Mohammed A. Al-Hajri, Thomas E. Schultz, Michael Howdeshell, Chad L. Felch, Matthew Patterson, Samuel Shafarik, Curt Cooley
USPTO Applicaton #: #20120279920 - Class: 210631 (USPTO) - 11/08/12 - Class 210 
Liquid Purification Or Separation > Processes >Treatment By Living Organism >And Additional Treating Agent Other Than Mere Mechanical Manipulation (e.g., Chemical, Sorption, Etc.)



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The Patent Description & Claims data below is from USPTO Patent Application 20120279920, Suspended media membrane biological reactor system and process including multiple biological reactor zones.

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RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 61/224,000 filed Jul. 8, 2009, and U.S. Provisional Patent Application No. 61/186,983 filed on Jun. 15, 2009, the disclosures of which are hereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to wastewater treatment systems and methods.

2. Description of Related Art

Effective handling of domestic sewage and industrial wastewater is an extremely important aspect of increasing the quality of life and conservation of clean water. The problems associated with simply discharging wastewater in water sources such as rivers, lakes and oceans, the standard practice up until about a half century ago, are apparent—the biological and chemical wastes create hazards to all life forms including the spread of infectious diseases and exposure to carcinogenic chemicals. Therefore, wastewater treatment processes have evolved into systems ranging from the ubiquitous municipal wastewater treatment facilities, where sanitary wastewater from domestic populations is cleaned, to specialized industrial wastewater treatment processes, where specific pollutants in wastewater from various industrial applications must be addressed.

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

Nonetheless, a need exists to treat wastewater containing biologically refractory and biologically inhibitory organic and inorganic compounds without disadvantages associated with using powdered activated carbon and other existing technologies.

SUMMARY

OF THE INVENTION

In accordance with one or more embodiments, the invention relates to a system and method of treating wastewater.

In accordance with one or more embodiments, the invention relates to a wastewater treatment system for treating wastewater. The system includes a first biological reaction zone, a second biological reaction zone and a membrane operating system. The first biological reaction zone is constructed and arranged to receive and treat the wastewater. The second biological reaction zone includes a separation subsystem and is constructed and arranged to receive effluent from the first biological reaction zone. A suspension system for adsorbent material is provided in the second biological reaction zone. The membrane operating system is located downstream of the second biological reaction zone and is constructed and arranged to receive treated wastewater from the second biological reaction zone and discharge a membrane permeate.

In accordance with one or more embodiments, the first biological reaction zone and the second biological reaction zone are segregated sections of the same vessel.

In accordance with one or more embodiments, the first biological reaction zone and the second biological reaction zone are located in separate vessels.

In accordance with one or more embodiments, the suspension system comprises a gas lift suspension system. The gas lift suspension system can include at least one draft tube positioned in the second biological reaction zone and a gas conduit having one or more apertures positioned and dimensioned to direct gas to an inlet end of the draft tube. The gas lift suspension system can alternatively include at least one draft trough positioned in the second biological reaction zone and a gas conduit having one or more apertures positioned and dimensioned to direct gas to a lower portion of the draft trough.

In accordance with one or more embodiments, the suspension system comprises a jet suspension system.

In accordance with one or more embodiments, the separation subsystem includes a screen positioned at an outlet of the second biological reaction zone.

In accordance with one or more embodiments, the separation subsystem includes a settling zone located proximate the outlet of the second biological reaction zone. The settling zone can include a first baffle and a second baffle positioned and dimensioned to define a quiescent zone in which the adsorbent material separates from mixed liquor and settles into the mixed liquor in a lower portion of the biological reactor. Further, the settling zone can include a screen or a weir positioned proximate the outlet of the second biological reaction zone.

In accordance with one or more embodiments, the invention relates to a wastewater treatment system in which a source of adsorbent material introduction apparatus in communication with the second biological reaction zone. In addition, a sensor is constructed and arranged to measure a parameter of the system. Further, a controller is in electronic communication with the sensor and programmed to instruct performance of an act based on the measured parameter of the system. The measured parameter can be the concentration of one or more predetermined compounds. The act can include removing at least a portion of the adsorbent material from the second biological reaction zone, and/or adding adsorbent material to the second biological reaction zone.

In accordance with one or more embodiments, the invention relates to a wastewater treatment system for treating wastewater. The system includes a first biological reaction zone having a wastewater inlet and a first zone mixed liquor outlet. The system also includes a second biological reaction zone having a mixed liquor inlet in fluid communication with the first zone mixed liquor outlet, a suspension system for adsorbent material, a second zone mixed liquor outlet, and a separation subsystem associated with the second zone mixed liquor outlet. The system further includes a membrane operating system located downstream of the second biological reaction zone having an inlet in fluid communication with the second zone mixed liquor outlet, and a treated effluent outlet.

In accordance with one or more embodiments, the invention relates to a process for treating wastewater. The process includes introducing mixed liquor into a first biological reaction zone to form a treated mixed liquor; passing the treated mixed liquor to a second biological reaction zone; suspending adsorbent material in the treated mixed liquor of the second biological reaction zone, the action of suspension operating under conditions that promote adsorption of contaminants in treated mixed liquor on the adsorbent material; and passing an effluent that is substantially free of adsorbent material from the second biological reaction zone to a membrane operating system while maintaining adsorbent material in the second biological reaction zone.

Still other aspects, embodiments, and advantages of these exemplary aspects and embodiments, are discussed in detail below. Moreover, it is to be understood that both the foregoing information and the following detailed description are merely illustrative examples of various aspects and embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and embodiments. The accompanying drawings are included to provide illustration and a further understanding of the various aspects and embodiments, and are incorporated in and constitute a part of this specification. The drawings, together with the remainder of the specification, serve to explain principles and operations of the described and claimed aspects and embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in further detail below and with reference to the attached drawings all of which describe or relate to apparatus, systems and methods of the present invention. In the figures, which are not intended to be drawn to scale, each similar component that is illustrated in various figures is represented by a like numeral. In the figures:

FIG. 1 is a schematic diagram of a membrane biological reactor system using a biological reactor which contains one or more zones with adsorbent material in suspension;

FIG. 2 is a schematic diagram of an embodiment of a system for treatment of wastewater using adsorbent material in a biological reactor upstream of a membrane operating system;

FIG. 3 is a schematic diagram of a second embodiment of a system similar to that shown in FIG. 2 which includes a denitrification zone;

FIG. 4 is a schematic diagram of another embodiment in which adsorbent material is maintained in suspension in only a portion of a biological reactor tank;

FIG. 5 is a schematic diagram of a further embodiment of a biological reactor divided into multiple sections that includes an anoxic zone;

FIG. 6 is a schematic diagram of an additional embodiment using a series of biological reactors in which adsorbent material is maintained in suspension in only one of the biological reactors;

FIG. 7 and FIG. 8 are embodiments of biological reactor systems depicting a jet suspension system for suspension of adsorbent material in mixed liquor;

FIGS. 9 and 10 are alternative embodiments of biological reactor systems depicting a jet suspension system for suspension of adsorbent material in mixed liquor, in which mixed liquor taken from a source that has had adsorbent material removed;

FIG. 11 is an alternative embodiment depicting a jet suspension system for suspension of adsorbent material in mixed liquor in which adsorbent material is not circulated through the jet nozzle;

FIG. 12 is a further embodiment of a biological reactor depicting a gas lift suspension system to provide circulation to maintain adsorbent material in suspension;

FIGS. 13A and 13B are further embodiments depicting a settling zone;

FIG. 14 is a chart depicting feed COD concentration (in milligrams per liter), and the remaining effluent COD concentrations (as percentages of the original), at various stages of biological acclimation in a membrane biological reactor system;

FIG. 15 is a schematic illustration of an embodiment of a jet nozzle of the type used in an example demonstrating use of a jet suspension system;

FIG. 16 is a schematic illustration of an system configuration used in another example herein;

FIG. 17 is a chart depicting suspension of adsorbent material under certain nozzle throat velocities and liquid flow rates as determined under various test conditions using the system configuration of FIG. 16;

FIGS. 18 and 19 depict top and sectional views of embodiments of biological reactors employed in the system configuration of FIG. 16;

FIG. 20 is a chart depicting attrition as a function of run time for various types of adsorbent material in another example herein using a gas lift suspension system;

FIG. 21 depicts a top and a sectional view of an embodiment of a biological reactor using a gas lift suspension system;

FIG. 22 is a schematic illustration of flow patterns using the gas lift suspension system of FIG. 21;

FIG. 23 depicts a top and a sectional view of an embodiment of a biological reactor using another configuration of a gas lift suspension systems; and

FIGS. 24 and 25 depict top, side sectional and end sectional views of embodiments of biological reactors using various configurations of gas lift suspension systems.

DETAILED DESCRIPTION

OF THE INVENTION

As used herein, “biologically refractory compounds” refer to those types of chemical oxygen demand (“COD”) compounds (organic and/or inorganic) in wastewater that are difficult to biologically break down when contacted with micro-organisms. The “biologically refractory compounds” can have varying degrees of refractory, ranging from those that are mildly refractory to those that are highly refractory.

“Biologically inhibitory compounds” refer to those compounds (organic and/or inorganic) in wastewater that inhibit the biological decomposition process.

“Biologically labile” means easy-to-digest, simple organics such as human and animal waste, food waste, and inorganics, such as ammonia and phosphorous-based compounds.

“COD” or “Chemical Oxygen Demand,” refers to a measure of the capacity of water to consume oxygen during a chemical reaction that results in the oxidation (decomposition) of organic matter and the oxidation of inorganic chemicals such as ammonia and nitrite. COD measurement includes biologically labile, biologically inhibitory and biologically refractory compounds.

“Mixed liquor suspended solids,” or “MLSS,” means microbes and other substances, both dissolved and suspended, present in wastewater being treated; “mixed liquor volatile suspended solids,” or “MLVSS,” means the active microbes in the MLSS; and “mixed liquor” means the combined mixture of wastewater and MLSS.

“Adsorbent” or “adsorbent materials” as used herein means one or more of granular activated carbon, including granular activated carbon that has been treated to provide affinity to predetermined chemical species, metals or other compounds found to be present in the wastewater that is to be treated; granular iron-based compounds, e.g., iron oxide composites; synthetic resins; and granular alumino-silicate composites.

“Substantially free” or “substantially prevented” in the context of describing the presence of adsorbent material in effluent passing from one section of a system to another, e.g., from a biological reactor containing suspended adsorbent material to a membrane operating system, refers to limiting the amount of adsorbent material passing to the membrane operating system to an amount that does not adversely effect the requisite efficacy of the membrane filtration process therein. For instance, in certain embodiments, “substantially free” or “substantially prevented” refers to retaining at least about 80% by volume of the predetermined amount of adsorbent material to be used in a given system within the biological reactor or one or more biological reaction zones, in further embodiments, at least about 90% by volume and in still further embodiments at least about 95% by volume, and in yet still further embodiments at least about 99% by volume. However, it will be appreciated by one of ordinary skill in the art based upon the teachings herein that these percentages are merely illustrative, and can vary depending on factors including but not limited to the type of membrane(s) used and their resistance to abrasion, the requisite effluent quality, the predetermined amount of adsorbent material to be used in a given system, and other factors.

This invention in directed to wastewater treatment systems and methods. “Wastewater” as used herein, defines any water to be treated such as surface water, ground water, and a stream of wastewater from industrial, agricultural and municipal sources, having pollutants of biodegradable material, inorganic, labile organic compounds capable of being decomposed by bacteria, biologically refractory compounds, and/or biologically inhibitory compounds, flowing into the wastewater treatment system.

Wastewater from industrial and municipal sources typically contains biological solids, and inert material and organics, including biologically inhibitory and refractory organics. Examples of biologically inhibitory and refractory organics may include synthetic organic chemicals, such as polyelectrolyte treatment chemicals. Other biologically inhibitory and refractory organics include polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polychlorinated dibenzo-p-dioxin, and polychlorinated dibenzofurans. Endocrine disrupting compounds are also a class of biologically inhibitory and refractory organics which can affect hormone systems in organisms and are found in the environment. Examples of endocrine disrupting compounds include: alkylphenolics, such as nonylphenol used for removing oil as well as natural hormones and synthetic steroids found in contraceptives, such as 17-b-estradiol, estrone, testosterone, ethynyl estradiol.

Other examples of wastewaters to be treated include: high strength wastewater; low strength wastewater; and leachate from landfills. Waters may also be treated to remove viruses. Other examples of pollutants in wastewater include: flame retardants, solvents, stabilizers, polychlorinated biphenyls (PCBs); dioxins; furans; polynuclear aromatic compounds (PNAs); pharmaceuticals, petroleum; petrochemical products; petrochemical byproducts; cellulose; phosphorous; phosphorous compounds and derivatives; and agricultural chemicals such as those derived from or used to produce fertilizers, pesticides, and herbicides.

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

In general, wastewater treatment facilities use multiple treatment stages to clean water so that it may be safely released into bodies of water such as lakes, rivers, and streams. Presently, many sanitary sewage treatment plants include a preliminary treatment phase in which mechanical means are used to remove large objects (e.g., bar screens), and a sand or grit channel where sand, grit and stones settle. Some treatment systems also include a primary stage where certain fats, greases and oils float to the surface for skimming, and heavier solids settle to the bottom, and are subsequently treated in an aerobic or anaerobic digester to digest biomass and reduce the levels of biological solids.

After preliminary and/or primary treatment, the wastewater is then sent to a secondary biological activated sludge treatment phase. Biological treatment of wastewater is widely practiced. Wastewater is commonly treated with waste activated sludge, in which biological solids are acted upon by bacteria within a treatment tank. Activated sludge processes involve aerobic biological treatment in an aeration tank, typically followed by a clarifier/settling tank. Settled sludge is recycled back to the aeration tank in order to maintain an adequate mixed liquor suspended solids concentration to digest the contaminants. Some alternatives available for disposal of excess bio-solids, e.g., sludge, include but are not limited to incineration, disposal in a landfill, or use as fertilizer if there are no toxic components.

In the aeration tank, an oxygen-containing gas such as air or pure oxygen is added to the mixed liquor. The oxygen from the air is typically used by the bacteria to biologically oxidize the organic compounds that are either dissolved or carried in suspension within the wastewater feed. Biological oxidation is typically the lowest cost oxidation method available to remove organic pollutants and some inorganic compounds, such as ammonia and phosphorous compounds, from wastewater and is the most widely used treatment system for wastewater contaminated with biologically treatable organic compounds. Wastewaters that contain compounds entirely resistant to bio-decomposition, biologically inhibitory compounds, and/or biologically refractory compounds may not be treated adequately by a conventional simple biological wastewater treatment system. These compounds can only be acted upon by the bacteria only during a hydraulic retention time within a treatment tank. Because the hydraulic retention time is generally insufficient for biological oxidation of sufficient biologically inhibitory compounds and/or biologically refractory compounds, it is likely that some of these recalcitrant compounds may not be treated or destroyed and can pass through a treatment process unchanged or only partially treated prior to discharge in either an effluent or excess residual sludge.

The mixed liquor effluent from the aeration tank typically enters a clarifier/settling tank where sludge, including concentrated mixed liquor suspended solids, settles by gravity. Excess biomass is wasted, i.e., discharged, to off-site disposal. However, based on the wastewater and economic needs, some biological oxidation systems use a different treatment method to remove the solids from the wastewater effluent. The clarifier/settling tank can be replaced with a membrane operating system, or another unit operation such as a dissolved/induced air flotation device can be used. The liquid effluent from the clarifier/settling tank, operating system or dissolved air flotation device is either discharged or given further treatment prior to discharge. The solids that are removed from the mixed liquor are returned to the aeration tank as return activated sludge for further treatment and in order to retain an adequate concentration of bacteria in the system. Some portion of this return activated sludge is periodically removed from this recycle line in order to control the concentration of bacteria in the mixed liquor.

One recent advance in conventional industrial biological wastewater treatment plant technology includes the addition of powdered activated carbon particles to the mixed liquor. In biological treatment processes utilizing powdered activated carbon, the organics can be adsorbed onto the activated carbon and remain within the treatment tank for a hydraulic retention time that is similar to the sludge residence time and therefore undergo both adsorptive and biological treatments that result in enhanced removal of certain biologically inhibitory or refractory compounds. In these processes, certain organic and inorganic compounds are physically adsorbed to the surface of the powdered activated carbon particles.

Powdered activated carbon has been used in conventional biological treatment plants because of its ability to adsorb biologically inhibitory and biologically refractory compounds, thereby providing an effluent with lower concentrations of these pollutants. Inclusion of powdered activated carbon in the mixed liquor provides a number of operational benefits. The carbon provides the advantages of a suspended media biological treatment system which include increased pollutant removal and increased tolerance to upset conditions. Additionally, the carbon allows the biologically inhibitory and biologically refractory compounds to adsorb onto the surface of the carbon and to be exposed to the biology for a significantly longer period of time than in a conventional biological treatment system, thereby providing benefits similar to that of a fixed film system. The carbon also allows for the evolution of specific strains of bacteria that are more capable of digesting the biologically inhibitory organic materials. The fact that the carbon is continuously recycled back to the aeration tank with the return activated sludge, i.e., the sludge residence time, means that the bacteria can work on digesting the biologically inhibitory organic compounds adsorbed onto the surface of the carbon for a period of time longer than the hydraulic detention time of the biological treatment system. This process also results in biological regeneration of the carbon and allows the carbon to remove significantly more biologically inhibitory and biologically refractory compounds than it could in a simple packed bed carbon filter system which would also require frequent replacement or costly physical regeneration of the carbon once the adsorption capacity of the carbon is exhausted. The carbon in the mixed liquor can also adsorb certain compounds and therefore provide an effluent that is free of or hasw a substantially reduced concentration of compounds that are not treatable by conventional biological oxidation or otherwise entirely resistant to bio-decomposition. One example of a known powder activated carbon system is offered by Siemens Water Technologies under the trademark “PACT®.”

However, because both biological growth and adsorption of organic and inorganic compounds occurs on the activated carbon in powder form, wasting of excess solids is required. In addition, the powdered activated carbon is discharged from the treatment process with the removal of biosolids and must, therefore, be continually replaced.

Increasingly, sanitary wastewater is being treated using membrane biological reactor technology, which offers improved effluent quality, a smaller physical footprint (more wastewater can be treated per unit area), increased tolerance to upsets, improved ability to process hard-to-treat wastewaters and a variety of other operational advantages. For example, wastewaters containing high total dissolved solids can experience settling problems in a conventional clarifier/settling tank and requires significantly more difficult-to-operate solids separation devices such as a dissolved air flotation device or some other solids removal system. However, while membrane biological reactors eliminate the settling problems experienced with clarifier/settling tank systems, they often present problems of membrane fouling and foaming that do not occur in conventional systems using clarifiers. Membrane fouling may be the result of extra-cellular polymeric compounds that result from the break-down of the biological life forms in the mixed liquor suspended solids, accumulation of organic materials such as oils, or by scaling by inorganic materials.

In addition, to date, membrane biological reactors have not been utilized commercially with powdered activated carbon addition. There has been some use of powdered activated carbon in surface water treatment systems that utilize membranes for filtration. However, it has been reported that these surface water treatment systems using membranes and powdered activated carbon have problems with the carbon abrading the membranes and the carbon permanently plugging and/or fouling the membranes.

Industrial wastewater that must be treated prior to discharge or reuse often include oily wastewaters, which can contain emulsified hydrocarbons. Oily wastewaters can come from a variety of industries including steel and aluminum industries, chemical processing industries, automotive industries, laundry industries, and crude oil production and petroleum refining industries. As discussed above, a certain amount of non-emulsified oils and other hydrocarbons may be removed in primary treatment processes, where floating oils are skimmed from the top. However, biological secondary wastewater processes are generally employed to remove the remaining oils from wastewater, typically the dissolved and emulsified oils, though some free oil may exist. Typical hydrocarbons remaining after primary treatment can include lubricants, cutting fluids, tars, grease, crude oils, diesel oils, gasoline, kerosene, jet fuel, and the like. These hydrocarbons typically must be removed prior to discharge of the water into the environment or reuse of the water in the industrial process. In addition to governmental regulations and ecological concerns, efficient removal of the remaining hydrocarbons also has benefits, as adequately treated wastewater may be used in many industrial processes and eliminate raw water treatment costs and reduce regulatory discharge concerns.

Other types of wastewater that must be treated includes contaminated process water from other industrial processes such as manufacturing of pharmaceuticals, various goods, agricultural products (e.g., fertilizers, pesticides, herbicides), and paper processing, as well as medical wastewater.

Commercial deployment of membrane biological reactors in the treatment of oily/industrial wastewater has been very slow to develop, mainly due to maintenance problems associated with oil and chemical fouling of the membranes. Testing of industrial/oily wastewater treated in a membrane biological reactor having powdered activated carbon added to the mixed liquor indicated the same treatment advantages as observed in conventional biological wastewater treatment systems including powdered activated carbon. It was also noted that the advantages of using a membrane biological reactor can also achieved. However, a side-by-side comparison of membrane biological reactors with and without the addition of powdered activated carbon demonstrated that the membrane biological reactor with powdered activated carbon provided treatment advantages as compared to the membrane biological reactors without activated carbon. Additionally, the membrane biological reactor without the carbon addition was very difficult to operate because of dissolved organics and extra cellular polymeric compounds fouling the membranes. Testing further demonstrated that while the addition of powdered activated carbon provided a very viable biological wastewater treatment system, the carbon had the deleterious effect of a significant amount of abrasion to and non-reversible fouling of the membranes. This abrasion and non-reversible fouling was significant enough to result in this system being very costly to operate, because of the significantly decreased life expectancy of the membranes and membrane cleaning frequency.

The systems and methods of the present invention overcome the deleterious effects of using powdered activated carbon, while providing the same and additional advantages.

Referring to FIG. 1, a wastewater treatment system 100 is schematically depicted including a biological reactor system 102 upstream of a membrane operating system 104. In certain embodiments, biological reactor system 102 includes a single biological reactor vessel. In additional embodiments, biological reactor system 102 includes a plurality of biological reactor vessels, one biological reactor vessel divided into separate sections, or a plurality of biological reactor vessels some or all of which can be divided into separate sections. The individual reactor vessels or segregated sections are generally referred to herein as biological reaction zones. During wastewater treatment operations according to the present invention, adsorbent material along with micro-organisms are maintained in suspension in all of the biological reaction zones or a subset of the total number of biological reaction zones. The membrane operating system 104 is maintained substantially free of adsorbent material using one or more of the separation subsystems described herein. An influent wastewater stream 106 can be introduced from a primary treatment system, a preliminary screening system, or as a direct flow of previously untreated wastewater. In further embodiments, the influent wastewater stream 106 can be previously treated wastewater, e.g., an effluent from one or more upstream biological reactors, including but not limited to aerobic biological reactors, anoxic biological reactors, continuous flow reactors, sequencing batch reactors, or any number of other types of biological treatment systems capable of biologically degrading organic and in certain embodiments some inorganic compounds.

The biological reactor(s) and/or certain biological reactor zones can be various types of biological reactors, including but not limited to aerobic biological reactors, anoxic biological reactors, continuous flow reactors, sequencing batch reactors, trickling filters, or any number of other types of biological treatment systems capable of biologically degrading organic and in certain embodiments some inorganic compounds.

In addition, the biological reactor(s) and/or certain biological reactor zones used herein can be of any size or shape suitable to suspend adsorbent material in conjunction with the suspension system. For example, the vessel may have a cross sectional area of any shape, such as circular, elliptical, square, rectangle, or any irregular shape. In some embodiments, the vessel may be constructed or modified in order to promote suitable suspension of the adsorbent material.

FIG. 2 schematically depicts the process flow of a wastewater treatment system 200 for producing a treated effluent having reduced concentrations of biologically labile, biologically refractory, biologically inhibitory and/or organic and inorganic compounds that are entirely resistant to biological decomposition. System 200 generally includes a biological reactor 202 and a membrane operating system 204. Biological reactor 202 includes an inlet 206 for receiving wastewater and an outlet 208 for discharging effluent that has been biologically treated, including mixed liquor volatile suspended solids and/or mixed liquor, to the membrane operating system 204.

The biological reactor 202 includes a distributed mass of porous 236 adsorbent material 234, and an effective amount of one or more micro-organisms 238, that are both adhered to the adsorbent material and free-floating and separate from the adsorbent material in the mixed liquor, for acting on biologically labile and certain biologically refractory and/or biologically inhibitory compounds in the mixed liquor. The adsorbent material adsorption sites, including the outer surface of the adsorbent granules or particles, and the wall surfaces of pores 236, initially serve as adsorption sites for the biologically labile, biologically refractory, biologically inhibitory and/or organic and inorganic compounds that are entirely resistant to biological decomposition. In addition, micro-organisms 238 can be adsorbed on the adsorption sites of the adsorbent material. This allows for higher digestion levels of certain biologically refractory and/or biologically inhibitory compounds without requiring proportionally longer hydraulic retention times and sludge retention times, due to the fact those certain biologically refractory and/or biologically inhibitory compounds are retained for extended periods of time on the adsorbent material, which are isolated or retained in the biological reactors.

Generally, biologically labile compounds and certain inorganics will be digested relatively quickly and predominantly by the micro-organisms that are not adhered to the adsorbent material, i.e., the free floating micro-organisms in the mixed liquor. Certain components including organics and inorganics that are entirely resistant to biological decomposition and very refractory biologically refractory and biologically inhibitory compounds will remain adsorbed on the adsorbent material or may be adsorbed and/or absorbed by free-floating biological material in the reactor(s). Ultimately, these non-digestible compounds will concentrate on the adsorbent to the point where the replacement of the adsorbent will be required to maintain the effluent at an acceptable level of adsorptive capacity. As the adsorbent material remains in the system according to the present invention, micro-organisms grow and are retained on the adsorbent material, generally long enough to break down at least certain biologically refractory and/or biologically inhibitory compounds in the particular influent wastewater, which have been concentrated on the adsorbent material. In addition, while not wishing to be bound by theory, it is believed that micro-organisms can eventually evolve into mature strains with specific acclimation necessary to break down the hard-to-treat compounds in the particular influent wastewater. Over additional time, e.g., several days to several weeks, in which adsorbent material having certain biologically refractory and/or biologically inhibitory compounds is maintained in the system, the micro-organisms having a high degree of specificity become second, third, and higher generations, thereby increasing their efficacy to biodegrade at least certain of the specific biologically refractory and/or biologically inhibitory compounds that are present in the particular influent wastewater as the system becomes acclimated. This is depicted by the step change in residual COD depicted in FIG. 14, which shows a plot of feed concentration (in milligrams per liter) of biologically refractory and biologically inhibitory compounds, and the remaining effluent concentrations (as percentages of the original), at various stages of the acclimation of a membrane biological reactor system with adsorbent material added, i.e., stage A that is before adsorbent material is added, stage B that is during the acclimation period, and stage C that is after acclimation.

Various influent wastewaters can be deficient in certain nutrients beneficial to the biology that occurs in the biological reactor 202. Further, certain influent wastewaters can have pH levels that are excessively acidic or caustic. Accordingly, as will be apparent to a person having ordinary skill in the art, phosphorus, nitrogen, and pH adjustment materials or chemicals can be added to maintain optimal nutrient ratios and pH levels for the biological life and associated activity, including biological oxidation, in the reactor 202.

Effluent from the biological reactor 202 is introduced via a separation subsystem 222 to an inlet 210 of the membrane operating system 204. This transferred mixed liquor, having been treated in biological reactor 202, is substantially free of adsorbent material. In the membrane operating system 204, the wastewater passes through one or more microfiltration or ultra-filtration membranes, thereby eliminating or minimizing the need for clarification and/or tertiary filtration. Membrane permeate, i.e., liquid that passes through the membranes 240, is discharged from the membrane operating system 204 via an outlet 212. Membrane retentate, i.e., solids from the biological reactor 202 effluent, including activated sludge, is returned to the biological reactor 202 via a return activated sludge line 214.

Spent adsorbent material from the biological reactor 202, e.g., granular activated carbon that is no longer effective in adsorbing contaminants such as certain compounds entirely resistant to bio-decomposition, biologically refractory compounds and biologically inhibitory compounds, can be removed via a mixed liquor waste discharge port 216 of the biological reactor 202. A waste outlet 218 can also be connected to the return pipe 214 to divert some or all the return activated sludge for disposal, for instance, to control the concentration of the mixed liquor and/or culture. Sludge is discharged from the apparatus with the waste activated sludge when it increases to the point where the mixed liquor solids concentration is so high that it disrupts the operation of the particular membrane biological reactor system. In addition, the mixed liquor waste discharge port 216 can be used to remove a portion of the adsorbent material, thereby removing some portion of the biologically refractory compounds, biologically inhibitory compounds, and/or organic and inorganic compounds that are entirely resistant to biological decomposition, rather than from the return activated sludge line with the waste activated sludge, resulting in a lower concentration of these biologically refractory compounds, biologically inhibitory compounds, and/or organic and inorganic compounds that are entirely resistant to biological decomposition in the discharge and a more stable biomass in the membrane biological reactor. An equivalent quantity of fresh or regenerated adsorbent material can be added.

A preliminary screening and/or separation system 220 can be provided upstream of the inlet 206 of the biological reactor 202. This preliminary screening and/or separation system can include a dissolved air floatation system, a coarse screen or a combination of these and/or other preliminary treatment devices for separating suspended matter of the type known in the art. Optionally, the preliminary screening and/or separation system 220 can be eliminated, or other types of preliminary treatment devices may be included, depending on the particular wastewater being treated.

In order to prevent at least a majority of the adsorbent material 234 from entering the membrane operating system 204 and causing undesirable abrasion and/or fouling of the membranes 240, separation subsystem 222 is provided. As shown, in FIG. 2, the separation subsystem 222 is located proximate the outlet of the biological reactor 202. However, in certain embodiments, the separation subsystem 222 can be positioned in a separate vessel downstream of the biological reactor 202. In either case, the separation subsystem 222 includes suitable apparatus and/or structures for preventing contact between at least a majority of the adsorbent 234 and the membranes 240 in the membrane operating system 204. Separation subsystem 222 can comprise one or more of a screening apparatus, a settling zone, and/or other suitable separation apparatus.

Suitable types of screens or screening apparatus for use in certain embodiments of the present invention include wedge wire screens, metal or plastic apertured plates, or woven fabrics, in cylindrical or flat configurations and arranged at various angles including vertically oriented, horizontally oriented, or at any angle therebetween. In further embodiments, an active screening apparatus can be employed such as a rotating drum screen, vibrating screen or other moving screening apparatus. In general, for systems in which the separation subsystem 222 is a screening apparatus, the mesh size is smaller than the bottom limit of the effective granule or particle size of the adsorbent material that is being used.

Other types of separation subsystems can also be used in the separation subsystem, as alternatives to, or in combination with, a screening apparatus. For instance, as further described below, a settling zone can be provided, in which adsorbent material settles by gravity.

In alternative embodiments, or in conjunction with previously described embodiments, separation subsystems can include a centrifugal system (e.g., hydrocyclone, centrifuge, or the like), an aerated grit chamber, a floatation system (such as induced gas flotation or dissolved gas), or other known apparatus.

Optionally, or in combination with the separation subsystem 222 proximate the outlet of biological reactor 202, a separation subsystem can be provided between biological reactor 202 and the membrane operating system 204 (not shown). This alternative or an additional separation subsystem can be the same as or different as separation subsystem 222, in type and/or dimension. For instance, in certain embodiments, a settling zone, a clarifier, a hydrocyclone separator, a centrifuge, or a combination of these can be provided as a distinct unit operation between biological reactor 202 and membrane operating system 204.

Note that the separation subsystem 222 is highly effective for preventing passage of adsorbent material in its original dimension to the membrane operating system. In certain preferred embodiments, the separation subsystem 222 prevents substantially all of the adsorbent material 234 from passage to the membrane operating system 204. However, during operation of the system 200, various causes of attrition of the adsorbent material, including inter-granule collisions, shearing, circulation, or collisions of granules within stationary or moving equipment, can cause particles to be created that are too small to be effectively retained with the separation subsystem 222. In order to minimize the detriment to the membranes and loss of adsorbent material to wasting, certain embodiments include a separation subsystem 222 that is capable of preventing passage of substantially all of the adsorbent material 234 within about 70 to about 80 percent of its original dimension. The acceptable percentage reduction in the original dimension can be determined by a person having ordinary skill in the art, for instance, based on an economic evaluation. If the reduction in the dimension results in an increase in the particles passing through the screening system, the membranes will experience increased abrasion. Thus, a cost-benefit analysis can be used to determine what is an acceptable percentage reduction of adsorbent material based on the cost of abrasion and eventual replacement of the membranes as compared to the costs associated with adsorbent material that minimizes breakage, and handling and operational costs associated with a separation subsystem capable of preventing passage of particles much smaller than the original adsorbent material granules or particles. In addition, in certain embodiments, some degree of inter-granule collisions, or collisions of granules within stationary or moving equipment, is desirable to strip excess biomass from the outer surfaces of the adsorbent material.

Screened or separated mixed liquor effluent from the biological reactor 202 can be pumped or flow by gravity (depending on the design of the particular system) into the membrane operating system 204. In a system using an external separation subsystem (not shown), the apparatus is preferably configured such that adsorbent material separated from the mixed liquor passing through an external fine screen or separator subsystem falls by gravity back into the biological reactor 202.

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

As the adsorbent material remains in the system and is exposed to wastewater constituents including biologically refractory, biologically inhibitory compounds and/or organic and inorganic compounds that are entirely resistant to biological decomposition, some or all of the adsorbent material will become ineffective for treating the constituents, i.e., the adsorption capacity decreases. This will result in a higher concentration of these constituents entering the membrane operating system 204, where they pass through the membranes, and are discharged with the membrane effluent 212. In addition, adsorbent material can become ineffective due to coating with bacteria, polysaccharides and/or extracellular polymeric substances. This layer of coating can reach levels where it blocks the pore sites and thereby prevents access for biologically refractory, biologically inhibitory and/or organic and inorganic compounds that are entirely resistant to biological decomposition, and consequently prevents adsorption and inhibits biodegradation. In certain embodiments of the present invention, this coating can be removed by a shearing action produced by one or more mechanisms in the system, such as collisions between adsorbent material granules suspended in the mixed liquor or shearing forces associated with suspension and/or movement of the adsorbent material.

When adsorbent material has lost all or a portion of its efficacy for reducing the effluent concentration of biologically refractory, biologically inhibitory and/or organic and inorganic compounds that are entirely resistant to biological decomposition, a portion of the adsorbent material can be wasted via waste port 216, e.g., by discharging a portion of the mixed liquor containing adsorbent material dispersed therein.



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stats Patent Info
Application #
US 20120279920 A1
Publish Date
11/08/2012
Document #
13378209
File Date
06/15/2010
USPTO Class
210631
Other USPTO Classes
210259, 210260, 210202, 210143, 210 962
International Class
02F9/14
Drawings
27


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Liquid Purification Or Separation   Processes   Treatment By Living Organism   And Additional Treating Agent Other Than Mere Mechanical Manipulation (e.g., Chemical, Sorption, Etc.)