Activated sludge wastewater treatment system and method

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Activated sludge wastewater treatment system and method Abstract A improved activated sludge system and method for treating wastewater containing contaminants is disclosed which offers a broad array of advantages over conventional activated sludge wastewater treatment systems, including smaller size, higher rates of operation, higher oxygen transfer efficiency, lower operating costs, and a substantially decreased level of excess sludge production. The improved activated sludge waste treatment system of the present invention has two processing tanks rather than the several tanks that are commonly found in activated sludge systems for treatment and sludge management equalizations, including anaerobic processes. The first processing tank is a contact tank which hosts a reaction which functions not merely to digest the maximum amount of contaminants, but instead to bind contaminants to the microorganisms through absorption, adsorption, precipitation, or digestion so that they can then be removed from the liquid in a solid/liquid separator. The activated sludge removed by the solid/liquid separator is then supplied to a digester tank containing a high concentration of activated sludge, where virtually complete digestion is achieved to minimize the volume of solids remaining. Activated sludge is provided from the digester tank to the contact tank to facilitate the reaction in the contact tank. 1. A waste processing system for removing contaminants from a wastewater stream, comprising: a first container having wastewater from said wastewater stream admitted thereinto, activated sludge being introduced into said first container to react with said wastewater contained therein to cause said contaminants to bind to microorganisms contained in said activated sludge; a solid/liquid separator for receiving said wastewater containing said contaminants bound to said microorganisms from said first container, said solid/liquid separator having as a first output wastewater from which said contaminants bound to said microorganisms have been removed, said solid/liquid separator also having as a second output an activated sludge including said contaminants bound to said microorganisms; and a second container for receiving said activated sludge including said contaminants bound to said microorganisms from said solid/liquid separator, said second container containing a sufficiently high concentration of activated sludge to ensure substantially complete digestion of said contaminants, said activated sludge in said second container comprising the source of said activated sludge which is introduced into said first container. 2. A waste processing system as defined in claim 1, wherein the concentration of activated sludge solids in said first container is between approximately 200 and 10,000 milligrams per liter. 3. A waste processing system as defined in claim 2, wherein the concentration of activated sludge solids in said first container is approximately 1,500 milligrams per liter. 4. A waste processing system as defined in claim 1, additionally comprising: apparatus for introducing an electron donor substance into at least one of said first container and said second container. 5. A waste processing system as defined in claim 4, wherein said electron donor is oxygen. 6. A waste processing system as defined in claim 4, wherein said electron donor is compressed air containing oxygen. 7. A waste processing system as defined in claim 6, wherein said apparatus for introducing comprises: a compressor pump which provides compressed air to said first container. 8. A waste processing system as defined in claim 4, wherein said apparatus for introducing comprises: first apparatus for introducing an electron donor substance into said first container; and second apparatus for introducing an electron donor substance into said second container. 9. A waste processing system as defined in claim 1, additionally comprising: mixing apparatus to mix a mixture contained in at least one of said first container and said second container. 10. A waste processing system as defined in claim 9, wherein said mixing apparatus comprises: a mechanical mixer to continually circulate the mixture contained in said at least one of said first container and said second container. 11. A waste processing system as defined in claim 9, wherein said mixing apparatus comprises: a pump to continually circulate the mixture contained in said at least one of said first container and said second container. 12. A waste processing system as defined in claim 9, wherein said mixing apparatus comprises: first mixing apparatus to mix the mixture contained in said first container; and second mixing apparatus to mix the mixture contained in said second container. 13. A waste processing system as defined in claim 1, wherein the concentration of activated sludge solids in said second container is between approximately 5,000 and 100,000 milligrams per liter. 14. A waste processing system as defined in claim 13, wherein the concentration of activated sludge solids in said second container is approximately 40,000 milligrams per liter. 15. A waste processing system as defined in claim 1, wherein the volume of said second container is substantially larger than the volume of said first container. 16. A waste processing system as defined in claim 1, additionally comprising: a valve to control the flow of wastewater from said wastewater stream into said first container. 17. A waste processing system as defined in claim 16, additionally comprising: a valve to control the flow of said wastewater containing said contaminants bound to said microorganisms from said first container to said solid/liquid separator. 18. A waste processing system as defined in claim 1, wherein said solid/liquid separator comprises: a dissolved air flotation system. 19. A waste processing system as defined in claim 1, additionally comprising: a pump to pump said activated sludge including said contaminants bound to said microorganisms from said solid/liquid separator to said second container. 20. A waste processing system as defined in claim 1, additionally comprising: a valve to control the flow of said activated sludge from said second container to said first container. 21. A waste processing system as defined in claim 1, additionally comprising: a pump for removing a portion of the contents of said second container if and when the level of inert solids contained in said second container builds up to the point where said activated sludge is unduly reduced in strength, the remaining contents of said second container then being diluted by adding wastewater from said wastewater stream. 22. A waste processing system as defined in claim 21, additionally comprising: a valve to control the flow of wastewater from said wastewater stream into said second container to dilute the contents thereof. 23. A waste processing system as defined in claim 1, additionally comprising: apparatus for introducing a first conditioner into at said first container. 24. A waste processing system as defined in claim 23, wherein said first conditioner comprises: a chemical to adjust the level of pH in said first container. 25. A waste processing system as defined in claim 23, wherein said first conditioner comprises: a surfactant to improve the reaction process in said first container. 26. A waste processing system as defined in claim 1, wherein said apparatus for introducing said first conditioner is controlled to maintain the pH in said first container between approximately four and eleven. 27. A waste processing system as defined in claim 26, wherein said apparatus for introducing said first conditioner is controlled to maintain the pH in said first container between approximately 6.5 and 8.5. 28. A waste processing system as defined in claim 26, wherein said apparatus for introducing said first conditioner comprises: a pump for pumping said first conditioner into said first container. 29. A waste processing system as defined in claim 1, additionally comprising: apparatus for introducing a second conditioner into at said second container. 30. A waste processing system as defined in claim 29, wherein said apparatus for introducing said second conditioner is controlled to maintain the level of said second conditioner at a level which facilitates and enhances the efficiency of digestion. 31. A waste processing system as defined in claim 30, wherein said second conditioner comprises a nitrogen-based nutrient. 32. A waste processing system as defined in claim 30, wherein said second conditioner comprises: a second strain of microorganisms to consume any microorganisms which may have died. 33. A waste processing system as defined in claim 29, wherein said second conditioner comprises: a surfactant to improve a reaction process in which substantially complete digestion of contaminants occurs. 34. A waste processing system as defined in claim 29, wherein said second conditioner is added to said wastewater containing said contaminants bound to said microorganisms from said first container, with the resulting mixture being fed into said solid/liquid separator. 35. A waste processing system as defined in claim 29, wherein said second conditioner comprises: a chemical flocculent material which causes solids to clump together. 36. A waste processing system as defined in claim 35, wherein said chemical flocculent comprises: a cationic emulsion polymer. 37. A method of removing contaminants from a wastewater stream, comprising: admitting wastewater from said wastewater stream into a first container; introducing activated sludge into said first container to react with said wastewater admitted into said first container to cause said contaminants to bind to microorganisms contained in said activated sludge; directing said wastewater previously admitted into said first container and containing said contaminants bound to said microorganisms into a solid/liquid separator having as a first output wastewater from which said contaminants bound to said microorganisms have been removed, said solid/liquid separator also having as a second output an activated sludge including said contaminants bound to said microorganisms; and providing said activated sludge including said contaminants bound to said microorganisms from said solid/liquid separator into a second container containing a sufficiently high concentration of activated sludge to ensure substantially complete digestion of said contaminants, said activated sludge in said second container comprising the source of said activated sludge which is introduced into said first container. 38. An aerobic, anaerobic, anoxic, or multiple aeration mode method of removing contaminants contained in a wastewater stream, comprising: admitting wastewater from said wastewater stream into a contact tank; introducing activated sludge containing microorganisms into said contact tank to react with said wastewater admitted into said contact tank to cause said contaminants to bind to said microorganisms contained in said activated sludge; aerating and mixing the contents of said contact tank; directing said wastewater previously admitted into said contact tank and containing said contaminants bound to said microorganisms into a solid/liquid separator having as a first output wastewater from which said contaminants bound to said microorganisms have been removed, said solid/liquid separator also having as a second output an activated sludge including said contaminants bound to said microorganisms; providing said activated sludge including said contaminants bound to said microorganisms from said solid/liquid separator into a digester tank containing a sufficiently high concentration of activated sludge to ensure substantially complete digestion of said contaminants, said activated sludge in said digester tank comprising the source of said activated sludge which is introduced into said contact tank; and aerating and mixing the contents of said digester tank. Description BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates generally to the field of treatment of wastewater, and more particularly to an improved system and method for treating wastewater containing contaminants which system and method offer a broad array of advantages over conventional activated sludge wastewater treatment systems, including smaller size, higher rates of operation, high oxygen transfer efficiency, lower operating costs, and a decreased level of excess sludge production. With an increased awareness of problems with water quality, particularly those caused by the discharge of wastewater from industrial sources, has come a demand for improved equipment and methods to treat wastewater prior to discharging it into a sewer, as surface
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water, or to other destination for effluent discharge. While such treatment systems and methods are generally not required to produce potable water, they are increasingly required by law to enhance the quality of wastewater prior to discharging it as effluent. For industrial waste, this treatment process must typically remove certain type of pollutants such as organic contaminants, nitrogen and phosphorus, metals, and suspended solids. The first wastewater treatment systems were of simple design, with a single container or tank being used for both treatment of the wastewater and the removal of solids from the wastewater, typically by allowing them to ...

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