Process for the purification of waste water
First Claim
1. In the activated sludge process wherein a first stage contaminated water containing less than about 20 ppm of hydrocarbons and less than about 20 ppm of solids is contacted with activated sludge for a period of time sufficient to biologically degrade contaminents in the water and in a second stage decontaminated water is separated from the activated sludge, a first portion of said separated sludge being recycled for recontact with the water in the first stage and a second portion of said separated sludge being treated in downstream operations, the improvement comprising:
- introducing oxygen into the water and sludge mix entering the second stage so that the sludge in the second zone is maintained in an aerobic state and separated decontaminated water from said second stage contains at least about 3 parts of dissolved oxygen per million parts of water.
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Abstract
Disclosed is a continuous process for purifying contaminated waste water. First the water passes through an equalization zone including at least two separate compartments, in one of which the pH of the water is adjusted to a range of from about 6.5 to 9.5. The water flows through the separate compartments such that the concentration of contaminants in the water exiting the equalization zone will approach about constant concentration which changes only gradually even though influent contaminant concentration changes rapidly. Water in at least one compartment of the equalization zone is aerated so that the dissolved oxygen in the water is at least three parts of dissolved oxygen per million parts of water. Solids are skimmed from the surface of the water in the zone, and coagulant is added to the effluent water from the equalization zone so that colloidal particles in the water flocculate. The water from this equalization zone is then filtered to remove flocculated particles. The effluent from the filter will preferably have less than about ten parts of suspended solids per million parts of water and/or less than about ten parts of oil and grease per million parts of water. This effluent is aerated, preferably by aspiration, and is treated in a four stage biological treating zone. In the first stage, the water contacts an activated sludge which decontaminates the water by biodegrading contaminants. In the second stage, water from the first stage is clarified to separate suspended sludge particles from decontaminated water. The bulk of the separated sludge particles is recycled to the first stage, and the bulk of the clarified, decontaminated water is withdrawn. In the third stage, that portion of the separated sludge particles not recycled is concentrated by removing additional residual water. In the fourth stage, the concentrated sludge particles are digested. In accordance with an important feature of our invention, the water-sludge mix as it flows between the first and second stages is aerated by aspirating air into the water-sludge mix and then subjecting this mix to a high hydrostatic pressure. Preferably the sludge flowing between the second, third and fourth stages is also aerated. The water separated from the second stage is filtered to remove any minute suspended sludge particles which may be present. The preferred filter medium is sand or combinations of sand and coal, and may be followed by treatment with activated carbon. Interstage aeration is conducted at pressures above atmospheric. This ensures substantial transfer of oxygen to the water. Also, activated sludge from the third and fourth stages may be recycled to the activated sludge-water mixture that exited the first stage. The average age of the sludge in the system is greater than ten days. The dissolved oxygen concentration in the water flowing into the second stage clarifier is at least about five parts of dissolved oxygen per million parts of water.
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Citations
74 Claims
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1. In the activated sludge process wherein a first stage contaminated water containing less than about 20 ppm of hydrocarbons and less than about 20 ppm of solids is contacted with activated sludge for a period of time sufficient to biologically degrade contaminents in the water and in a second stage decontaminated water is separated from the activated sludge, a first portion of said separated sludge being recycled for recontact with the water in the first stage and a second portion of said separated sludge being treated in downstream operations, the improvement comprising:
introducing oxygen into the water and sludge mix entering the second stage so that the sludge in the second zone is maintained in an aerobic state and separated decontaminated water from said second stage contains at least about 3 parts of dissolved oxygen per million parts of water. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of pretreating waste water including from about 25 to about 150 parts per million of solids per million parts of water and/or from about 25 to about 300 parts of hydrocarbons per million parts of water upstream of activated sludge treatment comprising, passing the water through an equalization zone including at least two separate water retention compartments in series so that the water is mixed in each compartment and flows from one compartment to the next compartment and a given quantity of water is retained for predetermined period in each of said compartments.
introducing air into the water in at least one of the compartments so that the water in the compartment is vigorously agitated and the effluent in the aerated compartment includes at least three parts of dissolved oxygen per million parts of water, adjusting the pH of the water in the equalization zone so that the pH of the water in one of the compartments and in the effluent from said zone ranges between about 6.5 and about 9.5, destabilizing colloidal particles suspended in the water, and filtering the effluent water from the equalization zone so that said filtered water includes no more than about twenty parts of hydrocarbons per million parts of water and no more than about twenty parts of suspended solids per million parts of water.
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25. A continuous process for purifying contaminated water including solids and/or hydrocarbons, comprising:
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(a) passing the water through an equalization zone where the pH of the water is adjusted to a range from about 6.5 to 9.5 and the contaminated water is distributed in a larger body of water so that the changes in concentration of contaminants in the effluent water to the equalization zone will produce gradual changes in concentration of contaminants in effluent water from said zone, (b) aerating the water in the equalization zone so that the dissolved oxygen in the water is at least about three parts of dissolved oxygen per million parts of water, (c) adding a destabilizing agent to the water so that colloidal particles in the water aggregate, (d) passing the water from the equalization zone through a filter so that particles and hydrocarbons removed therefrom and the effluent from the filter will have less than about twenty parts of suspended solids per million parts of water and less than about twenty parts of hydrocarbons per million parts of water, (e) passing effluent from the filter through a multi-stage biological treating zone having a first stage where the water flows into a contact zone and contacts an activated sludge which decontaminates the water by biodegradation of contaminants, a second stage where the water from the first stage is clarified to separate suspended sludge particles from decontaminated water, a portion of said separated sludge particles being recycled to the first stage and the bulk of the clarified decontaminated water being withdrawn from the second stage, a third stage where that portion of the separated sludge particles not recycled are concentrated by removing the bulk of the residual water therefrom, and a fourth stage where said concentrated sludge particles are digested. (f) aspirating air into the water and sludge mix as it flows between the first and second stages, so that the sludge in the second stage is maintained in an aerobic stage and clarified water from said second stage contains at least about three parts of dissolved oxygen per million parts of water, and (g) filtering separated water withdrawn from the second stage to remove minute suspended sludge particles not separated from this water in said second stage. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. An improved multiple-stage activated sludge process wherein the average age of the activated sludge in the biological zone exceeds ten days comprising
pretreating the contaminated water so that it contains no more than about 20 parts of hydrocarbons per million parts of water and no more than about 20 parts of suspended solids per million parts of water, contacting said pretreated water with activated sludge in the first stage for a period of time sufficient to biologically degrade contaminants in the water, introducing oxygen into the water and sludge mix entering the second stage so that the sludge in the second stage is maintained in an aerobic state and separated decontaminated water from said second stage contains at least about 5 ppm dissolved oxygen. separated decontaminated water from the activated sludge in the second stage and recycling a first portion of said separated sludge for recontact with the water in the first stage, and treating a second portion of said separated sludge in downstream operations.
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41. In the activated sludge process wherein a first stage contaminated water is contacted with activated sludge for a period of time sufficient to biologically degrade contaminants in the water and in a second stage decontaminated water is separated from the activated sludge, a first portion of said separated sludge being recycled for recontact with the water in the first stage and a second portion of said separated sludge being treated in downstream operations, the improvement comprising:
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reducing the level of contaminants in the contaminated water to the first stage to less than about 20 ppm of hydrocarbons and less than about 20 ppm of solids; and introducing oxygen into the water and sludge mix entering the second stage so that the sludge in the second zone is maintained in an aerobic state and separated decontaminated water from said second stage contains at least about 3 parts of dissolved oxygen per million parts of water. - View Dependent Claims (42)
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- 43. In a multi-stage activated sludge process wherein a first stage contaminated water is contacted with activated sludge for a period of time to biologically contaminants in the water and in a second stage decontaminated water from the first stage is separated from the activated sludge, the improvement comprising filtering the contaminated water prior to the first stage to reduce the level of oil and grease, and solids so that the waste water to the first stage has less than about 20 ppm of oil and grease and less than about 20 ppm of solids.
- 45. In a multi-stage activated sludge process wherein a first stage contaminated water is contacted with activated sludge for a period of time to biologically degrade contaminants in the water and in a second stage decontaminated water is separated from the activated sludge, the improvement comprising reducing the oil and grease, and solids content of the waste water to less than about 20 ppm oil and grease and less than about 20 ppm solids, prior to the first stage.
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47. In an activated sludge process wherein a first stage contaminated water is contacted with activated sludge for a period of time to biologically degrade contaminants in the water and in a second stage decontaminated water from the first stage is separated from the activated sludge, the improvement comprising maintaining the average sludge age in the first and second stages in excess of about ten days and treating the waste water to reduce oil and grease, and solids to less than about 20 ppm oil and grease and less than about 20 ppm solids, prior to the first stage.
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48. In the activated sludge process wherein a first stage contaminated water containing less than about 10 ppm of hydrocarbons and less than about 10 ppm of solids is contacted with activated sludge for a period of time sufficient to biologically degrade contaminants in the water and in a second stage decontaminated water is separated from the activated sludge, a first portion of said separated sludge being recycled for recontact with the water in the first stage and a second portion of said separated sludge being treated in downstream operations, the improvement comprising
introducing oxygen into the water and sludge mix entering the second stage so that the sludge in the second zone is maintained in an aerobic state and separated decontaminated water from said second stage contains at least about 5 parts of dissolved oxygen per million parts of water.
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59. A method of pretreating waste water including from about 25 to about 150 parts per million of solids per million parts of water and from about 25 to about 300 parts of hydrocarbons per million parts of water upstream of activated sludge treatment comprising, passing the water through an equalization zone including at least two separate water retention compartments in series so that the water is mixed in each compartment and flows from one compartment to the next compartment and a given quantity of water is retained for predetermined period in each of said compartments,
introducing air into the water in at least one of the compartments so that the water in the compartment is vigorously agitated and the effluent in the aerated compartment includes at least three parts of dissolved oxygen per million parts of water, adjusting the pH of the water in the equalization zone so that the pH of the water in one of the compartments and in the effluent from said zone ranges between about 6.5 and about 9.5, destabilizing colloidal particles suspended in the water, and filtering the effluent water from the equalization zone so that said filtered water includes no more than ten parts of hydrocarbons per million parts of water and no more than ten parts of solids per million parts of water.
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65. A continuous process for purifying contaminated water including solids and hydrocarbons, comprising
(a) passing the water through an equalization zone where the pH of the water is adjusted to a range from about 6.5 to 9.5 and the contaminated water is distributed in a larger body of water so that the changes in concentration of contaminants in the effluent water to the equalization zone will produce gradual changes in concentration of contaminants is effluent water from said zone, (b) aerating the water in the equalization zone so that the dissolved oxygen in the water is at least about three parts of dissolved oxygen per million parts of water, (c) adding a destabilizing agent to the water so that colloidal particles in the water aggregate, (d) passing the water from the equalization zone through a filter so that particles and hydrocarbons removed therefrom and the effluent from the filter will have less than about ten parts of suspended solids per million parts of water and less than about ten parts of hydrocarbons per million parts of water, (e) passing effluent from the filter through a multi-stage biological treating zone having a first stage where the water flows into a contact zone and contacts an activated sludge which decontaminates the water by biodegradation of contaminants, a second stage where the water from the first stage is clarified to separate suspended sludge particles from decontaminated water, a porton of said separated sludge particles being recycled to the first stage and the bulk of the clarified decontaminated water being withdrawn from the second stage, a third stage where that portion of the separated sludge particles not recycled are concentrated by removing the bulk of the residual water therefrom, and a fourth stage where said concentrated sludge particles are digested, (f) aspirating air into the water and sludge mix as it flows between the first and second stages, so that the sludge in the second stage is maintained in an aerobic state and clarified water from said second stage contains at least about five parts of dissolved oxygen per million parts of water, and (g) filtering separated water withdrawn from the second stage to remove minute suspended sludge particles not separated from this water in said second stage.
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74. An improved multiple-stage activated sludge process wherein the average age of the activated sludge in the first and second stages exceeds ten days comprising
pretreating the contaminated water so that it contains no more than 10 parts of hydrocarbons per million parts of water and no more than 10 parts of solids per million parts of water, contacting said pretreated water with activated sludge in the first stage for a period of time sufficient to biologically degrade contaminants in the water, introducing oxygen into the water and sludge mix entering the second stage so that the sludge in the second stage is maintained in an aerobic stage and separated decontaminated water from said second stage contains at least 5 ppm dissolved oxygen, separating decontaminated water from the activated sludge in the second stage and recycling a first portion of said separated sludge for recontact with the water in the first stage, and treating a second portion of said separated sludge in downstream operations.
Specification