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Tertiary Treatment Quality For A Secondary System Utilizing the Zurn-Attisholz Process RUDY VAN SOEST, Vice President GUATAM DAS, Process Engineer Van Luven Consultants, Limited Montreal, Quebec, Canaca INTRODUCTION It is becoming more obvious each year that the world's social and environmental problems are increasing and the cost of correcting these problems is becoming more and more difficult to bear. The treatment of domestic and industrial waste has become one of the most urgent problems of our time. For several years, scientists in Europe and elsewhere have sought to reduce the cost of biological treatment processes by employing very high loading rates (400 to 800 pounds of BOD versus 50-75 pounds per 1000 cubic feet of aeration tank capacity, employed in conventional activated sludge plants). To date, it is our feeling that certain modifications of this process offer not only low operational and capital costs, but also can produce effluent quality capable of meeting requirements of the regulatory agencies. With reduced land requirements and construction costs through reduction in tankage requirements, the high rate system can compete economically with most every alternative means of treatment, perhaps with the exception of lagoons. In general, for high rate systems, the reduction in volume results in a reduction in sludge age and hence, a worsening in settling characteristics. A preliminary consideration pf high rate systems then indicates a feasible decrease in aeration tankage, but only at the expense of larger secondary clarification tankage and/ or chemical addition. U nless the environment is then altered in some way to produce a settling floe (e.g. usage of oxygen and/or other means of selective acclimatization of cultures). Thus, settling properties alone can become a limitation. Despite predictions of poor settleability, several high rate processes have been developed and reviewed (1,2): (Step Aeration, Kraus Process, Biosorption, Contact Stabilization, Unox Process and the Zurn-Attisholz Process). Combinations of high-rate trickling filters and activated sludge has also been considered (3,4). Each is capable of providing BOD removals in excess of 85 percent. Others providing slightly less efficient treatment include Activated Aeration, Modified Aeration and Supra-Activation. The Zurn-Attisholz Process makes use of an interesting application of the two-stage activated sludge process. Two high-rate stages are employed, the first utilizing a mixed culture predominant in bacteria and lower fungi, and the second stage, a culture predominant in protozoan microorganisms. Although the first stage bacteria may form dispersed growths that cannot be easily settled from water, solids carried over from the first stage clarifier are readily consumed as food by the protozoa. The protozoa, in turn, are about 1000 times larger than bacteria and can be readily settled from the water in a second stage clarifier. With the definite application of multiple stage systems for removal of color, phosphorous and nitrogen (5,6,7,8,9) and the stability of the system relative to other activated sludge systems, Van Luven Consultants Limited have taken considerable interest in this process. 483
Object Description
Purdue Identification Number | ETRIWC197342 |
Title | Tertiary treatment quality for a secondary system utilizing the Zurn-Attisholz Process |
Author |
Van Soest, Rudy Das, Guatam |
Date of Original | 1973 |
Conference Title | Proceedings of the 28th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://earchives.lib.purdue.edu/u?/engext,23197 |
Extent of Original | p. 483-495 |
Series | Engineering extension series no. 142 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Date Digitized | 2009-06-02 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 483 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | Tertiary Treatment Quality For A Secondary System Utilizing the Zurn-Attisholz Process RUDY VAN SOEST, Vice President GUATAM DAS, Process Engineer Van Luven Consultants, Limited Montreal, Quebec, Canaca INTRODUCTION It is becoming more obvious each year that the world's social and environmental problems are increasing and the cost of correcting these problems is becoming more and more difficult to bear. The treatment of domestic and industrial waste has become one of the most urgent problems of our time. For several years, scientists in Europe and elsewhere have sought to reduce the cost of biological treatment processes by employing very high loading rates (400 to 800 pounds of BOD versus 50-75 pounds per 1000 cubic feet of aeration tank capacity, employed in conventional activated sludge plants). To date, it is our feeling that certain modifications of this process offer not only low operational and capital costs, but also can produce effluent quality capable of meeting requirements of the regulatory agencies. With reduced land requirements and construction costs through reduction in tankage requirements, the high rate system can compete economically with most every alternative means of treatment, perhaps with the exception of lagoons. In general, for high rate systems, the reduction in volume results in a reduction in sludge age and hence, a worsening in settling characteristics. A preliminary consideration pf high rate systems then indicates a feasible decrease in aeration tankage, but only at the expense of larger secondary clarification tankage and/ or chemical addition. U nless the environment is then altered in some way to produce a settling floe (e.g. usage of oxygen and/or other means of selective acclimatization of cultures). Thus, settling properties alone can become a limitation. Despite predictions of poor settleability, several high rate processes have been developed and reviewed (1,2): (Step Aeration, Kraus Process, Biosorption, Contact Stabilization, Unox Process and the Zurn-Attisholz Process). Combinations of high-rate trickling filters and activated sludge has also been considered (3,4). Each is capable of providing BOD removals in excess of 85 percent. Others providing slightly less efficient treatment include Activated Aeration, Modified Aeration and Supra-Activation. The Zurn-Attisholz Process makes use of an interesting application of the two-stage activated sludge process. Two high-rate stages are employed, the first utilizing a mixed culture predominant in bacteria and lower fungi, and the second stage, a culture predominant in protozoan microorganisms. Although the first stage bacteria may form dispersed growths that cannot be easily settled from water, solids carried over from the first stage clarifier are readily consumed as food by the protozoa. The protozoa, in turn, are about 1000 times larger than bacteria and can be readily settled from the water in a second stage clarifier. With the definite application of multiple stage systems for removal of color, phosphorous and nitrogen (5,6,7,8,9) and the stability of the system relative to other activated sludge systems, Van Luven Consultants Limited have taken considerable interest in this process. 483 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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