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Laboratory study on aerated stabilization basin operation at 3°C Atwater, James Wesley

Abstract

Aerated stabilization basins (ASB), like many other biological treatment systems, demonstrate a temperature dependency. A decrease in treatment efficiency usually results from a decreasing basin temperature and has often been related to a decrease in the reaction rate coefficient, K. This relationship to the reaction rate may well apply for other treatment systems, but it has not been clearly demonstrated for aerated stabilization basins. This study develops data on steady-state performance at 3° C in order to present a coherent reference point for future ASB temperature studies and to define performance characteristics at 3°C. The following performance criteria were documented in the study: 1. Substrate removal in terms of filtered substrate removal. (61 - 80 per cent COD removal and 76 -98 per cent BOD₅ removal for retention times of 1 - 16 days). 2. System treatment efficiency defined in terms of gross effluent COD and BOD₅. (23 - 50 per cent COD removal and 18 - 80 per cent BOD₅ removal for retention times of 1 - 16 days). 3. Net biological solids production (0.25 lbs/lb BODu or COD used). 4. Oxygen utilization requirements (0.123 lbs O₂/ lb COD removed and 0.143 lbs O₂/BOD₅ removed for retention times of 2 - 16 days. Endogenous respiration - 0.75 mg/hr/ gm MLSS). 5. Nitrogen transformation. (A transformation of Kjeldahl nitrogen in the biological solids to NH₃ nitrogen in the filtrate was found apparently as a function of retention time). 6. Post Settling. (One day's aeration with one day settling was found to give equivalent treatment as eight days aeration and one day settling). Data was obtained at two loadings to provide information on the influence of influent concentration on overall performance. Established in the experiment was that any of the common mathematical models used to describe ASB operation, McKinney's, Eckenfelder's, or first-order exponential, could predict system treatment efficiency at 3°C for retention times beyond two to four days. It was further shown that only the Chemostat model would describe the substrate removal measured in the study.

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