Evaluation of high-rate clarification for wet-weather-only treatment facilities. |
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Authors: | Domènec Jolis Meei-Lih Ahmad |
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Institution: | Water Pollution Control Division, San Francisco Public Utilities Commission, California, USA. djolis@sfwater.org |
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Abstract: | High-rate clarification (HRC) processes are well suited for enhanced primary treatment of wet-weather flows in combined sewer systems. Suspended solids removal in excess of 75% of influent concentrations can be achieved consistently. Chemical oxygen demand and five-day biochemical oxygen demand removal are better than 60%. However, although optimal treatment could be achieved in a matter of minutes when the units were started full, a delay of up to one-half hour was observed when the units were started empty. Operational strategies that minimize this effect need to be developed in full-scale tests before HRC processes can be implemented with confidence in wet-weather-only facilities. |
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