Particle size distribution in an effluent from an advanced primary treatment and its removal during filtration

The filtration efficiency of an Advanced Primary Treatment System (APT) was annualized in terms of suspended solids concentration, particle size distribution and helminth eggs counts. A study was carried out on three one-metre deep sand filters with a specific size (ES) of 0.6, 0.8 and 1.2 mm. More than 50 runs were done with operating rate of 7, 10, 12 and 15 m/h. Basic design-related information was obtained for the APT system. A filter with a 1.2 mm ES provided the best effluent, with 0.1 Helminth egg/L. The average suspended solid concentration in the effluent was 39 mg/L. The most recommendable filtration rate was 10 m/h with a run time of 33 h. A study of the particle distribution was made for each step of the process based on size. (C) 1997 IAWQ. Published by Elsevier Science Ltd.