Abstract

This research aims to assess treatment efficiency of model combined biological activated sludge (BAC) and biological sand filter (BSF) to domestic wastewater after secondary treatment so that reclaimed water quality can be achieved at low or medium level in Ho Chi Minh City. Combined model included BAC filer followed by BSF. The influent is taken from stabilization pond (Binh Hung Hoa wastewater treatment plant: dry season capacity: 28.000 m3/day; rain season capacity: 46.000 m3/day). Characteristic of influent is: color: 227 Pt-Co; COD: 42 mg/l, N-NH3: 11 mg/l, Fecal Coliform: 1,1x103 MPN/100ml. Results showed that it can choose loading of 2 – 3 m/h to BAC-BSF model, efficiency is rather good and stable; capacity is rather high and nitrification and denitrification is occurred well. When BACBSF model is applied to reclaim secondary domestic wastewater, quality of effluent may adapt to some reuse applications with medium level in some parameters such as BOD5, TOC and SS. However, total coliform, color and turbidity is still high. Turbidity and color is caused by mixing of raw wastewater of itself and some textile factories. Therefore, disinfection and supplemental treatment which uses coagulant before entering BSF is necessary. Using ozone followed by BAC may enhance removal efficiency of TOC, color and turbidity..