Removal of carbon and nutrients from low strength domestic wastewater by expanded granular sludge bed-zeolite bed filtration (EGSB-ZBF) integrated treatment concept

The performance of an expanded granular sludge bed (EGSB) reactor coupled with zeolite bed filtration (ZBF) for treating low strength domestic wastewater was monitored at 35 °C for 7 months. The whole operation period of EGSB system was divided into five phases. Each phase ran at up-flow velocity (m/h) of 0.51, 1.02, 3.57, 2.05, 9.69, and hydraulic retention time (HRT) (h) of 6, 3, 0.87, 1.5, 0.32, respectively. The influent chemical oxygen demand (COD) was kept approximate at 150 ± 100 mg/L. Under these conditions, the COD removal efficiency of using EGSB system in five phases reached to 81.08, 57.94, 82.79, 56.58 and 79.52%, respectively. Moreover, since nutrients such as NH4+ and PO43− were only removed to a limited extent by EGSB, additional treatment is required. The ZBF was employed in phase 2 as a post-treatment following EGSB. NH4+ and PO43− concentrations were decreased by 100%, respectively, in the first 2 or 3 d using fresh zeolite. The simple design and excellent treatment performance indicated that this system could be used as a novel Sewage Integrated Treatment System (SITS) for developing country especially in a tropical area.