Performance of the combined process of up-flow anaerobic sludge blanket (UASB) reactor and cascade sponge reactor (CSR) for sewage treatment was studied. UASB-CSR system was operated at HRTs of 24 h, 16 h, and 8 h at an average wastewater temperature of 29°C. It comprises of the most efficient combined process not only for CODT (98.9%), BODT (98.5%), TSS (99.3%), total nitrogen (89.1%), total phosphorus (99.0%), total coliform (99.9%) and fecal coliform (99.9%) removal but also for reducing excess sludge production. Fecal coliform counts were found 23 MPN/100 ml only in final effluents. The effluent quality of the system sufficiently meets the discharged standards which regulate wastewater discharge into drains. The parameters of CSR are closely related to those of the potable water after certain advanced treatment which can be reused in many ways. Moreover, it does not require any external aeration and thus the cost associated with energy and devices required for aeration are cut to zero.
Keywords: aerobic, cascade sponge reactor, coliforms, post treatment, up-flow anaerobic sludge blanket reactor