Efficiency of sequencing batch reactor (SBR) in the removal of selected microorganisms from domestic sewage

Abstract

The relationships between the loading factor (L.) and BODs, COD, TSS, total coliform, fecal coliform and coliphage removals were explored using three laboratory SBRs receiving a medium-to-low strength domestic sewage. The SBRs were operated with different FILL/REACT ratios in a 6-h cycle. Not unexpectedly results showed that increases in L(i) led to decreases in the removals of BOD5, COD, TSS and potential pathogen indicators. However, low SVIs (Sludge Volume Index) in the SBR need not necessarily mean good solids settleability. Good settleability is, however, necessary for good TSS removal as it led to better removals of total BOD5, total COD and indicators of potential pathogens. During FILL, fermentation reactions probably occurred and this resulted in up to 86% reduction of the initial dissolved BOD5 concentration. Degradation of waste then continued into the REACT period. This preliminary assessment showed that the SBR is, potentially, a viable option for domestic wastewater treatment especially since the aeration time required for treatment to achieve comparable effluent quality is shorter than the conventional continuous activated sludge systems which are usually operated with about 3-8 h of aeration time.