SEQUENCING BATCH REACTOR (SBR) REMOVAL OF TOXICITY FROM COMBINED SEWAGE

Change in light output of Photobacterium phosphoreum was used as a scr eening test for detecting the level of toxicity in clarified sewage, S BR-treated effluent, and mixed liquors. Besides using the 2% and 90% M icrotox screening test protocols, a 45% screening test procedure was d eveloped. Previously reported studies on SBR removal of BOD, COD, TSS and selected microorganisms have shown that effective and stable remov al of these would generally require two or more hours of REACT. This w ould also result in good effluent quality in terms of toxicity. The re moval of toxicants appeared to be due to their adsorption onto the bio mass during FILL followed by their conversion to less- or non-toxic pr oducts and/or the assimilation and accumulation of such toxicants in t he sludge. Some desorption of toxicants was observed during SETTLE. Ef ficient removal of toxicity, in excess of 90%, may be achieved with a REA CT of 1.5 h or more.