Assessment of endotoxin activity in wastewater treatment plants

Abstract

Endotoxic material, commonly associated to biological reactions, is thought to be one of the most important constituents in water. This has become a very important topic because of the common interest in microbial products governed by the possible shift to water reuse for drinking purposes. In this light, this study was conducted to provide an assessment of endotoxic activity in reclaimed wastewater. A bacterial endotoxin test (LAL test) was applied to water samples from several wastewater treatment plants (WWTP) in Sapporo, Japan keeping in view the seasonal variation. Samples were taken from several points in WWTP (influent, effluent, return sludge, advanced treatment effluent). The findings of this study indicated that wastewater shows high endotoxin activity. The value of Endotoxin (Endo) to COD ratio in the effluent is usually higher than that of the influent. Moreover, it is found that wastewater contains initially endotoxic active material. Some of those chemicals are biodegradable and but most of them are non-biodegradable. Batch scale activated sludge studies were undertaken to understand the origin of endotoxic active material in the effluent. This study showed that those chemicals are mainly produced during biological reactions, more precisely during decay process. Moreover, raw wastewater (RWW) contains high amounts of organic matter having endotoxicity which remains in the effluent.