Effect of chlorination on endotoxin activities in secondary sewage effluent and typical Gram-negative bacteria

Wastewater reuse is a viable and attractive method to address water shortage problems. However, wastewater can have high endotoxin activity. Endotoxins are toxic inflammatory agents and are considered a risk factor for wastewater reuse. In this study, the effect of chlorination on endotoxin activity in secondary sewage effluent was evaluated by Limulus (Tachypleus tridentatus) Amebocyte Lysate assay. It was found that chlorination could not decrease endotoxin activity of secondary effluent effectively under the conditions employed in this study. Chlorination of a pure cultured Gram-negative bacterium (Escherichia coli), and a Gram-negative bacterium isolated from secondary sewage effluent, resulted in a significant increase in endotoxin activity, suggesting that the presence of Gram-negative bacteria contributed substantially to endotoxin activity, masking any potential reduction that may be attributable to chlorination. Furthermore, the activities of both free and cell-bound endotoxins in pure culture increased significantly during chlorination due to cell wall damage induced by chlorination.

► Effect of chlorination on endotoxin activity was evaluated by LAL assay.
► Chlorination could not decrease endotoxin activity of secondary effluent effectively.
► Chlorination significantly increased endotoxin activity of pure cultured G− bacteria.
► Free and bound endotoxin activities in pure culture increased after chlorination.
► Chlorination may increase risk of endotoxin in water with a large amount of bacteria.