Trihalomethane Formation during Sludge Bulking Control with Chlorine

Effluent quality implications of bulking control with chlorine in activated-sludge treatment have been studied on laboratory scale. Batch chlorination of sludge samples led to the formation of trihalomethanes, mainly as chloroform (in hundreds of ùg/l) and even more non-specified organohalogens. Most organohalogens were formed from substances in the liquid effluent, and fewer out of the sludge solids. The presence of sludge lowered the concentration of extractable trihalomethanes in the effluent. Continuous chlorination in a laboratory-scale activated-sludge plant did not produce measurable quantities of any organohalogen compounds.