Formation of disinfection byproducts during chlorination of secondary effluent and renovated water

Disinfection byproduct (DBP) formation was studied in nonnitrified and nitrified secondary effluents from several treatment plants and renovated water following soil aquifer treatment. The wastewater was chlorinated using different concentrations of chlorine. The study included formation of trihalomethanes (THM), haloacetic acids (HAA), and total dissolved organic halogens (DOX). In ammonia-con raining effluents (nonnitrified), where stable chloramine is formed, applying a chlorine dose of 0.34 (weight ratio of Cl/C) produced an average ratio of DOX to dissolved organic carbon (DOC) of 8.5 mu g Cl/mg C, and insignificant concentrations of THM and HAA. In nitrified-effluents forming free chlorine residual, a Cl/C dose of 0.34 (weight ratio) yielded an average DOX/DOC of 49 mu g Cl/mg C. The THM formation varied widely with the effluent source and HAA/DOC formation was 2 to 3 mu g Cl/mg C. The DOX formation potential (DOXFP) per mg carbon averaged 28 mu g Cl/mg C for ammonia-containing effluents and 147 mu g Cl/mg C for completely nitrified effluents. The THM formation potential (THMFP) constituted 13 to 56% and HAAFP constituted 10 to 17% of the DOXFP, respectively. The results indicated that high concentrations of DBP are formed during chlorination of effluents, posing a contamination problem. Reduction of DBP formation can be achieved by applying treatment processes producing low-DOC effluents and leaving a small concentration of residual ammonia.