Effects of pH and Dissolved Organic Matter on the Formation of Disinfection By-Products by Chlorination and Chloramination

A major concern for water utilities is the formation of DBPs resulting from reactions between DOM and disinfectant. THMs and HAAs are the most common and have diverse toxicological effects. The formations of THMs and HAAs by chlorination with chlorine and chloramine at several DOM concentrations and pH's were investigated. Water sample was obtained from Istanbul Omerli Dam, isolated using a laboratory scale membrane system used for chlorination study at different organic matter concentrations. Diluted isolate samples were chlorinated according to UFC protocol. 24 hours after chlorination THM formation was in lower level at acidic pH, whereas at neutral or basic pH, higher concentrations of THMs formed. For all DOC conditions ultimate DBP levels were reached at 24 hours. Chloraminated samples slightly acidic (6) and slightly basic (8) pH resulted in lower THM from neutral pH. HAA formation in pH 6 and 7.2 were equal while lower at pH 8. Despite strong fluctuations ultimate levels were reached in the first 8 hours after chloramination. All formed DBPs except BF were considerably higher in chlorination. Effect of pH in the range of 6 to 8 was approximately the same in both disinfectants. Chloramination completes DBP formation reactions earlier and results in much lower quantities in terms of total THMs and HAAs.