Formation Of Emerging Disinfection By-products During Chlorination Of Reclaimed Water

Formation of emerging disinfection by-products(DBPs), includinghaloacetonitriles(HANs), haloacetamides(HAcAms) and haloketons(HKs) duringchlorination of reclaimed water was investigated. The effect of contact time, chlorinedosages, pH and characters of samples on these DBPs formation was also evaluated.Precursors of these DBPs in the reclaimed water were characterized based onfiltration fractionation and resin fractionation of organic matter. Formation ofdischloroacetonitrile(DCAN), trichloroacetamide(TCAcAm) and1,1,1-TCP followedan increasing and then decreasing pattern, however formation of dischloroacetamide(DCAcAm) was unlike in different samples with prolonged reaction time duringchlorination of two wastewater secondary effluent samples, With the increase ofchlorine dosage, DCAN, DCAcAm and1,1,1-TCP followed a similar pattern, that istheir concentration increased and then decreased or kept constant, but TCAcAmconcentration was increasing. The formation of DCAN and TCAcAm was higher atacid conditions. DCAcAm was higher at alkaline conditions.1,1,1-TCP was relativelylow at alkaline conditions. Samples including more DON and DOC formed moreDCAN and1,1,1-TCP, but samples including more aromatic compounds formedmore DCAcAm and TCAcAm. In reclaimed water, dissolved organic matter(DOM)and particulate matter are precursors of DCAN, at the same time DCAN precursorsrang from all molecule weight. Howerver, DOMs with molecule weight being lessthan1KDa are precursors of DCAcAm and1,1,1-TCP; DOMs with molecule weightranging from1KDa to10KDa are precursors of TCAcAm. After resin fractionation,hydrophobic neutrals is those emerging DBPs main precursor. In addition, aromaticproteins and humic acid are important precursors of DCAN, DCAcAm and TCAcAm;aromatic proteins are precursors of1,1,1-TCP.