Intrinsic disinfection byproducts in free chlorine and chloramine systems: Formation of chlorite, chlorate, perchlorate, and chloronitramide anion

Intrinsic disinfection byproducts are formed by reactions between disinfectant species and/or their decomposition products. In this review, we focus on a subset that accumulates in free chlorine and chloramine drinking water systems. First, we review the sequential formation of chlorite, chlorate, and perchlorate in hypochlorite feedstocks. Model simulations indicate chlorate and perchlorate can accumulate under realistic dosing conditions and can be managed with less concentrated feedstocks and climate-controlled storage. Second, we review the formation pathways of dichloramine and chloronitramide anion. Chloronitramide anion accumulation may be mitigated by increasing monochloramine stability and quenching reactive nitrogen species in its formation pathway. Highlights • Intrinsic DBPs form by reactions of disinfectants and their decomposition products. • ClO 3 − and ClO 4 − accumulate in concentrated hypochlorite feedstocks. • Hypochlorite feedstock concentration & temperature impact ClO 3 − & ClO 4 − formation. • Cl–N–NO 2 − is a chloramine decomposition end-product. • Enhancing chloramine stability mitigates Cl–N–NO 2 − formation.