NO3 - Promotes Nitrogen-Containing Disinfection Byproduct Formation in Corroded Iron Drinking Water Pipes

Nitrogen-containingdisinfection byproducts could be promotedby NO3 (-) in corroded iron drinking waterpipes. The coexistence of Fe(II) and iron oxide should be responsiblefor the promotion effect through strengthening Fe-O-Cbonding via pyrrolic N and decreasing Gibbs free energy of NO3 (-) reduction. Nitrogen-containing disinfectionbyproducts (N-DBPs) are highlytoxic DBPs in drinking water. Though, under normal conditions, NO3 (-) could not directly participate in disinfectionreactions to generate N-DBPs, here, we first found that NO3 (-) could promote the formation of N-DBPs in corrodediron drinking water pipes. The coexistence of corrosion produced Fe(II)and iron oxides is a critical condition for the transformation ofN species; meanwhile, most of the newly generated N-DBPs had aromaticfractions. The Fe-O-C bond formed between iron corrosionproducts and natural organic matter promoted electron transfer forthe N transformation with pyrrolic N as the intermediate N species.Density functional calculation confirmed that the coexistence of Fe(II)and iron oxides effectively reduced the Gibbs free energy for NO3 (-) reduction. & UDelta;G ofthe key rate-determining step from NO* to NOH* decreased from 1.55eV on FeOOH to 1.35 eV on Fe(II)+FeOOH. In addition, the large decreaseof cell viability of the water samples from 74.3% to 45.4% furtherconfirmed the formation of highly toxic N-DBPs. Thus, in a drinkingwater distribution system with corroded iron pipes, the low toxicNO(3) (-) may increase toxicity risks viaN-DBP formation.

Automated summary

Nitrogen-containing disinfection byproducts can be promoted by NO3 (-) in corroded iron drinking water pipes through strengthening Fe-O-C bonding and decreasing Gibbs free energy of NO3 (-) reduction.