N-Nitrosodimethylamine (NDMA), an important contaminant for potable reuse of municipal wastewater, forms from reactions of dichloramine and amine precursors. Injection of concentrated free chlorine stock solutions into wastewaters containing low levels of ammonia can promote NDMA formation because the high chlorine:ammonia ratio at the point of chlorine injection fosters dichloramine formation during mixing. This study combined chemical kinetic modeling, laboratory mixing studies using deionized water and authentic wastewater effluents, and a pilot-scale disinfectant contactor at a wastewater reuse facility to demonstrate that the distribution of the injection of concentrated hypochlorite stock solutions can reduce the level of NDMA formation by ≤50% compared to injection at a single location. Modeling and deionized water experiments indicated that this reduction was associated with a reduction in the level of dichloramine formation.
Dieldrin and DDx removal through wastewater treatment, ozonation, and microfiltration was assessed for a water reuse project for groundwater replenishment in Monterey, California, USA. Full-scale sampling was conducted at the wastewater treatment plant, and physical wastewater treatment processes, ozonation, and microfiltration were tested at the bench scale. Removals observed through wastewater treatment, ozonation, and microfiltration were 84%, 44% to 63%, and 97% to 98%, respectively, for dieldrin, and 93%, 36% to 48%, and 92% to 94% for DDx. These were sufficient to meet California Ocean Plan water quality objectives after wastewater treatment alone. Levels in the secondary effluent, ahead of ozonation, microfiltration, reverse osmosis and advanced oxidation in the advanced water purification facility, met drinking water standards. Removal of dieldrin and DDx through wastewater treatment occurred by physical treatment processes; removal through the full-scale wastewater treatment plant, which included biological and physical treatment processes, matched removal through the physical bench-scale wastewater treatment processes. Dieldrin and DDx removal correlated with removal of volatile suspended solids, suggesting that volatile suspended solids could be used as an indicator for pesticide removal through wastewater treatment. Dieldrin and DDx concentrations were highest in the solids contact process, where biomass is accumulated for carbon removal.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.