Advanced wastewater treatment for potable water reuse typically employs oxidants such as chlorine upstream of membrane processes to reduce biological and organic fouling on membrane surfaces. This oxidation of treated wastewater produces a wide variety of unintended oxidation byproducts, including low molecular weight carbonyl compounds such as formaldehyde and acetaldehyde. Due to their size, charge, and chemical properties, carbonyl compounds can pass through downstream treatment processes (e.g., reverse osmosis and UV/H<sub>2</sub>O<sub>2</sub>) and comprise up to 38% of the ~100 µg/L of organic carbon that remains after advanced wastewater treatment. This could pose a risk to the consumer since many of these compounds are confirmed or suspected carcinogens.  Although carbonyl compounds greatly impact final product water quality, the mechanism by which they are formed from the chlorination of wastewater effluent is not well understood. Previous research has identified tertiary alkylamines as potential precursors; however, these compounds are present at relatively low concentrations (i.e, &lt;5% of the total organic nitrogen). Therefore, they could not singluarly account for the concentrations for formaldehyde and acetaldehyde previously observed in potable water reuse systems. To better understand potential precursors, other model alkylamine compounds, such as methylamine, dimethylamine, trimethylamine, methylethylamine and diethylamine were chosen to react with chlorine. Results show that chlorine readily reacts with these nitrogenous precursors, resulting in high yields of carbonyl compounds under conditions and timescales relevant to the treatment process in potable reuse.

Formation of carbonyl compounds from alcohols in potable water reuse

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ACS Fall 2022

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