Effect of oxidation ditch and anaerobic-anoxic-oxic processes on CX3R-type disinfection by-product formation during wastewater treatment

The high chlorine dosages in wastewater treatment plants during the COVID-19 pandemic may result increased formation of disinfection by-products (DBPs), posing great threat to aquatic ecosystem receiving water body and public health downstream area. However, limited information is available on effect biological processes CX3R-type DBPs. This study investigated oxidation ditch (OD) anaerobic-anoxic-oxic (AAO), two widely used processes, five classes DBPs, including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetaldehydes (HALs), haloacetonitriles (HANs) halonitromethanes (HNMs), chlorination. Experimental results showed that effectively reduced dissolved organic carbon (DOC) UV254, while it nitrogen (DON), therefore ratio DON/DOC. In addition, increases contents soluble microbial product- humic acid-like matters, transformation molecular weight (MW) fractions matter into low MW were observed after OD AAO processes. Although decreased Cl-THMs, Cl-HAAs, Cl-HANs Cl-HNMs, DBCM, DBAA, BDCAA, DBCAA, DCAL, TCAL DBAN (where C = chloro, B bromo, D di, T tri) all significantly, due reactivity. Moreover, bromide/DOC bromine incorporation THMs, HAAs DHANs except for HALs THANs. Different from previous studies, this revealed some especially brominated despite efficient removal matters. It provides insights DBP risk control treatment, particularly pandemic.