Occurrence of organophosphate esters and their diesters degradation products in industrial wastewater treatment plants in China: Implication for the usage and potential degradation during production processing

Influent, effluent and sludge samples were collected from eight industrial wastewater treatment plants (WWTPs) in the Pearl River Delta, China. Samples were investigated for the occurrence of 10 organophosphate esters (OPEs) and 7 organophosphate diesters (Di-OPs). Most of the 10 OPEs were detected at total concentrations of OPEs (∑OPEs) ranging from 65.8 to 2842 ng L-1 in influent samples and exhibited different composition profiles. The results indicated that OPEs were widely used with different proportions in versatile OPE-containing products. Meanwhile, ∑OPEs in effluent were found in the range of 6.37-2710 ng L-1; these residuals were subsequently transported to municipal WWTPs for further treatment and posed extra pressure on the plants. Seven Di-OPs, possible degradation products of the OPEs, were also detected in influent, effluent and sludge. The results suggested that OPEs underwent degradation during rigorous industrial manufacturing procedures, such as thermal processes, highly alkaline pH, or processes that involved metal/metal oxide. In addition, high levels of dibutyl phosphate, di(2-ethylhexyl) phosphate and diphenyl phosphate were found in influent suggesting their possible industrial application.