Occurrence, distribution and risk assessment of phthalate esters in 51 urban wastewater treatment plants in Shaanxi Province, China

Abstract

Wastewater treatment plants (WWTPs) are both a major collection point for phthalate esters (PAEs) and an important point source for their entry into the natural water environment. In this study, we conducted a large-scale investigation on the occurrence, distribution and ecological risk of PAEs in 51 WWTPs in Shaanxi Province, which is located in the north-south transition zone of China. Benzylbutyl phthalate and diisobutyl phthalate were the major compounds in the influent and effluent, respectively, with average concentrations of 32.97 and 18.07 μg/L. However, there was no significant spatial difference in the concentration of PAEs in WWTPs wastewater in different regions of Shaanxi Province. The removal effect of PAEs from wastewater varied with different treatment processes for WWTPs. The anaerobic-anoxic-oxic (A2O) process showed the highest removal efficiency of ∑PAEs, which could reach 89.34 %. A risk quotient (RQ) was used to calculate the ecological risk posed by the PAEs detected in the effluent. Diisobutyl phthalate, dibutyl phthalate, butyl benzyl phthalate, and di(2-ethylhexyl) phthalate pose medium to high ecological risk to receiving waters (RQ = 0.51–3.70). It was estimated that the annual mass load of PAEs discharged to receiving water bodies through WWTPs wastewater in all Shaanxi Province was 32.34 tons.