Occurrence characteristics and risk assessment of chlorobenzenes in typically wastewater treatment plants from Zhejiang Province
Chlorobenzenes(CBs),a group of chlorinated organic compounds,have been concerned for their high toxicity,poor degradability,and strong ability of accumulation by the public.Wastewater treatment plants(WWTPs)play an important role in controlling the urban water pollution;whereas the research on CBs in WWTPs is extremely limited,reduction trends and emission characteristics of which are still not well-known.This study systematically analyzed the occurrence characteristics,removal efficiency,and potential risks of emission of CBs in different treatment processes of two typical WWTPs in Zhejiang Province.The results showed that CBs presented frequently in the wastewater samples from the WWTPs,but in low pollution levels.Concentrations of CBs in the effluents were in the range 17.4-75.1 ng·L-1,far below the related emission standard of China.Dichlorobenzene was the main component of CBs in the influents and effluents,accounting for 49.3％—64.1％of the total CBs.Anaerobic treatment and sludge adsorption precipitation had relatively good removal efficiency for CBs.However,the existing wastewater treatment processes generally had poor capacities for removing CBs,and some treatment processes were even found an increased effect on CB contents.Based on the evaluation results of ambient severity(AS)and risk quotient(RQ),it was indicated that the human health and ecological environmental impact of CBs in the effluent from the studied WWTPs was relatively low(AS＜1,RQ＜0.1).These findings contribute to a deeper understanding of the environmental behaviors and emission risks of CBs in WWTPs,also provide essential data for optimizing wastewater treatment processes and further controlling and reducing the CBs in wastewater.
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