Assessment of the potential ecological risk of residual endocrine-disrupting chemicals from wastewater treatment plants
Graphical abstract
Introduction
Endocrine-disrupting chemicals (EDCs) are a diverse range of synthetic and natural compounds that are able to disrupt or alter the functions of the endocrine system and consequently cause adverse health effects in an intact organism. The occurrence of EDCs in aquatic environments has received increasing attention due to their potential long-term adverse effect to humans (Swedenborg et al., 2009) and their negative effects, such as masculinization in females and feminization in males, thyroid disruption and reduction in reproductive success, on organisms living in contaminated aquatic environments (Huang et al., 2019; Jackson and Klerks, 2019; Xu et al., 2019). In addition to the conventional view that EDCs can severely disrupt reproduction (Sifakis et al., 2017), some reports also found that EDCs may be related to the sudden increase in the obesity rate and accompanying increase in other metabolic disease incidences, including that of type-II diabetes (Hatch et al., 2010; Chen et al., 2009). In addition, EDCs can cause disturbance of organisms at a very low concentration; once above the threshold concentration, these compounds may threaten the existence of wildlife. Larsson et al. (1999) found that exposure to estrogen in domestic wastewater affected the rainbow trout's endocrine system, leading to physiological disturbance of massive introduction of vitellogenin. In addition, the bioaccumulation of EDCs has been cited in previous studies (Liu et al., 2012). Thus, it is necessary to assess the underlying threat of released EDCs with environmental risk analysis.
EDCs have been widely detected in various aquatic environments, such as rivers, lakes and estuaries (Komesli et al., 2015; Bolong et al., 2009; Diao et al., 2017). Residual EDCs from domestic wastewater are regarded as one of the major sources of EDCs in aquatic environments (Luo et al., 2014), and they are commonly evaluated according to their amount in influent and their removal efficiencies. Thus, some studies have focused on the occurrence of EDCs in domestic wastewater treatment plants (WWTPs) to evaluate their environmental effects. EDCs have been found in the influent and effluent of WWTPs worldwide in previous publications (Huang et al., 2014; Yu et al., 2013; Ra et al., 2011; Tan et al., 2007; Nakada et al., 2006). For instance, in Japan, nonylphenol (Vieno and Sillanpaa, 2014) was detected at 1008.3 ng L−1 and 307.7 ng L−1 in influent and effluent, respectively (Nakada et al., 2006). Pessoa et al. (2014) found that the highest concentrations of estrone (E1) and β-estradiol (E2) reached 3050 and 3180 ng L−1, respectively. In China, previous studies also indicated the occurrence of EDCs in WWTPs. For example, Huang et al. (2014) reported the occurrence of EDCs in the WWTPs near Dianchi Lake in Yunnan Province, finding that the concentration of NP is 94.0–184.0 ng L−1 in the influent and that 17α-ethynylestradiol (EE2) has a concentration of 6.1–19.9 ng L−1 in the influent. Furthermore, according to previous studies, the removal efficiencies in different WWTPs around the world vary greatly according to their different types of treatment processes (Nguyen et al., 2014; Nguyen et al., 2013; Shi et al., 2010; Baronti et al., 2000; Liu et al., 2009). For instance, Shi et al. (2010) found that >95% of E1, E2 and EE2 could be removed using algae and a duckweed-based wastewater treatment system. However, Baronti et al.'s (2000) work showed that only 61% of E1 was removed following activated sludge treatment in Rome.
Insufficient removal by WWTPs and the subsequent discharge of effluents contribute to the occurrence of EDCs in surface water, and this waterbody might be reused in some production activities, such as by fisheries. Because dissolved EDCs are bioavailable and more difficult to remove than the particle-associated ones, it is necessary to evaluate their removal efficiency and ecological risk after wastewater treatment. Guangdong Province, as one of the most developed provinces in China, has a high population density, resulting in a large amount of pollutants, including EDCs. In addition, fisheries represent one of the most important economic sectors for Guangdong Province, with a total gross output value of 596.99 billion yuan in 2017. Thus, it is suitable to use Guangdong Province as a case study to evaluate the potential ecological risk of residual EDCs from WWTPs and link the potential risk to EDC input and removal efficiencies. This article uses influent and effluent samples collected from 38 WWTPs in Guangdong Province to 1) extrapolate the distribution of dissolved EDCs in Guangdong according to their concentrations in the influent and effluent of WWTPs and 2) quantify the removal efficiency of dissolved EDCs with 4 types of common treatments. Furthermore, the risk quotient (RQ) was used to estimate the potential ecological risk associated with the EDCs released from municipal WWTPs effluents. To the best of our knowledge, this study is the first to report the comprehensive distribution of EDCs from WWTPs in Guangdong Province.
Section snippets
Chemicals and reagents
Nonylphenols (NPs), hexestrol (HEX), diethylstilbestrol (DES), dienestrol (DE), estrone (E1), β-estradiol (E2), 17α-ethynylestradiol (EE2), 4-n-nonylphenol-d4 (4-n-NP-d4), 17α-ethynylestradial-d4 (EE2-d4), chlorobenzene and pyridine were purchased from Sigma-Aldrich (St. Louis, MO, USA). Methanol was purchased from CNW Technologies (Düsseldorf, Germany). Ultrapure water was prepared using a Milli-Q Advantage A10 system (Bedford, MA, USA).
A mixed stock solution of 10 mg L−1 4 EDCs (NPs, E1, E2,
Occurrence and composition profile of target EDCs in influent of 38 WWTP
As shown in Table 1, the detection frequencies of 7 target EDCs were variable across the 38 WWTPs. Some of the target EDCs had a high detection frequency in influent, such as NPs (100%), E1 (92.11%), E2 (76.32%) and EE2 (100%), and the others had a detection rate lower than 50%. High detection occurred in NPs, E1, E2 and EE2. Mean concentrations of NPs and EE2 were 4295.14 ng L−1 and 13.34 ng L−1, respectively, as shown in Table 1. The concentration of EE2 in the influent ranged from 4.96 to
Conclusion
This study investigates the occurrence, removal rate and ecological risk of 7 EDCs from 38 WWTPs around Guangdong. This study indicated that EDCs are widely distributed in WWTPs in Guangdong, while NPs were the predominant target EDCs detected in this study. Although a high removal rate of EDCs has been reported in other articles, the removal rate was found to be quite low when focused on dissolved EDCs, which are bioavailable. The inefficient removal leads to a high concentration of residual
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The National Key Research and Development Program of China (2018YFD0900604), the National Natural Science Foundation of China (No. 21707176, 21677183), the Fundamental Research Funds for the Central Universities (No. 17lgpy67) are gratefully acknowledged. The authors wish to thank all the personnel at the 38 wastewater treatment plants who assisted in wastewater sampling.
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