Several studies highlighted the potential of EOCs
Several studies highlighted the potential of EOCs to promote adverse effects on aquatic organisms. It was reported the toxicity of BPA to invertebrates and fish, and the effect of lipophilicity on toxicity was analyzed (Mathieu-Denoncourt et al., 2016). There was reported the effects of PPCPs on aquatic microorganisms (Smital et al., 2004). But the effects of EOCs on activated sludge microorganisms acting as important roles in municipal sewage treatment plants cannot be deduced from these toxicity studies on mode organisms. Despite of the abundance of PPCP toxicological studies by mode organisms, the toxicological studies of micro-pollutants and the activated sludge (AS) brucine in complex real environmental media was scarce. The growing consumption of EOCs has caused the increases of their concentrations in the treatment plant influent and their levels in biological reactors. For the compound degradation, biological treatment has a broad spectrum of effects. Therefore, the biological treatment method of sewage has been popularized, and the activated sludge method has been especially popularized. However, the presence of emerging EOCs could affect biological treatment effects and sludge activity (Wang et al., 2011; Li et al., 2017). It is worth attention that activated sludge bio-metabolism is closely related to a series of enzyme activities. Urease can catalyze the CN bond of the linear line amide and promote the hydrolysis of peptide bond in organic compounds as a typical acylcoenzymea, i.e. urease can catalyze urea to be broken down into ammonia and CO2. Thus, urease activity plays an important role in the ammonia removal process. In the biological degradation process, dehydrogenase working as main enzyme can transfer hydrogen generated by organic substrate bio-oxidation into microbial respiratory chain, and produce energy to facilitate cellular metabolic and biosynthesis process (Zhu et al., 2012). Invertase is an enzyme that catalyzes the hydrolysis of sucrose into fructose and glucose. It plays an important role in increasing the soluble nutrients in the activated sludge. The function of an enzyme is specific and is a direct reflection of sludge activity (Li and Ryszard, 2006). Therefore the abnormal situation of the sludge activity of the sewage treatment system could be promptly warned by measuring the effect of EOCs on the enzyme activity in the sludge and screening the sensitive indexes affecting the ecological functions of the sludge. Specific micro-pollutants and functional enzymes in activated sludge may have a close relationship. Research of the interaction between them could provide useful clue to predict the systematic risk leading to treatment rates of sewage. By far it has not been found the research of the effect of BPA or PCP on different types of enzyme in activated sludge. Most of the studies have focused on the analysis of single enzyme activity. It has been studied the effects of bisphenol S on lipid hydrolysis and interaction mechanism in sludge through multispectral, thermodynamic and molecular docking analysis (Yang et al., 2017, Yang et al., 2018). But there is no simultaneous comprehensive analysis of multiple enzyme activities. PCP and BPA were selected in view of their widespread occurrence and the well-known negative effects exerted on aquatic organisms (Duan et al., 2008). The test measured the changes of enzyme activity in activated sludge, simulated the different exposure levels of pollutants in the actual environment, and analyzed the systemic risks caused by residual pollutants. This will help to detect and diagnose the abnormalities of the sewage treatment system in a timely manner. The early diagnosis and risk assessment research can be conducted to purposely maintain and repair treatment system, which not only provides a reference for maintaining the stability of the treatment system and ensuring the quality of the effluent but also reduces the cost for system recovery. On the other hand, screening biological indexes more sensitive to PPCPs could provide a foundation for diagnosing and predicting the systemic risk of wastewater treatment and establishing baseline emissions for PPCPs, and a great number of effect data collected will become the solid foundation of the sequence modeling work.