| With the water resources shrinking and fresh water supply increasing,reclaimed water as an important second water source,has received more and more concern.With health awareness raising,reclaimed water safety has been a growing concern.Therefore,health risks assessment for reclaimed water is a matter of great urgency.However,the evaluation indexes of traditional methods are relatively simple,and can not provide comprehensive and systemic information for the health evaluation.With the post-genome era coming,the rapid development of omics methods provide a new idea to systematic evaluation of reclaimed water safety.Under this background,in this study,a typical reclaimed water treatment plant(located in the north area of Yangtze River,Nanjing)was selected.Water samples were collected from each processing unit,including oxidation ditch,coagulation tank,biofilter,and ultraviolet disinfection tank.Trace elements,semi-volatile organic compounds(SVOCs),and nitrogenous disinfection byproducts(N-DBPs)in the water samples were detected respectively.Meanwhile,these water samples were also used for mammalian exposure experiments.After the exposure,omics methods combining transcriptomics and metabolomics were used to reveal the toxic effects of the effluents from each processing unit.Finally,the environmental health assessment methods based on transcriptomics and metabolomics were established for reclaimed water.The primary results are as follows:(1)The general water qualities of effluents from the typical treatment process are in line with national standards and meet the reuse requirements.The results of trace element detection showed that Mn content exceeded in all water samples.Mn can not be effectively removed by the current treatment process.These water samples are not suitable for long-term irrigation.In this study,64 SVOCs and 9 N-DBPs were detected and the results indicated that 61%of SVOCs were not effectively removed.The concentrations of some SVOCs were significantly increased in the final effluent.In addition,6 N-DBPs were also detected in all water samples and the concentrations of some N-DBPs increased with the treatment process.These may lead to increased health risks of reclaimed water.(2)After exposure to reclaimed water for 90 days,the toxicity of effluents from each processing unit was evaluated gradually from the superficial to the mechanism.From tissue and organ levels,health risks were not decreased following the treatment process.ELISA analysis results suggested that water samples from each processing unit could induce oxidative damage.Compared with oxidation ditch effluent,the effluent from UV disinfection could also induce significant oxidative damage.The environmental health assessment methods based on transcriptomics and metabolomics were established and were used to evaluate the toxic effects of reclaimed water samples.The results suggested that the final effluent could induce transcriptomic toxicity and metabolomics toxicity by disrupting the normal function of pathways related to amino acid metabolism,lipid metabolism and energy metabolism.(3)Established omics methods were used to evaluate the toxic effects of new N-DBPs(three haloacetamide).The results suggested that the three haloacetamide could induce oxidative stress in mice and the rank order of iodoacetamide>bromoacetamide>chloroacetamide.In addition,based on significantly changed metabolites and biological pathways,it was found that the three haloacetamide mainly affected the normal function of the amino acid metabolism,energy metabolism,and lipid metabolism,and resulted in metabolic disorders and irreversible damage in mice.(4)The trace organic pollutants could not be removed by the typical treatment process in this study.In addition,disinfection and DBPs caused secondary pollution in the final eluent.As a result,potential health risk still persist in the final effluent.In order to protect the safety of reclaimed water,further measures should be taken to control the contamination of these organic pollutants. |
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