Multiple Biological Effects Detection Methods For Organic Pollutants In Wastewater And Its Application

Biological toxicity tests can directly reflect the toxicity characteristics of pollutants and environmental samples,and have gradually developed into an important supplement to the traditional water quality indexes.In recent years,as human activities intensify,more and more chemicals are both,directly and indirectly,discharged into the water environment,resulting in severe pollution.Because pollutants and wastewater have multiple biological toxicity effects,using a single biological toxicity test is insufficient to reflect its overall toxicity fully.Thus,it is necessary to apply multiple biological testing methods,which requires using many organisms as subjects,to evaluate the toxicity of pollutants comprehensively.Organic ultraviolet?UV?absorbers easily accumulate in sediments and aquatic organisms,mostly due to their high lipophilicity.Most especially,they are difficult to remove by traditional wastewater treatment processes.Thus,organic UV absorbers are frequently detected in the water environment.However,up to now,studies on the toxic effects of organic UV absorbers remain scarce.Moreover,urban sewage discharge is an important source of water pollution.Therefore,there is a need to evaluate the changes in biological toxicity and safety of effluents from various wastewater treatment processes.Such assessments also require the combination of multiple biological testing and water quality safety evaluation methods.Therefore,multiple methods were developed for the detection of biological effects using luminescent bacteria acute toxicity,genetic toxicity,yeast estrogen screen?YES?assay,and zebrafish test.These methods were used jointly for biotoxicity and water environmental safety assessment with the aim of controlling the biological effects of both organic UV absorbers and treated urban wastewater.To evaluate the biological effects of organic UV absorbers,a set of representative benzophenones?BPs?UV filters were selected,namely,benzophenones?BP?,hydroxylbenzophenone?2HB?,2-hydroxy-4-methoxybenzophenone?BP3?and2-hydroxy-4-methory-5-sulfonicacid-benzophenone?BP4?,2-ethyl-hexyl-4-trimethoxycinnamate?EHMC?,para amino-benzoic acid?PABA?,octocrylene?OC?.Subsequently,multiple biological effects testing was carried out to provide a comprehensive evaluation of their toxicities,both in vitro and in vivo.The findings were used to elucidate the biotoxicity characteristics of organic UV absorbers.The influences of function groups on toxicity effects of UV absorbers was also clarified.Furthermore,multiple biological testing for the safety evaluation of discharge from typical urban domestic sewage treatment plants were carried out.Consequently,the changes in biotoxicity in different treatment processes were determined.The main findings of this work are as follows:?1?The acute toxicity and genotoxicity of benzophenones were increased by the functional groups with negative energy on the benzene ring,while the electrondrawing group could reduce the toxicity effect.Moreover,the methoxy?-OCH₃?and sulfonic group?-HSO₃?on the benzene ring can produce space or ion interference,leading to a weakening of estrogenicity.PABA and OC displayed no estrogenicity,possibly due to the amino?NH₂-?and cyan-based?-CN?functional groups,which can reduce the affinity of the compound to estrogen receptors in vitro.The relationship between the octanol partition coefficient?logKow?and toxicity effects was studied for benzophenones.It was found that the luminescent bacteria toxicity and genotoxicity increased with the logKow,presenting a linear correlation,which provides a theoretical basis for the biological toxicity prediction of benzophenones.?2?BP3 and OC did not reflect significant acute toxicity,genetic toxicity and yeast estrogen toxicity effects in vitro.Thus,the zebrafish larvae test involved in multiple hormonal activities were applied to study their toxicities.Through zebrafish larvae experiment by 6 d exposure and RT-qPCR analysis of target genes,it was found that BP3 and OC had multiple endocrine disrupting effects.BP3 showed significant estrogenic activity,anti-estrogenic effect and antiandrogenic effect,while OC displayed obvious androgenic activity and estrogenic activity in zebrafish larvae.Zebrafish larvae experiments made up for the inadequacy of the in vitro tests,revealing the potential harm of UV absorbers to aquatic organisms.?3?Due to its high lipophilicity,OC can easily accumulate in organisms.Therefore,further in-depth studies were carried out on this toxicity effect of OC accumulation using zebrafish.Through chemical analysis,the total body accumulation of OC in zebrafish was found to reach 2321.01?“L”level?,31234.7?“M”level?,and 70593.4ng·g^-1?“H”level?,when the average OC exposure concentration was controlled at 28.61,505.62,and 1248.70?g·L^-1,respectively.Additionally,gross and tissue section microscopic observation of the ovaries were carried out.The gonad-somatic index?GSI?and percentage of vitellogenic oocytes were found to increase significantly in the ovaries of female zebrafish by the high-level accumulation of OC.Moreover,analysis by RT-qPCR showed estrogenic activity,androgenicity and antiandrogenic activity by modulating target gene expression.These effects are closely related to the gender and tissue organs of zebrafish.Therefore,these results indicated that the accumulation of OC had adverse effects on the growth and development of zebrafish.?4?Multiple biological effects detection methods were also used to determine the variation of biological toxicity of wastewater during treatment.The effects of primary precipitation treatment,secondary biological treatment?oxidation ditch,A²/O,etc.?and MBR depth treatment on reducing the acute toxicity of luminescent bacteria,genetic toxicity and estrogen activity were compared.The results show no obvious removal of the above toxicities by the conventional primary physical process.However,the removals of the toxicities of 65%⁸5%were achieved in the secondary biological treatment,and MBR could,especially,enhance the biological toxicity removal.However,the results from YES assay indicated that the effluents treated by MBR still had estrogenic activity.According to the analysis of target genes by RT-qPCR,the treated water concentrated by 2.5 times had an estrogenic effect and antiestrogenic effect on zebrafish.Therefore,although the secondary biological treatment had significant effects on the removal of biological toxicity,the effluent of the sewage plant was still potentially hazardous to aquatic organisms in the receiving water.?5?Based on multiple biological effects detection methods,the toxicity classification method was used to assess the quality of effluents from typical wastewater treatment processes.The results showed that the quality of domestic wastewater was of low toxicity,but after treatment with either an oxidation ditch or A²/O process,the treated water achieved a non-toxic level.When the potential ecotoxicity effects probe?PEEP?index was used to evaluate the toxicity level of urban sewage,the quality was found to be extremely toxic.After treatment with oxidation ditch and A²/O,the treated water was found to be still highly toxic.On the one hand,the application of the water quality safety classification method showed a quality of level C for domestic wastewater after oxidation ditch treatment.On the other hand,after an A²/O process treatment,the effluent quality was found to improve to level B.Overall,the dominant factor affecting the water quality is the acute toxicity of luminescent bacteria.Therefore,to protect the environmental and ecological safety of receiving waters,it is necessary to adopt multiple biotoxicity tests to evaluate the quality safety of wastewater treatment plant effluents.