Research On Biological Toxicity Evaluation Of Drainage Reuse Of Sewage Treatment Plant In Xuanhua District

China is a country with a serious shortage of water resources.Municipal wastewater has more economical advantages than other water sources because of its high emission and availability.Water quality of urban sewage is very complex,which consisted of domestic sewage and industrial wastewater.However,data of chemical analysis could not reflect the overall biological response of pollutants to the ecological ecosystems.In order to decrease the potential harm of reclaimed water to the environment,it is necessary to establish an appropriate toxicity evaluation method for biological toxicity of municipal wastewater.In this study,a battery of acute and inherent toxicity testing approaches was applied to determine adverse effects of influent and effluent samples from Yangfang wastewater treatment plant(WWTP).Results were obtained of acute toxicities of influent and effluent samples on luminescent bacteria Q67,Daphnia magna and Danio rerio,as well as inherent toxicity on the cells of Vicia faba root tip.Moreover,combined with the toxicity test results of different trophic level organisms and the daily treatment capacity of sewage treatment plant to evaluate the potential ecotoxic effects probe(PEEP)of the drainage,and based on evaluation results,suitable suggestions on reuse water for regional were put forward.Furthermore,analysis and toxicity testing were carried out on the suspected toxic substances in drainage.The acute toxicity and genetic toxicity of wastewater significantly decreased compared with the influent water.The toxicity of effluent was decreased by 18.93-69.42%compared with the influent water to luminescent bacteria,which still had moderate toxic effects.The 48 h-EC50 of Daphnia magna in the inlet water ranged between 52.33% and100%.The values of effluent were over 77.49%,which showed slightly toxic effects.The mortality of zebra fish in the influent was 100%,while the effluent did not have significant lethal effect on it.The genotoxicity of the effluent was decreased by 57.14%-75.28%,however,the effluent still showed heavy pollution.There are still significant ecological risks on the drainage of Yangfang WWTP.The PEEP value of the influent water was 5.00-5.20,which showed severely toxic waste water.The PEEP value of the effluent was 4.52-4.69,which showed highly toxic waste water.In order to explore the reuse possibilities of the drainage,dilution with water method and artificial wetland method were proposed to reduce the biological toxicity.The contaminants concentration of PAHs and antibiotics in influent and effluent water of the WWTP were very low,but the effects on organisms were significant.Therefore,PAHs and antibiotics may be the main toxic substances of wastewater.In summary,in order to protect the safety of reclaimed water and reduce its potential harm to the environment,the reuse water must pass the biological toxicity test,and we should establish toxicity management methods and evaluation standards of the drainage.