Biological Safety Evaluation On Reusing Secondary Effluent From Wastewater Treatment Plant In Landscape Water

During last past years,much attention has been paid to the water quality safety due to the increasing water pollution.The biological toxicity tests have become a promising means for the water quality monitoring,which can intuitively reflect the potential influence of pollutants on ecological environment and human health by the biological toxicity index.Different organisms have different toxic mechanism and responding sensitivity to the toxic pollutants.Developing toxicity test battery can effectively reflect the integrated biological toxicity of all pollutants and evaluate the ecological risk and environmental health effect.First of all,the testing organisms such as invertebrates,algae and bacteria were summarized;the testing methods such as acute and chronic toxicity test,teratogenic and mutagenicity test were comparative analyzed;the evaluation methods and their application in different water bodies such as Potential Ecotoxic Effects Probe,Toxicity Unit Classification System,Water Quality Safety Classification Evaluation and Integrated Biological Responses Method were summarized.Secondly,considering the different toxic mechanism of pollutants in water,three biological toxicity tests were chosen: chlorophy?fluoresence test,SOS/umu test and genetic recombinant yeast test.PNEC of three positive references were deduced according to the Logistic distribution SSD model,121.96 ?g/L,1.18 ?g/L,6.47 ng/L.Then,with the ratio of samples' TEQ and PNEC,toxicity index was defined and the safety grade evaluation was established.Furthermore,health risk assessment of the samples was made to supplement biological water quality safety evaluation method.At last,the water quality of wetland L and wetland T was assessed.The results showed that all of samples of these two wetlands reached Grade B.The acute toxicity equivalent of samples were made non-carcinogenic risk evaluation,genetic toxicity and endocrine disturbance effect equivalent were made carcinogenic risk evaluation.Both health risk value of two wetlands were lower than 10-6/a,the social population acceptable risk value which published by USEPA.Grade of reclaimed water plant origin water and after-coarse filter reached C;the other samples were Grade B.The continuous microfiltration was effective for the removal of genotoxicity.Two risk value of effluent from reclaimed water plant better than the constructed wetland.To sum up,toxicity test battery can provide more comprehensive data for different pollutants.The practical application results of the biological safety evaluation method built in this paper have similarity with other reports in previous study.This method is simple and easy to understand.Therefore,it can be regarded as a research direction of the water quality safety evaluation in the future.