Toxic Effects Of Typical Industry Wastewater On Daphnia And Fish

At present, the evaluation of industrial wastewater safety is mainly conducted by physical and chemical indicators, but in developed countries, such as Europe and America, toxicity index has been gradually introduced into the evaluation of wastewater, because physical and chemical indicators can not reflect the interaction between all pollutants in the wastewater and the risk to the water ecology. The toxicity (acute toxicity, chronic toxicity and genotoxicity) of industrial wastewater was investigated using two typical aquatic organisms (daphnia and fish) to evaluate the comprehensive biological toxicity of industryial wastewater.(1) Firstly, to clarify the sensitivity of three different types of daphnia, Daphnia magna, Daphnia carinata and Daphnia pulex were used to investigate the toxicity of K2Cr2O7, TBBPA and coking wastewater. The results showed that, the sensitivity order of three daphnia to K2Cr2O7 was D. pulex> D. magna> D. carinata. The sensitivity order of three Daphnia to TBBPA was D. carinata> D. magna> D. pulex. The sensitivity of D. pulex to coking wastewater toxicity was better than those of D. magna and D. carinata. The toxicity response of D. magna to influent and effluent was more distinct in the comparison of wastewater toxicity, thus, D. magna was more suitable as the testing organism in the toxicity comparison of different wastewater. Therefore, D. magna was adopted as the testing daphnia in the following tests.(2) Secondly, D. magna was used in the acute toxicity test to compare the acute toxicity of six typical industrial wastewaters. The results showed that, the toxicity order was acrylonitrile wastewater> pharmaceutical wastewater> printing and dyeing wastewater> pigment wastewater> municipal wastewater> petrochemical wastewater.(3) Thirdly, the toxicity removal efficiency of wastewater treatment process was investigated. Three different toxicity grading wastewater (printing and dyeing wastewater, pigment wastewater and acrylonitrile wastewater) were selected to clarify their acute toxicity effects to D. magna. The results showed that, treatment processes used in actual factories could reduce acute toxicity of industrial wastewater to D. magna effectively, and the removal rates were all higher than 90%. Some parts of treatment process, e.g. anoxic pond and hydrolysis-acidification pond, could increase the toxicity of wastewater while the acute toxicity of final effluents was below the detection limit.(4) On the basis of the acute toxicity test, reproduction toxicity test was used in the further toxicity evaluation of actual industrial wastewater. Printing and dyeing wastewater and acrylonitrile wastewater were selected to be the testing objects to investigate their chronic toxicity to D. magna. The results showed that, the effluents ofprinting and dyeing wastewater and acrylonitrile wastewater had no acute toxicity to D. magna, but still had certain effect on survival and reproduction of the neonatus. High concentrations of acryfonitrile wastewater can cause the increase of mortality and the decline of offsprings number in the next generation.(5) Lastly, Danio rerio was used as testing organism to analysis the actute toxicity and genotoxicity of printing and dyeing wastewater and acrylonitrile wastewater to fish (in the higher level of the aquatic organisms). The results showed that, the anoxic and anaerobic tank increased the toxicity of wastewater to fish and the treatment processes could not reduce the genotoxicity effectively.These findings may provide basic information to the choice of testing organism in bio-toxicity tests of wastewater and the study of aqua-ecosystem risk.