Study On Biological Toxicity Test Method Of Dyeing Wastewater

Textile dyeing industry is one of the most important ecoomic industry in our country, the amount of dyeing discharge is about 1.6×109t every year. Dyeing wastewater are so various and high toxic that the organics in the wastewater are difficult to be degraded efficiently by conventional activated sludge. Due to the assessment of water safety is still conducted by physical and chemical indicators in national and local environmental standard. A part of contaminants which are analyzed expensively exist in environment with low concentration, so it is not convenient by using chemical analysis. Based on the deficiency of analytical method, aquatic organism toxic testing methods are adopted to assess the quality of wastewater, the security guarantee of wastewater can be provided. At present, it is rare that the researches on comprehensive toxic of wastewater are assessed by the methods with many organisms and different experimental period. So the results of acute and chronic tests will be the most beneficial method that the wastewater with toxic effect can be analyzed carefully and the adequate treatment will be adopted to decrease the toxicity in wastewater.On account of the international standard and wide distribution of organisms, Daphnia magna straus and Japanese Medaka are adopted to test the toxicity of dyeing wastewater.Acute toxic experimental period of Daphnia magna straus is 48h, death rate and 50% lethal concentration can be calculated after acute experiment. According to the result of acute toxic experiment, the dilution of experimental solution can be determined in chronic experiment of Daphnia magna straus, experimental period is 14d. The survival rate, reproductive yield, reproduction of first brood, Time of first reproduction and broods of reproduction of Daphnia magna straus can be obtained after chronic experiment. The no observed effect concentration(NOEC) of each indictor are obtained. The toxicity of wastewater can be assessed, the acute and chronic toxicity unit can be calculated by LC50 and NOEC of reproductive yield of Daphnia magna straus.Acute toxic experimental period of Japanese medaka is 96h, death rate and 50% lethal concentration can be calculated after acute experiment. According to the result of acute toxic experiment, the dilution of experimental solution can be determined in chronic experiment of embryo, experimental period is 17d. On the fourteen day, the death rate, hatching rate and hatching time of embryo can be determined. On the seventeen day, the survival rate of juvenile after hatching successfully can be obtained. The no observed effect concentration(NOEC) of each indictor are obtained. The toxicity of wastewater can be assessed, the acute and chronic toxicity unit can be calculated by LC50 of juvenile and NOEC of hatching rate of embryo.The dyeing wastewater are selected to be the testing object in this reseach, Japanese medaka juvenile, embryo and Daphnia magna straus are adopted to test the wastewater with acute and chronic experiment of exposure. Toxic effect which is generated from wastewater to organisms will be assessed by Biological indicators. including the death rate of juvenile and Daphnia magna straus, the hatching rate of embryo and reproductive yield of Daphnia magna straus. The main results which are obtained in this paper are as follow:(1) Sample 2,3,6,9 and 10 have acute toxic effect to Daphnia magna straus. Among these samples, acute toxicity level of sample 9 which is the most significant is moderately toxic, and the acute toxicity unit is 16.23TUa. Sample 2,3,6 and 10 are low toxic, the acute toxicity unit are 1.12,1.01,1.28 and 5.02TUa respectively. In chronic experiments, the sample of no acute toxicity have no chronic toxic effect to Daphnia magna straus. When sample 9 is diluted to 0.05%, its breeding have no significant difference with control(p<0.05), the chronic toxicity unit is 200TUc. After a certain dilution, sample 2,3,6 and 10 also have chronic toxic effect to Daphnia magna straus, the chronic toxicity unit are 8.89,1.37,10 and 40TUc respectively. The acute and chronic experiment of Daphnia magna straus show a good correlation.(2) Sample 3,4,9 and 10 have acute toxic effect to medaka juvenile, sample 9 is moderately toxic, the acute toxicity unit is 9.93TUa. The other samples are low toxic or no toxic, acute toxicity unit are all below 2TUa. In the embryo chronic toxic experiment, the chronic toxicity unit of sample 3,4,9 and 10 are 1.73,2.22,5 and 3.03TUc. Sample 7 have no acute toxic effect to juvenile, but it show significant chronic toxic effect to embryo, no observe effect concentration(NOEC) of hatching rate of embryo is only 2.50%, chronic toxicity unit is 40TUc. Hence juvenile acute toxic experiment can be supplemented by embryo chronic toxic experiment.(3) Two species are adopted to test dyeing wastewater with different life stage and different experimental period, sample 2,3,4,7,9 and 10 have toxic effect to aquatic ecosystem, the others have no toxic effect. A variety of aquatic toxicity testing can assess toxic effect of wastewater and supplement the deficiency of physical and chemical indicators.