Toxicity Characterization Of Typical Chemical Wastewaters And Receiving River

Numerous chemical industry enterprises are located in the region along the Liao River, and the chemical industry wastewater has potentially negative effects on the aquatic ecosystem and human health. The presence of multiple pollutants in wastewater will cause combined pollution and joint toxicity. General physicochemical index can not accurately reflect the actual harmful effects of chemical wastewater. Therefore, attentions would also be paid on the development of efficient toxicity assessment and subsequent toxicity regulation and toxicity reduction for the wastewaters while controlling the concentions of major pollutants.In the present study, the biological toxicity of acrylic fiber wastewater and explosive wastewater from typical enterprises were evaluated. Different kinds of aquatic organisms at 4 nutrient levels were applied to evaluate the general toxicity, including bacteria (Photobacterium phosphoreum), phytoplankton (Scenedesmus obliquus), zooplankton {Daphnia magna) and fish (Demo rerio). The genotoxicity was evaluated by comet tail moment of Denio rerio hepatocyte. Two types of chemical wastewater had varied magnitudes of general toxicity and genotoxicity on aquatic organisms. Acrylic fiber wastewater generated low toxicity on Photobacterium phosphoreum and Scenedesmus obliquus, while the influent had acute toxicity on Daphnia magna and Denio rerio, with the acute toxicity units (TU) at 1.4 and 2.9, which were reduced to 0 and 0.5 after anaerobic-aerobic (A/O) treatment. Two types of explosive wastewaters displayed significantly acute toxicity on Photobacterium phosphoreum, Scenedesmus obliquus, Daphnia magna and Denio rerio, where the TU value of trinitrotoluene wastewater were 256-1429. TU values of dinitrotoluene wastewater were 17.2-71.4. Genotoxicity results showed, both acrylic fiber wastewaterand explosive wastewater caused DNA damage to Denio rerio hepatocyte, where the genotoxicity of effluent was still significantly higher than the negative control group. For acrylic fiber wastewater, correlation analysis between physiochemical parameters and toxicity indictors showed that (Chemical Oxygen Demand, COD) exhibited no significant correlation with toxicity. However, ammonia was significantly correlated with the toxicity, suggesting that ammonia may be the important toxicity factor of the acrylic fiber wastewater. Correlation analysis between physiochemical parameters and toxicity indictors for explosive wastewater showed that COD and ammonia were significantly correlated with the acute toxicity, but they had no significant correlation with genotoxicity.The toxicity of the receiving river in the Liao River for chemical industry wastewaters was assessed. The genotoxicity toxicity was evaluated by comet tail moment of Denio rerio and Pseudorasbora parva hepatocyte. The magnitudes of oxidative damage in the liver were tested after exposure to the water samples from the Hun-Dong Zhou River and Tai Zi River. The results showed that all the water samples did not generate acute toxicity on Denio rerio and Pseudorasbora parva. And the upper reaches of the Dong Zhou River and Dahuofang Reservoir induced no significant genotoxicity and oxidative damage on Denio rerio and Pseudorasbora parva. The water samples from downstream of Dong Zhou River, Tai Zi River of Liao Yang caused DNA damage to Denio rerio and Pseudorasbora parva hepatocyte, significantly diferrent from the negative control. In addition, the content of malonic dialdehyde and glutathione, and the activities of glutathione S-transferases, and superoxide dismutase in Denio rerio and Pseudorasbora parva in the treatment group showed significant differences with the control groups. It was suggested that the surface water induced oxidative stress in the fish, which might be the important reason for the DNA damage. This study provides scientific foundation for optimizing the reduction techniques for wastewater toxicity, and the establishment of the laws and regulations related to the management of the integrated wastewater toxicity.