Study On The Selective Reduction Characteristics Of Biotoxicity From Secondary Effluent By Typical Advanced Treatment Processes

The secondary effluent from the sewage treatment plant still adversely affect the aquatic ecosystem,even it meets the discharge standards.So people resort to tertiary treatment treatment processes for improving the water quality of the effluent from wastewater treatment plant.The macromolecular dissolved organic matter and trace organic pollutants contained in the secondary effluent from sewage plants are the main factors that adversely affect aquatic organisms in the ecosystem.Therefore,this thesis intended to study the selective reduction characteristics of three biotoxicity including(luminescent bacteria toxicity,photosynthetic inhibition effect and genotoxicity)by three tertiary treatment processes,including coagulation,activated carbon adsorption and reverse osmosis.At the same time,the physical and chemical indicators and the removal of trace organic pollutants were analyzed.This will provide a basis for the selection and optimization of tertiary treatment processes from an ecological safety perspective.The main results of this study are as follows:(1)In the laboratory,batch simulation experiments were carried out to find that the secondary treatment effluent from the sewage treatment plant was subjected to coagulation treatment,activated carbon adsorption treatment and reverse osmosis treatment,and the three biological toxicity of the effluent after three treatments were reduced to different extents.The coagulation treatment has a relatively good property for removing genotoxicity and photosynthetic inhibition effect,but the effect on aute toxicity removal is relatively poor.With the increase of polyaluminium chloride(PAC)dosage,the total concentration of trace organic pollutants decreased slightly.The total concentration of trace contaminants after treatment with 400 mg/L PAC was 1288.50 ng/L,and the removal rate was 8.90%.Coagulation treatment with 400 mg/L PAC could remove humic macromolecular organic compounds,aromatic compounds containing C=C bonds and C=O bonds,during which the removal of humic substances and fulvic acid is relatively high and the removal of trace organic contaminants and soluble microbial products is the lowest.(2)Activated carbon adsorption treatment has a good property on the removal of the three biotoxicity.The total concentration of trace organic pollutants in the effluent decreased from 1652.86 ng/L to 333.20 ng/L.At the same time,the removal of seven types of trace organic pollutantswere all above 71%.The removal of humic substances,fulvic acids,aromatic protein substances II and soluble microbial metabolites by 30g/L activated carbon were 85%,76%,52% and 86%,respectively.It can be seen that activated carbon has a good property on removal of macromolecular substances and trace contaminants.(3)The removal of the three biotoxicity from the secondary effluent after the reverse osmosis treatment were 99.85%,99.94%,and95.50%,respectively.After 7 times cycles,the removal of seven types of trace organic pollutants in the effluent was above 72%,except endocrine disrupying chemicals and flame retardant plasticizer.Reverse osmosis treatment has a good property on the removal of humic substances,fulvic acids,aromatic protein substances II,soluble microbial products and trace organic pollutants.