Study On The Enhanced Removal Of Biochemical Inhibitors In Traditional Chinese Medicine Wastewater By Coagulation Process

The water quality of traditional Chinese medecine wastewater was complicate. It contains many kinds of organics including toxic and hazardous substances, resulting in the following characteristics: high biotoxcity, high concentration of organic pollutants and suspend solid; high color. These features determined that it is difficult for treatment and biological treatment alone is generally difficult to achieve discharge standards. In this paper, coagulation-flocculation process was applied to the pretreatment of the traditional Chinese medicine wastewater with high toxicity, SS, COD and color to reduce the toxicity and improve biodegradability,and to reduce the wastewater pollutant load at the same time.In this way, favorable conditions for subsequent biological treatment will be created to improve the processing efficiency of the whole process.At first, the methods to evaluate the acute toxicity of wastewater was established; Secondly, the coagulation-flocculation properties on the reduction of conventional pollutant parameters and the acute toxicity were studied to determine the optimal parameters; Finally, a pilot study under the optimal conditions was carried out, the operation efficiency and stability of the coagulation and sedimentation reactor, as well as the impact on the overall operational efficiency of the process were studied.The optimum conditions of in acute toxicity test by luminescent bacteria method was determined: test p H ranging from 6.0 to 8.0, and the 15 min exposure time,Under this conditions, the acute toxicity of the wastewater was tested as EC50=8.12%. A higher luminous fit inhibition rate-Hg Cl2 concentration of the standard curve was established and applied in the paper.The coagulation performance on the removal rate of COD, SS and acute toxicity of PFS, PAC, AS and Fe SO4 was compared, and PFS was chosen as the optimal coagulant for the reduction of acute toxicity and the removal of COD and SS. When the raw water p H=6.60, and the dosage of PFS, PAC, AS and Fe SO4 were 500, 600, 700 and 800mg/L respectively, the acute toxicity decreased from EC50=8.12% to EC50 = 33.43%, 25.43%, 18.31%, 18.56%, respectively. Then, the effect of initial p H and coagulants aid(PAM and Chitosan)on the coagulation performance of PFS was investigated.And response surface methodology(RSM) was applied to dedetermine the optimum conditions for the coagulation-flocculation parameters, The optimal conditions for PFS dosage, PAM dosage and initial p H were 470mg/ L, 7.5mg/ L and 7.0 respectively, where the removal efficiency of COD, SS were 39.3%, 98.9% respectively, and the acute toxicity was reduced from EC50=8.12% to EC50=44.70%, the acute toxicity was decreased from the strong toxicity level to medium.The performance and the stability of the coagulation and sedimentation reactor were tested in a pilot scale, the results show that the coagulation sedimentation process, with strong resistance to impact load and get more substantial reduction of pollutant loads, the removal rates of conventional pollutant parameters COD, SS, color, and TP were above 30%, 90%, 95% and 85% respectively, the removel rate of the inhibition luminous was above 20% A evaluation on acute toxicity remove capacity of biological processes was carried out, the results showed that, aerobic process has obvious advantages in terms of acute toxicity reduction compared to anaerobic(Hydrolysis acidification) process, but the acute toxicity of the final effluent still exceeded. The coagulation process has a positive impact on the process for subsequent biochemical processes and the whole process, through the coagulation and sedimentation process the operational efficiency of the whole process were strengthened, the problem of the excessive of acute toxicity, COD and TP of the effulent was solved.