Experimental Study On Pre-treatment Of Pharmaceutical Wastewater By Coagulation-Fenton Combined Process

Pharmaceutical wastewater is difficult to meet the water quality requirements of the sewage pipe network by conventional biological treatment because of its complex composition,high concentration of COD,poor biodegradability and high toxicity,so it is of great significance to explore advanced pretreatment process.In this program pharmaceutical wastewater from a pharmaceutical company in Hubei was pretreated by using Coagulation-Fenton combined process.Through the enhanced pretreatment process to reduce refractory organic compounds in wastewater,improve the biodegradability of wastewater,so as to improve the effect of subsequent biological treatment.In the coagulation experiment stage,the optimum operating parameters of coagulation were obtained by orthogonal experiment and single factor study Experimental results showed that coagulation effect was the most significant when the PFS dosage was 700 mg/L,the dosage of PAM was 15 mg/L,the pH value was 8.0,the rapid stirring?200 r/min?was 90 s.Under this condition,the average concentration of influent COD_cr was 11523 mg/L,the effluent COD_cr concentration was 4448 mg/L,and COD_cr removal rate was 61.4%,the BOD5/COD_cr was increased from 0.26 to 0.29,the fractal dimension was about 2.037,the flocs were compact and the sedimentation effect was wellIn order to further improve the biodegradability of wastewater and reduce the organic load of subsequent biological treatment,Fenton oxidation method was used to further treat the coagulated effluent,and COD_cr removal rate was chosen as the main index.The single factor experiment was used to study the optimal process parameters the pH of the wastewater was adjusted to 4.0,the H₂O₂ dosage is 1.5 Qth?14.25 ml/L?,the molar ratio of H₂O₂ to Fe2+ was 15:1,after 60 min,then the pH was adjusted to 7.0,keep static for 2 h.The removal rate of COD_cr was up to 71.9%,the BOD5/COD_cr increased from 0.29 to 0.42,and the biodegradability of wastewater was obviously improved,which provided a good foundation for the subsequent biological treatment.The concentration of COD_cr and the initial concentration of H₂O₂ were chosen as the factors affecting the reaction rate,based on the chemical reaction kinetics equation V=?dP/dt?=KPaEb,The kinetic model of the Fenton method for the treatment of coagulated effluent was calculated as V=5.6×10-11P3.2512E0.5187 by the experimental data.With the help of the dynamic model,the reaction can be analyzed theoretically and the parameters are predicted,provide valuable reference for practical engineering application in the future.