Advanced Treatment And Design Of Coking Wastewater By Combined Process

Since January 1.2015, according to state regulations, present enterprises must implement 《Emission standard of pollutants for coking chemical industry》 (GB16171-2012). In this study, biologically pretreated coking wastewater effluent was treated by coagulation and sedimentation, Fenton-like catalytic oxidation and activated carbon adsorption in single factor experiment, respectively. Then the optimum operation condition was determined. In the experiment of coagulation and sedimentation, the types of coagulant, the dosage of PAM, pH of wastewater and the speed of fast mixing affected the removal efficiency. In the experiment of Fenton-like catalytic oxidation, through the orthogonal experiment, the temperature, time, solid-to-liquid ratio and active component concentration affected catalytic properties. Through single factor experiment, the dosage of catalyst, pH of wastewater, time, the dosage of H2O2 and reusability affected the removal efficiency. In the experiment of activated carbon adsorption, pH of wastewater, the dosage of activated carbon, adsorption time and regeneration affected the removal efficiency. The most appropriate combined process was selected according to treatment efficiencies of the combined processes. Conclusions of this study were as follows:(1)In the experiment of coagulation and sedimentation, the best operation condition is:the types of coagulant as PAC and PAM, which the dosage of PAC is 400 mg/L, the dosage of PAM is 2 mg/L, pH of wastewater is 8 to 9 and the speed of 300 r/min.(2)Through the comparison and analysis of the results of three different active components by orthogonal experiments, CuSO4 was chosen as the active component of the catalyst.(3)Using granular activated carbon as carrier of catalyst, through the results of orthogonal experiment and four factor variance analysis, the best preparation condition of the catalyst is:the active component of 2 mol/L CuSO4, solid-to-liquid ratio of 1:2.5, calcination temperature of 300℃ and calcination time of 2 hours.The effects of four main factors in the preparation of the catalyst were as follows:active component concentration> calcination temperature> calcination time> solid-to-liquid ratio.(4)In the experiment of Fenton-like catalytic oxidation, the best operation condition is:the catalyst dosage of 4 g/L, the pH of wastewater is 6, the time of 50 min, the H2O2 dosage of 1700 mg/L.(5)In the experiment of activated carbon adsorption, the best operation condition is:pH of wastewater is 8 to 9. the catalyst dosage of 2 g/L, the adsorption time of 30 min.(6)Contrast the removal efficiency of coagulation-activated carbon adsorption, activated carbon adsorption-coagulation, Fenton-like catalytic oxidation-activated carbon adsorption and activated carbon adsorption-Fenton-like catalytic oxidation. The removal efficiency of Fenton-like catalytic oxidation and activated carbon adsorption is the best in combined processes. The effluent of the combined process meets the requirements. To sum up. the method of Fenton-like catalytic oxidation-activated carbon adsorption was selected as the advanced treatment technology.(7)According to experimental results and the relevant design specifications, the size of treatment structures, the dosage of catalyst and H2O2 were design by water volume ratio. Biologically pretreated coking wastewater effluent was treated by regulating pool, Fenton-like reactor and activated carbon adsorption tank. The treatment scale of project of coking wastewater advanced treatment is 180 m3/h. The annual operating cost is RMB 4,708,112.00. Contrast membrane treatment process, the operation mode and the manual operation is relatively easy. The problem of concentrated solution does not exist and the cost of wastewater treatment is 2.99 yuan/ton, which has certain economic advantages and application value.