Research On The Advanced Treatment Pretreatment Technique Of Coking Wastewater For Reusing

Despite of biochemical treatment of coking wastewater, the concentrations of suspend, organic contaminants and chroma are still so high that cannot meet the water quality requirement of membrane separation advanced treatment process. Effective pretreatment process of advanced treatment must be carried out to reduce large amount of impurities in order to reuse the wastewater. On the foundation of investigation the methods of advanced treatment for coking wastewater, the method have been put forward, such as coagulanting, Fenton reagent oxidation. This study tries to find out a reasonable pretreatment of advanced treatment process for reusing to dispose coking wastewater in an easy process and lower cost manner.The research was studied on the removal coking wastewater after biochemical treatment (from WISCO)by using the combined pretreatment method of coagulanting and Fenton reagent. The whole experiment included three steps. Firstly, the optimum condition and the treatment effect of coagulation and treatment effect was studied by using PFS (polyferric sulfate) and PAC (polyaluminium chloride), followed by adding PAM (polyacrylamide) as inorganic coagulant. According to coagulation effect, the better coagulant was selected. Secondly, the apparent productivity of hydroxyl radicals in Fenton's reagent was indirectly determined by Fe(phen)32+ method, and the useful technique and theory parameters for Fenton reagent treating wastewater were offered. Finally, the optimum condition and the treatment effect of the combined pretreatment method of coagulanting and Fenton reagent were studied.The study results showed as follow: PAC/PAM was better than PFS/PAM. At the optimum condition, the coking wastewater after biochemical treatment treated with composite flocculant of PAC/PAM, the removal efficiency of COD, the chroma and turbidity could achieve over 42%, 66% and 88%, respectively; The apparent productivity of hydroxyl radicals in Fenton's reagent was indirectly determined by Fe(phen)32+ method, and the leading factors influencing the apparent productivity of hydroxyl radicals in Fenton's reagent were studied. At the optimum condition, the apparent productivity of hydroxyl radicals could reach to 86%; the combined pretreatment method of coagulanting and Fenton reagent was much better than the method which only used coagulating. Under the optimum condition of the pretreatment method,PAC and PAM optimum dosage was respectively 150 mg/L and 4mg/L,pH =7.5,the stirring time after adding PAM and the temperature of coagulant was respectively 8min and 40℃; Fe²⁺ and H₂O₂ (30%) optimum dosage was respectively 100 mg/L and 350 mg/L, pH = 3, oxidation time was 30min. The best removal rate of COD was over 82% and the removal rate of the chroma and turbidity of wastewater was over 91%.