Study On Treatment Of Oily Wastewater By Membrane Bioreactor And Fenton Combined Process

The oily wastewater used in this experiment was a kind of refractory industrial wastewater. To achieve discharge standard, a combined process of anaerobic-MBR-Fenton-Activated carbon adsorption was used to treat the oily wastewater.In this study, anaerobic process and Fenton advanced oxidation were compared as pretreatment process. The results showed that the effect of anaerobic process on oily wastewater was better than that of Fenton advanced oxidation. Maximum removal rate of wastewater COD by anaerobic process was54.3%, and biodegradability of oily wastewater improved from0.19to0.37. The effluent quality met the requirements of subsequent biological treatment.During anaerobic pretreatment of oily wastewater, the effect of initial COD, hydraulic retention time, reaction temperature and initial pH on effluent quality were investigated. The results showed that the optimum parameters of MLS S, reaction temperature, initial pH of wastewater, hydraulic retention time were4000mg/L,26.1-37.5℃,6.44-7.38and24h, respectively. After45days continuous running, the average COD, ammonia and oil concentration of treated water were2325.5mg/L,166.4mg/L and266.0mg/L. And average removal efficiency of COD, ammonia and oil concentration were50.6%,23.0%and71.0%, respectively.The operation conditions of Membrane bioreactor were following when treating the wastewater:MLSS was6600mg/L, HRT was12hours, SRT was18.2days, air-water ratio was20:1. The average COD, ammonia and oil concentration of treated water were796.6mg/L,24.6mg/L and75.1mg/L. And average removal efficiency of COD, ammonia and oil concentration were65.7%,85.2%and91.8%, respectively. The cost of oily wastewater during microbial treatment is0.3yuan/t.During the period of oily wastewater treatment by Fenton advanced oxidation, the H2O2/TeSO4molar ratio, retention time, dosage of FeSO4and initial pH on effluent quality were. The optimum conditions of Fenton advanced oxidation were determined. The results showed that the process parameters were optimized as the H2O2/FeSO4molar ratio was15:1, the dosage of FeSO4and H2O2were4mmol/L and60mmol/L, reaction time was2h, initial pH was3.0. It had a good effect for oily wastewater treatment. The average COD and oil concentration of oily wastewater was decreased from796.9mg/L to339.4mg/L and from76.3mg/L to20.7mg/L, the removal efficiency of COD and oil concentration were56.6%and72.9%, respectively. The cost of Fenton advanced oxidation is5.4yuan/t.Using activated carbon adsorption as deep treatment process, the effect of treatment on the wastewater was investigated by static and dynamic adsorption experiments. The results of static showed that the adsorption fit Langmuir adsorption isotherm and second order rate equation. The results of dynamic experiments showed that the effective running time was inversely proportional to filter speed, and in effective time activated carbon adsorption had a good effect on oily wastewater. When the filter speed was1.0m/s, the average of COD, ammonia nitrogen and oil concentration were57.3mg/L,5.3mg/L and6.2mg/L, respectively. The removal efficiency COD, ammonia nitrogen and oil concentration were80.4%,77.2%and75.8%. The cost of activated carbon adsorption on oily wastewater is23.7yuan/t.The COD,NH3-N and oil concentration in product were lower than60mg/L,8mg/L and10mg/L, respectively, after the treatment of anaerobic-MBR-Fenton-activated carbon adsorption combined process. The effluent quality met the requirements of the secondary standard of DB12-356-2008of Tianjin. The cost of the combined process used in experiment is29.4yuan/t, and compared with the traditional processes of oily wastewater, it has some advantages.