Pilot Study On Advanced Treatment Of Petrochemical Wastewater And Reuse By Double Membrane Method

In our country, water resource is relatively scarce, and water pollution is rather serious. With the rapid development of the petroleum industry, great amount of water was consumed, and environmental pollution was increasingly serious. Qilu petrochemical company also confronted the problem of water shortage, and wastewater reuse was carried out. This not only reduced dependency on groundwater, it also took into account the economic, social and environmental benefits, and it had a great significance to the company for the sustainable development strategy. Wastewater reuse project of Qilu petrochemical water supply and drainage plant was the important project of energy conservation, environmental protection and clean production in the local place.This study mainly focused on the secondary effluent of Qilu petrochemical water supply and drainage plant, and the optimized technological process was determined by conducting the pilot test of wastewater advanced treatment and reuse. The feasibility of application that petrochemical wastewater was treated by "ultrafiltration+reverse osmosis" process and the treated water was used as circulating cooling water was studied, and reliable and optimized operating parameters were provided, and commissioning and running experience was accumulated for actual production.The results of pilot test showed that the dosage of NaOH which was used as micro whirling coagulation softener was420mg/L, and total hardness of raw water reduced to170mg/L. The water yield of ultrafiltration system was stable, and the total recovery rate was 98%. The turbidity of producing water was reduced to below1.0NTU, and SDI was stabilized at1.5or less. It is suggested that "micro whirling coagulation+multi-media filtration+ultrafiltration" was feasible to use as pretreatment process. The quality of effluent could meet the requirements of influent of reverse osmosis, and recovery rates of reverse osmosis system were stabilized at70%to75%, and transmembrane pressure was approximately0.05MPa, and desalination rate was maintained at above98%.Each indicators of reverse osmosis producing water such as pH, total hardness, turbidity, color, alkalinity were all meet the water quality standards of circulating cooling water. The concentrated water was treated, and the CODCr of the treated water was approximately30mg/L, and that could meet the requirements of discharge standard. Overall, the advanced treatment system of wastewater was running stable, and that could meet the design requirements. The test results demonstrated that advanced treatment and reuse of petrochemical wastewater by double membrane method was feasibility.Finally, the producing water cost of proposed project was estimated. The production cost of recycled water was1.75yuan per ton, and13.5million yuan could be saved per year, and the economic benefit is obvious. Additionally, the advanced treatment and reuse project had obvious benefits to society and environment.