Experimental Study On Advanced Treatment Of The Cooking Wastewater For Recyling In Membrane Combination Technology

Coking wastewater is a typical refractory industrial wastewater with high concentration, high chroma, high toxicity. When being excessive discharged, it is very hazardous for human, fish and crops. Reaching the discharge standard for coking wastewater treatment is a basic requirement. The ultimate goals are contain wastewater reuse, reduce efflux and reuse of resources. To achieve "zero emissions", the best option is the wastewater advanced treatment and reuse. An efficient, low-cost treatment technology is urgent needed currently for the treatment process of coking wastewater.The membrane separation technology is one of the hot issues in terms of wastewater advanced treatment research in recent years, particularly applied to the advanced treatment and recycling of industrial wastewater. The water quality through membrane separation technology treatment is good, which can fully meet the standards-related reuse of process water, so as to achieve the purpose of energy conservation and emission reduction. And it has the stable and efficient processing capabilities, easy-operation, and no secondary pollution. Reverse osmosis is a kind of desalination membrane separation technology with high desalinization ratio. It can combine with other technologies, which will greatly improve effluent quality standards, then expand the scope of water reuse. In this experiment, the "Pretreatment+MF+RO" process, as the main craft, is applied in the advanced treatment of coking wastewater. The microfiltration, as a former treatment apparatus on the reverse osmosis, can effectively guarantee the stability of inflow quality for the reverse osmosis, then reducing pollution for reverse osmosis membrane and extending its life.By the orthogonal experiment, we have analyzed the coaction of four factors, namely operating pressure, inflow temperature, inflow pH and recovery rate on the test effects. The obtained results include the optimum operating parameters and experimental factors on the relationship between the primary and secondary.Then examine and adjust the optimum operating parameters by single factor experiment. The primary and secondary relationships:operating pressureâ†'inflow temperatureâ†'recovery rateâ†'inflow pH. The optimum working conditions are as follows:operating pressure is0.8Mpa, the inflow temperature is40℃, recovery rate is80%, and inflow pH is7.In single factor experiment, as the operating pressure increased, the COD, ammonia nitrogen removal and desalination rate of wastewater increased, water flux also increased meanwhile. When raising the temperature, the viscosity of the water would decrease, the filtration rate and flux of membrane are both increased. But if the temperature was high excessively, intense turbulence and loose film would happen, and then removal rate would decrease. The membrane has a good performance in a certain pH scope, so the inflow pH change has little effect on the treatment. But if beyond the tolerance range of the membrane, the membrane would be polluted, even damage the membrane module, which results a sharp decline for effect of treatment. Concentration polarization caused by high recovery rate on membrane surface will result in a sharp decline for water quality, and then treatment effect would be affected.In consideration of the actual situation and performance of the membrane, we choose that the operating pressure was0.8Mpa, recovery rate was80%, pH was6.0-9.0, inflow temperature was room temperature, which was used for advanced treatment of the coking wastewater. The results are as follows:the COD of effluent remained at below10mg/L and removal efficiency was more than95%. The electrical conductivity of contributing water was maintained at below100uS/cm, the removal rate of soluble salts was more than97%. At the same time, the mass concentration of ammonia nitrogen effluent was less than lmg/L, or the removal rate was more than95%. Its chroma was almost zero, the removal rate of turbidity was almost100%. Its concentration of total iron was below0.3mg/L, the hardness was much less than450mg/L. The important indicators above were all up to relevant standard of circulating cooling water. A combination method of physical reagents and chemical reagents was used for cleaning the membrane contaminated in experiments. Firstly, hydraulic cleaning was continued in20min, then a mixture of0.2%HCl,0.1%NaOH and0.3%H2O2was used for chemical cleaning, finally reverse osmosis water was rinsed30min. The water yield of the reverse osmosis membrane could be restored to97.5%of the original.