Experimental Study On Coking Wastewater Treated By Coagulation+Ceramic Membrane Microfiltration Process

Coking wastewater contains large amounts of tar oil and non-degradation organic compounds, which is difficult to remove by traditional chemical biological method. In addition, although coking wastewater from different sources have similar nature, their complex and varied components at different moments, this type of wastewater is difficult to be treated. Under suitable conditions coagulation can remove refractory organics in wastewater effectively. Ceramic membrane microfiltration can removal oil cheaply and efficiently. We postulate that if using the two methods together, First coking wastewater treated by coagulation, and then treated by ceramic membrane microfiltration. on the one hand we can reduce the burden of ceramic membrane microfiltration, extended using cycle, reduce recoil frequency; on the other hand microfiltration as a supplement of coagulation not only can reduce pharmaceutical dosage and cost, but also enhance treatment efficiency to ensure water quality .Firstly this article discribes method of ceramic membrane microfiltration to treat simulated wastewater (according to the characteristics of coking wastewater to prepare simulating wastewater), then systematically discusses the effect of operation mode and backwash conditions on the stable existence of ceramic membrane filters, and specifically investigates the effect of such as pressure, reverse washing pressure, cycle and time operating parameters on the separation efficiency of ceramic membrane, and obtains the optimum operation condition for separation, the conditions are as below: the pressure of membrane inlet is 0.2MPa, the pressure of reverse washing is 0.2MPa, the backwash cycle is 4h or start backwash until the pressure difference of membrane is reached 0.02 MPa, and the backwash time is 10 min.Secondly, discribes the method of coagulation to treat the residual ammonia of Ningbo Iron and Steel Co., Ltd., through choose different coagulants and combinations to confirm the best treat conditions,such as the drug dosage, the sediment time of coagulation, the PH and tempreture of the wastewater. The experiment results show that factors mentioned as before have siginificant effects on the coagulation effects. It is verified that the PAC + PAM system is the best combination of coagulant throught experiments. the optimum reaction conditions are as below: the dosage of PAC and PAM is respectively 150mg/L and 6mg/L, water temperature is 40 centigrade, pH value is between 6 and 7, coagulation sedimentation time is 30min. Under these conditions, the coking wastewater highest oil, turbidity and color removal rate were reach 60%, 92% and 65% treated after coagulation, at the same time the wastewater turned brown into light clarified.This thesis using coagulation + ceramic membrane microfiltration processes to pretreat coking wastewater before biochemical treatment in Pingxiang Iron and Steel Co., Ltd. On the best treatment conditions, The removal rate of wastewaters'turbidity, color, oil content and CODCr can reach up to 95%, 80%, 90% and 81% respectively. The result reflected the compatibility and complementarity of two wastewater treatment method-coagulation and ceramic membrane microfiltration, also showed high efficiency of coking wastewater treated by coagulation + ceramic membrane microfiltration technology. Finally raised burning program to dispose a large number of toxic oil sludge which is produced by coagulation process and be turned harmless and useful.For using ceramic membrane microfiltration process to treate coking wastewater,the biggest problem is the fouling and regeneration of membrane. For this reason, the regeneration process of ceramic membranes polluted by coking wastewater was studied, At first, the physical way of using tap water to clean contaminated membranes, This method can extend chemical cleaning cycle and membrane life significantly. But seriously polluted membrane should be cleaned by chemical methods, according to the nature of pollutants, select the appropriate chemicals for ceramic membrane cleaning experimental, The effect of the concentration of cleaning agents on the ceramic membrane cleaning was discussed. After using 0.6% NaClO(Step one)and 1.5% NaOH(Step two) to clean ceramic membrane, flux recovery rate can reach 95%, and the regeneration of polluted ceramic membrane can be solved effectively.