Photocatalytic Oxidation - Coagulation Experimental Study Of The Treatment Of Weak Gel Of Oil Extraction Wastewater

The produced swage containing weak gel in oilfield is characterized by high viscosity, serious emulsification of oil and water and steadily suspentive solid in water. So the separated velocity become slow in separate and electric dehydrate, the demulsification effect become weak by demulsifiers. The disposal of the sewage is very difficult. At present, the routine methods such as coagulation, electrochemistry, sedimentation, filtrate and so on have not well effect. Meanwhile, the sewage is increasing rapidly every year. Therefore how to effectively deal with the sewage containing weak gel has been payed attention to by people.The degradation of weak gel and produced swage containing weak gel was firstly studied by photic catalytic oxidation techniques in this thesis, The factors which affect oxidation were discussed and the optimal condition was conformed, meanwhile the reation mechanism and reaction dynamics were primary discussed. The experimental investigate showed: the degradation and viscosity breaking properties of weak gel are remarkable, the degradation rate of weak gel reached at 95%, the viscosity of weak gel is lowed to 1.2mPa.s. The removal rate of COD of The produced swage containing weak gel is also remarkable. The removal rate of COD can reach at 75% by UV/Fenton method. The reaction efficiency was improved through introducing oxalate or air into UV/Fenton system. The removal rate of COD can be respectively improved to 83% and 86%.In order to improve reaction efficiency and drop cost the combined method of photic catalytic oxidation and coagulation was proposed based on the properties of produced swage containing weak gel and techniques request in the thesis: First, the sewage was degraded by photic catalytic oxidation technique (UV/Fenton/air) which is acted as pretreatment method, and then was coagulated by coagulant. The experimental investigate showed, the optimal condition in pretreatment is that the dosage of H₂O₂ is 200mg/l_, Fe²+/H₂O₂(mol/mol) is 1:20, pH=3, reaction temperature 30℃, air exposure 30min; the optimal condition in coagulation is that the dosage of coagulant is 120mg/L, beating time 120s-150s,beating velocity 90r/min, pH=8-10, reaction temperature 30℃-50℃. The removal rate of oil in sewage reached at 99% and the oil in sewage less than 10mg/L, which reached at injecting water criterion after proposal. Meanwhile, combined techniques can not only reduce the dosage of coagulant and oxidant but also improve reaction efficiency. combined techniques is aneffective method which can overcome drawback of high cost of photic catalytic oxidation technique and low efficiency of coagulation.