Treatment Of Wastewater Containing HPAM Using Electrochemical Reactor

Due to the presence of partially hydrolyzed polyacrylamide (HPAM) in oilfield wastewater during polymer flooding, produced water treatment became more difficult. In this text, the electrochemical reactors were made by ourselves and used to degrade the HPAM in wastewater. Some parameters were optimized by measuring the COD value, HPAM concentration, AM concentration. After optimization, the performances of electrochemical reactor and the mechanism, kinetics of the degradation of HPAM in reactor were investigated.The electrochemical reactor parameters through treating simulated HPAM wastewater were: atmospheric pressure and ambient temperature, DC voltage 6.5V, Ti/RuO₂-IrO₂ anode, stainless steel cathode, 1.5mL A acid as electrolyte, current l50mA, electrode area 10cm², the gap of electrodes 1²cm, mono-polar electrode array, stirring.Electrolysis voltage should be higher than 3.6V; there was no great rise of the COD removal when DC voltage was 6.5V. The COD value of simulated sewage declined from 603.16mg/L to 7.57mg/L 90min treatment later when using Ti/RuO₂-IrO₂ anode, COD removal was 98.74%. Compared with stainless steel, iron, aluminum anodes, Ti/RuO₂-IrO₂ anode performed the highest electro-catalytic activity. CV curves showed that Ti/RuO₂-IrO₂ anode owned the best oxidation performance and lower potential of chlorine evolution, about 1.1V (VS Ag/AgCl). Acid medium was conducive to the HPAM degradation especially A acid as electrolyte, 45min treatment later, the COD removal was 96.34%. The optimal current was 150mA in the experiment, COD value in the sewage reduced to 37.1mg/L from 648.22mg/L 30min treatment later, COD removal was 94.28%, HPAM removal was 96.84%. Mono-polar electrode array made better results than bipolar array in degradation of HPAM 90min treatment later, COD removal efficiency was 98.98% and 91.39%, respectively. In optimal conditions, the concentration of acrylamide of simulation sewage was 2.55mg/L 30min treatment later; energy consumption was 2.36kWh/kgCOD. The values of COD, color, anionic surfactant were 70.85mg/L, 8 degree and 4.89mg/L 45min treatment later on the oilfield wastewater containing HPAM. The effluent met the first grade of national discharge standards after being treated. The synergic effect of ultrasound and electrochemical degradation was obvious than a single electrochemical process, COD removal was increased by 8% 30min later.Oxygen was not involved in the electrochemical reaction; the degradation of HPAM mainly depended on the combined action of hydroxyl radicals and active chlorine generated in the medium. There had not found intermediate products in the solution though UV absorption spectra. CV curves indicated that the degradation process of HPAM occurred at the chlorine evolution area of anode. Using graphic and differential methods, the degradation of HPAM was determined as a first-order reaction, the reaction rate equation was C=C_oe^-0.05t.The results were very satisfactory in the experiments treatment of simulated and actual sewage containing HPAM with electrochemical reactors made by ourselves.