Experimental Research Of Soybean Oil Refinery Wastewater Treatment With Microbial Electrochemical Systems

With the continuous improvement of people's living standards,global soybean oil production has increased over the past decade.In the process of refining soybean oil,a large amount of soybean oil refining wastewater is generated due to the process of elution and acid addition,and the soybean oil refining wastewater contains a large amount of organic matter,which can be rec ycled as an energy source.In traditional soybean oil plants,soy oil refining wastewater was used for digestion,therefore,it's more beneficial if the organic matter can be reduced in waste water,meanwhile the energy can be recycled and utilized.This method for wastewater treatment will not only meet the national energy conservation and emission reduction requirements,but also generate considerable economic benefits.In recent years,Microbial electrochemical system(MES),as a novel technology,has the unique advantage to achieve simultaneous degradation of organic matter and energy recovery,and has been widely studied in the world.This study explored the feasibility of using microbial electrochemical systems to treat soybean oil refining wastewater,and studied the effects of different COD concentration of soybean oil refining wastewater on the start-up and operation stages of microbial electrochemical system.In the research of microbial electrochemical system using soybean oil refining wastewater to produce electricity,it was found that the anaerobic digestion product acetic acid from soybean oil wastewater can be used to pretreat soybean oil wastewater instead of the externally applied citric acid.In order to make better use of soybean oil refining wastewater to recovery energy,four different COD concentrations of soybean oil refining wastewater had been diluted,corresponding to 8200±550 mg/L,4200±150 mg/L,2900±100 mg/L and 1740±100 mg/L.When the reactors started-up,the microbial electrochemical system with 2900±100 mg/L COD of soybean oil refining wastewater as the substrate showed the highest voltage in the start-up stage,which was the fastest starting reactor.The result shows different concentrations of soybean oil wastewater will affect the voltage and current density of the microbial electrochemical system.The microbial electrochemical system with 4200±150 mg/L COD of soybean oil refining wastewater as the substrate shows the highest voltage of 499mV in the stable operation stage.The microbial electrochemical system with 4200±150 mg/L COD of soybean oil refining wastewater as substrate has exhibited the highest power density of 746 mW/m~2 in the stable operation phase.In the methanogenesis research of microbial electrochemical system using soy oil refining wastewater,the addition of voltage to the microbial electrochemical system that has been successfully activated to produce methane.This study explored the gas production performance and organic matter removal performance of microbial electrochemical systems under different influent COD concentrations.When the voltage was 0.8V,the current density of the reactor decreased while the COD concentration increased.The reactor with the highest current density used1740 mg/L COD as substrates and reached 193 A/m~3 in the third cycle.This phenomenon lasted for a long time.The gas produced by the microbial electrochemical system in the treatment of soybean oil refining wastewater was mainly composed of plenty of methane and a small amount of carbon dioxide.The microbial electrochemical system with 4200±150 mg/L COD of soybean oil refining wastewater as the substrate were the highest of methanogenesis rate,methane gas content and methane conversion rate in the four different COD concentrations.The pH and protein removal rates were not much different in the four dilution rates.The experiment also added conventional anaerobic digestion as a control,and the results showed that the treatment of soybean oil refining wastewater by microbial electrochemical system was better than conventional anaerobic digestion.