Effect Of Carbon Sources On The Process Of Denitrifying Phosphorus Removal And Electrogenesis

If we can use the large amount of energy contained in municipal sewage,the problem of energy shortage will be resulted in the relief to a certain extent.The research on the new technology of the coupling of microbial fuel cell(MFC)and other wastewater treatment processes is one of the most promising research directions in the field of wastewater treatment.In this paper,a kind of denitrifying phosphorus removal process is introduced,which is based on the double sludge process.The anaerobic tank and the two sedimentation tank are used as the anode and cathode chamber of the microbial fuel cell.This process can remove nitrogen,phosphorus and organic matter in wastewater and produce electrical energy.Carbon source is not only an important factor of denitrifying phosphorus removal process,but also an important parameter of microbial fuel cell.Therefore,it is very important to study the effect of carbon source on denitrifying phosphorus removal system.Firstly,Denitrifying phosphorus accumulating bacteria and nitrifying sludge were acclimated with the way of Continuous Flow,and then the sludge was put into the corresponding reaction pool.The external resistor was set to 900 ohms.The dissolved oxygen concentration in the anaerobic tank,the nitrification tank and the anoxic tank was controlled by 0.2mg/L,2.0mg/Land 0.5mg/L,the temperature of the water in the device was controlled at 25°C.After 52 days,the device was started successfully.The removal rate of COD,phosphorus and ammonia nitrogen were 60%-67%,60%-70%and 55%-64%.The output voltage was about 0.53V,The current could reach to 0.62mA,the power density was fluctuated between 35-43.2mW/m2.Secondly,Sodium acetate,sodium propionate and glucose were used as carbon sources and kept the carbon-nitrogen ratio at 3.5-4.5、4.5-5.5 and 5.5-6.5 to get the optimal carbon-nitrogen ratio of different types of carbon sources for denitrifying phosphorus removal system.we could find that the best carbon-nitrogen ratio of sodium acetate and sodium propionate for the device was 4.5-5.5 and the processing effect of the two systems is not significant.The removal rate of phosphorus and COD could get to 65%,the total nitrogen of the effluent was fluctuated between 9mg/L and 17mg/L,the average voltage was 0.47V.The best carbon-nitrogen ratio of glucose was 5.5-6.5,but the removal efficiency of phosphorus was bad,the removal rate of phosphorus was fluctuated between 33%and 41%.But it had a better electrogenesis capacity and the average voltage could get to 0.53V.Thirdly,The effects of different carbon sources on the system of Denitrification Phosphorus Removal Electrogenesis was studied,and every carbon source was in its best carbon and nitrogen ratio.We found that the system had good adaptability for the the change of carbon source,and the system could maintain a good effluent quality.There was little effect on the system of Denitrification Phosphorus Removal Electrogenesis when using sodium propionate instead of sodium acetate as carbon source.The average removal rate of phosphorus was 63.41%,slightly lower than the sodium acetate system 65.52%,the average output voltage is about 0.48V.When the carbon source was turned to glucose,the phosphorus removal efficiency of the system is reduced,and the phosphorus removal rate is lower than 37%,and the average output voltage is 0.49V.The best carbon source for the process of denitrifying phosphorus removal and electrogenesis was sodium acetate.Finally,the effects of MLSS and HRT on the denitrifying phosphorus removal system were studied,And then we could know that the effect on phosphorus removal would be the best when MLSS in anaerobic tank was about 6536mg/L,the removal rate of COD would reach to 72%,concentration of Phosphorus was lower than 3mg/L;when MLSS in the anoxic tank was 6794 mg/L,the effect of denitrification and phosphorus removal would be the best.Therefore,when the MLSS was controlled by 6500-7000mg/L,the process would have a significant effect on the simulated domestic wastewater treatment.The HRT of each reaction tank was changed by adjusting the influent quantity,we could find that when the HRT of anaerobic tank and anoxic tank were controlled at 2.5h and 4.2h,the removal rate of COD is up to 77%.Although,the removal rate of COD in the system was slightly lower than that of the system which HRT of anaerobic tank was at 3.5h,but the phosphorus release was the highest which reached to 14-17mg/L and was able to produce consistent voltage,the maximum output voltage was 0.53V.