Study On The Performance Of Simultaneous Nitrification And Denitrification In MBR Intensified By Electro-coagulation

Simultaneous nitrification and denitrification in membrane bioreactor (MBR) is a new type of sewage treatment system, which integrates the membrane separation technology and simultaneous nitrification and denitrification technology. The unique interception of pollutants and microorganism with membrane module has provided advantages for the realization of simultaneous nitrification and denitrification, which makes nitrification and denitrification carried out in the same reactor, simplifies the operation and saves the energy. In order to further improve the treatment efficiency and operating stability of simultaneous nitrification and denitrification in MBR, the electro-coagulation membrane bioreactor (ECMBR) by placing the iron plates on both sides of the traditional membrane bioreactor was constructed to meet the increasingly strict emission standards of nitrogen and phosphorus in this paper, and then electro-coagulation was utilized to intensify nitrogen removal of simultaneous nitrification and denitrification in MBR.In this experiment, MBR and ECMBR were operated parallelly to treat artificial simulated domestic sewage. Impact factors of simultaneous nitrification and denitrification including DO, C/N, influent pH value, and HRT were studied in the paper. Also, the optimum operational conditions of reactors were determined. Furthermore, the strengthening effect ofelectro-coagulation on nitrogen removal of simultaneous nitrification and denitrification in MBR was discussed through comparing the treatment efficiencies and the characteristics of the sludge in different reactors.It was revealed that, the abilities of ECMBR and MBR to remove organics, nitrogen and phosphorus had almost achieved the best level on the condition that DO was 1.0 mg/L, C/N was 9 in the experiments. Under the above condition, the removal rates of COD were both maintained at above 93%; the removal rates of NH4+-N were 83.59% and 55.88%, respectively; the removal rates of TN were 73.68% and 51.22%, respectively; the removal rates of TP were 98.40% and 32.86%, respectively in ECMBR and MBR. The removal effect of nitrogen and phosphorus was better when the carbon source was added in batches rather than that of being added at one time.In the contrast tests of conducting MBR and ECMBR parallelly, it was found that, the optimum values of conventional experimental parameters for simultaneous nitrification and denitrification in MBR and ECMBR were as follows:DO=1.0 mg/L, C/N=10, influent pH was at 8.50-8.80, HRT=8 h, and the optimum operational condition of electric field was electrode voltage=2 V, plate spacing=8 cm. Under the optimum operational conditions, during the process of MBR with graphite electrodes and ECMBR with iron electrodes applied by an electric field, the average removal rate of COD, NH4+-N, and TN increased by 1.85% and 1.73%,1.37% and 11.80%, 1.22% and 6.09%, respectively, compared to the process of traditional MBR. The addition of iron plates made the zoogloea structure of activated sludge more compact and increased the particle size of sludge flocs in ECMBR. Electro-coagulation had a positive effect on intensifying nitrogen removal of simultaneous nitrification and denitrification in MBR.