The Performance Of Saline Wastewater Treatment Using Stacked BCMFC

Many processes generate high-salinity wastewater. High-salinity wastewater is often difficult to treat using biological processes. Saline wastewater contains not only high concentration of inorganic salt, but also different concentrations of organic matter, nitrogen, phosphorus and other nutrients. At present, the research around the removal of organics and ammonia using microbial fuel cell(MFC) are popular. However, viewpoint whether the effects of salinity on the above bioreactor are good or not is lacking. Moreover, the reports about the organic removal, nitrification and denitrification process, analysis in view of biology under different operational conditions are rare.Biological treatment processes of saline wastewater at home and abroad are studied and stacked bio-cathode microbial fuel cell is chosen for discussing the effects of different wastewater salinity and operational conditions on organic matter degradation. Besides, this paper focused on the nitrogen removal of wastewater, analysed the effects of model factors on nitrification-denitrification and optimized operating conditions on the basis of the organic matter degradation and nitrogen removal effect. These research are promotive to the biological treatment of saline ammonia-nitrogen wastewater. Through the above experiments, conclusions are as follows.(1) The system wholly performs well in disposing organic substances, nitrogen of municipal wastewater and electricity production performance.(2) The efficiency of organics removal is over 73%.The effect of salinity on COD removal efficiency is obvious. When the salinity is Og/L and 3.5g/L, the COD removal efficiency are over 90%.When wastewater salinity increases to 17.5g/L, COD removal efficiency decreases remarkably. It shows a poor performance in resistance to shock loading of ammonia nitrogen.In a whole, the best degradation effect could be obtained in the case of salinity 3.5g/L.(3) Influent ammonium concentration is a key index of removal efficiency in MFC. The COD removal efficiency shows an initial increase and a later on reduction trend with increasing ammonia nitrogen concentration. The results show that influent containing 0.3g/L ammonium chloride is found to be the optimum for the COD and ammonia nitrogen removal. Compared to salinity, aerobic denitrification rate is obviously affected by ammonia nitrogen concentration. High ammonia concentration has worse effect on denitrification rate.(4) Dissolved oxygen(DO) concentration is also a significant index of removal efficiency in MFC. Experimental results indicate that biodegradation of microorganism is inhabited when DO is under 3.4mg/L. At this time, degradation rate of COD is lower. When DO is above 4.6mg/L, degradation rate of COD increases significantly. When DO is 7.0mg/L, degradation rate of COD at different salinity is more than 97%. When DO is lower than 3.4mg/L, degradation rate of ammonia nitrogen is under 82.6%. When DO is 7.0mg/L, ammonia nitrogen removal has a substantial increase. It reached the maximum of 98.2% when salinity is Og/L Nitrification process in cathode chamber is inadequate when DO is rather low, therefore the denitrification process is affected in anode chamber. Denitrification rate can increase by 24% when DO increases from 2.0mg/L to 7.0mg/L.(5) Degradation of organic matter is greatly influenced by the HRT in anode chamber. It has a poor COD degradation effect when HRT is 8h.The result indicates that degradation rate increases with increasing HRT. When HRT is over 13.3 h, HRT has a little effect on COD degradation rate in the system. In order to ensure the removal efficiency of system and cost savings, the research chooses 13.3 h as the best condition. The influence of HRT on ammonia nitrogen removal has been tested by experiments that ammonia nitrogen removal of cathode effluent is effected greatly by HRT while anode effluent is little influenced.(6) Load resistance has a little effect on the degradation of organic matter and ammonia nitrogen, With the loss of the load resistance, the removal rate of COD in wastewater has an increasing trend generally. When the load resistance is above 100 Q, the oxygen is mainly used as electron acceptor in cathode chamber. When the load resistance is less than 100 Ω, part of nitrate was used to produce electricity. As a result, nitrate nitrogen removal rate increases. In this case, the denitrification effect is better.(7) The predominant member of microbial community at different salinity concentrations in the anode membrane is related to a-proteobacteria, β-proteobacteria, δ-proteobacteria and Actinobacteridae class.