| Microbial desalination cell (MDC) has become an emerging technology, whichcan transform the biomass energy in wastewater into electricity for seawaterdesalination. In recent years, many researchers from home and abroad have beenforcusing on MDC technology, which is low-energy consuming and can achievewastes recycling. Metallic wastewater is highly toxic, persistent, accumulative andnot easily metabolized but enriched by microorgasims. It not only can cause waterenvironment pollution but aslo seriously threaten the survival of humanbeings andqualitic orgasims.In this paper, the research about Microbial desalination cells included reactorstart-up, influence of increasing desalination chambers and decreasing externalresistance on MDC performance. The optimal MDC reactor configuration wasestablished based on the above research. A seriesly assembled MDC system wasconstructed and the number of MDC reactors, anolyte flow-rate, catholyte flow-rateand the operation mode of middle chambers were optimized. The electricitygeneration, COD removal, columbic effeicy, desalination efficiency and alkaliproduction of each reactor in the system were analyzed. Comprehensive evaluationwas given on the MDC system’s performace of simultaneous wastewater treatment,seawater desalination and metallic wastewater treatment.Firstly, the reactor performance of1SMDC,3SMDC and5SMDC werecontrasted. In fed-betch operation, increasing desalination chambers and deceasingexternal resistance significantly enhanced MDC’s output current and desalinationefficiency with sufficient COD removal and columbic efficiency. With an externalresistance of10Ω, a maximum output current of4.5mA and a maximum powerdensity of670mW·m-2were obtained by using a5SMDC reactor with an internalresistance of267Ω. The5SMDC reactor’s desalination efficiency was84%with acharge transfer efficiency of318%and a total desalination rate of0.0206g·h-1. The5SMDC reactor’s COD removal efficiency was84%with a columbic efficiency of29%.Secondly, a seriesly assembled5SMDC system was established. In continuousflow operation, increasing the number of5SMDC reactors in the system effectivelyimproved its performance. The optimal anolyte flowrate (0.2mL·min-1) andcatholyte flowrate (0.8mL·min-1) were determined. Compared with continuousdesalination, the three-stage desalination was quicker and more sufficient with anoptimal NaCl solution flowrate of0.14mL·min-1in the middle chambers. Under these circumtances, the5-5SMDCs system obtained a maximum output current of6.5mA and a maximum power density of745mW·m-2with an average internalresistance of178Ω. The total desalination efficiency was95%and the averagecharge transfer efficiency was266%with a NaCl removal rate of5.7mg·L-1·day-1.The total COD removal efficiency was94%and the average columbic efficiencywas46%. The total alkaline catholyte production was360mL·day-1with a solutionpH of11.9. A maximum metal ion removal rate of99%in the synthetic metallicwastewater was obtained by chemical perciptation. The effluent achieved Level1standard of Comprehensive Emisiions Standard for Sewage (GB8978—1996).Thirdly, the performance of each reactor in this system was analyzed. Withlower NaCl concentration in middle chambers, lower COD in anolyte and highercatholyte pH, the performance of each reactor along the flow direction was lesssufficient with larger internal resistance.Finally, a comprehensive evaluation on wastewater treatment and futureapplication was given for the seriesly assembled5SMDC system. |
PDF Full Text Request