The Research On The Solution For Disposition Of The Remaining Sludges By Microbial Electrolysis Cells With Different Cathode Structures

Due to the high volume of excess sludge, it has been a burning question to achieve sludge reduction and resource recycling for waste water treatment plants in China. With the advantages of removing organic components and recycling clean energy simultaneously, microbial fuel cells (MFC) and microbial electrolysis cells (MEC) are promising techniques to meet the challenges of excess sludge. Taking excess sludge as substrate, the present study investigated the effects of cathode structure on the voltage output, hydrogen production and organic removal of single-chamber microbial electrochemical systems. Carbon cloth cathodes with or without platinum-carbon catalyst and stencil cathodes were adopted for small-scale MEC reactors and drum upwelling MEC reactors, respectively.Small-scale MEC reactors were started as MFC, then converted to MEC. At MFC stage, the highest current density was180A/m3for reactors with platinum-carbon catalyst and30A/m3for the control group. When reactors were operated with MEC model, the highest current density, COD removal efficiency, hydrogen production each cycle, hydrogen yield, hydrogen production rate and volume current density for reactors with platinum-carbon catalyst were180A/m3,27%,70mL,9mgH2/gCOD,0.68m3/m3d and178A/m3, respectively. For control group, those were90A/m3,15%,20mL,4.8mgH2/gCOD,0.15m3/m3d and102A/m3. Experimental results showed that platinum-carbon catalyst greatly improved the hydrogen production of MEC for excess sludge treatment. However, considering the economic cost, cathodes without platinum-carbon catalyst are still employed widely.Drum upwelling MEC reactors with stencil cathode were also employed to treatment excess sludge, and the effects of applied voltage and sludge pretreatment were explored.The results of hydrogen production performance, sludge removal efficiency and electricity production performance showed that the drum upwelling reactors operated at an applied voltage of1.2V performed better than the reactors at0.8V applied voltage. And the hydrogen production performance was improved for reactors using alkali treatment sludge. This study demonstrated that the state of sludge, applied voltage would affect the performance of MEC reactors significantly. Alkali treatment of sludge, increasing applied voltage were favorable for improving the current density, COD removal and the hydrogen and methane production of MEC reaction system.