Development of Microbial Desalination Cell (MDC) for Seawater Desalination, Wastewater TREATMENT and Bioelectricity Generation /

Abstract

Water is increasingly becoming a scarce resource as freshwater sources are being depleted globally, leading to an increased interest in desalination, i.e. provision of drinking water from the saline sea water. Most desalination technologies are energy intensive while Microbial Desalination Cells (MDCs) represent a sustainable option that has the added benefit of solving the ever increasing waste water management problem. MDCs are a modified form of Microbial Fuel Cells (MFCs) that rely on the potential created by organic media to reduce salt concentration by a phenomena called electro-dialysis and provide renewable means of clean water production. The series of experiments were carried out to check the desalination ability of an indigenously designed experimental setup (Bio-electrochemical Assembly) using real domestic waste water inoculated with sewage sludge of Membrane Bioreactor (MBR) under standardized conditions. The electrochemical properties of the system, including polarization curves and Electrochemical Impedance Spectroscopy (EIS) were studied along with the extent of COD removal in order to characterize the cell. Acidic water and Phosphate Buffer Solution (PBS) were tested as potential catholytes against which the performance of the waste water was gauged at various salt concentrations. The maximum salt removal efficiency was 31%, achieved at salt concentration of 35 g/L that decreases with a reduction in salt concentration. The maximum current density and power density was 246 mA/m2 and 32 mW/m2 respectively achieved using acidic water catholyte. EIS experiments revealed that at higher salt concentrations internal resistance of the cell is lowest. Results also depicted that in terms of efficiency and economics acidic water type catholyte is more beneficial than the PBS.