Microbial Water Desalination and Bio-Electricity Generation - Role of Biomass Carbon

Microbial desalination cells (MDCs) are modified microbial fuel cells (MFC) that are energy-sustainable. They use organic matter in wastewater as the energy source for desalination. The electric potential gradient is caused by exoelectrogenic bacteria. A typical MDC has a middle compartment for water desalination between the anode and cathode chambers. Our study reports lab-scale desalination, for evaluating the role of carbon from biomass waste, i.e. coconut shells. Control experiments were performed in the absence of activated carbon. Different initial salt concentrations (25 and 35 gl^-1) were investigated. MDC produced a maximum voltage of 460 ± 13 mV simultaneously removing about 83.3 ± 1.3% of Na⁺ and 57.8 ± 1.1% of Cl^-, in the desalination cycle. The control MDC produced a maximum of 260 ± 8 mV and 69.3 ± 2% of Na⁺ removal and 51 ± 1.5% Cl^- removal. These results explain the role of using activated carbon for improved power production and water desalination. The SEM image of the biofilm shows pili (nanowires) with rod-shaped microorganisms. EDAX confirmed the presence of minerals such as Al, P, K, O, N, which may be due to chemical scale formation (especially P, Na and Ca).