Effect of thermal pre-treatments method on sludge degradation process prior usage in membrane-less microbial fuel cell for electricity generation

Abstract

Microbial Fuel Cell (MFC) is gaining high interest by researcher around the globe as this is a promising renewable technology that has capability in producing electrical energy. In this study, the effect of the thermal pretreatment method (60, 80, 100, 120 and 140 ºC) on dewatered sludge (DS) as substrate for electrogenic bacteria (EB) in ML-MFC was optimized using one-factor-at-a-time (OFAT) method. The treated sludge then was used in ML-MFC by exposing them to the constant incubation temperature (35 ºC) with constant parameter of pH (6), initial moisture content (30 % vol/wt) and electrodes distance (3 cm) for 7 days incubation period. The performance of ML-MFC was relied on generation of soluble chemical oxygen demand (SCOD), power generation and EB biomass. Results shows the thermal pretreatment at 80 ºC was the optimum condition as the DS degradation rate (increment 78 %) when DS was treated for 4 h time treatment prior used in the ML-MFC. The degradation of DS was further degraded in ML-MFC via bio-catalysis process (51 % of SCOD produced compared initial DS inserted in MFCs ≈ 66 % SCOD removal). It was important to have a high DS degradation as the EB in ML-MFC would obtain more ‘food’ to growth thus increased the voltage (239 mV) and power density (98.34 mW/m2) generation. In comparison, the control ML-MFC recorded low performance of DS degradation rate (21 %), voltage (24 mV) and power density 0.88 mW/m2. Thus, by combining the pretreatment method of dewatered sludge prior used in ML-MFC it could improve the performance and expanding the application of ML-MFC as future renewable technology for sustainability of power sources. The EB strains was Bacillus subtilis sp.