Simultaneous bioelectrochemical degradation of algae sludge and energy recovery in microbial fuel cells

Abstract

Treatment of algae-laden raw water in drinking water treatment plants can produce large amounts of algae sludge (AS), which can cause serious pollution of the environment if improperly treated. Microbial fuel cells (MFCs) provide a new opportunity for the sustainable production of electrical energy from the removed AS. After 120 h of degradation, the maximum power density was 2.8 ± 0.0 W m⁻³ and the electrical energy recovery was 0.14 kWh kg⁻¹ COD in raw algae sludge (R-AS)-fed MFCs. The total chemical oxygen demand (TCOD) removal efficiency was 33 ± 5%. More than half of the SCOD, soluble carbohydrate, soluble protein and VFAs were effectively removed in MFCs. Alkaline pretreatment was conducted to further increase the removal of organic matter and enhance the MFC performance. When using alkaline-pretreated algae sludge (A-AS), the maximum power density and TCOD removal increased by 46 ± 1% and 73 ± 4%, respectively. Analysis of microbial community structure in the anode biofilm of MFCs based on the 16S rRNA gene clone library showed that the AS was mainly degraded through syntrophic interaction between fermentation bacteria and electrochemically active bacteria.