Evaluation of full-strength paper mill effluent for electricity generation in mediator-less microbial fuel cells
In the search for renewable, sustainable and affordable energy sources, microbial fuel cells (MFCs) offer the advantage of a biological oxidation of pollutants to the direct generation of electricity by microorganisms. We thus examined the biodegradability and suitability of unamended paper mill effluent for power production in MFCs. In addition, an investigation of the response from indigenous waste microbes upon introduction of an exogenous Enterobacter cloacae culture was performed. Unamended effluent alone reached a substrate degradation rate (SDR) of 0.112 kg COD/m3day and 29.4 ± 2.4% total chemical oxygen demand (tCOD) removal, the power density peaked at 24 ± 3 mW/m2 and 47.7% glucose increase at the termination of the reactor cycle after 12 ± 3 days. The introduction of E. cloacae in separate setups lowered electricity generation, but benefited remediation, power density decreased to 13 ± 2 mW/m2 whereas the SDR increased to 0.257 kg COD/m3day. Also, there was 44.1% glucose removal in the presence of E. cloacae. It was concluded that unamended paper mill effluent can fuel electricity generation in MFCs with its concomitant remediation. The addition of E. cloacae to live paper mill effluent may be antagonistic in terms of electricity generation.
Key words: Microbial fuel cells, paper mill effluent, bioremediation, substrate degradation rate, wastewater, renewable energy, electricity.