Investigating the performance of constructed wetland microbial fuel cells using three indigenous South African wetland plants

Abstract

Constructed wetland microbial fuel cells (CW-MFC) can be used to treat wastewater while also generating bio-electricity. Most research on CW-MFCs have focused on cell configuration rather than the influence different wetland plants have on bio-electricity production.In this study, three different indigenous wetland plants were investigated: Cyperus prolifer, Wachendorfia thyrsiflora, and Phragmites australis. Bio-electricity production was assessed in terms of maximum power density and voltage variation. The highest power density and voltage was obtained from the C. prolifer plant species (229 ± 52 mW/m3; 510 mV). The removal efficiency of chemical oxygen demand was 97 ± 1% for C. prolifer, which was higher than W. thyrsiflora (94 ± 1%), P. australis (94 ± 1%) and the control (unplanted) system (90 ± 2%). Phosphorus removal was measured in terms of orthophosphate removal efficiency. The C. prolifer plant species achieved higher orthophosphate removal efficiency (98 ± 0%) than the control (72 ± 7%), W. thyrsiflora (58 ± 6%) and P. australis (81 ± 4%). It was determined that a high root specific area and biomass were advantageous to power production. It was also found that rapid acclimatisation to the wastewater was an important factor for generating power.From this study, it was determined that C. prolifer was the most suitable wetland plant in terms of bio-electricity, organic matter, ammonia and phosphate removal among the investigated plant species. Hence, in the design of a CW-MFC it would be advisable to use C. prolifer to simultaneously treat wastewater and produce bio-electricity.