Abstract
Soil microbial fuel cells (sMFC) are novel technique that uses organic matters in soils as an alternative energy source. External resistance (ER) is a key factor that influences sMFC performance and also alters the soil biological and chemical reactions. However, little information is available on how the microbial community and soil component changes in sMFC with different ER. Thus, the purpose of this study is to collectively examine the effects of different ER on paddy soil biotic and abiotic components. Eighteen paddy sMFC were constructed and operated at five different ER (2000, 1000, 200, 80, and 50 Ω) in triplicates for 90 days. The effects of the sMFC anodes at different ER were examined by measuring organic matter (OM) removal efficiency, trace elements in porewater, and bacterial community structure in contaminated paddy soil. The results indicate that ER has significant effects on sMFC power production, OM removal efficiency, and bacterial beta diversity. Moreover, ER influences iron, arsenic, and nickel concentration as well in soil porewater. In particular, greater current densities were observed at lower ER (2.6 mA, 50 Ω) as compared to a higher ER (0.3 mA, 2000 Ω). The removal efficiency of OM increased with decreasing ER, whereas it decreased with soil distance away from the anode. Furthermore, principal coordinate analysis (PCoA) revealed that ER may shape the bacterial community that develop in the anode vicinity but have minimal effect on that of the bulk soil. The current study illustrates that lower ER can be used to selectively enhance the relative abundance of electrogenic bacteria and lead to high OM removal.
Highlights
Organic carbon in sediments or soils can be used as a new source of energy when employed in microbial fuel cells (MFC)
The results indicated that External resistance (ER) has significant effects on Soil microbial fuel cells (sMFC) power production, organic matter (OM) removal efficiency and bacterial beta diversity
The current study illustrates that lower ER can be used to selectively enhance the relative abundance of electrogenic bacteria and lead to high OM removal
Summary
Organic carbon in sediments or soils can be used as a new source of energy when employed in microbial fuel cells (MFC). Soil microbial fuel cells (sMFC) are a special type of MFC that produce electricity by using organic chemicals present in soils as energy source [1,2,3,4]. In sMFC organic matter (OM) is oxidized at the anode by the soil microorganism, resulting in the production of electrons. SMFC that employ paddy soil has gained considerable attention recently because of the unique biological and chemical characteristics of paddy soil make them ideal for power production [5]. In addition to power generation, sMFC have found use in stimulating soil bioremediation. The anode of the sMFC can serve as an electron sink for anode respiring bacterial (ARB) and accelerate the bioremediation of both polycyclic aromatic hydrocarbons and redox active heavy metals [6,7]
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