Decreasing Sulfide Concentrations In Sediment Using Plant-sediment Microbial Fuel Cells

Hydrogen sulfide is ubiquitously present in sediment of water-plant-sediment system and needs to be removed for an economic, environmental and safety point of view as it is a toxic, corrosive and odorous compound being harmful to aquatic organism and workers’health. As phytotoxin, sulfide makes the roots rot and aquatic plants wither. Plant-sediment microbial fuel cells can eliminate sediment organic pollution and reduce the hazard of sulfion to aquatic plant while S2-acts as electron medium to generate electricity in the anode of microbial fuel cells. In this research, the arm is to reduce the hazard of sulfion by plant-sediment microbial fuel cells.The rice sediment microbial fuel cells and control reactors in a lab-scale rice field were developed to evaluate the effect of SMFCs on the sulfide concentration in2.5mm and5.0mm soil layer. A data acquisition device was used to record operating voltages. The operating voltages of SMFCs without rice was0.015V while the operating voltages of plant-SMFC with rice achieved0.035V. The sulfide concentrations in2.5mm and5.0mm soil layer in the rice field with SMFCs were (6.97±1.36) mg/U (8.33±1.76) mg/L and they are (12.9±3.06) mg/L and (16.5±4.63) mg/L in control reactors, respectively. To decreasing the sulfide concentrations in the sediment of plant-SMFCs, the external resistor, DO and COD in overlying water were optimized. In this research, the sulfide concentrations in sediment were the lowest with500Ω. of external resistor,300mg/L of COD and0.25L/min of air flow.Three lab-scale plant-SMFCs with acorus calamus, spathiphyllum, chamaedorea elegans were developed with external resistors of500Ω and data acquisition device to record operating voltages. Sulfide concentrations in lcm and2cm soil layers in the SMFCs were measured. The operating voltages of SMFCs without plants were0.05,0.018and0.017V while the operating voltages of plant-SMFC with the three plants achieved0.35,0.027and0.031V. The sulfide concentrations in lcm and2cm soil layer in the acorus calamus-SMFC and control reactor were (1.66±0.31) μmol/g,(9.29±3.46) μmol/gand (2.38±0.10) μmol/g,(24.2±1.02) μmol/grespectively. The results in the plant-SMFCs with spathiphyllum and chamaedorea elegans show the same trend. The sulfide concentrations in the sediment layers at both1cm and2cm depth for all three Plant-SMFCs are lower than that in their control reactors.The results illustrate that emergent aquatic plant can improve the electricity generation performance of sediment microbial fuel cells. The order of electricity generation in the plant-microbial fuel cells with four different emergent aquatic was acorus calamuscan, rice, chamaedorea elegans and spathiphyllum. Plant-sediment microbial fuel cells decreased sulfide concentration in sediment and inhibit the sulfide emission from the water-plant-sediment system, the order of decreasing sulfide concentration was acorus calamuscan, spathiphyllum, rice and chamaedorea elegans.