2 学生会員 広島大学 工学研究科 社会基盤環境工学(〒739-8527 広島県東広島市鏡山1-4-1) 3 正会員 工博 広島大学助教 工学研究院 社会環境空間(〒739-8527 広島県東広島市鏡山1-4-1) 4 正会員 工博 広島大学准教授 工学研究院 社会環境空間(〒739-8527 広島県東広島市鏡山1-4-1) Laboratory experiments were conducted to propose a microbial fuel cell-based technology for recovering electrons from the sludge deposited in estuarine regions, in order to improve the reduced environment (i.e. removal of hydrogen sulfide "H2S" and redox potential "ORP") of the sludge and the water environment. The results suggested that the electron recovery could perfectly remove H2S from the sludge and increase the ORP of the sludge. By electron recovery, the ORP of overlying water was kept higher and the electrical conductivity was kept lower comparing with those without the electron recovery. These ensure that the electron recovery could also confine the ion diffusion from sludge to overlying water, which lower the aggravation of water environment by the ion diffusion from the deposited sludge.

The method of improving bottom water environment using industrial wastes to suppress diffusion substances from bottom sediment has recently captured the attention of many researchers. In this study, wastewater discharge-derived sediment was used to examine an alternative approach involving the use of sediment microbial fuel cells (SMFCs) in relaxing the formation of hypoxic bottom water, and removing reduced substances from sediment. Concentrations of dissolved oxygen (DO) and other ions were measured in overlying water and sediment pore water with and without the application of SMFCs. The results suggest that SMFCs can markedly reduce hydrogen sulfide and manganese ion concentrations in overlying water, and decrease the depletions of redox potential and DO concentration. In addition, SMFCs can dissolve ferric compounds in the sediment and thereby release the ferric ion available to fix phosphate in the sediment. Our results indicate that SMFCs can be used as an alternative method to relax the formation of hypoxic bottom water and to remove reduced substances from the sediment, thus improving the quality of both water and sediment environments.

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