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.

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Many studies have reported variation in properties of the sediment within electrokinetic treatments (EKTs). However, we aim to reveal the variation in properties of the sediment following EKTs through laboratory experiments. We collected sewage-derived sediment from a littoral region, and passed it through a 2-mm sieve. We used a potentiostat to cause electrical current in EKT. We measured the sediment properties such as pH, redox potential (ORP), and hydrogen sulphide (HS) concentration at the end of EKT and at 30 days following EKT. Results showed decreases in pH, increases in ORP, and decreases in HS concentration at the end of EKT. Compared with the sediment without EKT, the decrease in ORP for the sediment within EKT was higher at 30 days following EKT. These suggest that anaerobic digestion of organic compounds occurs in the sediment following EKT, of which the oxidants produced by EKT serve as electron acceptors and organic compounds serve as electron donors. Furthermore, we found that EKT can remove HS from the sediment and reduce HS production in the sediment within EKT when compared to the case without EKT. These ensure that EKT can be used to remove HS and control HS production in the sediment.