Sediment Remediation Based On Floating Bed Plant-sediment Microbial Fuel Cell (P-SMFC) Systems

Black-odorous freshwater sediment, artificial wastewater and floating bed plants wereused in this study for constructing plant sediment microbial fuel cells (P-SMFCs). The maincontents in this paper including: the comparison of secretion ability of roots between Cyperusalternifolius and Canna indica, investigation of the capacity for P-SMFC to generateelectricity, and analysis of the sediment remediation and wastewater treatment based onP-SMFC. Several conclusions were got as follows.This study investigated and compared the secretory capacity and radial oxygen loss(ROL)rate of Cyperus alternifolius and Canna indica after they were domesticated by river sewageand Hoagland nutrient solution respectively. The results showed that, after domestication intwo different culture media, Cyperus alternifolius showed significantly higher secretorycapacity and ROL rate than Canna indica.This study set up a total of five treatment systems, including MFC-0(sediment, artificialwastewater+electrodes), MFC-C.i (ediment, artificial wastewater+electrodes+Cannaindica), MFC-C.a (ediment, artificial wastewater+electrodes+Cyperus alternifolius), C.i(ediment, artificial wastewater+Canna indica) and C.a (ediment, artificial wastewater+Cyperus alternifolius). Among these, the first three structures were P-SMFC systems. Theelectricity production of the three systems were observed and the results showed that the threeP-SMFC systems were successfully started up after two months of operation and the stablevoltage reached0.300,0.311,0.346V respectively. However, the power density of the systemswere relatively low, showing4.65mW·m-26.99mW·m-2and7.53mW·m-2respectively. Andthe internal resistance were1136Ω871Ω and942Ω respectively. The order of the electricityproduction was MFC-C.a>MFC-C.i>MFC-0, which was consistent with the fact that Cyperusalternifolius has higher ROL rate than Canna indica.The P-SMFC systems constructed in this study could be used to repair sediments. Theresults showed that the organic content in sediment remarkablely decreased with the existenceof electricity production process of P-SMFC and the reductions were9.58±0.58%(MFC-0)9.89±2.79%(MFC-C.i)10.40±1.40%(MFC-C.a) respectively, which were significantlyhigher than that of C.i (2.61±0.18%) and C.a (3.33±0.30%). Changes in ammonium, total phosphorus and heavy metals in the sediments showed a significant negative linear correlationto changes in organic content, which demonstrated that the existence of electrodes couldeffectively degrade the organic matter in sediment, increase the production of ammoniumaround the anodes, and in the meanwhile inhibit the migration of phosphorus and heavymetals to the overlying water. But the changes of nitrate in the sedment showed no relevanceto whether the electrodes exist or not.The P-SMFC systems could treat wastewater as well. The results showed that the CODremoval of MFC-C.i, MFC-C.a, C.i and C.a could reach up to90%, while MFC-0was just63.8±2.4%. Treatment systems based on Cyperus alternifolius showed higher removal ofammonium and total phosphorus than the groups based on Canna indica, which wasconsistent with the fact that Cyperus alternifolius had higher secretion capacity than Cannaindica. In addition, C.i and C.a showed higher ammonium removal than MFC-C.i andMFC-C.a, which might related to the changes of ORP aound the cathode. Among the fivetreatment groups, MFC-0reached the highest removal for ammonium (98.6±0.3%) and totalphosphorus (83.8±7.1%), which might related to the growth of algae according to theexperiments.