Abstract
MFC centered hybrid technologies have attracted attention during the last few years due to their compatibility and dual advantages of energy recovery and wastewater treatment. In this study, a MFC was integrated into a dewatered alum sludge (DAS)- based vertical upflow constructed wetland (CW). Powder activate carbon (PAC) was used in the anode area in varied percentage with DAS to explore its influences on the performance of the CW-MFC system. The trial has demonstrated that the inclusion of PAC improved the removal efficiencies of COD, TN and RP. More significantly, increasing the proportion of PAC from 2% to 10% can significantly enhance the maximum power densities from 36.58 mW/m2 to 87.79 mW/m2. The induced favorable environment for bio-cathode formation might be the main reason for this improvement since the content of total extracellular polymeric substances (TEPS) of the substrate in the cathode area almost doubled (from 44.59 μg/g wet sludge to 87.70 μg/g wet sludge) as the percentage of PAC increased to 10%. This work provides another potential usage of PAC in CW-MFCs with a higher wastewater treatment efficiency and energy recovery.
Highlights
Attempted to change the flow regimes[10] or optimize the cathode materials and configurations[11] to improve the system output
Diluted swine water with the designed concentration was continuously fed to five parallel CW-microbial fuel cell (MFC) systems
Compared to these operated under open-circuit condition (Table S1), it is clearly to see that the integration of MFC into CWs further enhanced the removal of COD, but no significant differences were observed in terms of reactive phosphate (RP), NO3-N and NO2-N
Summary
It should be pointed out that no significant nitrite-N was detected during the whole period This can be caused by the reasons that: 1) simultaneous nitrification denitrification (SND) process occurred in the system as presented by several previous studies36,41; 2) the existence of Nitrobacter can directly oxidize nitrite into nitrate owing to the sufficient DO provision in the upper layer of the CW-MFC system (NO2−+1/2O2 →NO3−+ΔG0, ΔG0 =−65 ~ −90 kJ/mol)[42]. In terms of the bottom area, the concentration of TEPS sharply decreased from 101.03 μg/g to less than 35.00 μg/g when the percentage of PAC increased from 0% to 10% This is different from the previous study on PAC dosage during the ultrafiltration process, where the PAC additions acted as a supporter for microorganisms and the adsorbed dissolved organic matter facilitated their propagation[44]. Wang et al.[51] showed that compared to abiotic-cathode, biocathode can significantly decreased the PAC (%) 0
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