Integration of microbial fuel cell techniques into activated sludge wastewater treatment processes to improve nitrogen removal and reduce sludge production

Abstract

Bioelectrochemical systems are emerging for wastewater treatment, yet little is known about how well they can be integrated with current wastewater treatment processes. In this bench-scale study, the microbial fuel cell (MFC) technique was incorporated into the Modified Ludzack–Ettinger (MLE) process (phase I) and later with the membrane bioreactor (MBR) process (phase II) to evaluate the performance of MFC assisted wastewater treatment systems (i.e., MLE–MFC and MBR–MFC). There was no significant difference in the effluent NH4+–N concentration between the systems integrating MFC and the open circuit controls. The average effluent COD concentration was significantly lower in the MLE–MFC, but it did not change much in the MBR–MFC because of the already low COD concentrations in MBR operation. The MLE–MFC and MBR–MFC systems increased the NO3−–N removal efficiencies by 31% (±12%) and 20% (±12%), respectively, and reduced sludge production by 11% and 6%, respectively, while generating an average voltage of 0.13 (±0.03) V in both systems. Analysis of the bacterial specific oxygen uptake rate, the sludge volume index, and ammonia-oxidizing bacterial population (dominated by Nitrosomonas through terminal restriction fragment length polymorphism analysis) indicated that there was no significant difference in sludge activity, settling property, and nitrifying community structure between the MFC assisted systems and the open circuit controls. The results suggest that the wastewater treatment systems could achieve higher effluent water quality and lower sludge production if it is integrated well with MFC techniques.