A novel fragmented anode biofilm microbial fuel cell (FAB\u2013MFC) integrated system for domestic wastewater treatment and bioelectricity generation

Tesfalem Atnafu,Seyoum Leta

doi:10.1186/s40643-021-00442-x

Abstract

BackgroundThe critical MFC design challenge is to increase anode surface area. A novel FAB–MFC integrated system was developed and evaluated for domestic wastewater treatment. It was operated in fed-batch flow mode at 1–3 days of HRT with 755 mg/L CODIN and 0.76 kg-COD/m3/day. The study includes anaerobic-MFC and aerobic-MFC integrated systems. Microbial electrode jacket dish (MEJ-dish) with hybrid dimension (HD) was invented, first time to authors’ knowledge, to boost anode biofilm growth. The treatment system with MEJ+ (FAB) and MEJ− (MFC) anode are called FAB–MFC and MFC, respectively.ResultsFragmented variable anode biofilm thickness was observed in FAB than MFC. The FAB–MFC (FAB+) simple technique increases the anode biofilm thickness by ~ 5 times MFC. Due to HD the anode biofilm was fragmented in FAB+ system than MFC. At the end of each treatment cycle, voltage drops. All FAB+ integrated systems reduced voltage drop relative to MFC. FAB reduces voltage drops better than MFC in anaerobic-MFC from 6 to 20 mV and aerobic-MFC from 35–47 mV at 1 kΩ external load. The highest power density was achieved by FAB in anaerobic-MFC (FAB = 104 mW/m2, MFC = 98 mW/m2) and aerobic-MFC integrated system (FAB = 59 mW/m2, MFC = 42 mW/m2).ConclusionsThe ∆COD and CE between FAB and MFC could not be concluded because both setups were inserted in the same reactor. The integrated system COD removal (78–97%) was higher than the solitary MFC treatment (68–78%). This study findings support the FAB+ integrated system could be applied for real applications and improve performance. However, it might depend on influent COD, the microbial nature, and ∆COD in FAB+ and MFC, which requires further study.Graphic abstract

Highlights

The modern wastewater treatment (WWT) system is expected to be energy-autonomous and zero liquid discharge (Li et al 2013; Stoll et al 2018)
Applications of Fragmented anode biofilm reactor (FAB)–Microbial fuel cell (MFC) This study presented a simple, practical technique (FAB) to increase anode surface area that influences the anode biofilm structure without chemical or thermal modification
The fragmented anode biofilm microbial fuel cell (FAB–MFC) (FAB+) integrated system improved the COD removal compared with solitary MFC

Summary

Introduction

The modern wastewater treatment (WWT) system is expected to be energy-autonomous and zero liquid discharge (Li et al 2013; Stoll et al 2018). The aeration demands 0.5–0.29 kWh/m3 (3–5% of developed countries national energy budget), which costs $0.12/m3 The wastewater is endowed with organic matter that can generate 9.3 times the energy required for treatment (Logan and Regan 2006), equivalent to 4.9–7.9 kWh/kg COD or 7.6 kJ/L that vary based on source (Heidrich et al 2011). Developing a WWT system that reduces pillar challenges, sludge and aeration, sound sustainable. A novel FAB–MFC integrated system was developed and evaluated for domestic wastewater treatment. It was operated in fed-batch flow mode at 1–3 days of HRT with 755 mg/L CODIN and 0.76 kg-COD/m3/day. The treatment system with MEJ+ (FAB) and MEJ− (MFC) anode are called FAB–MFC and MFC, respectively

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