Synergistic Effect of Magnetite and Bioelectrochemical Systems on Anaerobic Digestion.

Nhlanganiso Ivan Madondo,Emmanuel Kweinor Tetteh,Sudesh Rathilal,Babatunde Femi Bakare

doi:10.3390/bioengineering8120198

Nhlanganiso Ivan Madondo, Emmanuel Kweinor Tetteh + Show 2 more

Open Access

https://doi.org/10.3390/bioengineering8120198

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Abstract

Conventionally, the anaerobic digestion of industrial effluent to biogas constitutes less than 65% methane, which warrants its potential methanation to mitigate carbon dioxide and other anthropogenic gas emissions. The performance of the anaerobic digestion process can be enhanced by improving biochemical activities. The aim of this study was to examine the synergistic effect of the magnetite and bioelectrochemical systems (BES) on anaerobic digestion by comparing four digesters, namely a microbial fuel cell (MFC), microbial electrolysis cell (MEC), MEC with 1 g of magnetite nanoparticles (MECM), and a control digester with only sewage sludge (500 mL) and inoculum (300 mL). The MFC digester was equipped with zinc and copper electrodes including a 100 Ω resistor, whereas the MEC was supplied with 0.4 V on the electrodes. The MECM digester performed better as it improved microbial activity, increased the content of methane (by 43% compared to 41% of the control), and reduced contaminants (carbon oxygen demand, phosphates, colour, turbidity, total suspended solids, and total organic carbon) by more than 81.9%. Current density ( = 25.0 mA/m2) and electrical conductivity (275 µS/cm) were also high. The prospects of combining magnetite and bioelectrochemical systems seem very promising as they showed a great possibility for use in bioelectrochemical methane generation and wastewater treatment.

Highlights

Due to ongoing worldwide environmental concerns, anaerobic digestion is seen as having a high capability to reduce the need for freshwater whilst encouraging the depletion of global warming that is usually high when fossil fuel is used [1,2]
The results revealed a high increase in accumulated methane production of up to 21.5% over the control when using the digester with an electromagnetic strength of 7.5 mT, whereas carbon oxygen demand (COD) removal increased by 15%
This suggests that the microbes require about 2 days to fully adjust in the microbial fuel cell (MFC)

Summary

Introduction

Due to ongoing worldwide environmental concerns, anaerobic digestion is seen as having a high capability to reduce the need for freshwater whilst encouraging the depletion of global warming that is usually high when fossil fuel is used [1,2]. The process of anaerobic digestion is a physio-biochemical treatment system that breaks down complex substances by means of the syntrophic action of different kinds of anaerobic microbes, in an oxygen free environment, into biogas that consists mostly of methane and carbon dioxide [3]. The conventional anaerobic digestion system on its own is not economically effective enough especially if operated at room temperatures, mainly because of the slow rate of biochemical substrate removal, the need for large digesters, and low methane generation. Working at higher temperatures may result in process instability which may lead to reduced methane production [5,6]. Another drawback of thermophilic temperature is the high energy usage

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