Microbial fuel cells for polishing effluents of anaerobic digesters under inhibition, due to organic and nitrogen overloads

Abstract

BACKGROUND: Bioelectrochemical systems have been proposed as a possible polishing step for anaerobic digestion (AD). They can also be useful to overcome AD instability in case of AD inhibition while, at the same time recovering ammonia. Continuous assays with a microbial fuel cell (MFC) fed with digested pig slurry were performed to evaluate its operation during malfunction periods of the AD reactor and its feasibility as a strategy to recover ammonia, either by introducing volatile fatty acid (VFA) pulses in the MFC or by inducing AD inhibition. A microbial community assessment was performed to study MFC changes during its operation when fed with the digestate. RESULTS:The MFC achieved COD removal efficiencies of 50% during AD inhibition, reaching a maximum ammonium removal of 31% (11.19 g N m -2 d -1 ). A high throughput 16S rRNA gene based sequencing assessment revealed that the anode biofilm was different from the digestate fed, showing a reduction in microbial population diversity in the anode after a 182-day-operation period with digested pig slurry. The main enriched populations in the anode belonged to Bacteroidetes (Flavobacteriaceae), Chloroflexi (fermentative bacteria Anaerolineaceae), Methanosarcinaceae and hydrogenotrophic methanogens belonging to Methanobacteriaceae. CONCLUSION: MFCs have proven to be a reliable technology to complement the operation of AD, improving the quality of the effluent and recovering ammonia, particularly during AD inhibition.

Anaerobic digestion and electromethanogenic microbial electrolysis cell integrated system: Increased stability and recovery of ammonia and methane

“…On the second hand, BES can operate with low organic loading rates and may be used to polish the effluent of the AD [16][17][18] or even to absorb higher organic concentrations in the digestates due to AD destabilisation or inhibition [18,19]. Previous work has shown that integrated or multi-step systems can increase the energy production from complex substrates [4].…”

Microbial electrolysis cell as an emerging versatile technology: a review on its potential application, advance and challenge

“…Bioelectro-Fenton (bio-E-Fenton) as state-of-the-art technology was first proposed by Feng et al, 171 this concept is thus made possible by using the bio-electrons that have been produced from the microbial metabolism to drive an E-Fenton process. 172 Typical bio-E-Fenton systems are integrated MFC-Fenton and MEC-Fenton. Bio-E-Fenton has been studied for removing biorefractory organic pollutants.…”

Repeatability of low scan rate cyclic voltammetry in bioelectrochemical systems and effects on their performance

“…These systems currently are being studied for a wide range of potential applications such as recalcitrant pollutant removal, chemical synthesis, resource recovery and biosensors . For example, reduction of hexavalent chromium, ammonia recovery, remediation of xenobiotics, remediation of toxic metal contaminated soil, sulfate reduction or polishing effluents of anaerobic digesters are some of the applications reported recently for BES. Moreover, the generation of different products such as electricity, hydrogen, methane, biofuels, desalinated water or high‐value chemical products already has been reported.…”