Two-Phase Improves Performance of Anaerobic Membrane Bioreactor Treatment of Food Waste at High Organic Loading Rates

Abstract

Anaerobic membrane bioreactors (AnMBRs) are in use at the full-scale for energy recovery from food waste (FW). In this study, the potential for two-phase (acid/gas) AnMBR treatment of FW was investigated as a strategy to increase microbial diversity, thereby improving performance. Two bench-scale AnMBRs were operated in single-phase (SP) and two-phase (TP) mode across incremental increases in organic loading rate (OLR) from 2.5 to 15 g total chemical oxygen demand (COD) L•d −1 . The TP acid-phase (TP-AP) enriched total VFAs by 3-fold compared to influent FW and harbored a distinct microbial community enriched in fermenters that thrived in the low pH environment. The TP methane phase (TP-MP) showed increased methane production and resilience relative to SP as OLR increased from 3.5 to 10 g COD L•d −1 . SP showed signs of inhibition (i.e., rapid decrease in methane production per OLR) at 10 g COD L•d −1 , whereas both systems were inhibited at 15 g COD L•d −1 . At 10 g COD L• d −1 , where the highest difference in performance was observed (20.3% increase in methane production), activity of syntrophic bacteria in TP-MP was double that of SP. Our results indicate that AnMBRs in TP mode could effectively treat FW at OLRs up to 10 g COD•L day −1 by improving hydrolysis rates, microbial diversity, and syntroph activity, and enriching resistant communities to high OLRs relative to AnMBRs in SP mode.

Membrane processes

“…Amha, Corbett, and Smith (2019) investigated bench‐scale AnMBR treatment of Food Waste both for Single‐Phase and Two‐Phase (acid‐phase and methane‐ phase) by looking at biogas production and microbiological community dynamics of these systems at various Organic Loading Rates up to 15 g COD L/day. The two‐phased mode was found more effective in treating food waste at low pH.…”

Food‐processing wastes

“…The potential of a two-phase (acid phase followed by gas phase) anaerobic membrane bioreactor (AnMBR) to treat food waste by attempting to increase the microbial diversity and improve performance was evaluated by Amha, Corbett, and Smith (2019). The authors found that the two-phase AnMBR treatment improved the rate of hydrolysis, increased the diversity of the microbial consortium, and enhanced syntrophic activity in the system.…”

Investigation of Fats, Oils, and Grease Co-digestion With Food Waste in Anaerobic Membrane Bioreactors and the Associated Microbial Community Using MinION Sequencing

“…Anaerobic membrane bioreactors (AnMBRs), which combine anaerobic digestion and membrane separation to improve effluent quality and increase biogas production, are an attractive biotechnology for organic waste management (Smith et al, 2012;. Amha et al (2019) demonstrated that AnMBR management of food waste (FW) provided >95% chemical oxygen demand (COD) removal. Further, AnMBR was reported to produce 0.13-0.18 L CH 4 per g of COD removed during treatment of food processing wastewater with a net energy benefit of 0.16-1.82 kWh m −3 (Galib et al, 2016).…”

“…Our previous study on FW management in TP AnMBRs demonstrated a significant increase in methane production compared to SP AnMBRs at ORLs up to 10 gCOD L −1 d −1 . The increase, ranging from 15.2 to 20.3%, was a result of increased VFA production (up to three times compared to the influent FW) in the AP of the TP reactor and increased diversity of the microbial community with higher activity of syntrophic fatty acid oxidizers in the TP-MP reactor compared to the SP reactor (Amha et al, 2019). However, the economic feasibility of a TP over a SP AnMBR is yet to be evaluated.…”