Effects of Electrodialysis Physical and Operating Parameters on the Performance of an Anaerobic Digestion-Electrodialysis System for Volatile Fatty Acid Production and Recovery.

Authors

Holly Haflich, Hezhou Ding, Douglas F Call, Orlando Coronell

Published in

ACS omega. Volume 10. Issue 28. Pages 30167-30180. Jul 22, 2025. Epub Jul 07, 2025.

Abstract

Anaerobic digestion (AD) has two key challenges for producing volatile fatty acids (VFAs) from organic-rich wastes: (i) VFA production can become inhibited by VFA/NH₄ ⁺ accumulation, and (ii) VFAs must be selectively recovered. To address both challenges, VFAs and NH₄ ⁺ must be separated from the AD digestate, which has been previously accomplished using electrodialysis (ED) as a separation method. Previous studies have validated the technical feasibility of combining AD and ED to enhance VFA production and recovery but only for cases using one ED configuration. Therefore, the role of ED physical and operating parameters, which govern VFA/NH₄ ⁺ concentrations in the ED-treated digestate that is recycled back to the AD bioreactor, is unknown. We hypothesize that using ED parameters that enable high VFA/NH₄ ⁺ removal and recovery will enhance VFA production in a combined AD-ED system. Accordingly, our objective was to investigate how ED treatment conditions of AD digestate affect VFA production when the ED-treated digestates are recycled back into the AD bioreactors. To do this, we studied the effect of applied voltage, number of ion exchange membrane (IEM) pairs, and ED operation time on VFA/NH₄ ⁺ transport, energy consumption, current efficiency, and VFA production in a sequential batch AD-ED system. We found that VFA/NH₄ ⁺ transport scaled with voltage, increasing the number of IEM pairs improved VFA/NH₄ ⁺ transport and reduced energy consumption, and increasing ED operation time improved VFA/NH₄ ⁺ recovery with minimal impact on energy consumption. Recycling the ED-treated digestate back to the AD bioreactors led to small (7.91-19.8%, p = 0.30-0.66, three ED treatments) to moderate (40.4%, p = 0.06, one ED treatment) increases in VFA production relative to a control without ED-treated digestate recycling. However, we did not observe a strong or significant relationship between VFA production and the VFA/NH₄ ⁺ concentration in the AD bioreactors after ED-treated digestate recycling (R ² = 0.18-0.26, p = 0.49-0.58). Therefore, our results indicate that while recycling ED-treated digestate has the potential to increase VFA production in the AD bioreactor, the concentrations of VFAs and/or NH₄ ⁺ alone do not solely govern the extent of VFA production. Our results provide a foundation for further optimization of VFA production and recovery in an AD-ED system.

PMID:
40727729
Bibliographic data and abstract were imported from PubMed on 29 Jul 2025.

Read full publication at:
Please sign in to see all details.

Stats

1-terrible, 9-excellent. How would you rate this publication? Sign in in to submit your rating.

Post a comment

You need to be signed in to post comments. You can sign in here.

Comments

There are no comments yet.