Please use this identifier to cite or link to this item: http://hdl.handle.net/10125/62565

Oxidation-Reduction Potential-Based Micro-Aeration Control System for Anaerobic Digestion.

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Title:Oxidation-Reduction Potential-Based Micro-Aeration Control System for Anaerobic Digestion.
Authors:Nguyen, Minh Duc
Contributors:Molecular Biosciences & Bioeng (department)
Keywords:ORP
micro-aeration
process control
system stability
anaerobic digestion
show 3 morebioenergy
microbial community
metabolic pathway
show less
Date Issued:Aug 2018
Publisher:University of Hawaiʻi at Mānoa
Abstract:This study developed an intermittent oxidation-reduction potential (ORP)-controlled
micro-aeration system for anaerobic digestion (AD) to avoid volatile fatty acids (VFA)
accumulation at high organic loading rate (OLR). Without micro-aeration, AD of Napier
grass, a typical energy crop, at an OLR of 5.0 g volatile solids (VS)/L/day resulted in a
total VFA concentration up to 11.0 g/L as acetic acid, causing rapid drops in pH and
methane yield regardless of pH adjustments, and driving the digester to the verge of
failure. Once intermittent (every 24 h) ORP-controlled micro-aeration was introduced in
3 replicated studies, the average total VFA concentration decreased by 56% and the
methane yield enhanced by 252%, resulting in stable performance without the need for
chemical addition or OLR reduction. By combining reactor performance results, mass
balance analyses, microbial community characterization data, and bioenergetics
evaluations, this study suggested that an alternative pathway of VFA conversion could be
accomplished through a synergistic linkage between anaerobic and aerobic conditions,
bypassing syntrophic reactions typically found in anaerobic digesters. Meanwhile,
intermittent ORP set at +25 mV from anaerobic baseline level preserved niches of
anaerobic methanogens for effective methanogenesis. This novel operating approach can
be applied as an effective process control strategy for the digestion of lignocellulosic
biomass at high OLRs and offers significant economical and logistical merits.
Description:Ph.D. Thesis. University of Hawaiʻi at Mānoa 2018.
URI:http://hdl.handle.net/10125/62565
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: Ph.D. - Molecular Biosciences and Bioengineering


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