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

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dc.contributor.authorNguyen, Minh Duc
dc.contributor.departmentMolecular Biosciences & Bioeng
dc.date.accessioned2019-05-28T20:17:04Z
dc.date.available2019-05-28T20:17:04Z
dc.date.issued2018-08
dc.identifier.urihttp://hdl.handle.net/10125/62565
dc.subjectORP
dc.subjectmicro-aeration
dc.subjectprocess control
dc.subjectsystem stability
dc.subjectanaerobic digestion
dc.subjectbioenergy
dc.subjectmicrobial community
dc.subjectmetabolic pathway
dc.titleOxidation-Reduction Potential-Based Micro-Aeration Control System for Anaerobic Digestion.
dc.typeThesis
dcterms.abstractThis 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.
dcterms.descriptionPh.D. Thesis. University of Hawaiʻi at Mānoa 2018.
dcterms.languageeng
dcterms.publisherUniversity of Hawaiʻi at Mānoa
dcterms.rightsAll 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.
dcterms.typeText

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