Effect of dewatered sludge microwave pretreatment temperature and duration on net energy generation and biosolids quality from anaerobic digestion

Gokce Kor-Bicakci, Emine Ubay-Cokgor and Cigdem Eskicioglu

Energy, 2019, vol. 168, issue C, 782-795

Abstract: The effects of microwave (MW) final temperature (80 and 160 °C) and holding time (1 and 30 minutes) were evaluated by ten anaerobic digesters (AD). MW was applied to dewatered secondary sludge with total solids of 10.5 ± 0.5% (by weight) to minimize energy input. Mixed sludge was digested under thermophilic and mesophilic conditions at sludge retention times (SRTs) of 20, 12, and 6 days. MW final temperature had significantly higher effect on solubilization than holding time. At MW of 80/160 °C, longer holding times further enhanced solubilization but increased volatile fatty acid accumulation at thermophilic SRT of 6 days. While all mesophilic digesters met the Class B requirement in terms of pathogens removal, all thermophilic digesters produced Class A biosolids. MW-ADs were able to tolerate 15–20% higher loading rates compared to controls. Up to 21% higher organics removals were achieved by MW. MW at 160 °C generated the highest amount of extra heat that could be used within/outside of plant. However energy recovered from the enhanced methane production was not sufficient to cover the electrical energy consumed by MW. Therefore, a custom-designed electromagnetic heating unit based on dielectric properties of sludge is needed to minimize energy input and maximize energy recovery for full-scale applications.

Keywords: Anaerobic digestion; Biosolids; Electrical energy; Land application; Microwave pretreatment; Wastewater sludge (search for similar items in EconPapers)
Date: 2019
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Citations: View citations in EconPapers (7)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:168:y:2019:i:c:p:782-795

DOI: 10.1016/j.energy.2018.11.103

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