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.
| Original language | English |
|---|---|
| Pages (from-to) | 782-795 |
| Number of pages | 14 |
| Journal | Energy |
| Volume | 168 |
| DOIs | |
| Publication status | Published - 1 Feb 2019 |
Bibliographical note
Publisher Copyright:© 2018 Elsevier Ltd
Funding
Gokce Kor-Bicakci was supported by the 2214/A International Research Fellowship Programme of the Scientific and Technological Research Council of Turkey (TUBITAK) . This work has been carried out with the financial support of TUBITAK and The Natural Sciences and Engineering Research Council (NSERC) - Collaborative Research and Development Grant ( CRDP J462765-13 ). The authors express their gratitude to Tim Abbott (Ph.D. candidate at UBC's Okanagan Campus) for his assistance in providing sludge samples and Dr. Muneer Ahmad for his help during fecal coliform analysis. The authors would like to thank Dr. Ehssan Hosseini Koupaie (Postdoctoral Fellow at Ryerson University) and Dr. Deniz Akgul (Assist. Prof. at Marmara University) for their contributions for energy analysis.
| Funders | Funder number |
|---|---|
| TUBITAK | |
| Natural Sciences and Engineering Research Council of Canada | CRDP J462765-13 |
| Türkiye Bilimsel ve Teknolojik Araştirma Kurumu |
Keywords
- Anaerobic digestion
- Biosolids
- Electrical energy
- Land application
- Microwave pretreatment
- Wastewater sludge