| Effects of Microwave Pretreatment on Mesophilic Anaerobic
Digestion for Mixture of Primary and Secondary Sludges
Compared with Thermal Pretreatment |
| Woon-Ji Park, and Johng-Hwa Ahn† |
| Department of Environmental Engineering, College of Engineering, Kangwon National University, Chuncheon 200-701, Korea |
Corresponding Author:
Johng-Hwa Ahn ,Tel: +82-33-250-6357, Fax: +82-33-254-6357, Email: johnghwa@kangwon.ac.kr
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Received: January 18, 2011; Accepted: May 31, 2011. |
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| ABSTRACT |
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This work experimentally determined the effect of thermal and microwave pretreatments on the anaerobic digestion of mixtures of
municipal primary and secondary sludges in semi-continuous mesophilic digesters at hydraulic retention times (HRT) of 20, 15, 10, 7,
and 5 days. The ratio of soluble chemical oxygen demand (COD) to total COD in thermally pretreated and microwaved sludges at 80°C
was 2.7 and 3.2 times higher than that of raw sludge, respectively. The volatile solids (VS) and COD removal efficiencies in all three digesters
fed with raw (control), thermally pretreated (TM), and microwaved (MW) sludges decreased as the HRT was reduced. The highest
relative improvement in VS removal compared to the control occurred at the HRT of 5 days in the TM and MW (29 and 41% higher
than the control, respectively). At this HRT, improvement in the COD removal efficiencies in the TM and MW compared to the control
was 28 and 53%, respectively. Improvements in biogas production compared with the control increased in both the TM and MW as the
HRT was reduced to 5 days. The relative improvement in daily biogas production compared to the control from the TM and MW was 33
and 53% higher than the control at the HRT of 5 days, respectively. The results show that microwave pretreatment is more effective than
thermal pretreatment in increasing the solubilization degree and mesophilic anaerobic biodegradability of sewage sludge. |
| Keywords:
Biogas | Digester | Disintegration | Process | Sewage sludge |
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