Comparative Assessment of Sludge Pre-Treatment Techniques to Enhance Sludge Dewaterability and Biogas Production

Didem Okutman Tas*, Cigdem Yangin-Gomec, Tugba Olmez-Hanci, Osman A. Arikan, Deniz I. Cifci, Elif B. Gencsoy, Alpaslan Ekdal, Emine Ubay-Cokgor

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)


Effectiveness of ultrasonication, microwave technologies, and enzyme addition prior to anaerobic digestion is investigated using sludge samples taken from the secondary settling tank of a domestic wastewater treatment plant to improve methane production, enhance dewaterability characteristics of the sludge, and to reduce excess sludge. Microwave pre-treatment (1500 W, 10 min at 175 °C) results in better extra digester performance (compared to the control reactor) in terms of methane production (25 m3 ton−1 suspended solids (SS)) than ultrasound (no improvement) and enzyme pre-treatment (11 m3 ton−1 SS). While methane production is not improved as a result of ultrasonication pre-treatment (15 000 kJ kg−1 SS), a noticeable increase (19%) is observed in the case of microwave pre-treatment. Higher compactibility values are obtained after ultrasonication and microwave application compared to the control (i.e., from 7.1 to 8.7 and 9.2%, respectively) before anaerobic digestion. Although ultrasonication and microwave application decrease the dewaterability of the raw sludge (capillary suction time (CST) from 827 to 1364 and 2290 s, respectively), similar dewaterability results are obtained at the end of the anaerobic digestion process for all pre-treated sludge samples. An economic assessment of this study shows that pre-treatment with microwave results in more than 10-fold less net cost compared to the enzyme application.

Original languageEnglish
Article number1700569
JournalClean - Soil, Air, Water
Issue number1
Publication statusPublished - Jan 2018

Bibliographical note

Publisher Copyright:
© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


This study was supported by TUBITAK (Turkish National Scientific Council) under the project number 108G167: Management of Domestic/ Urban Wastewater Sludges in Turkey and I.T.U Research Fund, Project No: 34827: Effects of Ultrasound Disintegration on Anaerobic Treatment of Domestic/Urban Treatment Sludges.

FundersFunder number
Turkish National Scientific Council108G167, 34827


    • anaerobic digestion
    • enzymes
    • microwave
    • sludge minimization
    • ultrasonication


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