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Environments 2017, 4(3), 49; https://doi.org/10.3390/environments4030049

Effects of Physico-Chemical Post-Treatments on the Semi-Continuous Anaerobic Digestion of Sewage Sludge

1
Advanced Environmental Biotechnology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, Singapore 637141, Singapore
2
Faculty of Health, Engineering and Sciences, School of Civil Engineering & Surveying, University of Southern Queensland, Toowoomba 4350, Australia
*
Author to whom correspondence should be addressed.
Received: 20 June 2017 / Revised: 4 July 2017 / Accepted: 12 July 2017 / Published: 13 July 2017
(This article belongs to the Special Issue Advances in Environmental Engineering)
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Abstract

Sludge production in wastewater treatment plants is increasing worldwide due to the increasing population. This work investigated the effects of ultrasonic (ULS), ultrasonic-ozone (ULS-Ozone) and ultrasonic + alkaline (ULS+ALK) post-treatments on the anaerobic digestion of sewage sludge in semi-continuous anaerobic reactors. Three conditions were tested with different hydraulic retention times (HRT, 10 or 20 days) and sludge recycle ratios (R = QR/Qin (%): 50 or 100%). Biogas yield increased by 17.8% when ULS+ALK post-treatment was applied to the effluent of a reactor operating at 20 days HRT and at a 100% recycle ratio. Operation at 10 days HRT also improved the biogas yield (277 mL CH4/g VSadded (VS: volatile solids) versus 249 mL CH4/g VSadded in the control). The tested post-treatment methods showed 4–7% decrease in effluent VS. The post-treatment resulted in a decrease in the cellular ATP (Adenosine tri-phosphate) concentration indicating stress imposed on microorganisms in the reactor. Nevertheless, this did not prevent higher biogas production. Based on the results, the post-treatment of digested sludge or treating the sludge between two digesters is an interesting alternative to pre-treatments. View Full-Text
Keywords: sewage sludge; ultrasound; ozone; post-treatment; anaerobic digestion; biogas sewage sludge; ultrasound; ozone; post-treatment; anaerobic digestion; biogas
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Tian, X.; Trzcinski, A. Effects of Physico-Chemical Post-Treatments on the Semi-Continuous Anaerobic Digestion of Sewage Sludge. Environments 2017, 4, 49.

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