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Environments 2017, 4(3), 49;

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

Advanced Environmental Biotechnology Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, Singapore 637141, Singapore
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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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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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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