Decreasing activated sludge thermal hydrolysis temperature reduces product colour, without decreasing degradability

Dwyer, Jason and Starrenburg, Daniel and Tait, Stephan ORCID: and Barr, Keith and Batstone, Damien J. and Lant, Paul (2008) Decreasing activated sludge thermal hydrolysis temperature reduces product colour, without decreasing degradability. Water Research, 42 (18). pp. 4699-4709. ISSN 0043-1354


Activated sludges are becoming more difficult to degrade in anaerobic digesters, due to the implementation of stricter nitrogen limits, longer sludge ages, and removal of primary sedimentation units. Thermal hydrolysis is a popular method to enhance degradability of long-age activated sludge, and involves pressure and heat treatment of the process fluid (150–160 °C saturated steam). However, as documented in this study, in a full-scale system, the use of thermal hydrolysis produces coloured, recalcitrant compounds that can have downstream impacts (e.g., failure of UV disinfection, and increased effluent nitrogen). The coloured compound formed during thermal hydrolysis was found to be melanoidins. These are coloured recalcitrant compounds produced by polymerisation of low molecular weight intermediates, such as carbohydrates and amino compounds at elevated temperature (Maillard reaction). By decreasing the THP operating temperature from 165 °C to 140 °C, THP effluent colour decreased from 12,677 mg-PtCo L−1 to 3837 mg-PtCo L−1. The change in THP operating temperature from 165 °C to 140 °C was shown to have no significant impact on anaerobic biodegradability of the sludge. The rate and extent of COD biodegradation remained largely unaffected by the temperature change with an average first order hydrolysis rate of 0.19 d−1 and conversion extent of 0.43 g-CODCH4 g-COD−1.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 17 Feb 2022 03:46
Last Modified: 17 Feb 2022 03:46
Uncontrolled Keywords: Anaerobic; Melanoidin; UVT; DON; Biological methane potential; Ultrafiltration fractionation
Fields of Research (2008): 09 Engineering > 0907 Environmental Engineering > 090703 Environmental Technologies
Fields of Research (2020): 40 ENGINEERING > 4004 Chemical engineering > 400410 Wastewater treatment processes
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