High-rate methanogenesis as a new stabilisation technology

Ho, D., Jensen, P. and Batstone, D. (2012). High-rate methanogenesis as a new stabilisation technology. In: Bianca Di Salvo, AWA Biosolids and Source Management National Conference: Program and Abstracts. AWA Biosolids and Source Management National Conference, Gold Coast, Qld., Australia, (47-47). 18 - 20 June 2012.

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Name Description MIMEType Size Downloads
Author Ho, D.
Jensen, P.
Batstone, D.
Title of paper High-rate methanogenesis as a new stabilisation technology
Conference name AWA Biosolids and Source Management National Conference
Conference location Gold Coast, Qld., Australia
Conference dates 18 - 20 June 2012
Proceedings title AWA Biosolids and Source Management National Conference: Program and Abstracts
Place of Publication St Leonards, NSW, Australia
Publisher Australian Water Association
Publication Year 2012
Sub-type Published abstract
ISBN 9781921335204
Editor Bianca Di Salvo
Start page 47
End page 47
Total pages 1
Language eng
Abstract/Summary Conventional anaerobic digestion of particulates is relatively slow with an average hydraulic retention time of 16-20 days on activated sludges, and >20 days on primary sludges. This is the cause of probably the biggest disadvantage of anaerobic digestion, with large volumes causing a high capital cost, as well as increased mixing, maintenance, and heating costs. It would strongly enhance the competitiveness of anaerobic technologies if the process could be intensified by reducing digester volume. Compared to mesophilic anaerobic digestion, thermophilic anaerobic digestion has additional benefits including higher methane production and volatile solids destruction, and higher destruction of pathogens (Ge et al., 2011 UQ PhD Thesis; NSW EPA Guidelines). Disadvantages include increased sensitivity to ammonia inhibition. Improved performance in a TPAD configuration has been shown to be due to an increase in hydrolysis coefficients (Ge et al., 2011 ). However, it is also known that methanogenic performance increases substantially with increased temperature. However, the mechanisms and operational limits of this process ate not well understood. In particular, the link between performance, mechanism. and mediator (the microbe) is not well understood. In this presentation, we will outline the potential of high-rate, high temperature methanogenic digestion as a replacement technology for conventional mesophilic digestion. The analysis is based on operation of laboratory scale continuous anaerobic digesters operating on waste activated sludges (WAS) over one year, with a wide variety of techniques used to investigate activity and mechanisms of high-rate methanogenesis, including modelling, molecular, and activity based analysis of the digesters. In particular, we show that we can achieve stable destruction of >30% VSD on WAS in a single reactor configuration with hydraulic retention times down to 3 days (2 days will be tested before presentation). According to 16s Pyrotag sequencing, and ASH the community was dominated by Methanosarcina, which can cleave acetate or oxidise hydrogen to methane, whereas mesophnic communities are generally dominated by Methanosaeta, which is an obligate aceticlast. Methanogenic actlvity at the elevated temperatures is up to 1.5A±0.1 gCOD.gVS-1d-1A (i.e., 10X the activity at 35A"0), and appears lobe higher on formate/H2 than on acetate. This leads us to believe that the community is acetate oxidising, which is currently being verified by 13C/12C GC-IRMS. We also need to evaluate whether the oxidiser is Methanosarcina, or a bacteria such as Coprothermobacter. or Clostridia. The results are significant because (a) reducing volume to this degree would allow an order of magnitude decrease In digester construction costs, and (b) the high rates have been achieved with low effluent organic acid levels (<500 mg L·1 in general, and 100 mg L-1 achievable at a KS values of -0.3 gCOO L-1). Other acetate oxidising systems with high ammonia levels have generally had VFA levels of >1000 mgCOD L-1. Our presentation will also address other aspects, including the possibility of multi-stage systems, end comparative economics of heating and mixing.
Q-Index Code EX
Q-Index Status Provisional Code
Institutional Status UQ
Additional Notes Abstract no. 27

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Created: Mon, 23 Jul 2012, 15:59:04 EST by Dang Ho on behalf of School of Chemical Engineering