Assessment of solid retention time of a temperature phased anaerobic digestion system on performance and final sludge characteristics

BACKGROUND: This paper describes the results obtained during the thermophilic/mesophilic temperature phased anaerobic digestion (TPAD) of sewage sludge on a pilot scale. The aim of this research study was not only to optimize the anaerobic digestion process, but also to obtain a digested sludge suit...

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Bibliographic Details
Published in:Journal of chemical technology and biotechnology (1986) 2012-08, Vol.87 (8), p.1074-1082
Main Authors: Riau, V., De la Rubia, M.A., Pérez, M.
Format: Article
Language:English
Subjects:
Applied sciences
Biological and medical sciences
Biotechnology
Chemical engineering
class A biosolid
Exact sciences and technology
Fundamental and applied biological sciences. Psychology
Global environmental pollution
heavy metals
Methods. Procedures. Technologies
Other industrial wastes. Sewage sludge
Others
pathogens
pilot plant
Pollution
temperature phased anaerobic digestion (TPAD)
Various methods and equipments
Wastes
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Summary:BACKGROUND: This paper describes the results obtained during the thermophilic/mesophilic temperature phased anaerobic digestion (TPAD) of sewage sludge on a pilot scale. The aim of this research study was not only to optimize the anaerobic digestion process, but also to obtain a digested sludge suitable for agricultural applications according to the legal requirements. RESULTS: Four TPAD assays were carried out: 5/15, 3/15, 3/12 and 3/9 (days/days of solid retention time) with a specific methane production (expressed as LCH4 g−1 VSdestroyed) of 0.77, 0.83, 0.66 and 0.20, respectively. TPAD 3/15 and 3/12 reached pathogen concentrations of less than 1000 MPN g−1 TS (faecal colifoms) and 3 MPN per 4 g TS (Salmonella spp.); therefore, these digested sludges can be considered Class A biosolids, according to the US Environmental Protection Agency. Concentrations of heavy metals rose after the anaerobic digestion of mixed sludge, but the final values were always below the limits required by legal regulations. CONCLUSION: TPAD 3/15 is the best option in terms of organic matter removal, CH4 generation, and process stability. TPAD 3/12 obtained the best final dewaterability and pathogen reduction and in general, showed much better results than those obtained by anaerobic mesophilic control (15 days of SRT). Copyright © 2012 Society of Chemical Industry
ISSN:0268-2575
1097-4660
DOI:10.1002/jctb.3709