Pre-treatments to enhance the biodegradability of waste activated sludge: Elucidating the rate limiting step

Pre-treatments for waste activated sludge (WAS) are, in most cases, an attempt to increase the biodegradation and/or improve hydrolysis rate of WAS after anaerobic digestion. This review presents an extensive analysis of WAS pre-treatments effectiveness focusing on increasing the biodegradability. I...

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Bibliographic Details
Published in:Biotechnology advances 2018-09, Vol.36 (5), p.1434-1469
Main Authors: Gonzalez, A., Hendriks, A.T.W.M., van Lier, J.B., de Kreuk, M.
Format: Article
Language:English
Subjects:
Activated sludge
Anaerobic digestion
Anaerobic treatment
Anaerobiosis - physiology
Biodegradability
Biodegradation
Biodegradation, Environmental
Biotechnology
Carbohydrates
Heat treatment
Hydrology
Hydrolysis
Limiting factors
Methane - metabolism
Methane production
pre-treatment
Pretreatment
Proteins
Review
Sewage
Sewage sludge
Sludge
Waste Disposal, Fluid - methods
Waste-activated sludge
Water treatment
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Summary:Pre-treatments for waste activated sludge (WAS) are, in most cases, an attempt to increase the biodegradation and/or improve hydrolysis rate of WAS after anaerobic digestion. This review presents an extensive analysis of WAS pre-treatments effectiveness focusing on increasing the biodegradability. In the first part of the review, WAS is considered as a cluster of organic components: proteins, carbohydrates, humic substances and cells. Based on this breakdown into components, the effect of different pre-treatments on each component (and in combination) is described. Also, possible reasons for the contradictory results frequently found among different studies dealing with the same pre-treatment are included. In the second part, the review describes the effects on volatile solids removal by digestion after pre-treatment and on the dewaterability of the final digestate. The energy balance and potential limiting factors for each pre-treatment are also taken into account. From the published works it is concluded that some pre-treatment techniques, such as thermal hydrolysis, thermal phased anaerobic digestion and low-temperature pre-treatment are effective ways to increase energy production and to improve other sludge properties, such as dewatering. However, these techniques are very energy intensive and require a large capital outlay, so research on milder pre-treatment techniques is valuable.
ISSN:0734-9750
1873-1899
DOI:10.1016/j.biotechadv.2018.06.001