Thermal hydrolysis process for effective and sustainable sludge treatment at sludge centers

Ferraro, D., Sahu, A., Jimenez, A., Ugland, T.N.

Proc of the EcoMondo, 2019


For several small towns in close proximity equipped with wastewater treatment plants (wwtps), a common Sludge Treatment Center (STC) has been found to be a cost effective and a practical solution for sustainable sludge management. Sustainable sludge management is achieved when dewatered sludge from wwtps are treated anaerobically to produce bioenergy. In order to speed up the anaerobic digestion process, the use of thermal hydrolysis process (THP) is used as an effective pretreatment.  The aim of this paper is to present the benefits for sludge treatment by applying a THP before anaerobic digestion. 
Cambi is currently the world leader in Thermal Hydrolysis Process (THP) technology and has more than 60 plants all around the world since 1995. THP has been proven for increasing biogas production, increase the sludge load to existing digesters, and generating a low volume of non-odorous, well dewatered, homogenous and pathogen free biosolids. This in turn reduces the overall carbon footprint of several wwtps and the biosolids can be further used as soil conditioners for agricultural purpose. This has been tried in the UK where nearly 45% of UK sludge is treated by CambiTHP technology.
By importing sludges in a single plant (STC) and treating them with THP followed by advanced anaerobic digestion, is an effective way to increase sludge valorisation. The centralised STC solution has been successfully applied by 14 Cambi plants in Europe, Asia and Australia.
Spreading high quality biosolids on land is the cheapest and most sustainable way for sludge disposal.
A big part of the opposition to agricultural reuse of biosolids has been based upon the appearance and the odour of the product. This study will bring to the attention the experience of applying Cambi biosolids to agriculture and to the characteristics of the cake.