Fountain, P. and Macedo, F., Thames Water, UK
(free)Thermal pre-treatment of sludge has significant advantages – but care does need to be taken in how digesters are feed. Historically people have feed conventional digestion using fill and spill: sludge is feed into the digester and then there is a riser pipe leading to a limpet box where sludge overflows out from the digester. While this does work for THP digestion, there are some unique aspects relating to sludge density which can cause significant operational issues. Thames Water have had issues with feeding THP digesters, and are aware that others sites may have also had issues. There are ways around the problem – but if this isn’t addressed it will cause very significant disruption.
The paper would look at:
The whole life cost benefits of Thermal hydrolysis digestion are very significant. Thames Water’s strategy is to recover as much energy and resource from the sludge as possible and then to recycle quality biosolid fertilizer to farmers fields. Thames Water are actively getting away from such technologies as liming and composting – which offer no energy or resource recover, have proven very expensive, and are operationally full of complications – and bringing that resource into THP digestion. Thames Water are also converting a number of their conventional digestion plants to THP digestion.
Keywords: THP digestion, feed arrangements for primary digestion
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