Client: Celtic Anglian Water
Solution: CambiTHP - B12
The WWTP at Ringsend Dublin was originally operating a two train drum drying systems for drying the raw primary sludge to meet the requirements of pasteurisation in Ireland.
The plant was extended by the addition of SBR biological treatment reactors to the existing primary treatment plant. Therefore the quantity of sludge was doubled and the dewaterability of the sludge reduced with the addition of secondary treatment. This would normally have led to a tripling of dryer expansion because of the much greater water evaporation requirement. However, by adding Cambi THP the volume of digested cake was reduced and the dryer project only had to be expanded by 50%.
The area for extensions is limited and it was important to choose a sludge treatment method which was compact. The digestion process is carried out in three 4,500 m³ digesters that are fed at about 6 kg VS/m³/day and routinely achieve 60% VS conversion. The Cambi digestion system made the overall energy balance positive so that up to 4 MWs of electricity can be generated. In this case the best technical solution was also the best financial solution.
The sludge treatment is designed for 36,000 tonnes DS sewage sludge annually to be dewatered, hydrolysed, digested and dried. The intermediate digested cake is a pasteurised product and is also used in agriculture in the Dublin area .
The overall project was won by a consortium led by Black and Veatch. The Cambi contract was carried out by Cambi UK ltd.