Operational experience with Thermal Advanced Digestion in Dwr Cymru Welsh Water

Wilson, S.1, Brown, R.¹, Oliver, B.2, Merry, J², 1Dwr Cymru Welsh Water, 2 Imtech



Dwr Cymru Welsh Water’s strategy for AMP 5 has now been fully implemented, including the CAMBI Advanced Digestion plants at Cardiff and Afan, which have now been operational for over two years. This paper explains the operational experience at these sites and the ongoing improvement programme including the drive to power self-sufficient waste water service. Industry leading performance levels have been maintained and the plants have operated reliably allowing the targeted operational savings of £7 million/year and operational carbon saving of over 50,000 tonnes CO₂ to be achieved. Some aspects of the plant have been improved such as pre-dewatering and post dewatering, improved gas cleaning is being included to overcome the increasing levels of siloxanes present in the biogas. Solids destruction levels across the overall process exceed 50% and the high fertilizer value of the enhanced sludge cake has increased demand from local farmers. Focused training and operational and maintenance learning has been applied across all of Dwr Cymru Welsh Water’s other sludge treatment centres.

Keywords Advanced Digestion, Cambi Thermal Hydrolysis, Operational experience, Carbon reduction, Fertiliser value of enhanced sludge quality, power self-sufficient operation, operational savings.


This paper builds on previous technical papers1, 2 and describes the ongoing operational and maintenance experience associated with Cambi thermal advanced digestion plants built at Dwr Cymru Welsh Water’s Cardiff and Afan Waste water treatment works. Both plants were commissioned in September 2010 and have now been in continuous operation for over two years. Overall, the plants have proven to be reliable and continue to deliver operational savings in excess of £7M/y when compared to the original thermal drying plants. This paper explains the ongoing plant performance standards, challenges, operational improvements, and planned future improvements.

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