Increasing digester process performance – A comparison of UK refurbishment techniques for existing anaerobic digestion assets

There is a large international asset base of anaerobic digestion. It is still the preferred stabilisation process for many countries. This asset base is coming under increasing pressure from the new demands of modern sludge processing. These changes include thicker sludges, polymer thickened sludges and increased levels of pathogen reduction. There are also other drivers such as energy production which will become more important in the future as biosolids will become an increasingly important revenue stream for many sludge-processing facilities.This paper focuses on refurbishment techniques, processes and equipment to deal with these new challenges. Anaerobic digestion will have to be better in the future than it has been in the past. These digestion assets will become more valuable in the future and whilst the civil structures will be in good condition the mechanical, electrical and process elements will require continual refurbishment over the lifetime of the assets to deal with the increasing demands.The elements that typically will need upgrading are heating, mixing, gas handling systems, instrumentation and control systems. This paper will explore the various refurbishment techniques for a number of these systems to allow a comparison of UK practice. A number of case studies will be presented at the conference. This paper will provide a valuable platform for engineers to discuss the most appropriate refurbishment technique for their anaerobic digester project.