Complete refurbishment of a 2.5ML Anaerobic Waste Sludge Digester. The floating metallic roof was lowered to the ground for a complete overhaul, involving the removal of all corroded elements, and reinstatement of the structural integrity and protective coatings. The concrete tank structure was cleaned, fitted with a new water sealing launder, and protective coatings reinstated. Modifications were implemented to improve safety in operation, structural integrity, and automated monitoring systems were upgraded to improve operational visibility and provide early warning when outside optimal parameters. All monitoring and control systems are fully integrated with plant SCADA and Network Operations. A highly challenging and successful project.