Proceedings

Over 10% of the 550+ anaerobic digesters in the UK are now preceded with Advanced Digestion systems. The range of processes is diverse with Cambi thermal hydrolysis, pasteurisation, 2 stage acid gas mesophilic digestion, TPAD, ATAD and plug flow anaerobic digesters to name a few.

This paper reviews one of these processes, Enzymic Hydrolysis, which now accounts for a quarter of all advanced digestion sites in the UK. The engineering of the unique plug flow reactor is reviewed and the benefits realised by optimising the anaerobic digestion process discussed.

Operational data from all the Enzymic Hydrolysis sites is presented and the ability of a biological mesophilic process to produce a Treated sludge shown. Finally the addition of a thermophilic stage to the largest Enzymic Hydrolysis plant at Blackburn is presented, and the ability to generate Enhanced Sludge product discussed.

KEY WORDS: Advanced digestion, anaerobic digestion, hydrolysis, pathogen reduction, plug-flow reactor, pre-treatment, mesophilic, thermophilic, two-stage digestion.