Proceedings

Over the last ten years, a variety of pre-treatment technologies have emerged claiming to
optimise anaerobic digestion. Of all these technologies, biological hydrolysis (Monsal Enzymic
Hydrolysis) is the most widely adopted technology in the UK. Monsal Enzymic Hydrolysis has
now been selected for eleven plants; eight operational, one under construction, and two in
design, and the technology has been adopted by five water utility companies, and is currently the
technology utilised at the largest Advanced Digestion plant in the UK.

Originally designed as a cost effective alternative to secondary digestion, the paper reviews the
development of the Monsal Enzymic Hydrolysis process since 2002 to the present day. Current
levels of performance are highlighted demonstrating biogas production of >400m3
/tds, pathogen free centrifuge cake without regrowth, energy self-sufficiency, rheology conditioning,
dewaterability >28%DS and seamless plant integration. New plants under construction are
presented introducing new advances such as raw cake back mixing allowing feeds of 8% and
digester loadings of >4.5kgVS/m3 .day.

KEY WORDS
Advanced Digestion, Biological Hydrolysis, Energy Balance, Pathogen Reduction, Plant
Engineering, Steam Heating, Sludge Rheology, Digester Loading.