Optimizing THP — The intermediate thermal hydrolysis process

Thermal hydrolysis has proven to be an efficient pre-treatment process for sludge before anaerobic digestion (AD), by thermally enhancing organic matter hydrolysis, the rate limiting step in AD (Shana et al., 2013). Recent research (Wilson and Novak, 2009, Shana et al., 2012, Mills et al., 2014) has shown that a new configuration with the existing technology can further enhance the efficiency of the system. The intermediate THP gave good results at laboratory scale, with volatile solids destruction of 64-67% and an average overall specific gas production of 500 m3 per tonne of dry solids (Shana et al., 2012).For the past year, intermediate thermal hydrolysis has been tested in the Sludge and Energy Innovation Centre pilot plant located at Basingstoke sewage treatment works.The pilot facility has allowed operational considerations to be explored and understood to inform the design and construction of full scale intermediate THP. Data and operational experience from the pilot plant is discussed and presented in this paper.