Proceedings

The Thermal Hydrolysis Process (THP) has been successfully employed as a pre-treatment to anaerobic digestion across the world for over 15 years. Since the first UK plant at Thames Waters Chertsey STW, the drivers for the application of the technology have changed. It is now well understood that increased energy recovery from sludge reduces exposure to raising energy prices and offers one of the only mechanisms for net carbon reduction within a carbon intensive industry. For these reasons and increasing constraints on the land bank have driven the development of new second generation THP variations which improve energy recovery and cake quality.

In this paper conventional THP is compared against, SAS only THP and Intermediate THP. Using economic life cycle assessment it is shown that Intermediate THP offers the best anaerobic digestion based solution for energy recovery. SAS only THP is competitive economically with conventional THP. These options are best suited to larger sites with existing AD assets. Conventional THP still remains an excellent solution when AD volume is constrained.