Second Generation Thermal Hydrolysis Processes

The Thermal Hydrolysis Process (THP) has been successfully employed as a pre-treatment to anaerobic digestion (AD) across the world for over 15 years and has recently been installed at DC Water’s Blue Plains WWTP. The first UK THP plant at Chertsey WWTP in UK was commissioned in 1999 and since that time 18 projects have been developed in UK and Ireland accounting for over 20% of all sludge treated in the British Isles. The technology has evolved and new configurations exist or are being developed to meet new demands.In this paper conventional THP is compared to WAS only THP and Intermediate THP. Data captured from operational sites, laboratory scale experiments and the newly commissioned Sludge & Energy Innovation Centre, was used to model each process and allow technical & economic life cycle assessment. The results show that Intermediate THP offers an excellent solution for energy recovery having the economic return, but overall the largest CapEx. WASonly THP and ITHP areboth best suited to larger sites with existing AD capacity. Conventional THP still remains an excellent solution when space and AD volume is constrained.