Thermal Hydrolysis Full Scale System Performance

There is growing significant interest in the use of thermal hydrolysis process (THP) technology in conjunction with anaerobic digestion (AD) to manage biosolids in the North America marketplace. This interest is being driven by the desire to obtain Class A exceptional quality biosolids, to improve the dewaterability of the biosolids and to reduce the amount of solids that subsequently must be managed while at the same time optimizing the use of existing digestion assets and increasing biogas production. Because of this interest, several thermal hydrolysis vendors are entering the marketplace. Cambi has developed the most operating THP facilities worldwide. In North America Cambi has one operating facility at DC Water since late 2014 with several more in the design or construction phase. The first North American chemical-thermal hydrolysis system offered by CNP - Pondus also began operation in Kenosha, Wisconsin in early 2016. Other vendors are aggressively working to enter the thermal hydrolysis marketplace in North America including Veolia with the Kruger Biothelys and Exelys offerings, Sustec/Turbotec, Haarslev and Lysotherm. Many claims are being made in vendor literature related to these technology offerings and only recently has more information about full scale performance become available. Published full scale THP plant performance data from 18 references found in the literature were reviewed in detail to determine if consistent performance conclusions can be ascertained. Four consistent conclusions are drawn from this review:Decreased viscosity of THP treated sludge allows feeding the AD systems with a much higher solids content material, typically between 9 and 11 percent solidsTHP treated sludge results in significant increases in volatile solids reduction (VSR) and enhanced biogas production when processed through ADSignificant improvement in dewaterability of the digested biosolids is reported at a number of THP facility retrofit installationsProcessing of both waste activated sludge and primary sludge through THP prior to AD can produce Class A exceptional quality biosolids.AmmoniaThe purpose of this paper and presentation is to provide an unbiased review of the various full scale thermal hydrolysis systems currently available in the marketplace and to provide comparisons of full scale performance of several operating systems as reported in the literature. This information will be useful for water resource recovery facility engineers, operators and owners when considering, planning and designing thermal hydrolysis systems with anaerobic digestion as part of a facility’s sludge management strategy.