Thermal Hydrolysis Process (THP) Explained


Greg Knight, senior process engineer with Black & Veatch, describes the function and implementation of thermal hydrolysis for sludge handling and resource recovery.

Sitting down with Water Online Radio’s Todd and Kelly, Knight first defines the process:

“[The] thermal hydrolysis process, or THP … is basically a process whereby biosolids are pressure-cooked at high temperature and pressure to improve the digestibility of the biosolids, usually before anaerobic digestion.

“Basically, the biosolids are heated using steam to about 165 degrees Celsius, held for about 20 to 30 minutes, and then transferred to anaerobic digestion.”

Why invest in THP? Knight explains:

“One of the key benefits is … enhancement of the digestion process, so you need about half the digestive volume that you would need with conventional anaerobic digestion.

“You get improved conversion of volatile solids in the digestive process, and that leads to a number of other benefits. You get better dewaterability of the biosolids, so you get a drier cake at the end of the day. Because the solids are being cooked at a high temperature, you also get a Class-A biosolids which can be used for land application beneficial reuse. You get more biogas, and you also get less odor in the final product.”

Knight offers additional insight on favorable conditions for THP performance, impacts on facility footprint, the utilization of recovered resources, and much more. Tune in below to hear the full story.