Thermal Hydrolysis Pretreatment for Digestion Intensification

Fewer resources. Better results

Wastewater treatment plants (WWTP) are continually processing water to remove pollutants and return treated effluent back into the water cycle. As plants continue to work within constrained footprints, operate more sustainably, and increase capacity to meet forecasted demands, it’s imperative we research and confirm more efficient and effective treatment technologies.

The costs of sludge management typically account for 30% or more of a WWTP capital costs and upwards of 50% of the operational costs[1]. However, improved sludge management has the potential to generate revenue, reduce costs and improve sustainable operations. Brown and Caldwell has been partnering with WWTPs to research and apply data-driven solutions including series thermophilic digestion (1990’s), temperature phased anaerobic digestion (2000’s) and thermal hydrolysis (2014)to reduce sludge mass, stabilize solids, and produce clean marketable biosolids products. With this experience as our foundation, we introduced and applied the very first use of thermal hydrolysis technology in North America, and the largest such facility in the world at DC Water.

Thermal hydrolysis intensifies the digestion process by applying high temperature and pressure ahead of a mesophilic digestion process. This pretreatment step nearly doubles the loading capacity of the digestion process when compared to conventional digestion processes. When the entire sludge stream is treated, it produces a high-quality Class A biosolids product with soil-like properties that stacks well, is low in odor, and is low in water at 30 percent cake solids. Methane from the digestion process can be recovered and converted into usable electric power and recoverable heat.