Thermal Hydrolysis – The Next Generation

The Trinity River Authority (TRA) Central Regional Wastewater System (CRWS) provides wastewater collection and treatment services to all or portions of 21 jurisdictions in the Dallas-Fort Worth (DFW) metroplex, as well as the DFW International Airport. Over the past 5 years, TRA has embarked on a solids management program with long-term sustainability and the ability to ensure reliable, low cost solids handling within the plant. After evaluating several alternatives, TRA has elected to pursue a system incorporating thermal hydrolysis and anaerobic digestion to replace the existing lime stabilization facilities.Thermal hydrolysis is a process that heats and pressurizes sludge in order to break down sludge cell walls. This enhances digestion and solids destruction; and consequently, reduces the amount of solids to be moved offsite, thus reducing transportation costs. Biogas production is also enhanced. The rupturing, or lysis, of cell walls makes the material in the cells more available—and hence, biodegradable. When used in combination with downstream mesophilic digestion, the process generates Class A biosolids.While thermal hydrolysis has been implemented at more than 30 facilities worldwide, there is only one operating facility in North America located at the Blue Plains Advanced Wastewater Treatment Facility in Washington, DC. The CRWS design is based upon the general process used at DC Water, with many lessons learned garnered through the design, construction and operation of that facility. The paper presents the advances in the thermal hydrolysis offering from Cambi, Inc. along with the improvements and differences in the process between the TRA and DC Water facilities.