DC Water biosolids and energy process. Blue Plains advanced wastewater treatment
Parry, D. and Loomis, P., CDM Smith, USA
(free)
Abstract The 1,400 million liters per day (370 million gallon per day, average daily flow) Blue Plains Advanced Wastewater Treatment Plant is operated by the District of Columbia Water and Sewer Authority (DC Water) and serves the metropolitan DC area. Currently, 100 percent of lime stabilized, dewatered Class B biosolids are land applied. DC Water evaluated several biosolids management alternatives to the current practice based on critical factors including biosolids product quality and marketability, limited space availability at the Blue Plains plant, implementation cost, and operating cost. DC Water selected a new Class A biosolids main process train that will decrease operating costs, reduce the volume of biosolids, produce biogas, and be located within a relatively small footprint at the Blue Plains plant. A design build project delivery system was selected to ensure that this project would not be constructed as a low bid, but by a team that represented the best combination of technical approach and cost. The new $208 million biosolids process is 75 percent constructed and includes 5 mm sludge screening, centrifuge pre-dewatering, four thermal hydrolysis trains, and four mesophilic anaerobic digesters. Critical design issues included pretreatment before thermal hydrolysis, sludge cooling before digestion, and management of digested sludge and biogas. The digesters are some of the largest in the world at 14 million liter (3.8 million gallon) each. When complete, the new main process train will be the largest thermal hydrolysis system in the world capable of processing up to 410 dry tonnes (450 dry tons) of solids per day. Class A biosolids will be provided for land applied beneficial use after belt filter press dewatering. The biogas will be used to fuel three 4.6 MW gas turbines in a new combined heat and power (CHP) facility providing steam for the thermal hydrolysis process and generating 11.8 MW of power.
Keywords: Thermal Hydrolysis, Anaerobic Digestion, Resource Recovery, Biosolids, Biogas, Energy, Bioenenergy
