Engineering News-Record
The Top 10 Biggest Wastewater Treatment Plants
The Top 10 Biggest Wastewater Treatment Plants
2. Deer Island Sewage Treatment Plant Boston, USA. Capacity: 1.27 billion gallons per day. Owner: Massachusetts Water Resources Authority (MWRA). Driven by a federal court order in 1986 to end the discharge of 500 million gallons of poorly treated wastewater a year into Boston Harbor, the MWRA launched an 11-year, $3.6 billion program to upgrade treatment for the greater Boston area. ICF Kaiser Engineers provided construction management. Three pump stations bring the influent, which flows through grit chambers and then is routed to 48 primary treatment clarifiers. Secondary treatment is accomplished using both gravity treatment and an oxygen-activated sludge system, handled by twelve 140-ft tall, 90-ft dia egg-shaped sewage sludge digesters, the largest digesters in North America at that time. The methane produced by digestion is fed to a generator, producing 3MW of electricity. The sludge is dried further and processed into fertilizer pellets. 75 tons per day of the pellets are produced, and sold to blenders of agricultural fertilizers, landscapers, and golf courses. Following primary and secondary treatment, the wastewater undergoes disinfection to kill bacteria, first mixing it with sodium hypochlorite, followed by adding sodium bisulfite to dechlorinate the water so that the discharge will not threaten marine organisms. The plant includes both a five-mile-long, 14-ft dia underwater tunnel bringing influent from the Nut Island primary treatment plant, and a 9.5-mile long, 24-ft dia outfall tunnel to deposit the treated effluent into Massachusetts Bay. The plant handles sewage from 2.5 million people in 43 communities in the greater Boston area.
Massachusetts Water Resources Authority

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