This story also appeared in the January issue of Water & Wastes Digest.
The sprawling Blue Plains Wastewater Treatment Facility is the largest advanced wastewater treatment plant in the world, with a capacity to treat an average of 370 million gallons of sewage a day. Some $4 billion in recently completed projects and work now in progress are making the plant more efficient and taking its green operations to new levels. Built in the 1930s, the facility serves more than 2 million customers in the greater Washington, D.C., Metro Area, and its peak daily capacity is 1 billion gallons.
The District of Columbia Water and Sewer Authority (DC Water), which owns and operates the plant, is a partner in the Chesapeake Bay Agreement of 1987, aimed at improving the overall quality of the Potomac River and Chesapeake Bay watersheds. As part of that effort, the Blue Plains facility has completed or is in the process of completing sweeping improvements on the environmental side.
It’s fitting that several parts of the environment-oriented work at the Blue Plains plant are using more than 2,600 tons of AMERICAN Ductile Iron Pipe, which is an environmentally-friendly product made from recycled scrap materials. AMERICAN supplied Fastite, Flex-Ring and fabricated flanged and grooved pipe in 4-inch through 48-inch diameters. “Ductile iron pipe, which is made from recycled materials and impermeable to hydrocarbons, is an ideal product for this state-of-the-art plant that converts waste into energy,” said AMERICAN Sales Engineer Raj Arora.
“Ductile iron pipe, which is made from recycled materials and impermeable to hydrocarbons, is an ideal product for this state-of-the-art plant that converts waste into energy.”
Boston-based CDM Smith has served as the design engineer for two key projects at Blue Plains and is participating on the construction side with Vermont-based PC Construction in a joint venture that includes high-profile work to improve the quality and reduce the volume of bio-solids generated at the plant — some 1,200 wet tons a day.
The project at the facility will make it the first in North America and largest in the world to use the Cambi-Thermal Hydrolysis Process (THP) for treating bio-solids, resulting in significant cost and energy savings and a smaller carbon footprint. The bio-solids program consists of the Main Process Train (MPT), which includes the THP and digester facilities, a combined heat power (CHP) facility and dewatering facilities.
The MPT will feed methane gas to the CHP, which in turn will generate 13 megawatts of power and provide about a third of the power required to operate the Blue Plains plant. The CHP will in turn feed steam to the THP process using shared, renewed power sources, said CDM Smith’s Brian Hagerich.
The second project in the joint venture between CDM Smith and PC Construction includes a 250-million gallon per day tunnel dewatering pumping station and enhanced clarification facility. These facilities will dewater a system of deep tunnels, now being constructed to store wet weather flows that currently exceed the facility’s capacity during heavy storms, and treat them prior to discharge. Along with other benefits, these projects will enhance efforts to reduce nitrogen levels in the Chesapeake Bay. High levels of nitrogen are toxic to wildlife and lead to dissolved oxygen depletion, which leads to more algae, which in turn is bad for all plants, animals and humans.
Through previous work, the Blue Plains plant has already significantly reduced its nitrogen discharges into the Potomac River. In recent years, the amount of nitrogen discharges at the Blue Plains plant have decreased from 15 mg/l to around 4 mg/l, which is lower than federal standards.
AMERICAN supplied 660 tons of ductile iron pipe for the earlier nitrogen reduction projects, which were anchored by the Enhanced Clarification Facility (ECF). Contractors for that effort were Ohio-based Ulliman Schutte, which did the mechanical and electrical; and PC Construction, which handled site work and some tankage.
In all, AMERICAN will supply 1,945 tons of ductile iron pipe and fittings for the bio-solids project (MPT) and construction associated with the Tunnel Dewatering Pump Station (TDPS) and Enhanced Clarification Facility (ECF).