Ductile iron pipe used in largest wastewater treatment plant
The sprawling Blue Plains Wastewater Treatment Facility is the largest advanced wastewater treatment plant in the world, with the capacity to treat an average of 370 million gal per day (mgd) of sewage. 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 Washington, D.C., metropolitan area, and its peak daily capacity is 1 billion gal.
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.
Several parts of the environment-oriented work at the Blue Plains plant are using more than 2,600 tons of AMERICAN brand ductile iron pipe, made from recycled scrap materials. The company supplied Fastite, Flex-Ring, and fabricated flanged and grooved pipe in 4- to 48-in. 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 Raj Arora, sales engineer.
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 biosolids generated at the plant—some 1,200 wet tons per day.
The project will make the Blue Plains facility the first in North America and largest in the world to use the Cambi Thermal Hydrolysis Process (THP) for treating biosolids, resulting in significant cost and energy savings and a smaller carbon footprint. The biosolids 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 MW 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-mgd 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 Chesapeake Bay. High levels of nitrogen are toxic to wildlife and lead to dissolved oxygen depletion, which results in more algae, which is bad for plants, animals and humans.
Through previous work, the Blue Plains plant already has significantly reduced its nitrogen discharges into the Potomac River. In recent years, the nitrogen discharges at the Blue Plains plant have decreased from 15 to approximately 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 work; 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 biosolids project and construction associated with the Tunnel Dewatering Pump Station and ECF.