Back River Wastewater Treatment Plant
Enhanced Nutrient Removal Upgrade Project
2019 Outstanding Civil Engineering Achievement
Over $20 Million
Baltimore City Department of Public Works | Owner
Whitman, Requardt & Associates, LLP | Consultant
Archer Western Construction, LLC | Contractor
The Back River Wastewater Treatment Plant (BRWWTP) began construction in 1907 and was opened in 1911. It is situated on the west shore of the Back River; a tributary of the Chesapeake Bay. The plant occupies a 466-acre site and has a 35-foot elevation difference from influent to outfall, allowing wastewater to flow through the plant entirely by gravity. An estimated 1.3 million residents in a 140 square mile area of Baltimore City and County are served by this plant. The BRWWTP currently employs approximately 300 people, including supervisory, operations, maintenance, and laboratory personnel. Twenty-four hour, year-round plant operation is maintained. The facility has evolved into a tertiary treatment plant and is currently designed to treat 180 million gallons per day (MGD) of wastewater utilizing fine bubble, air distributed, activated sludge. Utilizing phosphorus control by chemical addition and nitrogen control by biological processes, we currently remove a majority of these nutrients. Hydraulically, the BRWWTP can handle peak flows of over 400 MGD.
Wastewater from both Baltimore City and County enters the Back River plant through two large conduits. At the plant’s Influent Metering Building, flow rates are measured by two 78-inch diameter magnetic flow meters. After treatment, as described in the following paragraphs, approximately forty percent of the final effluent is diverted through two 6-mile long pipelines to Severstal Corporation at Sparrows Point for industrial purposes. The remaining effluent passes through a 1,200-foot long outfall structure where it is gradually aerated and diffused into Back River.
The Baltimore City Department of Public Works (DPW) has newly constructed Enhanced Nutrient Removal Facilities (ENR) at The BRWWTP. The $285 million ENR upgrade at the Treatment Plant was completed in 2018 with final acceptance in 2019.
DPW’s ENR improvements are part of Baltimore City’s commitment to citizens, Baltimore City, the state, and the Chesapeake Bay Restoration Program. The Chesapeake Bay is one of the largest estuaries in the US, with a watershed area of over 64,000 square miles and home to more than 15 million people. ENR means an overall cleaner effluent to the Bay. It allows 95% more nitrogen and phosphorus to be removed. This improves aquatic conditions, with fewer algae blooms and a better environment for fish.
ENR further refines the Biological Nutrient Removal process with removal of 95% or more of the bio-available nitrogen and phosphorus meeting Maryland’s goals for Total Nitrogen (TN) and Total Phosphorous (TP) of 3 mg/l and 0.2 mg/l, respectively.
This significantly reduces the amount of nutrients discharged into the Chesapeake Bay. Benefits to the community and to the Chesapeake Bay include an overall cleaner effluent to the Chesapeake Bay which improves aquatic conditions, resulting in fewer algae blooms (which reduce the oxygen content in water and cause fish kills) and a better environment for fish, plants and other aquatic life.
The ENR facility at Back River, has already won a Grand Award in the American Council of Engineering Companies (ACEC) 2019 Engineering Excellence Awards competition. This puts it in the running for the association’s Grand Conceptor award. In 2016, the project won the “Top Project” award from Water and Wastes Digest magazine. In addition, this project was highlighted in the ASCE Magazine prior to construction and Baltimore City hosted a number of tours during construction for the ASCE local institutes.
The engineer for the Back River ENR project is Whitman, Requardt and the construction contractor is Archer Western Construction.
Back River WWTP is a tertiary treatment plant that treats 180 mgd. For Back River ENR, the scope of work includes:
Construction of a new flow distribution structure (primary effluent) and related structures;
Denitrification Pumping Station and Denitrification Diversion Chamber;
Denitrification Filter Facility;
Denitrification Chemical Facility;
Backwash Treatment Facility;
Modification to the existing Activated Sludge Plants No. 2&3;
Lime Silo demolition;
Blower Building No.3 control modifications;
Nitrification Chemical Building Ferric Chloride System Modifications;
Electrical Power Distribution related to all work;
Plant Control System (PCS) and Communication System for the entire plant.
ENR has a significant positive impact on the Bay’s water quality. Improvements to the bay’s water quality will have significant economic, social and environmental benefits not only on the bay itself, but also to the surrounding ecosystem and regional communities that are integral with the bay.