Baltimore City Department of Public Works Back River WWTP Process and Construction Overview Michael F. Gallagher, Chief Wastewater Facilities Division
Wastewater Treatment Chesapeake Bay Restoration Water Quality Improve dissolved oxygen (DO) levels Reduce dead zones Increase submerged aquatic vegetation (SAV) Improve marine habitat Factors affecting Chesapeake Bay Water Quality Sediment loading Nutrients Nitrogen and Phosphorus (N and P) loading Wastewater Treatment Plants (point-sources) Reduce levels of N and P through best available technology
Original facilities constructed in 1907; operational 1912 Today the plant occupies 466-acres and serves 1.3 million people. Among the largest wastewater treatment plants in the mid-atlantic region. Physical, chemical and biological treatment processes 24-hour operation. Can process flows over 400 million gallons per day and handle peak flows up to 800 MGD w/flow equalization after head works upgrade.
Current permit through the Maryland Department of the Environment (MDE) under the National Pollutant Discharge Elimination System (NPDES) to meet stringent effluent limits (monthly averages): BOD5 10 mg/l Total Suspended Solids 10 mg/l Seasonal ammonia-n 2.0 / 5.7 mg/l (summer/winter) Total nitrogen ( BNR ) 8 mg/l (annual average) Total Phosphorus 0.2 mg/l E.coli (disinfection) 126 MPN/ 100 ml
ENR Improvements Biological Nutrient Removal (BNR) (in late 1980 s): Reduce total nitrogen (TN) 30 40 mg/l 8 10 mg/l Reduce total phosphorus (TP) 4 6 mg/l 0.2 mg/l Enhanced Nutrient Removal (ENR) (in late 2016): Reduce total nitrogen (TN) 8 10 mg/l 3 mg/l Reduce total phosphorus (TP) 0.2 mg/l 0.3 mg/l
ENR Improvements Back River WWTP receives about 35,000 lbs. of Nitrogen and 6,000 lbs. of Phosphorus every day with the influent Back River WWTP began nutrient (N and P) reduction in the late 1990 s targeting about 70% reduction of the incoming Nitrogen using Biological Nutrient Removal (BNR) technology More than 90% of the Phosphorus is already being removed through chemical treatment ENR will remove over 90% of the Total Nitrogen
ENR Improvements
PHASED CONSTRUCTION PROGRAM
CONSTRUCTION PROGRAM DURATION Started construction in the fall of 2013 Construction completion by end of 2016 Plant must achieve permit compliance by September 2017
BENEFITS TO THE COMMUNITY AND BAY Overall cleaner effluent to Back River and the Chesapeake Bay 95% or more of the bio-available nitrogen and phosphorus will be removed this improves the aquatic conditions, with fewer algae blooms and better environment for the fish Baltimore City/County commitment to the State, and the Chesapeake Bay Restoration Program
APPROXIMATE CONSTRUCTION COSTS Back River WWTP Upgrade: Phase I - $275 million Phase II - $300 million Patapsco River WWTP Upgrade: Phase I - $115 million Phase II - $145 million Total costs more than ¾ billion dollars Funded in part by the State (about 70%)
Patapsco Plant Aerial view
Patapsco BAF and De-Nitrification Filter
2008 cogeneration facility constructed to reduce the purchase of electrical power by $1.4 million annually by using the methane gas produced at Back River to generate electricity. 2012 solar array: 4,200 American-made panels, installed at a cost of about $4 million, supply about 5 percent of the energy up to 1,000 kilowatts per hour needed to run the plant.
SC-918 Headwork Improvements Screen and Grit Facility improvements New influent wet weather pumping station Peak flow equalization (36 MG storage) to protect downstream treatment processes
Very flat slope - 0.025% to 0.04 % Hydraulic restriction BRWWTP grit tank weir Two primary influences: Contributes to grit and sediment deposition in the Outfall Sewer(s) Reduces conveyance capacity during wet weather events and increases the potential of sanitary sewer overflows (SSOs)
Project Goals and Objectives Provide Influent Pumping Station at the Back River WWTP to: Remove the hydraulic restriction in the Outfall Sewer System Increase hydraulic capacity of the Outfall Sewer System Provide new Head works Facilities with capacity to treat future, model predicted wet weather flows: Coarse Screen Facility Fine Screen Facility Grit Removal Facility Provide Equalization Pumping and Tanks for storage of wet weather flows in excess of the hydraulic and treatment capacities of the headworks facilities and downstream plant processes
10 MW Emergency Generators Influent Pumping Station Equalization Pumping Station 16.5 MG Storage Tank Coarse Screen Facility Fine Screen Facility Grit Removal Facility 3 MG Storage Tank
QUESTIONS?