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Boston Harbor Pipe Dreams Come True! USGS Visits the Deer Island Sewage Treatment Plant and a Cleaner Harbor


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historic steam-powered pumping station
Above: The historic steam-powered pumping station rehabilitated in the recent upgrade of the Deer Island Sewage Treatment Plant. Photograph by Dann Blackwood.

Charles Warren Tyler
Above: Charles Warren Tyler, an MWRA program manager, leads a tour of the Deer Island Sewage Treatment Plant. Photograph by Dann Blackwood.
How long after a flush does it take that water to end up in Massachusetts Bay? How clean is it once it reaches its final destination? What really happens in the "eggs" out on the island? These were some of the burning questions going through my mind as the Mass Bay Project Team from the U.S. Geological Survey (USGS)'s Woods Hole Science Center visited the Massachusetts Water Resources Authority (MWRA)'s wastewater-treatment plant on Deer Island in Boston Harbor on January 17, 2006. Charles Tyler, a program manager in the process operations group for MWRA on Deer Island, conducted an exceptional tour of the facility, emphasizing the processes and scientific background that make the plant a major part of an environmental success story. Multidisciplinary research by the USGS in Boston Harbor and Massachusetts Bay has helped predict and document this success.

The Deer Island Sewage Treatment Plant continues longstanding use of the island for sewage disposal. The first big, steam-powered pumping station was constructed on Deer Island in the late 1800s, and a new, more elaborate primary-treatment facility was built in the 1960s. In the 1990s, hundreds of engineers and thousands of construction workers brought into being the secondary-treatment plant that now serves greater Boston. Today's 150-acre wastewater-treatment facility serves 43 communities and 2.5 million people.

The waste generated by homes, businesses, and runoff requires five main treatment steps, which together eliminate 80 to 90 percent of the contamination. To begin the process, raw sewage is pumped to various headworks in the Boston area, which remove large debris (such as logs, sticks, and rocks) and gritty material (such as sand and eggshells). From the headworks, the sewage flows to Deer Island. The next treatment step removes solids in the primary settling tanks, or clarifiers, where 50 to 60 percent of total suspended solids and as much as 50 percent of pathogens and toxic contaminants are removed. Stage three begins the secondary-treatment phase, employing microorganisms and pure oxygen to consume 80 to 90 percent of the remaining organic and toxic wastes. Much of the microbe-rich sludge that settles to the bottom is recycled back to the secondary aeration process, but some is removed and mixed with the concentrated primary sludge, then heated, consolidated, and anaerobically digested (that's what happens inside those eggs!). The resulting stabilized sludge, called "biosolids," is shipped to MWRA's pelletizing facility in Quincy, where it is further processed into fertilizer that is useful for garden-soil enhancement. In the fourth stage, the treated wastewater is chlorinated (known as disinfection), then dechlorinated to protect marine life from harmful effects of residual chlorine. Finally, the effluent begins the 9.5-mile trip 250 feet beneath the sea floor through a 24-foot-diameter tunnel to the 100-foot-deep waters of Massachusetts Bay. It takes about 12 hours for wastewater to travel from a household in Boston through the secondary treatment plant, out the tunnel, and into the bottom waters of Massachusetts Bay. The sewage effluent is rapidly diluted as it is released through 55 diffusers, evenly spaced along the last 1.5 miles of the tunnel. Extensive environmental monitoring by MWRA confirms that water quality of the bay is not compromised by the discharge. Steps to control odor are taken throughout the treatment process, leading one visitor to remark of the odor, "There isn't any" (see the Boston Phoenix article). That's good news for the town of Winthrop, which has the plant in its backyard.

Dann Blackwood and Tim Milbert peeking into a gravity thickener diffuser on display at the Deer Island Sewage Treatment Plant
Above left: Dann Blackwood and Tim Milbert peeking into a gravity thickener used to consolidate the sludge from primary treatment for later digestion in the egg-shaped digester tanks. Photograph by Sandy Baldwin.

Above right: This diffuser on display at the Deer Island Sewage Treatment Plant is like the 55 diffusers that are underwater along the last 1.5 miles of the sewage outfall tunnel, which extends 9.5 miles eastward from the treatment plant and Boston Harbor into Massachusetts Bay. Photograph by Dann Blackwood.

Since 1989, USGS oceanographers Mike Bothner and Brad Butman and their team from the USGS, the Woods Hole Oceanographic Institution, and the U.S. Coast Guard have worked with MWRA staff on monitoring and research to better understand and predict the fate of contaminants introduced to Massachusetts' coastal waters. USGS research has defined the regional framework of sediment and contaminant transport in this coastal system and has specifically helped guide management decisions concerning site selection for the present outfall and the design of a court-ordered monitoring program. While walking down the plant's miles of passageways, which have enough concrete to repave the Massachusetts Turnpike, I felt a sense of pride to be involved in the efforts to clean up Boston Harbor. The scale of the plant is overwhelming, as is the amount of effort and manpower focused on restoring the harbor to cleaner conditions.

For a synthesis of USGS research in coastal waters off Boston, please see the recently published "Processes Influencing the Transport and Fate of Contaminated Sediments in the Coastal Ocean—Boston Harbor and Massachusetts Bay" (USGS Open-File Report 2005-1250). Additional information about the USGS work is posted at URL http://woodshole.er.usgs.gov/project-pages/bostonharbor/. To learn more about the Deer Island Sewage Treatment Plant, visit URL http://www.mwra.state.ma.us/03sewer/html/sewditp.htm.

Sandy Baldwin standing underneath one of the digesters, or "eggs," holding 3 million gallons of sludge. A few of the 12 egg-shaped digesters
Above left: Sandy Baldwin standing underneath one of the digesters, or "eggs," holding 3 million gallons of sludge. Photograph by Dann Blackwood.

Above right: A few of the 12 egg-shaped digesters using heat and microorganisms to break down solids and toxins from the effluent at the Deer Island Sewage Treatment Plant. Photograph by Dann Blackwood.


Related Sound Waves Stories
Turning Point in Boston Harbor Clean-Up
October 2000
Clean-Up of Boston Harbor
March 1999

Related Web Sites
Processes Influencing the Transport and Fate of Contaminated Sediments in the Coastal Ocean—Boston Harbor and Massachusetts Bay
U.S. Geological Survey (USGS)
Boston Sewage Outfall: The Fate of Sediments and contaminants in Massachusetts Bay
U.S. Geological Survey (USGS)
Deer Island Sewage Treatment Plant
Massachusetts Water Resources Authority

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in this issue: Fieldwork
cover story:
Surf-Zone Hydrodynamics at Ocean Beach

Research Scientists Recreate Shaking from 1906 San Francisco Earthquake

Outreach Science Workshops for Girls

GIS Specialist Shares Expertise with Local Community

Spoonbill Bowl

Awards David Scholl Selected as AGU Fellow

Staff USGS Visits Deer Island Sewage Treatment Plant

Geomorphologist Joins the WCMG Team

Publications April 2006 Publications List


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