Boston Harbour Clean Up
Like many harbours near cities along the eastern seaboard, the Boston Harbour in Massachusetts has been put to use for hundreds of years as a receptacle for raw and partially treated sewage from the city of Boston and surrounding towns. In the late 1800s, Boston designed a sewage and storm water collection system. This sewage system united millions of gallons of untreated sewage from residences, schools, hospitals, factories, and other buildings with storm water collected from roads during intervals of moderate to heavy rain.
The combined sewage and storm water accumulated in the sewage system was discharged untreated to Boston Harbour on outgoing tides. Sewage from communities surrounding Boston was likewise piped to Boston’s group system and released to Boston Harbour and the big rivers leading to it: the Charles, Mystic, and Page 218 Neponset Rivers. Most of the sewage conduits, tunnels, and other infrastructure constructed in the late 1800s and early 1900s are still in use today.
In the 1950s, the City of Boston was concerned with growing health dangers of swimming in and eating shellfish harvested from Boston Harbour in addition to doors and aesthetic issues that resulted from releasing raw sewage into harbour waters. The city constructed two state-of-the-art primary sewage treatment plants during the 1950s and 1960s on two islands settled in Boston Harbour. The very first sewage treatment plant was constructed on Nut Island; it treated roughly 110 million gal/ per day (416 million l/per day).
The next sewage treatment plant was constructed on Deer Island; it treated roughly 280 million gal/per day (1060 million l/per day). Both sewage treatment plants removed about half the total suspended solids and 25 percent of the biological oxygen demand seen in raw sewage. The outgoing tide in Boston Harbour was still used to flush the treated wastewater and about 50 short tons (46 metric tons) per day of sewage sludge (also called bio solids), which was created as a byproduct of the complex primary treatment procedure. The sewage sludge types from solids in the sewage settling in the base of tanks.
During the 1960s, the resources allocated to preserving the city’s maturing sewage system fell. Consequently, the sewage treatment plants, pipes, pump stations, tunnels, interceptors, and other essential elements of Boston’s sewage infrastructure started to fall into disrepair. Gear failures, sewer line breaks, and other issues resulted in the discharge of raw and partially treated sewage to Boston Harbour along with the rivers leading to it. In this period, the Metropolitan District Commission (MDC) was the agency in charge of sewage collection, treatment, and administration.
In 1972, the United States Congress enacted the Clean Water Act. This was landmark legislation to boost the grade of our country’s waters. The Clean Water Act required that sewage released to United States waters must meet secondary treatment levels by 1977. Secondary treatment of sewage means that at least 85 percent of total suspended solids and 85 percent of biological oxygen demand are removed from sewage. Rather than working towards fulfilling this national requirement, the MDC requested a waiver from this new duty from the United States Environmental Protection Agency (EPA). In 1983, the EPA denied the waiver request.
The MDC reacted by changing its waiver request to assure the city would build a 9.2-mile (14.8-kilometer) outfall to realize increased dilution of the sewage by releasing to deeper, more flushed waters. As part of its own waiver, MDC also guaranteed an end to release sewage sludge in the harbour and initiation of a combined sewer overflow abatement project to stop flow into Boston Harbour from eighty-eight overflow conduits. In 1985, EPA refused the second waiver request.
During EPA’s thought of Boston’s waiver request, in 1982, the City of Quincy filed a suit against the MDC for violating the Clean Water Act. In 1983, the Conservation Law Foundation filed two suits; one was against MDC for violating the Clean Water Act as well as the other was against EPA for not fully implementing the Clean Water Act by neglecting to get Boston to obey the law. The Massachusetts legislature reacted to these pressures by replacing the MDC with the Massachusetts Water Resources Authority (MWRA) in 1984.
The MWRA was made as an independent agency with all the ability to increase water and sewer rates to cover updating and preserving the group and treatment of the area’s sewage. The subsequent year, the federal court ruled the MWRA must come into conformity together with the Clean Water Act. As an outcome of this opinion, the MWRA developed a listing of sewage enhancement jobs which were needed to update the existing sewage treatment system and clean up Boston Harbour.
The Boston Harbour cleanup consists of $4.5 billion worth of sewage treatment developments that comprise the building of a 1,270 million-gal/per day (4,800 million- l/per day) primary sewage treatment plant, a 1,080 million-gal/per day (4,080 million-l/per day) secondary sewage treatment plant, a dozen sewage sludge digesters, disinfection sinks, a sewage screening facility, an underwater tunnel, a 9.5-mile (15.3-kilometer) outfall pipe, ten pumping stations, a sludge-to-fertilizer facility, and combined sewer overflow treatment facilities.
Now, about 370 million gallons/per day (1,400 million l/per day) of sewage effluent from over 2.5 million residents and companies is released to Boston Harbour. Nearly half the overall flow is stormwater run-off from roads and groundwater infiltrating into cracked sewer conduits. The combined sewage and storm water is moved through 5,400 miles (8,700 kilometers) of conduits by gravity and with the help of pumps. Five of the ten pumps have already been replaced.
At least two of the pumping stations which were replaced as an element of the cleanup attempt dated back to 1895. The sewage is pumped to Nut Island where more than 10,000 gal/per day (37,800 l/per day) of floatable pollution such as grease, oil, and plastic debris are now removed by its Page 219 new sewage-screening facility. The facility also removes any grit, sand, gravel, or big items. A 4.8-mile (7.7-kilometer) long deep-stone tunnel will be used to transport screened wastewater to Deer Island for additional treatment.
Among the very major changes which have happened as a member of the Boston Harbour cleanup project is the reconstruction of Deer Island. Prior to 1989, Deer Island had penitentiary buildings, World War II military bunkers, and an aging sewage treatment plant. All the old edifices and constructions have been removed as well as the isle was reshaped to accommodate twelve huge sewage sludge digesters, 60 acres (24.2 ha) of a new primary sewage treatment plant, and a new secondary treatment facility. The most important sewage treatment plant has reduced the amount of suspended solids released to Boston Harbour from 138–157 short tons daily (126–52 metric tons).
The final stage of the secondary sewage treatment plant on Deer Island was finished in March 2001. It uses settling tanks, as are seen in primary sewage treatment plants, in addition to microorganisms, that’ll use up organic matter in the sewage thus raising treatment amounts. Secondary treatment of Boston’s sewage has resulted in a rise in the removal of total suspended solids from 50–90 percent and biological oxygen demand from 25–90 percent.
Following the sewage is treated and disinfected to eliminate any remaining pathogens (disease-causing organisms), the effluent is released through a 9.5-mile (15.3-kilometer) outfall tunnel into the waters of Massachusetts Bay. Huge tunnel boring machines were used to drill the tunnel below the ocean floor. The outfall has fifty-five diffuser conduits joined at right angles to it along the last 1.25 miles (2.01 km) of the outfall. The diffuser pipes increase dispersion of the treated sewage in the receiving waters. The tunnel was started in September 2000.
The outfall has been a source of controversy for a lot of residents of Cape Cod and for the users of Massachusetts Bay along with the Gulf of Maine. There’s concern about the long-term impact of contaminants from the treated sewage on the region, which is used for transport, recreation, fishing, and tourism. Some options to the sewage treatment plant and also the 9.5-mile (15.3-kilometer) outfall pipe were developed by civil engineers at the Massachusetts Institute of Technology.
The options contained changes to the complex primary treatment facility plus a smaller secondary treatment facility together with the effluent released to Boston Harbour. Because there wasn’t enough evidence to convince EPA that water quality standards would consistently be satisfied in the harbour, EPA rejected the options.
As a section of the Boston Harbour cleaning, sewage sludge is not any longer released to the harbour. Twelve sewage sludge digesters in Deer Island were built in 1991. The digesters break down the sewage sludge by using microorganisms including bacteria. Various kinds of microorganisms are utilized in the sewage sludge digestion procedure than in the secondary treatment process. As the microorganisms use up the sewage sludge, methane gas is generated which is used for heat and electricity. Prior to 1991, all the sewage sludge was released to Boston Harbour. Since 1991, the sewage sludge was sent to a facility that converts the digested sewage sludge into fertilizer.
The sludge-to-fertilizer facility dewaters the sludge and uses rotating high-temperature dryers that make fertilizer pellets with 60 percent organic matter, and important nutrients like nitrogen, phosphorus, calcium, sulphur, and iron. The fertilizer is advertised in volume as well as sold as Bay State Organic, which is sold locally to be used on golf courses and landscape.
This huge endeavor to clean up the harbour by updating its sewage treatment facilities was among the world’s biggest public works jobs. These changes have resulted in quantifiable progress to Boston Harbour. The harbour nourishes a multimillion dollar lobster fishery per annum in addition to flounder, striped bass, cod, bluefish, and smelt recreational fisheries.
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