Cape Cod vacation town uses ozonation to improve taste and quality of drinking water
Falmouth, Massachusetts, built a new water treatment plant using two Xylem Wedeco ozone generator systems that significantly improve the quality of the water.
When summer arrives in Falmouth, so do the tourists. Beaches, boating, fresh seafood, a ferry to Martha’s Vineyard and other activities make it an idyllic vacation destination. But the influx of out-of-towners to this small coastal town in the Cape Cod region can multiply the town’s water demand by as much as five times. That means the water department needs to increase its output to service a summer population of up to 120,000 people, compared to just 31,000 permanent residents.
Until recently, a pump station that had been in use since 1898 provided most of Falmouth’s water supply throughout the year, sourced from the nearby Long Pond reservoir. While the water that the station provided was safe, it wasn’t filtered. This could give the water an unpleasant taste, smell and cloudy appearance, making it less than ideal for both residents and summer tourists. Algal blooms, an increasing risk for many water sources, can also contribute to these undesired qualities.
Mandate to improve the water treatment process
When new EPA and Massachusetts Department of Environmental Protection (MassDEP) water-quality standards went into effect, the Long Pond Water Treatment Plant needed to change its treatment process. This is because the high doses of chlorine needed to treat the unfiltered supply reacted with the organics in the raw water to form disinfection byproducts, which did not meet the new standards. In 2014, a MassDEP mandate gave Falmouth the option to add another disinfectant to its existing water treatment process or build a new facility.
“When you have surface water supply, water quality can change at any given time,” said Michael Reghitto, Chief Treatment Plant Operator for the Long Pond WTP. “We have a relatively clean reservoir – that’s why we were unfiltered for over 100 years, but it does turn once or twice a year and we also sometimes get unexpected raw water quality.”
As a result of the MassDEP mandate to improve certain water-quality measures, the town voted to allocate $46 million to construct a new water treatment and filtration plant on the east shore of Long Pond. The new treatment plant would not only have filtration, but a new treatment train. The chlorination step would be replaced with a combination of ozonation and filtration to address four treatment goals: algae removal, disinfection, metal oxidation, and filtration, along with a final disinfection step with sodium hypochlorite for distribution.
Ozonation process improves water quality and disinfection
Construction on the new Long Pond Water Treatment Plant began in April 2015. The plant, which became operational in October 2017, delivers approximately 70% of all the water that is used in the public water system in Falmouth. The facility draws water from Long Pond and treats it in four separate processes: algae removal, ozonation to improve taste and odor, activated carbon filtration and sodium-hypochlorite disinfection.
Long Pond WTP incorporates two ozone generator systems from Xylem. With Xylem’s 2G ozone electrode technology, the Xylem Wedeco SMOevo-510 units use the required doses of ozone to deliver reliable disinfection throughout the process. The ozonation disinfection stage removes bacteria and viruses, and reduces metal concentrations by oxidizing iron, manganese and sulfur.
The new plant, which handles an average of 8.4 million gallons per day, can adjust to accommodate fluctuating flow rates of 2.5 million gallons per day during the winter up to a peak 12 million per day in the summer, when the tourist population swells.
Xylem’s ozonation solution comes with sophisticated, built-in control technology, which enables the plant to adjust the dosing to these fluctuating flows.
“The system is unique in that it offers great variability,” said Reghitto. “It’s exciting."
Efficient gravity media filtration to remove solids
Another key step in the plant's treatment process is gravity media filtration, which uses Xylem's Leopold filtration systems with underdrains for high flow rates and efficient backwash. Leopold gravity media filtration systems remove small solids before disinfection, resulting in finished water that is stored for distribution. In the summer, about 6,000 gallons of water a minute run through the plant, which is spread evenly among four filters.
“The town selected these filters because of the consistency of the water they provide, not only with filtering, but also backwashing,” said Reghitto. “Backwashing is crucial to how the filters operate. If you look at the channels inside the underdrain, you can see that there are channels for air and channels for water. When we're pumping air and water together, we need them to mix evenly throughout the filter, and these underdrains allow for that.”
New system requires less staffing and maintenance
Since the new plant went online in late 2017, it has significantly improved both the water supply’s taste and quality. And using the latest control and information technologies, the state-of-the-art plant can be minimally staffed to help keep operating costs and hiring demands down.
The Effizon 2G ozone electrodes, which have a 10-year warranty, are designed to be exceptionally reliable. At the plant, they have worked flawlessly to create the ozone gas needed for the process, and have required no service or replacement by the plant or factory technicians during the time in service.
“We have not had to open the contained ozone generator vessels to have any sort of look or repair, which is what we expect with good quality technology like this,” said Reghitto. “The filters have been so reliable that we've been in operation for five years, and we've yet to have any maintenance needed.”
The Long Pond WTP also takes advantage of Xylem’s Preventative Maintenance Agreement (PMA) to protect its investment in Xylem Wedeco ozone technologies. The PMA gives the plant’s operators peace of mind and helps ensure reliability. Although plant staff are fully trained on the Xylem Wedeco ozone system, having a PMA enables factory technicians to regularly service the system so that emergency repairs and fixes are less likely.
“Our factory technicians are Xylem employees,” said Richard Nash, Aftermarket Territory Manager – Treatment, Xylem. “We don’t use third-party contractors, sales agents or manufacturers’ reps for factory preventative maintenance services.”
Along with Xylem factory technicians, the Long Pond WTP staff can also rely on Xylem’s Aftermarket, Engineering and Service team for remote support whenever questions or issues arise.
“Xylem has been a great partner for the town of Falmouth,” said Reghitto. “It’s very beneficial to us to know that we have the reliability of not just the equipment but the company behind us to make clean water.”
Watch the video about the Falmouth solution
Learn more about Xylem’s disinfection and filtration solutions
The Xylem Wedeco SMOevoPLUS ozone system is specially manufactured to operate with maximum energy efficiency, resulting in very low lifecycle costs. The Leopold Type S underdrain air flow adjustability allows for more control and saves energy and water.