Automated plant delivers cleaner, better-tasting water to a Cape Cod vacation town and meets fluctuating water demand with one staff shift.
When the summer arrives in Falmouth, Massachusetts, so do the tourists. Beaches, boating, biking, fresh seafood, a ferry to Martha’s Vineyard and other activities make it an ideal destination. And the water department for this small coastal town in the idyllic Cape Cod region suddenly needs to increase its output to service from about 25,000 permanent residents to a summer population of up to 120,000 people.
This influx of out-of-towners can multiply the town’s water demand by as much as five times.
Until recently, a pump station that had been in use since 1898 provided most of Falmouth’s water supply throughout the year. 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 visitors.
That’s why the Massachusetts Department of Environmental Protection mandate to improve certain water-quality measures may have been a blessing in disguise. The mandate led to the town building a new $42 million water treatment and filtration plant that 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.
Quality and Staffing Challenges
Chlorine is essential to providing safe drinking water. But when it mixes with organic material like algae, it creates chemical-compound byproducts known as trihalomethanes.
The EPA’s maximum allowable annual average level for total trihalomethanes (TTHMs) is 80 parts per billion (ppb). Most sampling sites in Falmouth regularly measured below this level, but in some instances, tests did exceed 80 ppb.
These findings spurred the need for a new treatment and filtration plant that would remove algae from water prior to treating it. Removing the algae would lower the water’s TTHM levels and reduce the use of chlorine to provide more pristine, better-tasting water to the town’s homes and businesses.
However, state laws regarding water treatment plants created concerns about staffing it.
“According to state regulations, you must staff these plants whenever they’re running, unless you get a waiver for it to run unmanned in certain hours,” says Steve Rafferty, water superintendent for Falmouth.
Staffing the plant 24/7 simply wasn’t feasible. For eight months out of the year, the plant would only need to be staffed one shift per day to meet the public’s water-supply demands of about 75 to 90 million gallons per month. But during the busy summer, it would need to run and be staffed 24 hours a day to meet demand that can exceed 250 million gallons per month.
“I would have needed a minimum of eight more highly skilled operators if the new plant were manned 24/7 instead of just a single shift,” Rafferty says. “You have to consider the town’s cost of staffing those highly paid positions. Also, it’s extremely difficult to find, attract and retain that many skilled workers.”
The only option was to meet the state’s waiver requirements by building a highly automated, highly resilient and remotely connected plant that could meet any month’s water demands with just a single staffed shift.
Creating a Reliable Control and Information Architecture
The new plant would draw water from the town’s primary water source, Long Pond, and treat it in four separate processes: algae removal, ozonation to improve taste and odor, activated carbon filtration and sodium-hypochlorite disinfection.
Rafferty worked with R.E. Erickson, a systems integrator that specializes in water and wastewater treatment, and consultant Tata & Howard, to develop the plant’s control and information architecture. During this process, maintaining the plant’s availability was paramount.
“We started with a good, conventional SCADA system design for the new plant,” Rafferty says. “But it was only 99% reliable, meaning that we could have a downtime event about three times per year. That wasn’t good enough.”
To boost that number to 99.99%, R.E. Erickson incorporated Stratus virtual servers with VMware software into the system design. The servers are fault tolerant with no failover time and are continuously monitored by Stratus Technologies, an Encompass™ Product Partner in the Rockwell Automation PartnerNetwork™ program.
The plant’s two Allen-Bradley ControlLogix® controllers from Rockwell Automation provide redundant control and are connected on an EtherNet/IP™ network architecture that uses a fault-tolerant device-level-ring (DLR) topology. NorthEast Electrical, a Rockwell Automation Authorized Distributor, provided local support and installation.
R.E. Erickson chose FactoryTalk® Historian software for logging and analyzing plant data and generating on-demand reports. XLReporter software from Encompass Product Partner SyTech helps with on-demand reporting, and alarms-and-event software from Encompass Product Partner WIN-911 provides critical information to operators.
The FactoryTalk View human-machine interface (HMI) software and ThinManager® thin client software were chosen to give operators in the plant access to information on both HMI thin clients and mobile tablets. The ThinManager technology also is used to provide remote access to the plant over an encrypted VPN connection. This allows on-call operators working remotely to monitor operations and address issues that arise outside normal plant hours.
“In our old pumping station, on-call operators had to come in about six times a week to resolve some kind of abnormality,” Rafferty says. “Now, probably 19 out of 20 times they can address the issue from home, on their computer, in about five minutes.”
Reliable, Pristine Water
The new water treatment and filtration plant became operational in October of 2017. It met the state’s requirements for an automated treatment plant and today is running on a single shift, even in the busy summer months. Rafferty estimates these improvements are saving the town about $1.3 million per year.
The highly reliable plant also hasn’t experienced a single interruption to date — even following a severe storm that took down one of the plant’s servers.
The plant’s TTHM levels are in the low 20s and dropping. And that decline has coincided with cheers from the community about the town’s improved water quality.
“Many people have commented on the quality,” Rafferty says “In fact, I got a call from a scientist who has always used water filters in his home. He changed his filter this spring and accidentally left it in bypass mode. He says he couldn’t believe the great water he was getting was from our plant.”
The plant’s modern control and information architecture has helped reduce the demands that the much more sophisticated operations have put on operators. This reduces the demands on operators and improves system performance through real-time visibility into the production process.
“The historian software has allowed us to automate our reporting to the state, which previously was paper-based,” Rafferty explains. “We’re also using the historian for more advanced trending to help operators make better decisions. For example, they can monitor ozone demand by tracking the rate of change on the plant’s oxidation reduction potential (ORP) analyzers. As values trend one way or another, operators can increase or decrease the ozone dosage as necessary.”
Rafferty says he’s encouraging operators to simply explore what’s possible with analytics.
The new plant has won multiple local awards, including an ENR New England Best Project award in 2017 and an Associated Builders & Contractors of Massachusetts Eagle award.
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