Darien gets its water from six different reservoirs and three wells during high demand, according to Mike Liberante, manager of treatment at Aquarion’s Easton facility. The reservoirs are the Hemlock, Laurel and North Stamford reservoirs, and three reservoirs in New York state — Mill, Trinity and Siscowit. Under high demand, the town could also get water from other parts of the state, including from Norwalk’s water system, the Rewak Well, and Canal Street and Coleytown wells in Westport.

Aquarion employees monitor activities within the watershed, looking for potential areas for runoff that could contaminate the drinking water supply. Animal farms that produce manure or places that use chemical fertilizers or pesticides are watched to ensure runoff is avoided if possible, Liberante said.

The reservoirs cannot be fully dammed, and are required to keep downstream rivers flowing for wildlife and recreation. Overfilled reservoirs dump back into the downstream river.

Once water wiggles its way into a reservoir, Aquarion employs one of two types of surface water filtration at each of its nine Connecticut facilities — sedimentation and dissolved air flotation. Both methods remove larger particles that give water its brown color and earthy odor.

In dissolved air flotation, the kind used for Darien water, the water is pressurized with compressed air and then released at atmospheric pressure, causing the particles to float to the top where they are then skimmed off. Sometimes a coagulant is added, such as aluminum sulfate, to help the particles stick together for easier skimming.

Sometimes, under high demand, Darien will get water from other sources, such as the Easton plant. Here, the reservoir water is taken in and aluminum sulfate is added to give the particles weight. The alum, as it’s called, is positively charged and the negatively charged particles in the water attract to it chemically, Liberante noted. Long chain cationic polymers are also added to make the particles, called floc, stronger.

Chlorine, in the form of sodium hypochlorite, or bleach, is also added to help kill disease-causing microbes. Once the floc is heavy enough, it settles to the bottom and the surface water heads to a sand and anthracite, or coal, filter.

From here, the water filtration process is the same at both types of facilities. Using gravity, the water falls through the sand and anthracite filter where remaining particles are removed. After that, more chlorine is added as a disinfectant for the distribution process, and a phosphate-based corrosion inhibitor is also added.

Fluoride, in the form of hydrofluorosilicic acid, is then added as per state Department of Health regulations that require fluoridation of water for populations over 20,000. It’s added under the assumption that fluoride is good for dental health, although a 1998 lawsuit against the EPA, filed by the National Resources Defense Council on behalf of EPA scientists, claims more needs to be learned about fluoride’s affects on public health before its use in public water supplies is continued. (See next week’s story for more)

If the acidity is too low, caustic soda is added to bring it within EPA-acceptable ranges. Low pH can lead to harmful byproducts of the chlorination products, such as trihalomethanes and haloacetic acids. This happens when the temperature is high, the water has a low acidity, and the organic particle content is high. The chlorine reacts with the organic matter and produces bromide, which is a precursor to haloacetic acids and trihalomethanes, according to the EPA.

In 2011, Darien water averaged 29 parts per billion (or 29 micrograms per liter) for trihalomethanes, and 28 parts per billion for haloacetic acids. The maximum concentration allowable by the EPA for trihalomethanes is 80 ppb, and 60 for haloacetic acids. Tests of Darien’s water supply ranged from 2-56 ppb for the trihalos, and 1-50 for the haloacetics.

Extended exposure to high levels of these chlorination byproducts can have adverse health affects, according to the EPA.

Water is then stored in storage tanks before it is sent out to homes and businesses. Most of the pipes that carry the water are made from cast iron or ductile iron, and some are made of concrete. Whereas iron can oxidize to create rust, Aquarion still chooses to use this material in most applications because of its durability and other factors, Liberante said.

“We’re fighting corrosion everywhere,” Liberante said. “It’s a natural thing.”

Peter Fazekas, a public relations manager for Aquarion, said that his company tests 11 locations throughout town twice a month to monitor water quality. These places include Holmes, Hindley and Tokeneke elementary schools, a Post Road Station, St. Luke’s Church, a Park Lane Station, Springdale Florist, and locations on Hollow Tree Ridge Road, Brookside Road and at 280 Tokeneke Road.

Aquarion also tests the Rewak Well, which is on the Stamford border. Water from this well accounts for only 2.5% of the total water consumed by Darienites, who consume about 3 million gallons per day. Stamford has the capacity to put out 35 million gallons daily.

Rewak has the capacity to provide up to 400,000 gallons per day, according to the town. In the early 1980s, regulators detected high levels of volatile organic compounds in Rewak. “The primary source was the Stamford industrial land uses across the Noroton River,” states the town’s 2006 Plan of Conservation and Development. “An air stripper was installed that works continuously to remove VOCs and the problem is being corrected.” Current testing indicates there are no VOCs in Rewak, according to Fazekas.

Aquarion also conducts periodic lead and copper testing for residents who volunteer their homes for testing. More information on lead and cooper testing can be found at Aquarion.com

Aquarion is also required to monitor the water’s clarity, known as turbidity, as well as the water’s odor and overall color. They also test for certain bacteria such as cryptosporidium and fecal coliform, and they measure amounts of barium, copper, fluoride, lead, nitrate, chloride, sodium and sulfate.

“It’s a highly regulated industry with specific ranges,” Liberante said. “We pride ourselves in our water quality. I would probably say we have some of the best water quality in New England.”

The company also keeps a close eye on potential backflow areas. When water pressure is low, contaminated water can end up in the water system, so Aquarion monitors these locations and ensures that backflow prevention devices are installed and working properly.

Originally published in The Darien Times.