The town of Marana opened two new water treatment facilities on Tuesday, March 23, after finding unregulated contaminants above EPA health advisory levels in late 2016.
In August 2018, the Mayor and Town Council approved the creation of the two treatment facilities at the affected water systems, Picture Rocks (Continental Reserve area) and the Airline/Lambert (Saguaro Bloom area) system. Construction for both sites began January 2019.
The Airline/Lambert water treatment campus is now fully operational, while the Picture Rocks water treatment campus is still undergoing processing tests, said Marana interim water director Stephen Dean.
In late 2016, Tucson Water notified Marana Water and Metro Water that they found 1,4-Dioxane and PFAs above Environmental Protections Agency’s health advisory recommendations.
Dioxane is a synthetic industrial chemical and byproduct of paint strippers, dyes, greases, antifreeze and aircraft deicing fluids. There is no federal contaminant level for drinking water, but the EPA health advisory level is 0.3 parts per billion. PFAS, called per- and polyfluoroalkyl substances (PFOA and PFOS), are used in non-stick pans, furniture protection, microwave popcorn bags, to-go food containers and cleaning products as well as fire-fighting foams. The EPA health advisory level is 70 parts per trillion, but like dioxane, it is not federally regulated.
While human health effects to low-level exposure to either chemical is unclear, according to the CDC, laboratory animals exposed to large amounts of PFAS experienced effects to reproduction, thyroid function and their immune systems, while people unintentionally exposed to dioxin developed a skin condition called chloracne and liver
In order to remove dioxane and lower PFAS levels in the water, the water from the well goes through a series of treatment processes. The treatment facility first removes as much sediment in the water as possible to avoid damage and also reduce the use of hydrogen peroxide, which they use to remove 1,4-Dioxane to a target level of zero.
The treatment facility uses a concentration of 35% hydrogen peroxide, which is injected into the water at a level of eight parts per billion, said Bridgette Peña, Marana water quality operator at the Airline/Lambert water treatment campus. The water mixed with hydrogen peroxide passes through the UV light reactor, which generates hydroxyl radicals that react to and break apart the 1,4-Dioxane into harmless molecules, carbon dioxide and water.
Afterwards the water is processed through the Granular Activated Carbon (GAC) tank treatment. The facility has four tanks, with each tank holding 20,000 pounds of GAC, a square of black charcoal that when zoomed in looks like a little sponge. The GAC tank is used to treat any residual peroxide and the PFAs, said Marana Water Quality Operator Kaulana Breitenbach. He explained the one granule of GAC is like Pac Man gobbling up PFAs like a long trail of dots, ghosts and cherries. One little square can treat three football fields of water.
After going through this process there should be no 1,4-Dioxane and a target of level for PFAS of 17.5 parts per trillion, lower than the 70 parts per trillion health advisory level.
Dean said town officials “felt compelled” to make sure they were under the health advisory levels.
“For now and for years to come, we wanted to make sure we were providing safe drinking water in this entire area,” Dean said.
At the final stage, the treated water is disinfected with chlorine to kill almost all bacteria and any residual hydrogen peroxide, said Peña. The water is then pumped into the reservoir to go out to Marana customers.
The water treatment facilities will also reuse and recycle water. As of March 23, the Airline/Lambert water treatment facility had collected 12,540 gallons of treated water that would either go through the treatment process again or be used by the community, like Marana Public Works, instead of dumping it into the sewer which could then create chemical by-products, said Breitenbach.
The Airline/Lambert water treatment facility will treat on average one million gallons of water a day and the Picture Rocks facility will treat about 1.4 million gallons a day for the residents, said Dean.
Due to the pandemic, a project that was expected to be completed by fall of 2020 was delayed and incurred greater costs. Including design, construction and post-construction services, Dean said both sites totaled a cost of $16.1 million. In January 2019, the Water Infrastructure Finance Authority of Arizona (AZWIFA) approved a loan to the Town of Marana for $15 million. After an increase in the original estimate of $15 million to $16 million, the town secured a WIFA loan to cover the extra million in costs in August 2019.
Dean said the pandemic brought about challenges obtaining resources and materials, as well as labor challenges, with whole crews impacted or shipments delayed.
“It took many, many months to complete it and we had some challenges with COVID, as far as resources and materials and supplies being brought to this site, but we’re happy that we’re finally brought to fruition,” Dean said.
Despite the costs and challenges, Deputy Town Manager Erik Montague believes the town council delivered on its promise to its constituents.
“Marana has a long history of being proactive and very thoughtful about its investments in infrastructure to help ensure that the people that are here today, and the ones that are coming tomorrow have, in this case, safe water delivered to their homes and their businesses,” said Montague.