At a September work session, Ann Arbor City Council members asked city staff if the current water treatment plant could accommodate equipment to remove 1,4 dioxane, just in case it becomes necessary in the future. In this installment of 89.1 WEMU’s “The Green Room,” we look at what such a water treatment process looks like in action.
Barbara Lucas (BL): When Gelman Sciences treats Ann Arbor’s groundwater, the after-treatment water contains dioxane at levels up to 10 ppb, and that water is discharged to Honey Creek. But Tucson Arizona’s new plant removes dioxane completely, and they serve the after-treatment water directly to customers.
Jeff Biggs: So from here you can see the blue piping I talked about earlier. The water comes up from underground, right through here.
BL: Jeff Biggs is administrator for the Tucson Water Department, and he is proud of their new system.
Biggs: Those pumps that you can hear, boost the pressure of the water to be able to force it through the UV light, the reactors.
BL: Their dioxane treatment plant has a ____square feet footprint, and treats water from a plume that covers about four square miles.
Biggs: So here is the plume, we are cleaning it up. The water flows through these pipes up to here. We treat it and then the water is actually delivered to basically the downtown area. About 60,000 people drink this water, about 8 million gallons of water a day.
BL: Biggs says they first found out they had dioxane in their drinking water in 2002. Their concerns took on urgency when…
Biggs: In January 2011, the EPA came out with a new health advisory. The old advisory was 3 ppb, the new one was .35 ppb. An order of magnitude lower.
BL: They built the plant in just 14 months. They were in such a rush, they built the walls before the equipment was completed, leaving the roof off. When the equipment was ready, it was lowered in with a crane.
Biggs: So everyone was really nervous as we watched them swaying as they lowered them down and set them in. But we had to keep moving to meet our schedule.
BL: The plant cost them about $18 million to build, and they used city funds to build it, confident the federal government would pay them back. That’s because the Unites States Air Force is the main Responsible Party—airplane manufacturing decades ago resulted in TCE and dioxane-contaminated groundwater.
Biggs: They’ve agreed to a number and now it’s just working it through the process. So, that’s the history of TCE removal and dioxane removal in Tucson. We can go inside and I can describe each step of the process.
BL: He says there’s not much to it—the water is mixed with hydrogen peroxide, then pumped past a series of UltraViolet light bulbs—864 of them.
Biggs: At that stage, between those two processes, the 1,4-dioxane is destroyed.
BL: He says it takes a lot of energy to power those light bulbs. It costs almost a million dollars a year, but the Air Force will cover that too. They considered going solar, but it would take such a huge array, and…
Biggs: Our main concern at the time was to get this up and running.
BL: It may be energy intensive, but it is not manpower intensive. Today, no staff are in sight. Aside from changing a lightbulb now and then....
Biggs: It’s monitored remotely, 24 hours a day.
BL: Overall, he says Tucson is very happy with the plant.
Biggs: The concentration of dioxane coming in averages 4-5 ppb and when it leaves it is non-detect at below .1 ppb. We are well below the existing health advisory of .35. Costs are high but it is so efficient it is well worth it. It’s very simple, not a lot of moving parts, and it works really well. No complaints at all.
BL: Michigan will soon lower the legal limit of allowable dioxane from 85 to 7.2 ppb, while the State of Arizona has no legal limit at all. But that hasn’t stopped Tucson’s water from being cleaned down to less than 0 ppb.
(BL): Barbara Lucas, 89 One, WEMU.
RESOURCES:
Info on how Tucson’s “Advanced Oxidation Process” (AOP) dioxane treatment works
Youtube video on Tucson’s AOP Water Treatment Plant
Info on Tucson’s treatment plant sent to customers, prior to construction
