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May 29, 2023

Restrictions, emerging contaminants add to challenges of AZ water treatment

Published: May 18, 2023 Listen to this story Your browser does not support the

Published: May 18, 2023

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Monitoring, testing and cleaning up Arizona drinking water is a gargantuan task. The Arizona Department of Environmental Quality (ADEQ) regulates 1,500 water systems across the state, from something as large as the Phoenix municipal network to something as small as a Mohave County gas station.

"Our responsibility is to make sure that those water systems are regularly sampling for water contaminants," said Trevor Baggiore, director of ADEQ's Water Quality Division.

That division helps ensure public water systems meet EPA Safe Drinking Water standards for around 90 microbes, chemicals and radiological particles. But the EPA cannot set standards until the research is in — if then.

"The science around emerging contaminants is continually evolving," said Baggiore.

So, could — or does — Arizona water treatment cope with emerging contaminants?

Treavor Boyer, a professor in ASU's School of Sustainable Engineering and the Built Environment, and program chair for school's environmental engineering degree, has his doubts.

"It's not really designed to remove total dissolved solids; not designed to remove things like nitrate; not designed to remove pharmaceuticals; not designed to remove PFAS," he said, referring to per- and polyfluoroalkyl substances, the synthetic "forever chemicals" used in many nonstick, stain-resistant and water-resistant products.

Put another way: Treatment and detection will always lag industry, and it could take years to grasp the impact of what plants don't remove.

And water treatment plants already cope with more than enough contaminants.

A glance into one of the 24th Street Water Treatment Plant's many monitoring rooms reveals charts, graphs and camera feeds covering everything from chemical balance to weather, security, and potential overflows and floods.

The plant's central monitoring hub is called the operator room. The one at 24th Street boasts all the necessities: sample sinks, testing tools — and goldfish.

"We actually have goldfish down at the raw water that would alert us if there was any kind of contamination or anything in the canal," said water facility supervisor Jeremy Smithson, who took KJZZ News reporters on a tour of the plant.

Goldfish make ideal coalmine canaries for detecting contamination, especially since they can survive in water loaded with sediment from large rainfalls, snowmelts or wildfires. Such events often affect the Salt and Verde Rivers that feed this plant.

Rivers are the great collectors: silt and soil, ash and algae, microbes and mud, and hazardous chemicals and fire retardants load them up, causing cloudiness, or turbidity, which scientists measure in NTUs (Nephelometric Turbidity Units — a measure of light scattered by particles in a sample).

During peak events like wildfires and floods, turbidities flowing into the plant have reached around 4,000 NTUs. For comparison, anything above 100 NTU is very high and, if allowed to persist too long, can pose dire risks to lake and river life. EPA standards require treated water to reach well below 1 NTU.

Turbidity also interferes with water treatment processes, so plants offer chemical encouragement to clear it out: in this case, ferric chloride and C-308 coagulant polymer. Polymers are long, repeating chains of molecules that, among other things, give structure to fibrous strands, from silk to cellulose.

"The ferric chloride, that's going to attach to all the organics or the dirt, and then the polymer kind of comes in like a giant spider web, traps all that and helps settle it out," said Smithson.

Most groundwater treatment skips this step since wells mainly contain stuff that is dissolved, like sugar in coffee, rather than suspended, like fruit in a smoothie.

"So, you want to select different processes, because groundwater and surface water are different," said Boyer. "And then the EPA rules and the state rules also treat groundwater and surface water differently."

Arizona's mineral richness filled its coffers and clad its capitol in copper. But it can also leach arsenic or uranium into groundwater, which is also more likely to contain PFAS.

"Because of the way the chemical is used on the land surface, you see it showing up in groundwater in many places throughout the state," said Boyer.

A more common problem for groundwater is hardness caused by calcium and magnesium.

Whether ground or surface water, plants typically soften it before treating or sending to customers.

"If we use regular drinking water, then the caustic will start reacting with that natural water," said Smithson.

"Caustic" is a nickname for lye, or sodium hydroxide. Lye isn't just for making soap and pretzels; it can help coagulate particles and boost chlorine disinfection by balancing water's pH. Unbalanced acidity or alkalinity can affect how water looks, tastes and smells and can damage pipes.

Plant personnel also sometimes use lime to balance pH, which should come as no surprise to gardeners.

If it sounds like water treatment involves dumping loads of scary stuff in to get other scary stuff out, it does. But plants are highly regulated and closely monitored. Chemists check for chemicals, organic carbon and other factors that can affect operations or harm health.

"We test the raw water that comes in from the canal; we test it at a couple of different sampling points within the plant; and then the final product that goes out," said Kelly Smith, a chemist at the 24th Street plant.

In the end, what goes in must come out, though plants differ in the methods and technologies they use. At Deer Valley, pressure forces water through sand filters, where collisions, diffusions and electromagnetic attractions cause particles to stick to sand grains.

Such plants boast a smaller footprint and greater speed. But Smithson says rapidity cuts both ways: When something goes wrong, it leaves less time to react.

"That one is a very sensitive process; you can lose stuff very quick, because it's all meant to speed up very fast and get you to the final product faster," he said.

By comparison, the 24th Street plant is fairly bulletproof: slow, gravity-powered settling plays out across a chain of sloped tanks equipped with submerged collector rakes, which guide sludge into sumps. Of course, there's a tradeoff: Such a languid flow leaves ample time for algae to grow during the warm season. The plant combats it with copper sulfate, a common herbicide.

"We usually start about April 1 to the end of October," said Smithson. "That really keeps our filters clean."

Removed solids pass through a centrifuge — a spin cycle on steroids that squeezes out remaining water — and then are trucked to the State Route 85 Landfill near Buckeye. Smithson says it's a far cry from a few decades ago, when plants has no sludge tanks and instead held National Pollutant Discharge Elimination System (NPDES) permits that let them dump solids back into the canal.

Smithson says toxic chemicals and hazardous waste only rarely reach the plant. When they do, it's usually via a spill that flows from streets and neighborhoods into the Arizona Canal Diversion Channel, which also captures flash flood runoff from Phoenix highways.

"We capture it, and we have a third-party contractor come out and dispose of it at a disposal facility for us," said Smithson.

Elsewhere, the clear water passes through charcoal filters, which can remove odors, bad tastes, pesticides, herbicides and some industrial pollutants. It's possible filters might trap long-chain PFAS, but short-chain molecules could still slip through.

"Those are less effectively absorbed. And so what that means is your activated carbon bed is going to have to be replaced more often," said Boyer.

Those filter beds cost tens to hundreds of thousands of dollars. A cheaper and more eco-friendly approach involves regenerating them by removing contaminants and re-activating the carbon. Either way, it's a disruptive process within an interconnected system that already requires, if not Swiss-watch timing, then at least some square-dance choreography.

"If you're not following processes, you can easily back up a plant," said Smithson.

After sedimentation comes chlorine dioxide disinfection, which kills viruses and parasites. Giardia, a parasite found in feces-contaminated soil, food and water, is easy prey; but another parasite, cryptosporidium, resists chlorine and requires a multi-pronged approach and stronger measures like ozone or UV light.

Other disinfection techniques used by plants include hydrogen peroxide and UV light, and membranes and reverse osmosis.

All have their pros and cons, costs and wear-and-tear. Smithson said he struggles to get this point across to superiors who push to exceed compliance standards.

"Compliance is always going to be number one, but at what cost?" he said. "As long as you're meeting compliance, we don't need to drive compliance to make it even better, if we're hurting the plant."

But Smithson says Phoenix water treatment faces problems from lower-level staff, too: They can't hire enough of them.

"All of the cities are having a problem hiring people. Nobody wants to be an operator anymore," he said. "And it's the best job you could ever ask for. You get trained, you get inside or you work on equipment out here. You know, you're never going to be without a job."

Water Systems Operations pumps treated water to the distribution system which, thanks to the Drought Pipeline due for commissioning on June 1, will soon deliver SRP water to North Phoenix for the first time. The area normally receives CAP water sourced from the oft-contested Colorado River.

"It's kind of a backup in case, our water credits, we don't have enough," said Smithson. "And it creates more flexibility for us to transfer water."

Officials have yet to bring such bold responses to bear on emerging contaminants like microplastics — tiny plastic debris less than 5.0 mm long (0.2 inches). Microplastics come from things like synthetic fabrics and microbead exfoliants.

Baggiore says they’re "more of a surface water issue" than a groundwater one.

"The water systems that do use surface water are pretty sophisticated for the most part — City of Phoenix, City of Tucson — and they know, and have monitored for, many of those types of microplastics or other emerging contaminants," he said.

But Troy Hayes, water services director for the City of Phoenix, says they don't currently test for them because they’re currently unregulated and because the Salt and Verde Rivers "aren't under the influence of any industrial or wastewater streams."

Yet, microplastics abound in oceans and lakes, and even the dearth of studies that have examined the problem so far have detected the contaminants in soil and groundwater.

"All the chemicals that leave our house and leave commercial and institutional buildings find their way back into the water supply as well," said Boyer.

Some current technologies might already remove some microplastics and pharmaceuticals; we don't know, because relevant personnel lack the means, methods and perhaps motivation to ask the question.

Under the Unregulated Contaminant Monitoring Rule (UCMR), the EPA can ask ADEQ to require public water systems to monitor for certain unregulated substances, including PFAS. Hayes says Phoenix detected no PFAS listed under the two most recent UCMRs.

But Baggiore says UCMR3 listed only six PFAS, and experts can currently only measure about 27 PFAS compounds. What's more, EPA standards now under consideration place PFAS limits near the lower end of what testing can detect.

"There's not methods to measure any of the other contaminants that are out there. And so there's special techniques that need to be used, which both EPA and Arizona, to a more limited extent, are exploring," said Baggiore.

For now, one of the best ways to keep pharmaceuticals out of the water is to dispose of them properly, via take-back programs, mail-back programs or household hazardous waste disposal.

Meanwhile, ignorance might be a luxury Arizona can no longer afford, if effluent water finally rounds the U-bend and flows from the waste stream to the SodaStream.

"In the past, we would just keep drinking water in one box and wastewater in another box, but they're really very connected," said Boyer.

As water restrictions have tightened, toilet-to-tap consumption — rebranded by officials as "direct potable reuse" (DPR) — has shifted from a distasteful NIMBY issue to a serious option.

"That is a supply that right now is discharged to the Salt River, which potentially could be sent to an advanced water purification facility to be treated and eventually put back in as drinking water," said Hayes at a water panel hosted by KJZZ.

Hayes said such a move could deliver up to 60 million gallons a day, compared to 125 million gallons of Colorado River water that reaches taps daily.

In 2022, the Arizona legislature charged ADEQ to finish its DPR regulations. Following an imminent public comment period and a review by the Governor's Regulatory Review Council, they aim for rules to go into effect by next July. States like California, Colorado and Texas are already moving forward with similar plans.

Hayes says climate change's alarming pace is forcing our hand.

"It's going at a faster pace than I would expect, and so I'm hopeful that everybody understands that and makes the appropriate decisions to be able to react quickly enough," he said.

In the end — river or well, influent or effluent, it's all one water. Barring better answers and some careful but courageous action, this "round river" — to borrow a term from conservationist Aldo Leopold — could make Arizona water infrastructure not unlike some Class VI rapids: dangerous, congested and often unrunnable.