Fluoride Action Network

Western Springs: An overview of reverse osmosis in the new water plant

Source: Western Springs Patch | January 24th, 2012 | By Darren McRoy
Location: United States, Illinois

By now, most Western Springs residents are aware than an approximately $8 million project—the most expensive in Village history—is underway to completely transform the Village water-treatment plant at 614 Hillgrove Ave. into a reverse-osmosis system, one which will provide Village residents with higher-quality water than ever before. (See photos of the progress here.)

And at the same time, plenty of residents might also be asking: what exactly is “reverse osmosis,” anyway? How did this massive project come about, why was it necessary and how are we paying for it? What’s going on with our water right now, and how and how soon will it become the cleaner, softer water we’re been promised?

We sat down with (no longer “Acting”) Director of Municipal Services Matt Supert and read through some files to see if we could tackle some of those questions. Some of the answers were surprising—and many were actually pretty cool, too.

(A note: Timber Trails is on a separate water system from the rest of the Village, and, like many neighboring municipalities, uses Lake Michigan water.)

Equipment from the 1950s

Village staff and Boards have known for some time now that the Western Springs water plant couldn’t hold out much longer. The plant was built in the 1930s and has virtually no equipment newer than the 1950s—meaning the stuff being used to treat your water was probably made when Dwight D. Eisenhower was president.

For decades, the process has involved sand filters, lime (calcium hydroxide) treatment and a clarifier (to filter out the lime.) But by the mid-1990s, the Board of Trustees was faced with a tough decision: just how should the Village deal with its aging filtration equipment?

“There were issues of the sand filters beginning to get towards the end of their life cycle,” Supert said, illustrating one of many quandaries the Board faced. “If we’re rebuilding the plant a different way, maybe we don’t need sand filters. Is it worth investing $75,000 in [another] sand filter?”

It soon became clear that there were three options for the Board. One: replace the old sand-and-lime treatment with new, upgraded versions of the same technology. Two: abandon the Village’s long-upheld aquatic independence and join surrounding communities in importing Lake Michigan water. Or three: take a chance on this new, emerging technology called “reverse osmosis.”

There was a pros-and-cons list for each option. Lime treatment could be easily phased in over several years, but retained high costs, including labor. Pumping in lake water involved the cheapest capital (construction) cost, but would surrender much autonomy over treatment and involve the Village in water politics. And reverse-osmosis dodged all these pitfalls—but came with a wildly expensive price tag.

A decision on the matter stalled for years—long enough for reverse-osmosis treatment to come down significantly in cost. With annual expenditures for reverse-osmosis comparative to lime treatment and decisively less than for lake water, and the fading facilities demanding a decision the Board finally pulled the trigger on RO and set construction to begin in November of 2011.

How reverse osmosis filtration works

Labeling the new form of water treatment as “reverse osmosis” doesn’t really do the full process justice. The actual reverse osmosis is only one step of the sequence, and one not even applied to all the water that goes through the plant.

In the coming system, seen in the diagram attached to this article, water is pulled from two Village wells, #3, behind Village Hall, and #4, in the Public Works yard south of the Rec Center. (Well #1 is only used for emergencies, and Well #2 is capped.) The water then is pumped upwards into the treatment plant using booster pumps. There, it is processed by Amiad “iron filters”—which actually filter all particles larger than two microns (1/12,500 of an inch), but perhaps most importantly, iron.

“We tend to have a lot of what we call ionized iron, Fe+, and when that gets exposed to air, it turns to rust,” Supert explained. “It shows up in your washing machine, ruins clothes.”

From there, between five and 15 percent of the water—all from Well #4, since Well #3 has trace amounts of radium too high to be unfiltered—skips the next two steps. This, Supert explains, is because there is such a thing as too-pure water, and the reverse-osmosis process produces just that.

“That water is so soft it’s actually is like almost slimy, slippery—you wouldn’t be able to get soap off your body when you take a shower,” Supert said. “You want some taste, because pure water doesn’t taste good. And you want to have some minerals in there to give it quality.”

The rest of the water then travels though cartridge filters, an extra step to remove further impurities and ensure that nothing can get through that could gunk up the reverse-osmosis piles. Then, at last, the water reaches the step for which the plant is named.

Osmosis, a critical process within all cellular life forms, refers to a process that equals the concentration of a solvent (say, salt) within a solute (say, water) on opposite sides of a membrane. For instance, if fresh water and salt water were placed on opposite sides of a salt-permeable membrane, the salt solvent would move into the freshwater solute, an example of osmosis.

But since the aim in filtration is to remove impurities from water—solvents from a solute—reverse osmosis turns the process upside down. A long, thick tube-shaped selectively-permeable membrane is fitted within a pipe, and the to-be-treated water flows through the interior before being pressure-forced through the membrane to the outside. The process removes virtually anything except pure H2O molecules: the exact opposite result from normal osmosis.

This water is then rejoined with the small percentage permitted to pass with slight mineral content, treated with fluorine and chlorine and balanced to a 7.3 pH before being sent to a 500,000-gallon reservoir behind the water plant. From there it can either go straight to homes and businesses, or to the million-gallon tower in Spring Rock Park or the two million-gallon standpipe next to Bennett Field.

What your water is like right now

Of course, all of this is still in the future—about a year out, actually.

One of the key setbacks to a reverse-osmosis water plant as opposed to an updated lime-treatment plant, other than the cost, was the fact that it was a 100 percent system overhaul that would take 12 months or more. But in that year, the citizens of Western Springs would still need water.

So the Village took their best possible alternative. They waited to begin until water usage neared its yearly nadir—the winter, with no sprinklers or garden hoses running—of about a million gallons per day (the summer high is just under three million.) Now, as they simultaneously dismantle much of the plant, they’re using just Well #4 and running it through sand filters alone, leaving you with harder, mineral-rich water. (The fluorine levels of the Well are just above where they’ve been forced to issue a warning about dental fluorosis in children.)

“Most commonly, you’ll see [calcium deposits] in your dishwasher, because when it goes through the dry cycle it’s precipitating the calcium out,” explained Supert. “In the lime softening process, that would have been removed.”

The overall cost of the project will be just over $8 million, funded by a 1.25-percent 20-year loan from the Illinois Environmental Protection Agency (IEPA.) About $6,628,000 of that is for construction by Joseph J. Henderson & Sons; the rest goes towards engineering (Camp, Dresser & McKee), IEPA coordination (Benton & Associates) and consulting (Daryl Gavle) and a contingency cost.

“Especially in this old a building, it’s [to counter] one of those scenarios of, oh, we pulled back this wall and whoa, we didn’t see this thing of asbestos,” Supert semi-joked.

When will your water stop being so hard? Depends on how well construction goes, but if all goes as planned, the Amiad filters (that filter down to two microns) are scheduled to be online by late spring and the membrane system by mid-summer.

Hopefully by this time in 2013, all of Western Springs will indeed be enjoying from their taps the promise that former Trustee James Maragos offered in December of 2010: water “better than bottled water.”