Reducing Cooling Tower Water Consumption through Advanced Water Treatment Technology


It might cover 71% of the earth, but water is one of our most precious resources. Headlines around the world warn of water shortages, and water demand globally is projected to increase by 55% between 2000 and 2050 [1]. But, one innovative company is working to address a small slice of this concern.

For decades now, evaporative cooling has been the principal means to regulate the temperature of buildings. And with more than 50% of total building water usage dedicated to heat transfer, there are major opportunities for water savings.

Enter EVAPCO, a manufacturing company focused on heat transfer applications and a world leader in designing and manufacturing evaporative cooling products. I spoke with Dustin Cohick, Product Manager at EVAPCO, and Josh Boehner, Marketing Applications Engineer, to learn more about heat transfer and how EVAPCO’s technology can save water. The interview that follows has been edited for clarity and length.

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EVAPCO’s eco-ATWB is one of the company’s water saving technologies, with high dry-bulb switchover temperatures.

EVAPCO is a major name in the evaporative cooling world. Can you give us a sense of EVAPCO’s scale?

We are an international company, engineering and manufacturing products in 24 locations in 10 countries, with clients all around the world. With a reputation for technological innovation and superior product quality, our products lead the way in efficiency, reliability, and sustainability.

Given EVAPCO is a manufacturer, why is the company concerned with water treatment?

Cooling towers use a great deal of water. In the past, clients acquired their cooling tower systems from a manufacturer, then were on their own to treat the water, which is crucial to operate the system at its optimal efficiency. Given we know our equipment the best and are world leaders in evaporative cooling, we saw the opportunity to overhaul this dynamic by helping our clients get the most out of our products. With sustainability at the forefront of our company’s culture, we have invested heavily in water treatment. Our Water Saver technology can save clients an immense amount of water and decrease the amount of treatment chemicals.

Do most cooling tower manufacturers offer water treatment?

No, it’s unique to EVAPCO. It’s very abnormal for cooling tower manufacturers to focus on water treatment and invest in resources such as our own in-house water laboratory. Ultimately, the purpose of all of this is to help our customers achieve maximum water savings.

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With its own water analytical service laboratory, EVAPCO is unique among cooling tower manufacturers.

Let’s take a step back. How do cooling towers use water in the first place?

For any piece of evaporative equipment, such as a cooling tower or a closed-circuit cooler, the equipment transfers heat from the water into the atmosphere through evaporation. Warm water enters the cooling tower where it is exposed to ambient air passing through the tower. Some water evaporates while the rest is significantly cooled. This remaining water is then recirculated into the system.

Where does water quality fit into this?

When water evaporates through heat transfer, it leaves behind ions that are naturally occurring in the water. The quality of that water and the number of ions it contains determines the amount of water needed. A common analogy I use is boiling a pot of water. If you let all the water evaporate, the result is a whole bunch of dried minerals on the inside. Those are the ions naturally occurring in the water. In a cooling tower, you reject heat, so you need to add fresh water, or makeup water, back into the tower because a certain volume of water is required.

What is the connection between these ions that are left behind and the quantity of water used?

Generally speaking, the more ions that are in the water, the more often blowdown will occur. Blowdown is when a new cycle of makeup water enters the cooling tower. The goal of a water treatment system is to maximize the efficiency of the water being used inside the tower without scaling or corroding the system. By decreasing the concentration of ions in the makeup water before it ever enters the cooling tower, it allows you to operate at higher cycles of concentration.

What is cycles of concentration and why does it matter?

Cycles of concentration is the ratio of dissolved ions in the recirculating water divided by the concentration of dissolved ions in makeup water. The higher cycles of concentration, the less makeup water is needed. The key is identifying the cycles of concentration that maximizes the efficiency of the water used inside the tower without overburdening the system. Reducing the ions by 50%, EVAPCO’s Water Saver technology can safely double the cycles of concentration. These are amazing savings for our clients.

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Increasing the cycles of concentration is essential to reducing water use.

What does it look like to overburden a system?

Usually it’s one of two things. Either you’re going to form scale in the system quickly, or elevate levels of corrosion. All water is corrosive to some degree as water is the universal solvent. In a cooling tower situation where you’re recirculating water, the higher levels of ions and particulate matter can eventually scale or corrode the system if not maintained properly.

So how does EVAPCO’s Water Saver technology work? How do you pre-treat the water?

If the water quality at a location has a conductivity of 500, our technology lowers it to 250. That ultimately doubles the cycles of concentration and that’s where water savings happen. Capacitors remove dissolved ions from the water, and over time the capacitors will fill up and the Water Saver will perform a flush cycle. We switch the positively and negatively charged capacitors, and when that happens, the ions come off the capacitor and get sent to drain at a lower flow, so as not to waste water.

This might sound like a silly question, but what is a capacitor?

It’s a conductive piece of metal that isn’t particularly special until the Water Saver sends it the electrical charge. And that electrical charge attracts the ions, which is the whole point of the system.

EVAPCO Video

Can you provide a real-world example of this technology in practice?

At an Indiana high school we received a water sample from them and ran it through our water model, determining its maximum cycles of concentration as 2.5. They were looking to replace their cooling towers and optimize water treatment. We helped them with their chemical treatment program and they purchased our Smart Shield and Water Saver system. These modifications improved their makeup water 50%, allowing them to double the cycles of concentration to five, ultimately saving them 1.5 million gallons of water annually.

Let’s say a new client is interested in incorporating your Water Saver technology. Where do you start? How do you approach evaluating an overall system?

There are three different components to assess – the chillers, the water treatment, and the evaporative equipment, meaning the cooling towers or evaporative condensers. Each of these areas requires an independent look. Take the water treatment, for example. We look at several areas within the water treatment, including how they’re treating the water, how much that costs, and the quality of the water.

How do you approach evaluating the water treatment system and assessing water quality?

The first step is understanding the quality of the makeup water. Most of the time a water treater will have an idea of the local water quality, but it’s still important to evaluate.

Second, is taking a close look at the evaporative equipment system. When we’re out in the field, we inspect things like what type of piping is in use, ensuring there are no dead legs, and ultimately identifying what the water is contacting. It’s critical this assessment is conducted in person. There are no one-size-fits-all solutions in water treatment.

Third, is identifying the type of evaporative cooling equipment. Is it a cooling tower, an evaporative condenser, or is it a closed-circuit cooler? The type of equipment in use impacts the overall water treatment.

The fourth step is assessing the types of materials used in construction. Whatever the water will touch is important – whether it’s the tower, piping, heat exchangers involved, the chiller, or anything else. The materials of construction of everything in the system influence the overall water treatment.

It’s interesting that in steps two through four, you’re not looking at the water itself.

Correct, the most important part of the evaluation is what the water is contacting. We, of course, pull a sample of the makeup water and recirculating water, but we don’t even look at that until later. What we’re most interested in is everything that’s physically part of the system.

Are there any other steps?

The next step is evaluating the temperatures. Higher temperatures mean that scale and corrosion both happen faster. Traditional HVAC temperatures are 95 oF into the tower and 85 oF out, but industrial sites are typically higher. I have even visited sites with temperatures close to water’s boiling point. Identifying the temperature matters, whether it’s high or low, as it strongly influences the treatment plan I propose.

After you assess the system, how do you analyze the makeup and recirculating water?

We have our own in-house laboratory. This helps us not only for the original evaluation at a new site, but also existing customers. Analyzing the makeup and recirculating water helps inform our decision- making when installing or retrofitting a current system, as the composition of the water can help us decide, for example, whether to use galvanized or stainless steel.

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A makeup water sample analysis from a system in Phoenix shows high levels of conductivity.

I would imagine in different locations there is different quality water. How does that impact the goal of using less water?

It’s critical to assess each system on a case-by-case, plant-by-plant basis, as the water is often drastically different. The difference in the water for a plant in Iowa versus one in Arizona will drive the type of system needed and the technology used. This makes life difficult for companies with plants across the country and even the world.

What works well in one place won’t necessarily work somewhere else. Take New York City, for example. They have some of the best water anywhere on the planet. New York City water has 100 conductivity. The conductivity of water is how well water can conduct electricity. The lower the conductivity, the better the water quality. There are less minerals and ions in the water. In contrast, Phoenix, Arizona, has a conductivity of 1,000 – ten times the amount of minerals coming out of the faucet than New York City. What that means is New York City cooling towers operate at 12 cycles of concentration. This is stellar water efficiency. Not every location can operate at this high a level of water efficiency without corroding the system. Meanwhile, Phoenix operates at 2.5 cycles. There is only so much you can control depending on where the system resides. Places that operate with lower cycles of concentration have the greatest opportunity to save water.

Ultimately, how much water can people save if they implement your technology?

Historically, clients who use our water treatment technologies to save water, in conjunction with the technology in our evaporative box, approach 40-50% less water usage. And the savings can be even more than that; each system is different.

Those are huge savings. What else do your clients save besides water?

The big one is time, and of course, time is money. We have worked with industrial clients that prior to incorporating our technology, spent an inordinate amount of time on maintaining their system. Cleaning flow meters, valves, and many other components of the system. And it all comes back to water treatment. The typical operating expense of maintaining their entire system is often reduced.

Thank you for sharing your insights on this topic.

For more information, visit www.evapco.com.

All photos courtesy if EVAPCO.

To read similar Cooling Tower Technology articles visit http://www.coolingbestpractices.com/technology/cooling-towers

[1] http://www.bbc.com/future/story/20170412-is-the-world-running-out-of-fresh-water.