With droughts underscoring the need now more than ever for water efficiency, the elements involved in water storage have taken a more significant role in that effort. “A fundamental component of efficiency—reduced usage—is retaining and storing used water reserves for future use, which is where storage tanks come in,” says Tom Tietjen, vice president of sales and marketing for Xerxes Corp., which manufactures fiberglass tanks for a wide range of uses.
“Without storage, water capture or water supplies in excess of what is used for the immediate need is lost.” Xerxes’ corrosion-resistant fiberglass tanks require no maintenance and are available in underground or aboveground models.
Bill Neighbors, president and CEO of Tank Connection, points out that “it is always interesting to note that within a relatively short period of time, the topic of water usage went from being viewed by both consumers and municipalities as an unlimited commodity to a scarce resource.” Drought conditions add to water scarcity making it a “valuable, scarce resource,” he adds. “Any valuable resource should be protected in a storage containment system that is safe, reliable, and will provide decades of trouble-free service. Potable drinking water should be protected and stored in high quality aboveground reservoirs.”
These days, such ground reservoirs are constructed utilizing a hybrid tank design, using a concrete foundation with a bolted rolled, tapered panel (RTP) tank sidewall and aluminum dome cover, says Neighbors. “In storage tanks, inputs and outputs can easily be measured. Aboveground storage tanks address efficiency by ensuring that no water is wasted or lost at the source.” If an aboveground steel storage tank leaks, it can be visually seen and promptly fixed, he adds.
“That efficiency is lost as soon as the water supply enters the complex maze of underground piping,” he says. “It is difficult to fix what you can’t see, and underground piping remains a major waste category of an aging infrastructure system.”
Tank Connection supplies bolted RTP storage tanks, with a hybrid approach utilizing a bolted steel RTP tank sidewall design set in a concrete foundation and covered with an aluminum geodesic dome cover. The company provides LIQ Fusion 7000 FBE, a high-tech coating system for water storage applications.
Tank Connection’s storage tanks are designed to have high quality water containment, low installation cost, shortened field installation time, low life cycle costs, and low maintenance. In installing new water storage tanks, factors that need to be considered in sizing include current and future consumer consumption, adequate quantities of surplus water, and sufficient water pressure. The volume and tank size is dependent on diameter and/or height restrictions as well as job specific requirements and limitations, says Neighbors.
Maintenance of Tank Connection liquid storage tanks include removing the tank from service and an annual inspection provided by the tank vendor. A municipality should engage in a preventative maintenance program applicable for the water storage tanks and all system equipment such as valves and hydrants, following design provisions for removing the tank from service, says Neighbors. Tank inspection should be scheduled every three to five years, he adds.
“Inspection should include the tank shell sheets, cathodic protection, floor, vents, hatches, other system equipment, and any other component that ensures continuous, trouble-free operation of the tank,” says Neighbors.
Inspection should be visual and not rely on cameras or remote-controlled underwater equipment, he says. “There is no substitution for a visual inspection,” adds Neighbors. Any coating touch-up or other repairs should be made, and the tank is ready for service.
Landmark provides services in composite elevated tank manufacturing (a concrete pedestal with a steel water storage tank) and asset management.
“Asset management is a way that municipalities can maintain a certain level of depreciation of the tank over time instead of the old mindset that a tank life cycle is 50 years and they’re going to depreciate that tank every year until it’s non-commissioned in that 50th year,” says Gary Stanford, manager of the water mixing division.
While a goal of 100% of the tank would be “far too much” for anybody to maintain, “we can establish an agreed-upon level of maintaining that tank, such as 80%,” he says. “We’ll do an initial inspection and determine where the tank is and where we need to get it to because it needs a tank rehab, a tank re-lining, exterior coating, different piping changes. We establish that and continue the asset management of that.”
Each year, Landmark does an inspection and writes a report to ascertain any components that require maintenance. “Generally, every three to five years, we would recommend taking that tank out of service and performing any maintenance that we had documented throughout the previous three to five years, which would include a tank cleanout, touch-up, and spot repair as needed to prolong the interior lining system,” says Stanford.
Exterior coating problems are addressed as well. “You’ll see algae or microbial build-up, excessive sweating on the tank exterior,” he says. Landmark provides services of power washing and exterior coating repair.
The company’s mixing system division installs a series of piping and valves inside the tank “that essentially create a momentum inside the tank from the influent water. That water coming into the tank is the energy that provides the mixing action. We don’t require any kind of external electrical supply or generators.”
Stanford points out that the EPA’s Stage 2 Disinfectants and Disinfection Byproducts Rule requires municipalities to test water quality samples more stringently, specifically related to total trihalomethanes (TTHM). “It’s gotten to a level that is not allowing them to average their results over all of their test points,” he says. “Now they have to maintain within that regulation at each individual test point.”
Water mixing provides a solution for water quality improvement, adds Stanford.
Water efficiency is another benefit of water mixing. The goal of mixing is to achieve consistent flow patterns that prevent a “last-in/first-out” or short-circuiting flow, eliminate thermal stratification, avoid stagnation or dead zones, inhibit aging and accelerated disinfectant depletion, equalize chlorine residuals, and preclude the formation of ice caps, he says.
One event that may impact the chlorine level is thermal stratification, which takes place within a tank during the warmer months, says Stanford. When water utilities cannot maintain a proper chlorine level—it can be too high or too low—water is dumped, typically through a fire hydrant onto the ground, says Stanford.
“When you’re mixing that water, you’re really controlling that water age,” says Stanford. “Our system doesn’t necessarily remove TTHM. That happens as a byproduct of chlorinating the water as a reaction that occurs when chlorine comes into contact with organic material and over time that separates. If we can control that water age, we can essentially control TTHM.”
Another way of controlling TTHM is spraying a fine mist of water, he adds. “Essentially, you’re trying to expose the most surface area of water to the environment or to the area itself so it can exhaust through the tank vents,” says Stanford. “It’s an evaporation effect of the TTHM, so by mixing this water, we’re exposing more surface area of the water to the atmosphere so it can release.
“You’re going to get more reduction from passive mixing than no mixing at all, but it’s not necessarily a removal technique. Our goal is to preserve the water quality initially and not allow it to get to the point of beyond regulation.”
In water storage, the design process can be somewhat challenging because of the different flow rates and distribution systems, notes Stanford. “A lot of times, municipalities may not know exactly what their flow rates are going to be, especially on new tanks,” he adds. “They haven’t operated that tank yet, so they’re going off of hydraulic models.
“We try to get as much information as we can to establish what these flow rates are going to look like so that we can size the valves appropriately and offer a recommendation on how to operate that tank in terms of the target draw-down.”
Municipalities need to plan for the future and the possibility of drought and water shortages, points out Tex Enoch, water tank market manager for Induron Protective Coatings.
If a water utility’s current need is for 750,000 gallons, for instance, Enoch suggests constructing an elevated tank or reservoir for one million gallons to be ready for water shortages. While that will entail more funding, it’s preferable to hoping a water district’s membership will consent to a significant reduction in water consumption, he says.
Since the water also is used for fire protection, those who manage a water utility do not want to run short of capacity for that important need as well as potable water, he adds.
Water storage tanks help to maintain efficiencies by working off of gravity, says Enoch, adding that if there is an electrical outage, a utility’s operation will still be working at its fullest capacity. That also reduces “needless energy, therefore reducing a utility’s carbon footprint,” says Davies Hood, company president.
Induron Protective Coatings furnishes coatings for the water storage tanks that not only fight corrosion but also allow for community pride when a town’s name or high school mascot is painted on the tank, says Enoch.
The lifespan of the water storage tank is “infinite” with proper maintenance, says Enoch. The only drawback would occur if a municipality or water district does not have the funds or grants in which to cover costs. Hood points out that there are several welded steel water tanks currently in operation that are in excess of 100 years old, and that the Steel Tank Institute/Steel Plate Fabricators Association has an award for 100 year-old-water tanks.
Hood says the coatings industry has come a long way in recent times. “I have been inside 25-year-old potable water tanks that did not need repainting,” he says, adding that Induron sells paint systems that include a 15-year warranty for both interior and exterior surfaces.
Sizing for water storage mostly comes down to service area, population, and fire protection requirements, affecting not only the tank’s capacity, but the height to the overflow of the tank, says Enoch.
Hood adds that the larger the service area, the higher the overflow, and the higher the demand in terms of usage, the larger the volume.
Aqua Pennsylvania, affiliated with the water utility Aqua America, recently awarded Induron a contract to supply all water tank-coating requirements on 20 tanks. “We’re probably one of the first water utilities to standardize across all of our Aqua America states on this,” notes Joe Thurwanger, P.E., manager of capital planning for Aqua Pennsylvania. “On the inside of the tanks—the part that comes into contact with the water and affects people’s health—we’ve migrated from three-part epoxies, which are the traditional way to paint water tanks, to 100% solid epoxy,” he says.
The 100% solid epoxy does not have solvent in it and does not emit volatile organic compounds into the air that affect the ozone layer, says Thurwanger. “It’s a two-part painting system versus a three-part, so we’ve eliminated an extra coat of labor in doing the tank painting work,” he adds. It also protects water quality by curing quickly, says Thurwanger.
“When you paint with traditional three-part epoxies, sometimes depending on the humidity and the temperature, there is some waiting and hoping that solvents are all cured. There is no easy litmus test to determine whether the traditional three-part epoxy is cured, so in some cases, we ended up having to dump a tank, then bring in more power ventilators and help the paint cure a little more, particularly if it’s in high humidity,” he adds.
Through using the Induron coatings, Aqua Pennsylvania has standardized on a thickness level of 20–25 mils, which is thicker than the traditional three-part paints the utility used in the past, Thurwanger notes. “It allows a thicker barrier and should allow our tanks to last even longer than what they normally do,” he says.
Beyond coatings, managing water quality is an ongoing challenge that Aqua America is focused on mitigating with respect to water storage.
“There are a lot of regulations that have to do with disinfection byproducts, nitrification, and water age,” he says. “In the old days, you just kept the tank full at all times waiting for that fire to happen. Now we have to blend our management of water quality in all of our tanks along with the hard traditional line of making sure there’s emergency supply available for firefighting and things of that nature. That’s our biggest challenge with tanks.”
Because various regulatory bodies have different interpretations, Thurwanger says he is pleased that in Pennsylvania, “the Commission allows us to capitalize the painting of tanks; it’s not considered an operating expense. By capitalizing it, the commission is saying it’s OK to extend the useful life of a steel tank asset. It incentivizes us to not run our tanks until they look so industrial that they’re an eyesore.”
There are often problems with water tank corrosion, he adds. “Because we have to chlorinate our water to disinfect it, the steel that is above the water level in the tank—if it’s not coated, or if there’s a thin coating in the nooks and crannies up there—can corrode pretty quickly,” says Thurwanger. “It’s hard to get abrasion equipment in the nooks and crannies up there and get a good primer coat and a finish coat on there. That’s a challenge that we have going forward.”
Linings play a key role in water storage and water efficiency.
For the sake of water efficiency, especially in times of drought, water utilities “need to maintain the integrity of their storage vessels whether they are steel, concrete, or fiberglass structures,” notes Rob Pearlman, senior containment systems engineer for Amtech Tank Lining & Tank Repair. “It always seems that problems occur at inopportune times, just when the storage capacities of the tanks are most needed.”
With periodic inspection, failures and maintenance issues can be caught and corrected, he adds. “Steel and concrete tanks failures can be caused by steel oxidizing or lining failures in already coated tanks,” says Pearlman. “Water can reach the steel, causing corrosion. Coating materials and/or corrosive materials can end up getting into the potable water. A good inspection and preventative maintenance program is part of best practices for any water facility.”
Amtech offers the Durachem 580pw and other Durachem products.
“Durachem products are thick layered lining systems. It’s almost like having a Tupperware lining inside the tank,” says Pearlman. “If there is some lining disbondment, you most likely won’t experience a failure, like a thin mil coating, because it remains a monolithic lining. The area of disbondment is very unlikely to break away from the area around it, thus preserving the barrier between the stored water and the substrate.
“Unlike the life cycle of a thin mil epoxy coating, Durachem 580pw’s modified polyureas in water storage usages can have life cycles up to 25 years and beyond. No maintenance is required to maintain the integrity of the lining. Any maintenance would be the standard industry hygiene required for any water storage vessel.”
BTL Liners fabricates large single panels of heavyweight reinforced polyethylene (RPE) geomembrane liner products for water storage. The panels can exceed 150,000 square feet. The use of the panels helps in water efficiency and critical in areas of water shortages, notes Michael Baron, company president.
In a recent West Coast installation, the company provided liners for a new 40-acre irrigation reservoir for pistachio and almond growers in 4.5 days. “In the past, the growers had to use approximately 40% more water to maintain the reservoir at the required level because so much seepage occurred through the ground,” notes Baron. “Now that it’s lined, that seepage has been halted.”
The liners require maintenance against the damaging effect of UV rays. “Our products and the UV inhibitors that we use are 100% effective, as well as water in covering the liner,” says Baron. “It doesn’t have to be soil, dirt, concrete—all it has to be is water.”
Burke Environmental Products supplies open top reservoirs with CSPE, formally known as Hypalon, and also provides the same material in a floating cover. “For all intents and purposes, we put a floating roof over reservoirs,” says Stephen Roades, vice president of the environmental products and roofing division, Burke Environmental Products.
The tension floating cover is a series of segmented floats and weight tubes. The cover can last 30 years, says Roades. As rain hits the reservoir, water can be pumped out with a sump formed with the floats and tubes.
The product is typically used in large configurations to cover reservoirs of 20,000 to more than one million square feet. It is more typically used on the West Coast and East Coast. Because it reduces evaporation, it is desirable in places where drought is a factor such as in California where water infrastructure is unable to meet the massive needs, says Roades.
“If you have an open-top 200 million gallon reservoir, the evaporation rate is astronomical and water is not cheap,” he adds. In addition to controlling evaporation, the covers also eliminate airborne contaminants, he adds.
The CSPE membrane has long been used on the Hinkle Reservoir in Granite Bay, CA since its reconstruction in 1980. The floating reservoir cover has attracted engineers, administrators, and legislators from throughout the US to learn about its design.
The San Juan Water District (SJWD) had considered steel and concrete tanks with rigid covers and opted for the reservoir with the floating cover from Burke Industries. The Hinkle Reservoir is part of the SJWD, which provides water resources to more than 265,000 people annually in the Sacramento, CA region. It has an approximately 62 million gallon capacity, with a 12.5 acre surface area. The floating cover, when fully extended, is almost 14 acres in size.
During the summer, the reservoir turns over two times per day. The winter months are slower, with turnover being every two to three days. With the large amount of people that the reservoir serves, as well as the rate of water turnover, the floating cover membrane performance is critical.
With the initial 25-year warranty on the floating cover nearing its close, and to assess how well the cover was still performing, the SJWD recently contracted an independent outside firm to test the membrane. Results showed the SJWD could potentially get another 20 years of service from the cover.
Turbidity has been at .03 NTUs over the life of the installation. The reservoir loses only one-tenth of a part of chlorine in contrast to the hundreds of tons lost prior to the cover’s installation.
Loop-Loc manufactures high-strength polypropylene covers to protect water from contamination from waterfowl and debris, reduce evaporation and heat loss, and help with odor control. The mesh option allows rain to pass through while solid fabric prevents water evaporation. They are designed to fit any size or shape water tank.
Both fabrics are designed to block UV rays to prevent growth of algae. The covers require no maintenance and can be removed and stored during routine tank maintenance.
By preventing debris such as leaves from entering the water, the covers help to reduce the chemicals water utilities have to use and also reduce the time needed for maintenance, points out Maryellen Comitino, director of sales for Loop-Loc. “The difference between our covers and the harder aluminum covers is that our covers can come on and off—depending on the size of the tank—in a half an hour,” she says.
The cover can be used for aboveground or at-grade water storage.
A spring tension can attach the cover to the ground or to the sides of the tank—another anchoring system is provided for grade-level water storage. An opening provides access to look into the tank and to clean it. “It’s geared towards people being able to access the areas they need to access while protecting the other areas from debris and also malicious intent
if anyone tries to sabotage the water,” notes Comitino.
“The covers are tensioned and tight,” she adds. “Unless you have the correct tool to open up the cover, no one will be able to get into the water. Some end users have drains put into it where a very fine amount of water can go through.”
The covers, which have a lifespan of 10–15 years, can be recycled.
Alternative methods of water storage are gaining traction. Case in point: Rain Water Solutions, which helps companies harvest and use rainwater.
In addition to manufacturing rain barrels geared toward residential use, Rain Water Solutions also designs and installs large rainwater harvesting systems to collect and use rainwater onsite.
“Rainwater is a great source of water, especially in the Southeast, where we get steady rainfall all of the time,” notes Mike Ruck, company president. “As long as there is a roof, we can help people collect and reuse their rainwater.”
Ruck points out that Americans are not paying the “true cost” of water. “You look at the amount of water any municipality produces and uses, and the average customer is not paying the real cost of water,” he says. “To clean, pipe, and take the wastewater and clean it again to put it back to where they took it form is a lot more expensive than municipalities are actually charging.”
Additionally, the costs of maintaining aging infrastructure such as the clay pipes is a “ticking time bomb,” says Ruck. “Every time one starts leaking, they’ve got to dig it up and fix it.” Rain Water Solutions focuses on the nonpotable uses: irrigation, toilet flushing, and laundry. “Every gallon we help offset is pressure off of a municipality or well source of water,” says Ruck. “Stormwater utilities want to see how we can slow down and keep as much water onsite as possible. That helps with water quality issues and flooding.”
Businesses will use harvested rainwater for flushing toilets. Schools that use it can save thousands of gallons “very quickly,” Ruck notes.
“The average is three flushes per kid per day, so if there are 1,200 kids in a school, you can see the benefits of that very quickly,” he adds.
In an installation at the Walnut Creek Wetlands Center in Raleigh, NC, Rain Water Solutions helped the organization collect rainwater for irrigation. The system collects the water off of a large roof, where it is stored in a 3,000-gallon tank, kept for irrigation.
“We’ve installed systems for municipalities that use the water for washing vehicles,” says Ruck. “Street cleaners can use a lot of rainwater to cut down on dust as opposed to using municipal-sourced water.”
Codes are the biggest challenge to rainwater collection systems, says Ruck. “In North Carolina, we’re only allowed to use rainwater for flushing toilets, laundry, and wash-downs,” he says. “Places like Georgia and Texas have potable water standards where rainwater can be collected and taken to a level of treatment that makes it safer for human consumption.”
Ruck says he believes a lack of education underscores codes that are resistant to rainwater harvesting systems. Another factor is that people want to know what kind of return they’ll get on investment in such technologies, he says.
“It’s expensive to build your own water treatment facility to supply clean, reliable, safe water,” he says. “It’s a lot easier for regulators to go with what they know than to wrap their heads around the fact that this technology is here and the ability for people to do this is available right now.”
Ruck also contends that with water utilities “dependent on selling water to keep their coffers full, if everyone started using their own rainwater system, then it’s money out of their pockets.”
In sizing rainwater harvesting systems, Ruck’s company looks at average rainfalls for a particular area, the size of the roof areas that will be collecting the water and then run the numbers to see how much storage can be put into a system design. “Sometimes we don’t have the ability to store all the water they need,” says Ruck. “We may not be able to meet 100% of the water demand, but can meet 50 or 75% of it. We’ve seen it a lot of times when the site plan or the building is already done and rainwater harvesting is an afterthought and you have to come up with a solution that’s the best fit and that’s not always what you would have done had you been brought in at the design level of doing a facility.”
The life cycle of the system can go from 10–30 years on the pumps, says Ruck. Inlet filters have to be maintained quarterly. Water treatment is part of ongoing maintenance and can range from the minimal amount to keep solids out to something of a level needed for toilet flush water in a school. UV bulbs and filter cartridges need to be replaced, typically on an annual basis.
