There is no life without water. And like life, water is something that many people take for granted. While some parts of the United States, particularly the Southwest, face very real shortages, it doesn't look as though we'll be reduced to wearing the water-capturing suits of Frank Herbert's desert-world Dune novels any time soon.
There is no life without water. And like life, water is something that many people take for granted. While some parts of the United States, particularly the Southwest, face very real shortages, it doesn’t look as though we’ll be reduced to wearing the water-capturing suits of Frank Herbert’s desert-world Dune novels any time soon. That being said, freshwater isn’t as bountiful as many would think.
“It is constantly going to be more expensive to acquire potable water,” says Kim Shinn, P.E., LEED AP, principal and division director with TLC Engineering for Architecture’s Nashville office.
While the earth’s surface is more than 70% water, less than 3% of that is freshwater, and only a fraction of that is potable and readily accessible to the human population—especially in places like Phoenix and Las Vegas. “We’re increasingly putting our buildings in places where there is not an abundance of water, and we’re doing it with sort of a blind eye toward that,” says Shinn.
According to the Rocky Mountain Institute, a nonprofit organization based in Snowmass, Colo., nonresidential consumption accounts for 53% of total water used by U.S. communities, and 70% of that is for commercial, industrial and institutional use.
“We’re building and consuming at a rate that’s unsustainable,” Shinn says. “We’ve got to match our [water] consumption to make it more equivalent to what the earth’s natural cycle can provide us with.”
The problem isn’t limited to the West. Shinn notes that Florida has traditionally relied on underground aquifers for its potable water. However, he explains, the population is outstripping the ability of this natural resource to recharge. “It rains virtually every day somewhere in Florida, but there is a true water crisis coming [there],” he says.
Shinn’s message is clear: Our water resources are overtaxed and we need to be using them more responsibly. While it’s difficult to convince the typical consumer to take on the extra burden of thinking about how to use water efficiently, nonresidential building systems have the opportunity to set a good example, and many of them already are. But guidance and motivation are crucial to the overall push for water efficiency in buildings, and discussions with multiple experts reveal that two continuous efforts must be made: First, educate people on the benefits of both using less water and using it more efficiently; and second, help them get past the idea that having non-potable water running through their buildings is a bad thing.
Making the case
When it comes to education, the main challenge is water’s relatively low cost. “Water in this country is still cheap, and as long as it stays cheap, people will not think twice about conserving it,” says John Apostolopoulos, plumbing department operations director with RG Vanderweil Engineers’ Boston office.
“People think it’s OK to waste something if they think they can afford it,” agrees Shinn. “I think the mindset of ‘waste is OK’ needs to change. There’s no really good excuse for wasting something.”
Apostolopoulos points out that water metering is the norm in Europe. Not only that, but water there is more expensive. As such, people simply use water more efficiently.
Alan Traugott, principal, CJL Engineering, Moon Township, Pa., notes that the idea of metering is spreading in the U.S., but it’s not really at the top of the public agenda yet, even though it’s happening to some people without them even knowing. For example, Traugott says one developer in New York installed meters in apartment buildings and found a roughly 40% drop in water use. The irony is that in many buildings that employ this tactic, the metering is done at the building level and not the tenant level, so tenants just pay the bill without thinking about it.
Of course, metering is not necessarily something that consulting engineers can control; that’s up to local governments and building owners. But they can certainly push the issue in their overall program of educating building owners on the environmental and economic benefits of using water more efficiently.
Even engineers need to get up to speed, says Jerry Yudelson, P.E., Interface Engineering, Portland, Ore. “The question is, is [a potential water shortage] going to come in three, five or 10 years, and most of us are pretty much consumed with the day-to-day, so three years out is something we put on the backburner.”
John Rattenbury, P.E., Rattenbury Engineering LLC, Hull, Mass., agrees and feels that more awareness of the resources at hand is necessary. “Most HVAC engineers are not concerned about the flushing of toilets and only want to know where to drain the condensate,” he says. “Plumbing engineers, on the other hand, are not very concerned about building dehumidification and don’t consider condensate as a viable source of water for their plumbing systems.”
Next to pushing the practice of using less water, the other major challenge is convincing people that it’s OK for a building to contain two water systems—for potable and non-potable. Further, it’s convincing tenants that potable water doesn’t need to be used for a majority of a building’s processes. “We need consumers to trust the quality and safety of recycled water for at least non-potable applications,” says Rattenbury. This includes processes that traditionally use potable water but don’t need to, such as toilet flushing.
According to Yudelson, state and local governments also need be on board if water conservation measures, especially those involving recycled water, are truly to be embraced. “The fear of the plumbing [code] folks is if you have a major emergency, people would use the water in the toilet tanks for emergency drinking water because it is [traditionally] clean tap water,” says Yudelson.
But he stresses that in general, code authorities are rapidly growing familiar with “new” water conservation measures, such as rainwater harvesting, and are usually flexible about allowing unorthodox water conservation measures, or at least open to workarounds. For example, a municipality concerned about untreated, recycled water being confused with potable water could consider options like signage or even locking toilet tanks. More than anything else, trust between engineers and local code enforcers is key. “Our approach to permitting is no surprises,” Yudelson says.
The widespread use of advanced water conservation methods will take time to develop. In the interim, some owners have opted for low-cost options. Since the inception of the Energy Policy Act (EPAct) of 1992, flushing fixtures are required to consume no more than 1.6 gal. per flush (1.0 gal. for urinals), and these fixtures have become a standard in plumbing engineering. Other low-flow fixtures—for sinks and showers—have also seen widespread use, as have sensor-activated sinks, toilets and urinals.
Elsewhere, Yudelson is starting to see a push for waterless urinals, particularly in institutional settings where it is economically advantageous. Similarly, dual-flush toilets—half flush for liquid waste, full flush for solid—are beginning to make inroads. Apostolopoulos adds that he has noticed that U.S. manufacturers are starting to show an interest in producing them.
As efficient as these tactics are—low-flow fixtures can reduce water usage 20% below current codes—they are only a small part of the larger story. And while they are a good first step, some building owners are taking the plunge into more involved and complex approaches.
One such practice that is gaining momentum is gray/black water reuse. Gray water systems are those that capture, treat and recycle water that has seen “light” use, such as shower or bathroom sink water. Black water systems perform the same task, but with water that contains human waste or food. While water from both system types is generally reused for similar purposes—toilet flushing and irrigation—the piping is slightly different. Both systems have two sets of supply piping: one for potable and the other for reclaimed water for non-potable uses. But black water systems only require one set of waste piping, while gray water systems require two: one for gray water to be recycled and one for black water containing human waste and food, which a gray water system does not reuse. As such, while black water systems deal with the treatment of more complex waste, they require less piping than their gray water counterparts.
Various building types have adopted such systems. The Solaire, a high-rise residential building in New York that has been billed as the nation’s first environmentally responsible residential high-rise, employs both black water and rainwater systems. The David L. Lawrence Convention Center in Pittsburgh also uses a black water system (see “A River Runs Through It,” CSE 01/04 p. 42). And a completely different type of facility, Gillette Stadium in Foxborough, Mass., home to the NFL’s New England Patriots, captures gray water, along with rainwater, and treats and uses the water for irrigation and toilet flushing (see “Rewarding Patriotism,” CSE 10/03 p. 46).
While economic and green benefits were driving factors in these projects, Rattenbury recalls a building he visited in Massachusetts where a gray water system was all but a necessity. The owner wanted to build an office in an area without municipal sewer access. As such, sewage disposal options were limited to an on-site septic system and leaching field. However, there was not enough land available for the latter. Reducing the septic system was an alternative, but this required reducing overall waste discharge. The solution came in the form of a gray water treatment system that collected water from bathrooms and janitorial sinks and treated it with a combination of filtration, anaerobic bacteria, activated carbon clarification and chlorination. As such, the building is able to reuse the water in non-potable areas, including toilet flushing, mechanical processes and irrigation.
Old is new again
Recycling building water is just one method engineers are using to battle the water crunch. Another practice that’s seeing increased implementation is a variation on an old theme.
“The practice of rainwater harvesting is just the reapplication of ancient technology,” says Rattenbury, noting that up until the late 19th century—when municipal water supplies and indoor plumbing began rising to prominence—rainwater cisterns were the norm. But the new infrastructure began the phase-out of this simple, yet effective practice.
The good news is that rain or storm water harvesting is on the rise again. Of course, today’s applications are on a much larger scale, but they’re still based on common sense. The roof is the primary collection point, although hardscaped areas, such as parking lots or plazas, can also be utilized. Building size, however, matters. Taller buildings are less susceptible to collecting debris, such as leaves and twigs, but generally have smaller roof footprints. Lower buildings generally require screening or other tactics to minimize debris in the water flow, but many systems have methods for separating “dirty” water from clean. Ed Crawford, vice president of Rainwater Systems, Inc., Salem, Va., a designer of rainwater harvesting systems, notes that his company’s products employ a patented “roof-washing” system that diverts the first 10 out of every 1,000 gal. of rainwater collected. This is important, he says, as those first gallons contain the detritus.
Storage tanks can be installed above or below ground, although Yudelson suggests creative locations, such as under plazas or in “dead space” in parking garages. When it comes to tank size, Yudelson explains that size is best determined by balancing the following factors: available collection area, annual rainfall, intended use of water and, finally, cost. He notes that about 80% of total rainwater is collected; storms that provide more water than the tank can hold, as well as misting, account for the other 20%.
Treatment depends on the use; Toilet flushing, irrigation and fire suppression are common areas. In its installations, Rainwater Systems typically uses a 50-micron filter on water going into the tank and another 50-micron floating cistern filter on water removed from the tank. From this point forward, no sterilization is performed unless the water is being captured for potable use. The company uses ultraviolet filtration in most cases and also employs a carbon filter to get rid of any odor or taste in the water.
The conservation advantages of this technology are clear—they offer reduced use of water from the utility and less water discharge—but the question remains, are these systems economically feasible? Yudelson admits that rainwater collection systems can be expensive and there is a relatively long payback period of 10 to 15 years in most cases. However, Apostolopoulos notes that in municipalities with much higher water rates, such as in Massachusetts, the payback period can be greatly reduced.
So where are the best places to employ such a practice? Common sense would dictate that it should only be attempted in areas with frequent rainfall, but Yudelson says this is not necessarily the case, pointing out that typically dry areas, such as Arizona and Texas, can often be subject to periodic flash storms—”gullywashers”—that provide large amounts of water in short periods of time. But he does concede that buildings in areas with higher rainfall are the best candidates. One such project, for which his firm provided the system, is Portland State University’s Epler Hall, completed last year. The 65,000-sq.-ft. building has a 10,000-sq.-ft. roof and an expected rainwater harvesting capacity of 230,000 gal. per year. The water is stored in a 5,600-gal. underground tank and supports water closet and urinal flushing on the ground floor. Excess water is used for landscape irrigation.
Another of Interface’s university projects is a building at Humboldt State University in Arcada, Calif. While rainfall here isn’t quite as frequent as Portland, its timing is perfect. Yudelson notes that the area typically doesn’t receive much rainfall in the summer, but there’s also far less building use during this season. The building captures 100% of the storm water from the building’s 15,000-sq.-ft. roof and a hardscaped plaza area. As such, there is no sewer hookup for the site. “Now, all of a sudden, the economics change dramatically, because you’re avoiding all of the hookup charges,” he says. In addition, the building met first-cost objectives—even with the rainwater system—and is gunning for LEED gold certification.
On the East Coast, the new Ray and Maria Stata Center on the Massachusetts Institute of Technology campus in Cambridge also employs a rainwater harvesting system, designed by Vanderweil, with a 50,000-gal. storage tank. The water is used for toilets within the building and wetland irrigation, and is also pumped to the municipal network when the tank reaches its capacity.
Raising the bar
Besides universities and residential and office buildings, there’s yet another facility type that can benefit from water conservation. Hospitals, says Shinn, also have a lot to gain. “One of the things that really surprises a lot of folks, including hospital professionals, is how much of their potable water use is going to essentially non-potable process use,” he says. In his estimation, domestic water use in hospitals generally accounts for only one-third of total potable water use. The rest goes to process use, and that, he feels, is something that needs to change.
And change is something that Shinn is working for. He is the working group leader for water efficiency in both the Green Guide for Healthcare Construction and the LEED Application Guide for Healthcare , both of which adhere closely to the LEED rating system.
Shinn’s groups are looking at structuring some credits to help hospital staff identify and fix problem areas. Additionally, he’d like to examine the general LEED formula for calculating potable water usage and create a customized version for hospitals.
Shinn’s work with LEED demonstrates how people are paying attention to the program, and this includes plumbing and wastewater engineers. Within the water portion of the LEED rating system, there are eight possible credits: two for reducing potable water use for landscape irrigation—the first for reducing it below half of a typical baseline and the second for eliminating potable water completely from landscaping use; one for reducing a project’s use of potable water for sewage conveyance by 50% or more below what’s required by EPAct; two for the general reduction of potable water for typical domestic uses below the EPAct baseline—one for a 20% reduction and another for a 30% reduction; up to two points for storm water reduction; and one point—innovation credit—for installing above-code measures that result in 40% water savings.
While people are clearly paying attention to LEED, Rattenbury notes that the reasons are varied. “Sometimes the incentive is to achieve a LEED rating level for its own sake,” he says. “Other times, design teams and even municipalities use LEED to minimize the environmental impact of a proposed development and achieve a building permit. And sometimes economic incentives alone drive the effort.”
And then there’s the goal of simply setting a good example, which is why, Apostolopoulos says, the government and schools are particularly interested in LEED and water conservation measures in general. But private industry is showing interest, too, he notes, explaining that LEED can be a tool for building owners to get the most out of their engineers. “With every other project, there’s always a conversation about it,” he summarizes.
Taking the lead
It’s clear that there are multiple options for meeting the goals of using less water or using the same water more than once. But employing them requires an understanding and appreciation of their long-term financial and environmental advantages.
In the end, being more water-conscious must include not only the private sector, but the general populace, as well. But that acceptance requires education, and Traugott thinks that he and his peers need to take the initiative: “As engineers, I think we have a moral obligation to bring the water issue to our clients.”
Besides promoting recycling water from human use and rain showers, John Rattenbury, P.E., Rattenbury Engineering LLC, Hull, Mass., is also an advocate of reusing another readily available source of building system water: air-handling unit condensate. Buildings typically discharge AHU condensate as wastewater, but reclaiming this water, or “dew harvesting,” is yet another opportunity to take advantage of “free” water. He offers an example: In an office building requiring 50,000 cu. ft. of outside air makeup per min., psychometrics show that if air at an outside temperature of 80°F and 70% relative humidity is cooled down to 45°F and 100% relative humidity, then up to four gal. of condensate water is produced each minute by the HVAC equipment collectively. “That amounts to 240 gal. per hr. during the day, enough water to flush 150 toilets in one hour,” says Rattenbury. “Almost 2,000 gallons could be collected during working hours, not to mention the additional water that could be collected and stored during the evening.”
Kim Shinn, P.E., principal and division director, TLC Engineering for Architecture, Nashville, adds that this practice is also uniquely qualified to generate water for another building water need: cooling tower makeup. He points out that the cycle is very closely matched; that is, when there’s a lot of humidity in the air, that’s generally when the cooling towers have to do most of their work.
TLC is currently working with Lehigh Valley Hospital and Health Network to employ dew harvesting for cooling tower makeup at an addition to its Cedar Crest campus in Allentown, Pa.
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