Water Re-use: The Time Has Come
Greywater and reclaimed water strategies make good use of water resources, especially when implemented in conjunction with efficient plumbing systems.
By Mark Sanders
Given the onslaught of sustainability in the building industry, it’s no wonder that taking care of natural resources has become part of everyday culture. One of the most prominent issues in the plumbing industry is water conservation and using water more efficiently.
While recycling is a term generally applied to aluminum cans, glass bottles and newspapers, water can be recycled as well. Through the natural water cycle, the earth has recycled and reused water for millions of years. Water recycling, though, generally refers to using technology to speed up these natural processes. Recycling water and putting it back to use is commonly thought of in two different water usage strategies: reclaimed water and greywater.
Reclaimed vs. greywater systems
Although some make the mistake of using the terms reclaimed water and greywater interchangeably, they are not the same, and it’s important to distinguish between these systems.
Putting it in the most simplistic terms, reclaimed water is wastewater effluent/sewage that has been treated according to high standards at municipal treatment facilities and that meets the reclaimed water effluent criteria. It is treated offsite and delivered to a facility. Most common uses for reclaimed water are for non-potable purposes, such as agriculture, landscaping, golf course irrigation, dust control, soil compaction and processes such as concrete production and cooling water for power plants.
The use of reclaimed water is gaining in popularity, especially in California, where openness to innovative, environmentally friendly ideas converges with a very real and critical water crisis. Orange County, Calif., for example, began delivering purified wastewater last year, one of the first “toilet-to-tap” systems in the United States.
Greywater, on the other hand, derives from domestic water use such as showers, washing machines and sinks. It does not include wastewater from kitchen sinks, photo lab sinks, dishwashers or laundry water from soiled diapers: These sources typically produce blackwater, which has serious contaminants and cannot be re-used. Using greywater is a point-of-source strategy. In other words, greywater collected from a building will be re-used in the same building.
The two broad categories for greywater use include indoor and outdoor re-use. Outdoor greywater is usually filtered and then used for watering landscape. Indoor greywater use mainly recycles water for flushing toilets. Similar to reclaimed water, other applications of greywater include construction activities, concrete mixing and cooling water for power plants.
System approaches
As local municipalities and individual facilities struggle with meeting water needs in the face of dwindling water supplies, a variety of reclaimed water and greywater system approaches are emerging. Facilities from coast to coast are considering their options in light of today’s economic and environmental outlook.
Reclaimed and greywater systems range in size and complexity: On the high end are the multi-building installations that draw wastewater from municipal sources. The middle tier includes buildings that have installed storage tanks capable of collecting thousands of gallons of water from rainwater, sinks and steam condensate, which is then treated and funneled to the water re-use sources. Keeping it simple and more affordable on a smaller, yet significant scale are under-counter systems that do on-the-spot treatment of water that flows down sink drains, which is then pumped directly into toilet tanks.
It’s preferable to build more complex systems into new construction rather than to retrofit them later. On-the-spot collection systems, however, can be implemented at any time. Of course, when specifying sustainable systems and technologies, staying within budget is a matter of setting goals and performing research up front to determine the additional value and payoff.
UCSB: Moving slowly with reclaimed water
The University of California, Santa Barbara (UCSB) is cautiously experimenting with reclaimed water usage for toilet flushing. UCSB found it was an easy choice to use greywater for landscaping needs; greywater currently takes care of about 90% of its landscaping water requirements. It takes more money, however, to implement interior applications. UCSB administrators are weighing the costs of installing special piping systems for delivering reclaimed water to toilets against the environmental benefits and long-term utility savings of using less fresh water.
Donald Bren Hall, which houses UCSB’s School of Environmental Science & Management, has been the model of sustainability and has earned the U.S. Green Building Council’s coveted Leadership in Energy and Environmental Design (LEED®) Platinum standard. The building has applied numerous water-efficiency measures, including using reclaimed water for toilet flushing. To minimize the need for and cost of special piping, use of reclaimed water was limited to first floor restrooms. As it is the first and only building on campus so far to deploy a reclaimed water system, administrators are experimenting at Bren Hall before considering wider deployment on campus.
According to the Irvine Ranch Water District, which provides recycled water for toilet flushing in high-rise buildings in Irvine, Calif., the cost of providing a dual piping system for both fresh and recycled water adds about 9% to the cost of plumbing for new buildings of more than seven stories. Estimates for installing dual piping on upper floors of Bren Hall were similar.
Daniel Marquez, UCSB’s lead plumber, reports that the reclaimed water system is working quite well, although there have been a few minor hitches in the system. Reclaimed water from UCSB’s local sanitary district is unavailable on some occasions, which is the main factor limiting the university from a more wide-scale approach.
Marquez recommends installing flush valves that are engineered for harsh-water conditions. Sloan’s Royal® diaphragm Flushometers and Gem•2® piston Flushometers, among other models, have high copper/low zinc brass castings for dezincification resistance and are suitable for most restrooms. When water conditions are far more adverse than ordinary, including saltwater applications, Sloan Naval® and Dolphin® Flushometers are more appropriate.
Building Bren Hall in a sustainable manner added 2% to the overall costs. Planners considered the money well spent, however, because energy savings would quickly recoup the investment. When reclaimed and greywater systems are implemented in conjunction with high-efficiency, low-consumption plumbing systems, the advantages are doubly attractive. As part of its overall conservation strategy, UCSB installed numerous water-efficient plumbing products, including dual-flush Flushometers, low-flow faucets and waterfree urinals.
Consider the 300,000 gallons of water that Bren Hall’s waterfree urinals alone are saving: Based on a national average utility cost of 1.5 cents per gallon of water and wastewater, saving 300,000 gallons of water would reduce the university’s water/wastewater utility bill by $4,500 a year. Those savings are on top of the savings the university reaps from its water re-use systems.
Greywater demonstrations
The amount of greywater produced in a building depends on the facility type. Whereas a typical office building may not yield as much greywater as a college dorm or multi-use retail and condominium building, the benefits are all about economies of scale and deriving value from the system, no matter how large or how small they may be.
Consider how much potable water can be saved in a typical four-person household. On average, each person will use 80 - 100 gallons of water per day. The largest contributor to this use is flushing the toilet. Kitchen and bathroom sinks combined only use 15% of the water that comes into a home. This is significant: 100% of the water that comes into the home has been treated and made potable for drinking.
When the largest single source of fresh water in the home can be accommodated to use greywater instead, the household can make real gains on re-using water that is perfectly suitable for toilet flushing. For household or small commercial facilities, a greywater system that incorporates a reservoir, which is installed under the sink and attached to the toilet, may be the most appropriate solution. These greywater systems enable the toilet to first draw from collected water in the reservoir. The system remains connected to the fresh water pipes so that, if flushing depletes the amount of water stored in the reservoir, the toilet can then secondarily draw from outside water. Because the toilet is the number one consumer of water in households, this type of system can save up to 5,000 gallons per year.
The greywater flushing system makes water recycling accessible at a basic level. This is demonstrated by research conducted by the Canada Mortgage and Housing Corporation (CMHC) at the Conservation Co-op located in the Sandy Hill district of downtown Ottawa. The four-story, 84-unit apartment building was the evaluation site of a greywater system to flush toilets. Eight of the bathrooms in the 84 apartments were converted to dual plumbing systems. One plumbing system allowed the bathrooms to operate normally. The other parallel system connected the drains of the bathtubs to a greywater treatment system. The project demonstrated that greywater could save water and reduce the sewage and water demands on municipal systems.
Another greywater demonstration project, also sponsored by CMHC, is a 20-unit apartment building in North Vancouver, British Columbia. So far, results indicate a reduction of water demand and associated water supply costs of about 40% and reduction in wastewater flows of about 40%, with associated reductions in the size and cost of an on-site wastewater treatment and disposal system.
Differing greywater policies and regulations between states affects the extent to which facilities and homeowners can deploy greywater systems. Arizona, for example, has greywater guidelines to educate residents on how to build simple, safe, efficient, greywater irrigation systems. If people follow the guidelines, their system falls under a general permit and is automatically “legal;” that is, the residents don’t have to apply or pay for any permits or inspections. California also has a greywater policy, but it is very restrictive and usually makes it unaffordable to install a permitted system. Whereas some states have no greywater policy and don’t give permits at all, other states give experimental permits for systems on a case-by-case basis.
Recycling water by whichever means provides great benefits, such as reducing stress on potable water resources, reducing nutrient loading to waterways, putting less strain on failing septic tanks or treatment plants, using less energy and chemicals and costing less than potable water. All of these benefits add up to savings in both water and energy.
Long-term savings
For many plumbing systems, engineers are finding that low-consumption fixtures and strategies cost more at first. The real value is realized when specifiers factor in long-term operating costs, including water and wastewater utility bills, plus the energy it takes to heat water for faucets and showerheads, for example.
Although, even five to 10 years ago, purchasing environmentally sound building components that met LEED compliance standards could have added more than 10 percent to total building costs, plumbers, engineers and other specifiers now are finding that they can adopt higher sustainability standards without necessarily spending extra. And when they do have to spend extra, the long-term payoff is worthwhile.
Utilities account for about 30 percent of an office building’s expenses, according to Flex Your Power, California’s energy-efficiency marketing and outreach campaign. A 30% reduction in energy consumption can lower operating costs by $25,000 a year for every 50,000 square feet of office space.
The public is taking greater notice of how companies and facilities expend water and energy, and users and communities alike are holding building owners accountable for their use of precious local resources. Engineers need to stay abreast of water- and energy-efficiency options in the restroom and elsewhere in their facilities to keep operating costs in line and help ensure that buildings meet LEED standards.
Mark Sanders is the product manager for Sloan Valve Company’s AQUS Greywater System.