Capturing and treating the indoor greywater to be reused for outdoor applications can halve water usage, decreasing the freshwater demand of the home. Of course, homes are not the major consumers of local water sources—commercial and major manufacturing facilities have far bigger impacts. For instance, in Prineville, Oregon, Apple Inc. used 102,000 m3 (133,400 cy) of water last year to run its facilities and evaporative cooling systems in its data centers. (See Sara Jerome’s article, “Apple Enters the Wastewater Business,” in Water Online.) Due to the high volume of water consumption, many large corporation campuses and high-rise buildings look to develop their own wastewater treatment facilities and reroute the piping to reuse water.
For projects facing challenges with topography, small lots, or distance to groundwater, water recycling helps to push approvals through for permitting. (For more information, visit www.constructionspecifier.com/achieveing-water-construction-goals-greywater-recycling.) Recycling greywater onsite could potentially increase project density, unit counts, or reduce onsite sewage system due to less water to manage and treat. The lower infrastructure costs with utility connections can also be attractive for the initial investment of greywater treatment systems, in addition to requiring smaller potable water meters. Better water management of the water onsite means less water discharging into stormwater drains, thrown away in sanitary sewer systems, or polluting local waterways.
Under the Leadership in Energy and Environmental Design (LEED) rating program, greywater systems can help a project team earn points for water use reduction and innovative wastewater technologies.
Only available as guidelines (rather than standards), the criteria for these points can be found in the sections on Sustainable Sites (SS) and Water Efficiency (WE), under Innovative Wastewater Technologies. Other areas as outlined in green building guidelines can include credit for innovative or adaptive reduced generation of wastewater and potable water demand, while increasing the local aquifer recharge.
Ideas and typical water use efficiency categories within many of the national green building programs promote sustainable wastewater management to include reusing a building’s wastewater onsite. For commercial buildings, water reuse activities can use recycled wastewater (onsite or municipally supplied), as well as other nonpotable sources such as:
- swimming pool backwash operations;
- air-conditioner condensate;
- cooling-tower blow-down water;
- foundation drain water;
- steam-system or ice-machine condensate;
- discharge from fluid coolers, food steamers, and combination ovens;
- industrial process water;
- fire pump test water; and
- municipally supplied treated seawater.
Reused water must meet the applicable local code for its intended use (e.g. onsite irrigation, toilet flushing, or cooling tower) to demonstrate the system design and location with how much of the water type was reused. Greywater systems with control panels can easily monitor this and provide the necessary data information to satisfy the requirements.
Most state ‘greywater requirement section’ codes allow treated greywater to be used for toilet flushing. The term ‘treated’ usually means a method that kills 100 percent of bacteria, virus, coliphage, and other pathogens, removes suspended solids down to 100 µm, and greatly lowers turbidity—this is an expensive endeavor. When a lush, green landscape is sought, it might be wise to skip this expense and instead use untreated greywater to irrigate the grounds.
Additionally, greywater-reuse systems can help meet increasing regulations and water rationing in some jurisdictions; these requirements are the result of growing cities requiring new water infrastructure, restrictions on the amount of water a city can withdraw, and increases in the cost of energy to treat and supply water.
Ultimately, however, it is not solely about the cost of water—it is the amount of fresh water sources that can be saved due to the volume and frequency of greywater produced and the number of times the toilet is flushed.
Jennifer Cisneros is the director of marketing at Bio-Microbics Inc., and formerly chaired the Marketing Committee for the National Onsite Wastewater Recycling Association (NOWRA). She has worked for the past 10 years with the regulatory, engineering, and environmental technical practices (field services) departments at Bio-Microbics to create content for the water industry. Cisneros presented “Small Lot? BIG Options!” on the various options available to villages and small municipalities during Wastewater Education’s Earth Month Earthy Matters series. She can be reached via e-mail at firstname.lastname@example.org.