Defining Green Plumbing Terms: Reclaimed, recycled, re-use… what’s the difference?
Recycled, Reclaimed, Re-use and Gray water
A guy I did some traveling and training with once told me, “Dilution is the Solution to Pollution.” In much simpler times with a smaller population, that may have been all that was needed to solve the problems of not enough useable water. In today’s world I don’t think that will be sufficient.
As you might imagine, I end up reading quite a few articles associated with water and energy efficiency. Some of them are pretty good and others … well, let’s just say they are a long way from being ready for prime time. There seems to be confusion over some of the terms used, especially in water efficiency. Let’s begin with four terms often used interchangeably: Recycled, Reclaimed, Re-use and Gray water.
Gray water (aka grey water or graywater) is untreated wastewater that has not come into contact with toilet waste, kitchen sink waste, dishwasher waste or similarly contaminated sources. Gray water includes waste water from bathtubs, showers, lavatories, clothes washers and laundry sinks. The reason kitchen sink and dishwashers are excluded is because of organic waste discharging from these fixtures.
Clothes washers are included and are a major source of gray water but also a potential hazard. Clothes may contain unintended human discharge (yes, any you can think of). With the proliferation of disposable diapers, that is no longer the hazard it could have been if cloth diapers were still used, but as our society ages and oldsters become incontinent, care must be taken to redirect that washing machine waste from gray water use to regular wastewater discharge. Depending on what is accepted locally, gray water may be used immediately or it may require some form of treatment (chlorine is the most common treatment). Once again depending on local requirements, it may be stored for up to 72 hours.
Gray water use is typically limited to irrigation with the delivery through subsurface or subsoil discharge. The gray water must stay on the property where it originated and aerosolizing is almost never permitted unless treated to a very high quality.
The terms “recycled” and “reclaimed” are synonymous. The reason there are two terms is because different states, which commonly set the treatment standard, call it by different names. This is water supplied by a municipal water utility. Municipal water recycling involves the process of treating wastewater to a secondary — and sometimes tertiary level — which is then suitable for a direct beneficial use. Its quality is regulated by the states rather than EPA. In many municipalities recycled/reclaimed water is stored, and distributed via a separate and distinct distribution system consisting of purple pipes, indicating that it is a non-potable water source.
Once again, recycled or reclaimed water is treated off-site by a municipality to a state-regulated (but non-potable) standard. Examples of where it might be used would include: landscaping and golf course irrigation, industrial process water, cooling tower make-up water, firefighting, cooling water for electric power plants, groundwater recharge, wildlife habitat, stream augmentation, toilet or urinal flushing and direct potable reuse (injected into existing aquifers or reservoirs).
In its broadest definition, “re-use” is water that is used more than one time before it passes into the natural water cycle. The source water would include gray water, recycled (reclaimed) water and rainwater.
In its strictest definition, “re-use” means the source originated on the property where it is then reused. It would include gray water and rainwater.
Earlier in this article I mentioned “subsurface” and “subsoil” irrigation fields. By definition a subsurface irrigation field is a gray water irrigation field installed below finished grade within the topsoil, while a subsoil irrigation field is a gray water irrigation field installed in a trench within the layer of soil below the topsoil. This system is typically used for irrigation of deep-rooted plants.