By Kathleen Ferris
A phrase “toilet to tap” has appeared in a recent spate of stories about cleaning and recycling wastewater. While the catchy phrase is irresistible to headline writers, it is not popular with city water managers.
They are the people who are charged with making water stretch for decades so we can continue to have water for our morning coffee and daily showers, for washing our dishes and laundry, and for flushing our toilets. Demand for water supplies continues to grow, and recycling wastewater so it can be reused in many ways, including for drinking water, is part of the solution.
Water professionals across the country are still wrestling with a vocabulary they can agree on when talking about the complexities of providing recycled water for any use.
Tim Thomure, a recognized water reuse expert with HDR Engineering, notes there is a bit of a disconnect between what people are saying and what they mean, whether they are professionals talking with their peers or with the public.
So, for now, with the help of reuse specialists Brian Biesemeyer of the City of Scottsdale and Robin Bain of the City of Peoria, here’s a guide to help readers understand generally accepted words used when talking about recycled water.
Effluent: Let’s start with the basics. Arizona law defines effluent to mean wastewater collected from homes and businesses in a sewer system for later treatment in a facility regulated by the Arizona Department of Environmental Quality. These facilities are known as wastewater treatment plants.
Treatment: This refers to cleaning the wastewater. Wastewater treatment facilities use several methods and technologies to clean the water to primary, secondary or tertiary levels. Water that reaches tertiary levels is so clean Arizona ranks it as A+, A, and B+ grades. None of these grades means the wastewater is approved for drinking, but it is clean enough for a wide variety of uses.
Advanced Treatment: Previously used to describe tertiary treatment, this term is now more frequently used to describe additional treatment, beyond tertiary, for the purpose of further removing contaminants of concern to public health. This may include membrane filtration, reverse osmosis, advanced oxidation, and disinfection with ultraviolet light and hydrogen peroxide.
Recycled or Reclaimed: These two overarching terms are used interchangeably to describe wastewater that is treated to a level that allows for its reuse for a beneficial purpose. AMWUA’s ten member cities recycle nearly 100 percent of the wastewater they treat. This A+ tertiary level treated wastewater is used to irrigate sports fields, golf courses, and commercial landscapes, and to restore riparian habitats and recharge groundwater aquifers.
Indirect potable reuse: The blending of advanced treated recycled water into a natural water source—such as a groundwater basin or surface water reservoir (referred to as an “environmental buffer”)—that could be used for drinking (potable) water after further treatment. Indirect potable reuse is allowed in Arizona and is already used by many cities. In fact, indirect potable reuse is common in the United States. Many cities treat their recycled water and release it into a natural waterway, where it becomes blended, to then be reused by downstream cities as their potable supply. For example, Las Vegas releases much of its recycled water to Lake Mead, and some of that water, blended with Colorado River water, is eventually treated to drinking water standards and reused by AMWUA cities downstream.
Direct potable reuse: This is recycled water that is treated with advanced technologies to be safe for drinking then delivered directly to customers without an environmental buffer. Direct potable reuse is exceptionally rare in the United States and usually involves blending the recycled water with surface water or groundwater at the water treatment plant. Arizona does not currently allow direct potable reuse, but that could change in the future as the public gains confidence in the established, advanced technologies that are in place to protect their health and safety.
Remediated: This word most often refers to contaminated or polluted water that is found in a natural source, such as groundwater, a lake or river, has been cleaned, and is available for other uses. For example, there are several sites in Arizona where groundwater has been polluted by uses on the land surface. These sites are under state and federal actions to ensure that the groundwater is pumped and cleaned. The “remediated” groundwater can then be injected back into the ground or used for another purpose, such as irrigation.
So there, you are beginning to break the code of water recycling. No, it’s not good enough to impress an environmental engineer or a water manager, but it’s everything you need for your kid’s next science project.
For 45 years, Arizona Municipal Water Users Association has worked to protect our member cities’ ability to provide assured, safe and sustainable water supplies to their communities. For more water information visit www.amwua.org.