6 Things You Need To Know About Your Wastewater
By Warren Tenney
Each time you wash dishes, wash a load of clothes, take a shower or flush a toilet you create wastewater. The wastewater leaves your home and enters your city’s collection system where gravity and pumps help it flow to a treatment plant. Then need, law, and technology turns Arizona’s wastewater into anything but waste. Water professionals now refer to treated wastewater as reclaimed or recycled water. Here are five things you need to know about the water that drains from your home.
1. In 1973, treated wastewater became a commodity in central Arizona. AMWUA negotiated an agreement with APS on behalf of its five original members - Phoenix, Glendale, Mesa, Scottsdale and Tempe – to sell and deliver treated effluent from the 91st Avenue Wastewater Treatment Plant 36 miles west to cool the Palo Verde Nuclear Generating Station. Palo Verde generates electricity for 4 million people in four states and is the only plant in the world to be cooled by treated wastewater. Palo Verde also is a lesson in the rising value of recycled water. In 2010, Palo Verde paid the cities about $60 per acre-foot of recycled water and by 2025 that cost is expected to rise to about $200 an acre-foot.
2.. In 1989, an Arizona Supreme Court ruling assured that cities and towns are free to dispose of effluent as they see fit. A lawsuit brought by the late developer John F. Long argued the cities couldn’t sell treated effluent to APS. The suit argued that the treated wastewater had to be returned to the river, as it had been before, to flow downstream for use by others. The court ruling in this case made it clear that cities and towns have the right to sell the treated water or put it to other beneficial uses, ensuring the cities could rely on recycled water as an important part of their supplies. This isn’t always possible in other states.
3. The 91st Avenue Wastewater Treatment Plant reuses everything you send it. Aside from the recycled water sent to the Palo Verde Nuclear Generating Station, the 91st Avenue Wastewater Treatment Plant provides recycled water for use on irrigate crops and to create a wildlife wetlands project called Tres Rios. The wastewater plant also treats and transforms solid waste – all the stuff ground up in garbage disposals and flushed down toilets – into fertilizer for non-food crops, such as hay, alfalfa and cotton. This year the plant will stop burning off the mostly methane gas it creates as a by-product. Instead, the plant will transform the by-product into renewable biogas and sell it for more than $1.2 million a year.
4. AMWUA’s ten member cities put nearly 100 percent of their treated wastewater to use. Cities treat the recycled water to the state’s A+ standard and use it to irrigate sports fields, golf courses, and commercial landscapes, and to create or restore riparian habitats and recharge groundwater aquifers and to store underground for use during shortages. The A+ standard means the wastewater is treated and disinfected until there are no routinely detectable disease-causing bacteria. In 2001, the Arizona required new or expanding wastewater treatment plants with an outflow of more than 250,000 gallons per day to produce A+ reclaimed water.
5. This year, Arizona permitted recycled water to be used as a drinking water source. This change is possible because of advances in technology to purify recycled wastewater and monitor its quality. The new rule will allow Arizona to issue permits for “Advanced Reclaimed Water Treatment Facilities” where highly treated wastewater would be purified to drinking water standards. Drinking water treatment plants would be allowed to use this purified and monitored water as “source” water. Drinking water treatment plants would continue to process this new source water following federal Safe Drinking Water Act requirements.
6. In fact, you have been drinking recycled water all along. It’s called indirect potable reuse. Here’s how it works: cities blend advanced treated recycled water into a natural water source—such as in an aquifer or a river water reservoir (referred to as an “environmental buffers”)—that could be used for drinking (potable) water after further treatment. Indirect potable reuse is allowed in Arizona and is common in the United States. Many cities treat their recycled water and release it into a natural waterway, where it becomes blended and 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 cities downstream.
If all Central Arizona homeowners used water exclusively inside their homes, water use per household wouldn’t vary much, and most of it would be recycled. Outside water use – primarily landscape irrigation – drives the big differences in monthly demand among residential users. Central Arizona homeowners may use as much as 70 percent of their drinking water outside. When you use water outside it can never be treated and recycled. It’s one of the reasons cities work hard to help residents design, select, plant and efficiently water drought-tolerant landscapes.
Photo: City of Phoenix
For 49 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.