Southern Nevada Water Authority proudly proclaims that the valley's water supply is constantly recycled from the lake to homes and businesses, then through the treatment plant and back to the lake for the next cycle. Is there testing done to check for all the pharmaceuticals that people add to the water? If so, how are these drugs removed before the water is released back to the public?
For this answer, we yield the floor to Southern Nevada Water Authority Public Information Officer Corey J. Enus, who graciously explains the process.
“The question from your reader is a very good one and the short answer to the question is yes. There is testing done to check for pharmaceuticals both in raw and finished water, but before getting to that answer, it’s important to understand how the process works.
"Any time each of us in Southern Nevada takes a shower or washes our car at a commercial facility, the used water flows into the sanitary sewer. This sewer water travels to a wastewater treatment facility, where it is treated. The highly treated wastewater is returned to the Colorado River via the Las Vegas Wash, which flows into Lake Mead.
"The Wash is an 'urban' river — it exists in its present capacity because of the urban population here. It is a flow of water that is comprised of urban runoff, shallow groundwater, reclaimed water, and storm water. Wetlands are known to act as the 'kidneys' of the environment, cleaning the water that runs through them, filtering out harmful residues from fertilizers, oils, and other contaminants that can be found on our roadways and in the surrounding desert. By allowing Mother Nature to filter the water received from the urban landscape, we also reap benefits in improved water quality, creation of habitat for various outdoor activities and wildlife uses, and increased aesthetic value.
"The water returned to the lake earns us return-flow credits, which can be used to draw more water above our apportionment. By treating Colorado River water after it is used and returning it to the lake, Southern Nevada is able to extend its Colorado River resources. For every gallon of treated Colorado River water returned to the Colorado River, Southern Nevada can withdraw and use an additional gallon beyond Nevada’s base allocation.
"Once that water reaches Lake Mead, it then enters one of the Southern Nevada Water Authority’s (SNWA) two advanced water-treatment facilities designed to do one thing — provide drinking water that meets or surpasses all state and federal Safe Drinking Water Act standards for water quality. Water from Lake Mead is treated with small quantities of chlorine as it is withdrawn to deter invasive quagga mussels, which do not impact water quality, but can plug pumping equipment and pipelines.
"Water is then sent to either the Alfred Merritt Smith Water Treatment Facility or the River Mountains Water Treatment Facility, where it is treated with ozone to kill potentially harmful microscopic organisms that may be present. A multi-stage filtration system is then used to remove particles from the water. As the water leaves the water treatment facilities, chlorine is again added to protect it on the way to residents’ taps. It also is treated to minimize corrosion in the pipelines. Because it is naturally filtered, water drawn from the Las Vegas Valley groundwater aquifer is simply treated with chlorine as it enters the distribution system."
Now we get to the question about pharmaceuticals in the water supply.
"Pharmaceuticals and personal care products, known in the water industry as PPCPs, are a group of compounds consisting of human and veterinary drugs (prescription or over-the-counter) and consumer products, such as fragrance, lotions, sunscreens, and housecleaning products. These compounds have been detected in trace amounts in surface water, drinking water, and wastewater effluent sampling, because water professionals have the technology today to detect more substances, at lower levels, than ever before.
"Many PPCP compounds are being found at extremely low levels, typically single-digit parts per quadrillion (one part per quadrillion is roughly the equivalent of one grain of sand on a beach). Drinking-water standards are typically set in the parts-per-billion range (one part per billion is equivalent one small drop of water in an Olympic-size swimming pool). The fact that a substance is detectable in drinking water does not mean the substance is harmful to humans. To date, research throughout the world has not demonstrated an impact on human health from trace amounts of PPCPs found in drinking water.
"The water community is committed to protecting the public health. Water professionals are examining the occurrence of PPCPs in drinking-water supplies and the effectiveness of current treatment techniques of removal, and are paying close attention to health-effects research in this area, including research being conducted by the Southern Nevada Water Authority (SNWA). In addition, the Environmental Protection Agency (EPA) maintains an active program called the Contaminant Candidate List to identify contaminants in public drinking water that warrant detailed study. While the list does not currently include any PPCPs, the EPA may consider these compounds in the future."
Tomorrow: what the SNWA is doing in the future to improve water quality.
