California is leading the way in a trend that’s picking up around the world: municipal wastewater being treated, disinfected and reused near its source for a variety of purposes, from wetlands restoration to irrigation — and, yes, drinking.
Water recycling, also known as reuse or reclamation, is not new; non-potable (not for drinking) water recycling systems have been in place for decades. In arid states, including Texas and Nevada, and rainy states, such as Florida and Virginia, municipal wastewater is collected and treated to an extent that doesn’t meet drinking water standards, but is approved for certain uses that don’t involve human contact, such as agriculture, landscaping and golf course irrigation.
Today, due mainly to increasing drought conditions and groundwater depletion, non-potable uses are expanding. Municipalities are figuring out more ways to treat sewage less like waste and more like a resource. In addition to watering golf greens, recycled water is being used for street cleaning, fire-fighting, geothermal energy production, preventing seawater intrusion into freshwater aquifers, industrial processing, commercial laundering, restoring natural wetlands, and creating constructed wetlands.
Recycled water flows along the San Antonio River Walk, which touts itself as Texas’ No. 1 tourist attraction. “Everything that goes down the drain here is treated and reused,” said Greg Flores, vice president of public affairs for the San Antonio Water System, citing university campuses, the San Antonio River Walk and Toyota and Microsoft facilities as examples. The San Antonio Marriott Rivercenter is also a big contributor as it converts its food waste into water, with the Eco-Safe Digester adding approximately 12,000 gallons of net new water to San Antonio’s Water System for reuse each year.
A growing number of municipalities are now shifting toward or considering “potable reuse” — recycling wastewater into drinking water.
In 2008, Orange County, California started operating its now-celebrated Groundwater Replenishment System, which injects treated wastewater into the water supply of nearly 600,000 residents. The project, said Orange County Water District president Shawn Dewane, is “taking water reuse to the next level. Instead of pouring it on the ground, in terms of landscape irrigation, [we are] turning it into drinking water.”
With a capacity of 70 million gallons per day, the Orange County system is the world’s largest for water purification and potable reuse. Primarily because of its scale the system has attracted interest both nationally and internationally. Experts say reuse technologies have been proven, and treatment plants can get wastewater as clean as distilled water. The three-step process used in Orange County — microfiltration, reverse osmosis and a combination of ultraviolet treatment with hydrogen peroxide — is becoming the standard for potable reuse.
Water reuse is regulated at the state level — although the EPA has issued guidelines for reuse approximately every decade since 1980 — and more than half the states have some kind of regulation in place. Aside from serving as a way for cities to supplement their increasingly stressed water sources, reuse can provide a variety of benefits.
- In the Pacific Northwest, reuse is growing because of decade-old temperature restrictions imposed by state agencies on wastewater treatment plant discharges to rivers. Effluent is warmer than rivers, so what folks are doing is they’re looking to treat the effluent to a standard that allows it to be used on the land.
- Water reuse can reduce the amount of freshwater diverted from sensitive ecosystems, as well as the amount of wastewater and the pollution it carries discharged to waterways.
- Although wastewater reuse is energy intensive, it often yields an energy savings because pumping imported water (from outside sources) consumes much energy itself. In Orange County, recycling water for the groundwater replenishment system takes half the energy of importing water.
Water reuse, however, is not automatically right for every circumstance. There are a lot of places where the wastewater would have otherwise been important in returning to, say, a river or stream.
The biggest hurdle, however, lies in gaining public acceptance. When people hear about “toilet to tap” technology, they get nervous and grossed out. That’s why when municipalities look at reuse, the hardest part usually isn’t figuring out the right technology or engineering the system; it’s educating the public and involving them in the process in order to gain their approval. As public understanding of water reuse grows, so will the acceptance of its practice.
There’s no way to tell where else potable reuse, direct or indirect, will be adopted, but it’s clearly the direction more municipalities are taking. As water scarcity becomes a closer reality for many, people have no choice but to overlook the “yuck factor” that may have constrained the pursuit of reuse in the past.
Water reuse is not inexpensive but new sources of water are even more expensive to come by which is why turning food waste into water with the Eco-Safe Digester makes sense and fits in nicely with cities utilizing water reuse technology.
Portions of this article was first published by Rachel Cernansky on December 16, 2013