All water, conventional scientific wisdom goes, is recycled. The Earth’s water has been here since the planet formed some 4.6 billion years ago, and any given molecule may have passed through the bodies of dinosaurs, fish throughout the oceans, the living tissue of giant trees and numerous human beings.
But water recycling in the more immediate, industrial sense refers to sewage water or gray water from our showers and sinks that is captured before it flows out to sea, purified with advanced technology and re-circulated back into the water grid. Many people believe the future of California, and much of the world, will rely on such water recycling.
The drought has not ended, California’s population is growing, and supplying communities and farms with water while protecting natural resources may become one of the greatest challenges of the century. While many state leaders and water agencies are pushing for new reservoirs, desalination plants and massive water conveyance projects to meet these challenges, others believe in a much simpler remedy: treating and reusing the water we already have — instead of dumping it into the ocean — to lessen the demands on our most precious natural resource.
In fact, it’s becoming common practice in many parts of the state. In El Dorado Hills, hundreds of new homes are being built with dual plumbing systems that send potable water to indoor taps through one pipe, and treated recycled water to outdoor sprinklers and spigots through another. A separate project in the planning stages will supply farmland near Elk Grove with recycled water, eliminating growers’ reliance on potable groundwater.
“This would reduce demands on groundwater and potentially free up about the amount of water used by 100,000 homes in a year,” says José Ramirez, a senior civil engineer with the Sacramento Regional County Sanitation District, one of the local water agencies with plans to increase water recycling.
According to the State Water Resources Control Board, 1.3 million acre-feet of water was discharged by coastal water treatment plants into the sea in 2014. That’s about the capacity of a mid-sized reservoir. Some experts say most of this water could be recycled. In 2009, the state recycled 670,000 acre-feet of water — a fraction of the total potential. The Los Angeles region, where about a third of the water supply originates in the Sacramento-San Joaquin River Delta, may have the most room to improve. Just 11 percent of the region’s wastewater that gets treated at coastal facilities is recycled.
“So, we’re diverting water from the Delta and rivers, moving it hundreds of miles, treating it to drinking water standards and then dumping it into the ocean,” says Doug Obegi, a senior attorney with the Natural Resources Defense Council. “That’s a huge waste of a resource.”
Most water, unfortunately, is used this way: It is drawn from rivers, lakes or aquifers, made clean enough to drink by local suppliers, then used once before being treated and discharged by sewage plants. If the water is discharged into a river — as happens after municipal use in cities like Sacramento — the water may be recaptured downstream, so it isn’t necessarily wasted. But when discharged into saltwater, the water is essentially lost until natural processes deliver it again via precipitation.
Advocates of water recycling say it would be much more efficient — and even necessary, given California’s projected population of 50 million people by 2050 — to capture that water before it flows into the sea, treat it so that it is again potable or nearly so, and then pump it back into the state’s water system, whether for municipal, industrial or agricultural needs.
In fact, the state is moving that direction, or is at least talking about it. State water officials have set a voluntary goal of recycling 1.5 million acre-feet of water per year by 2020. That’s about 20 percent of the state’s urban water use and may be an unrealistically ambitious target at this point. More realistic might be the aggressive legislation recently introduced by Senator Robert Hertzberg, a Southern California Democrat, which would require coastal wastewater treatment plants to recycle half of their ocean discharges by 2026 and, by 2036, all of them.
Routes to Recycled Water
Water can be recycled in different ways. The simplest is to treat the water to a level of purity so that it’s not quite suitable for drinking but can be used via separate piping systems for irrigating lawns, city parks and landscaping, as well as some types of agriculture. The gold standard of water recycling is potable reuse, which itself comes in two forms —indirect potable reuse, in which potable treated water is injected into a groundwater basin or reservoir before it goes back into the municipal supply, and direct potable reuse, in which water is treated to the highest purity standards, then pumped almost directly back into the water grid.
According to George Tchobanoglous, a professor emeritus in the UC Davis Department of Civil and Environmental Engineering, all of these innovations will play a key role in California’s future.
“Our population is growing, and El Niño didn’t get us out of our water crisis, and people are recognizing that we’re going to have to do something about water,” Tchobanoglous says. “We can’t count on weather, which is somewhat fickle. If it turns out we have another drought year, we could go on having them for another five years, so we need to think of alternatives and we need to get on with it.”
Desalination plants are being promoted by coastal communities, the advocacy group CalDesal and a private engineering firm called Poseidon Water as a solution for California’s water woes. But desalination is very different than water recycling, and the process can have major drawbacks: A large plant went online last year in Carlsbad, San Diego County that will remove the salt from more than 50,000 acre-feet of water each year. However, the energy costs — and the carbon footprint — of desalinating seawater are huge, and it has been argued that the carbon emissions from building and operating desalination plants could accelerate climate change and indirectly worsen, not alleviate, California’s water supply problems. The effluent water from desalination plants is also so densely saline that it can harm or kill marine life.
“So, we’re diverting water from the Delta and rivers, moving it hundreds of miles, treating it to drinking water standards and then dumping it into the ocean.” Doug Obegi, senior attorney, Natural Resources Defense Council
Major construction projects, like the proposed Sites Reservoir, in the western Sacramento Valley, and the controversial twin tunnels that could divert much of the Sacramento River into the San Joaquin Valley, and to cities farther south, have also received a strong push from farm lobbyists and powerful water agencies. However, these projects, critics are fast to point out, only change the way existing water is stored and transferred. That is, they will not create new water.
Neither does water recycling. However, by treating and reusing water that currently flows into the sea or other waterways, Californians could ease the strain on existing supplies to the tune of at least one million acre-feet each year, possibly two or three times that. Such advances would considerably lessen demands on water supplies in the Central Valley, from which millions of coastal Californians receive their water.
“So, we’re diverting water from the Delta and rivers, moving it hundreds of miles, treating it to drinking water standards and then dumping it into the ocean.”
About five million acre-feet of water are pumped out of the Sacramento-San Joaquin River Delta each year to help supply California’s cities and farms. Such diversions directly and indirectly kill fish and have, through the years, dramatically altered the flow mechanics of the Delta ecosystem. Populations of several fish species, including the winter-run Chinook salmon, are now threatened with extinction. Obegi, at NRDC, says the impacts to the Delta of these diversions — which agricultural interests often claim are the result of factors other than water pumping — could be alleviated with the help of water recycling efforts in the communities receiving the Delta’s water.
“We’re already taking too much water out of the Delta,” Obegi says. “We need to be taking out less water and be much more efficient with the water that we do take.”
Millions of acre-feet of potable water are used every year to irrigate California’s lawns, parks and gardens. Local water recycling projects currently in the planning stages will help curb this wasteful use of high-quality water. The El Dorado County Irrigation District is planning on fitting new homes in El Dorado Hills with dual plumbing systems that provide recycled water for outdoor use and potable water only for indoor use. Near Tracy, thousands of residents in planned homes may soon be able to recycle the water from their faucets and showers and use it to water their lawns. The Sacramento Regional County Sanitation District has similar plans to connect city landscaping irrigation lines to their own recycled water supply. There is also a small project being planned by Regional San to encourage customers to visit the treatment plant at certain hours and fill containers as large as 300 gallons with treated recycled water and take it away for home irrigation use. This program began in May.
But Regional San’s South County Ag Program is the most substantial local water recycling project in the planning. The project, which could be completed by 2023, will send as much as 50,000 acre-feet of water per year — about 10 percent of the Sacramento area’s total potable water demands — to alfalfa, hay and row crops a few miles south of Elk Grove that currently use potable groundwater for irrigation.
As for indirect potable reuse, California is moving forward. The Orange County Water District currently serves its 2.4 million customers via a groundwater basin. To help recharge this aquifer, the district began diverting water several years ago from a nearby wastewater plant and treating it via reverse osmosis, distillation and ultraviolet exposure, a process that removes and destroys particulates and microbes. The water, potable at this point, is pumped into the groundwater basin, where it mixes with the existing supply.
Mike Markus, the general manager of the Orange County Water District, says this project diverts, in total, 130 million gallons of wastewater per day. As this water is treated, almost 25 percent is lost in the purification process, and in the end 100 million gallons of clean water are pumped into the region’s groundwater supply. That’s still about 103,000 acre-feet of water per year — enough to supply 850,000 people — and represents about 15 percent of all the water recycled statewide.
A similar but smaller project went online in 2014 at the Santa Clara Valley Water District, and water agencies elsewhere in Southern California are planning to launch indirect potable reuse projects. In the Los Angeles region, plans have been discussed for a large indirect potable project that would outsize even Orange County’s.
“But the problem with indirect potable reuse is that you have to have a groundwater basin to add your treated water to,” Markus says. Regulations are now being written that would allow surface water reservoirs to be used for the same purpose of storing potable recycled water.
Still, there are many communities, including some in the Sacramento area, that have neither a groundwater basin nor a reservoir. For them, direct potable reuse may be a better option. It requires no storage basin and, in this way, is simpler than indirect potable. However, direct potable reuse is a little bit riskier, since there is no room for error.
“It’s not like with indirect, where you have more time to react if there is a problem with the quality of the water because it’s being pumped into what we call an environmental buffer, in this case a groundwater reservoir,” says Jennifer West, the managing director of WateReuse California, the Sacramento-based branch of a national organization that lobbies for water recycling.
In other words, direct potable reuse requires a flawless purification system since the water, after treatment, is pumped almost directly back into the community’s plumbing system. The most advanced direct potable project in the world is probably that of Windhoek, Namibia. Here, about a quarter of the city’s water needs are met via wastewater that has been treated and sent back into the water grid. This system has brought some degree of water security to a naturally arid region that several years ago — between 2012 and 2013 — went a full season with virtually zero rainfall.
Several locations in Texas and New Mexico have also had success with direct potable reuse. Building such systems in California will first require establishing exhaustive safety regulations — rules and protocols that do not yet exist. A panel of water experts has been convening regularly and is working toward drafting a set of direct potable regulations. West says it may be another five years before the necessary regulatory framework is in place to build direct potable systems in California.
West says water recycling is especially cost-effective in Southern California, where two-thirds of the supply is imported via long canals. “It’s a very energy intensive activity to pump their water over the mountains,” she says. “So, especially with this imported water, we should be using it more than once.”
Even in regions that receive relatively abundant annual rainfall, like the North Coast, water recycling must be developed as a source of water.
“Water recycling has gone from being a niche source of water to mainstream,” West says. “Whether we’re in a drought or not, we’re going to see continued massive population growth. We have a lot of vagaries with climate in the state, and we can’t depend on rain anymore.”