When a Stanford University student flushes a toilet on campus in the not-too-distant future, the wastewater that's produced may not only irrigate the university's lawns, but could also be used to create energy needed for the treatment process.
Stanford yesterday broke ground on a $3 million facility to explore better ways to reclaim water using innovations developed by in-house researchers. At the William and Cloy Codiga Resource Recovery Center, Stanford faculty aim to test and scale up reclamation technologies on campus that could later be used by California's water-strapped cities.
In California, "some years are wet and some years are dry, but on average, we don't have enough water. It's a chronic problem," said Richard Luthy, a professor of civil and environmental engineering at Stanford.
Luthy, who was instrumental in launching the center, said "it's not going to solve the drought this year, but it can help us deal with drought in the future."
When Stanford students turn on the tap, the water that flows out comes from the Hetch Hetchy Reservoir in the Sierra Nevada. Although the Hetch Hetchy has fared better than other California reservoirs this year, the San Francisco Public Utilities Commission in late January asked its customers to voluntarily reduce their water consumption by 10 percent in response to the drought.
Thanks to aggressive efforts to curb water use, Stanford is currently using only about two-thirds of its total allocation, said Tom Zigterman, the university's associate director for water services and civil infrastructure -- a third of which is used to water lawns and other landscaping. But without further action, Zigterman added, Stanford could reach its allocation limits in two decades as the school grows and California's water supplies become more strained.
Plenty of raw material
Stanford's student and faculty population of about 25,000 produces about 1 million gallons of wastewater per day, according to Luthy.
"We could reclaim easily half of that," he said. "Half a million gallons a day would make up for a shortfall in a drought restriction and also would help us meet our future water supply needs going forward."
The new center aims to transform what flows down drains and toilets into a potential resource for both energy and potable water, explained Craig Criddle, a Stanford professor of civil and environmental engineering and the Codiga Center's new director.
One of the technologies that might make this happen is a new method to remove dissolved contaminants from wastewater under anaerobic conditions, meaning the energy-intensive aeration process that's traditionally needed during treatment can be bypassed. In the end, methane is produced, which can be used as fuel.
This technology, called a staged anaerobic fluidized membrane bioreactor, has been proved at laboratory scale by Perry McCarty, a professor emeritus of civil engineering at Stanford, along with a team of scientists at Inha University in South Korea.
Through this process, Criddle said, Stanford "could potentially get net-energy-positive wastewater treatment."
Another technology the new facility will attempt to scale up is called the "Coupled Aerobic-anoxic Nitrous Decomposition Operation" -- or CANDO for short.
Developed by Stanford postdoctoral scholar Yaniv Scherson, this process uses bacteria to convert the ammonia in wastewater into nitrous oxide gas. The nitrous oxide can then be added to a biogas like methane (such as the methane created by McCarty's technology) to supercharge the energy produced when the gases are burned.
Using the energy in sewage to clean it
Finding better ways to remove nitrogen and produce energy would be highly useful for today's water utilities. The District of Columbia Water and Sewer Authority, for example, is spending close to $1 billion on a facility to meet U.S. EPA nitrogen limits that will significantly increase its energy needs -- and its carbon footprint (ClimateWire, Jan. 13).
"The idea is to really speed up the process of getting a new technology that can be used to recover water for a whole lot of applications," Criddle said. "... This is clean water that can offset the demand for imported water, and it also can be obtained without importing energy."
Up to 40,000 gallons per day of Stanford's wastewater will be eventually be diverted to the new center, which will be about the size of a shipping container. The researchers will also deploy their technology in small trailers that can be taken to various locations around campus.
These portable units serve multiple purposes, Criddle explained. Not only will they save energy by making it unnecessary to pump the wastewater to a central location, but it will also be possible for water utilities like the Bay Area Water Supply and Conservation Agency, which supports the project, to test the new treatment processes on their home turf.
According to Luthy, construction on the center should be completed by next spring.
"I think it's going to revolutionize the way we think about wastewater treatment," Luthy said.