The Delta Diablo Sanitation District in Antioch, California, is the first to test a process that will enlist bacteria to create nitrous oxide gas from ammonia in wastewater. The facility regularly allows scientists to test new processes to help fill the gap between research and industry. Delta Diablo Sanitation District
A scientist from Stanford University sees the ammonia in wastewater as the key to generating nitrous oxide, helping to make treatment facilities around the country more sustainable.
December 10, 2013—A former rocket scientist from Stanford University is now installing a pilot energy recovery system at a wastewater treatment plant in northern California that could change the way engineers think about ammonia in the waste stream.
Yaniv Scherson, Ph.D., a researcher at Stanford, began his work on capturing energy from wastewater while looking for an alternative source of nitrogen for the nitrous oxide gas his rockets used as propellant. “I discovered nitrous oxide is actually an unwanted byproduct in wastewater because it’s a greenhouse gas,” says Scherson, whose doctoral work in mechanical engineering resulted in the process known as CANDO—Coupled Aerobicanoxic Nitrous Decomposition Operation—which enlists bacteria to create nitrous oxide gas from ammonia in wastewater.
In a typical wastewater treatment plant, bacteria are used to break down the ammonia in the waste stream, resulting in nitrogen gas. However, in Scherson’s system, a different type of bacteria and an adjusted chemical mix results in the production of nitrous oxide, which is then captured and can be used to make combustion engines more powerful.
Nitrous oxide, says Scherson, is a more powerful oxidant than oxygen, something the rocket propulsion and automotive industries have understood for years. For example, nitrous oxide is commonly sold in kits to car enthusiasts who hope to get more power out of their engines.
Scherson is working with the Delta Diablo Sanitation District in Antioch, California, to prove his concept can work both outside of a laboratory and on a larger scale. The nitrous oxide collected in the project will be introduced to the wastewater treatment plant’s methane-burning cogeneration engines with a goal of helping the plant consume less power from the grid.
Ultimately, though, he has bigger plans: “We want to make wastewater treatment facilities net exporters of energy,” says Scherson, whose pilot system will include three 10 ft tall tanks. “This kind of energy, over solar or wind, is sustained in a baseline. It’s a constant supply,” he says. “It’s very close to end users, you don’t have the transmission issues, and it’s getting the constituents out of wastewater that have to be removed anyway.”
The Delta Diablo plant was a strong match for Scherson’s project, says Amanda Roa, P.E., a civil and environmental engineer who serves as the environmental compliance engineer for the facility. The connection was made with the help of an initiative known as ReNUWit—Reinventing the Nation’s Urban Water Infrastructure—a research center funded by the National Science Foundation and operated in partnership with Stanford, University of California-Berkeley, Colorado School of Mines, and New Mexico State University. Stanford is leading the initiative.
CANDO is not the only piece of forward-looking technology that will be installed at Delta Diablo within the next year. “If we see a potential for a technology to move forward and be commercially available and benefit us in the long-term, we’d like to do our part to help out,” says Roa, who calls her plant midsized, handling up to 16.5 million gallons of wastewater per day. Roa says there’s been a lot of discussion recently about how many technologies “die in the valley” between academic research and commercialization. “There are some other projects we’re working on where we see that happening, so we wanted to play some small part in trying to bridge that gap,” she explains.
Delta Diablo was not the first facility Scherson contacted, but it was by far the most receptive to the idea of helping him test his system on a larger scale. “One of the challenges in trying out new ideas is getting funding and people who are willing to take a little risk in support of new ideas,” Scherson says. “We talked with a lot of facilities and companies and [Delta Diablo] were the only ones who were supportive in every kind of way. They made financial contributions, [devoted] lots of staff time, and have been incredibly supportive of giving us the space to try out this new technology.”
Scherson, Roa, and their colleagues have already been planning the current phase of the project for a year, and once a set of larger tanks are online—probably within the next two months—the process will run for roughly a year. The team is looking to make sure CANDO works on a larger scale, and if it does, it will be scaled up again to test its use at an industrial-sized level.
“I know a lot of wastewater plants are really focused on resource recovery with a goal of being energy neutral or net energy positive in the long run,” Roa says. “I don’t think many plants are there yet, but there are a couple, and a lot of us are aspiring to do that.” Some treatment plants are required to remove nitrogen, but currently Delta Diablo is not one of those. However, if requirements change, Roa and her colleagues across the country want to be prepared, and CANDO may offer a solution with a side benefit.
At the same time, scientists around the world are looking into recovering energy from wastewater because, according to a paper published by one of Scherson’s colleagues at Stanford—Yi Cui, Ph.D., an associate professor in the Department of Materials Science and Engineering—and overseen by his advisor, Craig Criddle, Ph.D., three percent of the energy used by developed countries comes from the treatment of wastewater. (Read “Wastewater Microbes Fuel New Type of Battery,” on Civil Engineering online.) Consequently, projects such as Scherson’s are receiving more attention than ever.
“Our technology would just be one piece of moving toward a goal to make wastewater treatment facilities more like resource-recovery centers,” says Scherson, who has started a company, NGen, devoted to commercializing the CANDO process if it is successful in Antioch. “Ultimately, we’d produce the most valuable resource of all, which is reclaimed water.”