Pilot projects at Delta Diablo test technologies with potential to save energy, enhance resource utilization and improve treatment.
The wastewater industry is changing, and Gary Darling is excited about the shift from merely treating water to creating new resources.
“There’s a significant amount of energy in wastewater,” says Darling, general manager of Delta Diablo Sanitation District, a resource recovery district in Antioch, Calif., 45 miles east of San Francisco. “Figuring out ways to get at that energy is very intriguing.”
He notes that capturing that energy could solve 16 percent of the nation’s electrical needs, according to the National Association of Clean Water Agencies.
The 16.5 mgd Delta Diablo treatment facility is involved in several partnerships exploring new technologies that include producing energy from biosolids, capturing nitrous oxide from wastewater for fuel and a new way to clean effluent that may also help desalinate brackish waters.
“It takes a lot of effort and cooperation to get new equipment to the market,” says Darling. “Our industry is conservative when it comes to that. We’re all managing public dollars, and we take our public trust responsibilities very seriously.”
One answer is to share the effort and risk, he says: “We’ve formed a couple of coalitions in our region to invite new technology into the San Francisco Bay Area. The overarching interest is to see new technology come to market.”
An energy group
The Bay Area Biosolids to Energy Coalition was formed in 2006 to create sustainable energy sources. Delta Diablo is hosting a demonstration of a technology, developed by Chemergy, that converts biosolids to hydrogen. It is conducted through a partnership with Lawrence Livermore National Laboratory and Chemergy.
The $1.75 million project is funded by the California Energy Commission and Chemergy. It uses reduction-oxidation thermoelectrochemistry to produce renewable hydrogen gas from wet biosolids. The hydrogen will be used to make electricity using a fuel cell provided by the U.S. Department of Energy Fuel Cell Technologies Office and the U.S. Department of Defense Construction Engineering Research Laboratory.
Chemergy will process about 1 ton of biosolids per day to produce up to 30 kW of electricity for use in the plant. Excess process heat can be used for local heating, while the hydrogen is converted to energy in a vehicle or stationary generator.
No laughing matter
Another pilot at Delta Diablo uses bacteria to create nitrous oxide from ammonia in wastewater. Better known as laughing gas, nitrous oxide is a fuel used in rockets and some race cars that can be used in cogeneration engines.
“It’s a new nitrogen removal process that will give engines more power with the same amount of fuel,” says Amanda Roa, environmental compliance engineer. “Nitrogen removal is very energy-intensive. When we were approached with a new process that may require less energy, or possibly even produce energy, we were very interested.”
CANDO was developed by Dr. Yaniv Scherson of Stanford University. “A lot of processes use the anammox bacteria to convert ammonia to nitrogen gas,” says Roa. “CANDO adds a twist by converting ammonia to nitrous oxide. The pilot will determine how much ammonia can be removed and how much nitrous oxide can be recovered.”
Bench-scale studies conducted by Stanford and Delta Diablo showed close to 95 percent ammonia removal and 80 percent conversion to nitrous oxide. This year’s six-month test is the first time the technology has been used in a real-life setting.
The TomKat Center for Sustainable Energy at Stanford is funding the equipment. Other support is coming from the National Science Foundation Engineering Research Center for Reinventing the Nation’s Urban Water Infrastructure (ReNUWIt), along with grants from the National Science Foundation and Veolia Water.
Forward and reverse
In another project, with Porifera, Delta Diablo is helping develop a new method of treating effluent using a combination of forward osmosis and reverse osmosis technology. “The technology has recently reached commercial stage,” says Darling. It could cost 30 percent less than conventional reverse osmosis through reduced chemical use, less maintenance and lower energy consumption.
The same technology could be used to desalt brackish water for irrigation, potentially cutting energy use by 90 percent. Other configurations of the technology can generate electricity using treated wastewater and high-salinity waste streams.
“It’s a potential game changer if it works,” adds Darling. “2013 was the driest year on record in California, so we’re in a significant multiyear drought. That in combination with sea level rise is making our water supply more salty. If somebody can come up with a new way, it has great potential worldwide.”
Darling says such cooperative efforts help new ideas survive the “valley of death” that exists between an idea and getting it to market. “In the past, private industry may have assisted new technologies to market. Now the trend is that they sit back and watch. If it’s successful, they will buy it. Public agencies don’t typically have a research and development budget but we can invite these new technologies to use our facilities in a careful and deliberate manner.”