Demonstration ​Anaerobic ​Treatment Plant ​Tests Stanford ​Technology

A new wastewater treatment plant under construction in Redwood Shores will be the largest to test Stanford-developed technology that significantly reduces the cost of cleaning water. The key: bacteria that eschew oxygen while producing burnable methane.

Billions of years ago, when Earth’s atmosphere reeked of unbreathable gases, microbes evolved in the absence of oxygen. As Earth matured and the nitrogen-oxygen atmosphere formed, these anaerobic, or oxygen-averse, bacteria retreated into the mud of the ocean floor and other environments where they would be safe from oxygen-rich air.

Now Stanford environmental engineers Craig Criddle and Bill Mitchare putting these ancient microorganisms to work in the largest demonstration of a more cost-effective wastewater treatment process, supported by a $2 million grant from the California Energy Commission (CEC). Smaller plants based on anaerobic bacteria are currently treating wastewater in South Korea and on the Stanford campus.

Working closely with environmental engineers from Silicon Valley Clean Water (SVCW), a water treatment utility, the Stanford team will help build and operate a small anaerobic treatment plant in Redwood Shores, California, alongside the enormous conventional plant that purifies wastewater for a quarter million people and businesses from Redwood City to Menlo Park.

The group has broken ground on the demonstration plant, which is slated to come on line in fall 2018. It will eventually process 20,000 gallons of wastewater per day to provide validation and operating experience for what could become a full-scale plant capable of processing millions of gallons of wastewater per day.

“Anaerobic processing can reduce energy use and decrease costs, and make wastewater treatment more sustainable” said Criddle, a professor of civil and environmental engineering.

In addition to cost-effectiveness, the researchers believe anaerobic processing could prove better at filtering household and industrial chemicals out of the waste stream, so that the treated water can drip back underground to replenish aquifers or even, one day, yield water pure enough to irrigate the garden or even quench one’s thirst.

“Anaerobic treatment is a fundamental shift in water recycling technology,” said Mitch, also a professor of civil and environmental engineering.

Reducing cost is just one advantage of wastewater treatment based on anaerobic bacteria, according to Sebastien Tilmans, the civil engineer who runs the Codiga Resource Recovery Center on the Stanford campus. At Codiga, which has a smaller version of the technology, the oxygen-averse bacteria clean wastewater and belch out methane. Commonly known as natural gas, this output can be burned as fuel or used as a chemical feedstock to make biodegradable plastics. That, Tillman said, exemplifies a change in thinking.

Anaerobic water treatment technology was pioneered decades ago by Stanford environmental engineer Perry McCarty, now a professor emeritus. But back in the 1950s, when he first began working with these oxygen-averse, methane-making bacteria, energy seemed cheap and inexhaustible. There was no compelling reason to test an energy-saving alternative.

Source: Stanford News

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