As the American West faces an unprecedented drought, one promising solution is to expand water recycling programs and technologies. The William and Cloy Codiga Resource Recovery Center (CR2C) at Stanford was fueled by demand for solutions and continues to expand as it fulfills its mission of researching the recovery and recycling of water and energy resources.
In recent years, water systems in the American West have come under increasing pressure, culminating in today’s severe drought. The water resources in the west are scarce, but the population continues to grow, so that sustainable solutions are urgently sought.
“The fact that we are back in drought a few years after a severe drought – that’s problematic and a real problem,” said Newsha Ajami, director of urban water policy at Stanford’s Water in the West program. “It’s a really problematic topic, especially as we are experiencing drier and hotter droughts than before.”
But due to the past drought, most California jurisdictions have addressed the “lowest hanging fruit” issue when it comes to water conservation, said CR2C Executive Director Sebastien Tilmans MS ’10 Ph.D. ’15 said. So the solution is not just to reduce water usage, as much of the current water demand is pretty rigid; Instead, according to Tilmans, water recycling is of crucial importance for a sustainable water system in the long term.
But funding and regulation are lagging behind. Many current water recycling systems in California, including many built around the passage of the Clean Water Act in 1972, are nearing the end of their life cycle or exceeding it. More importantly, they use technologies that use a significant amount of electricity to run. And this is exactly where the CR2C research initiatives come into play.
CR2C is an active research facility on the Stanford campus, hidden behind a police station and bank. It consists of a humble collection of sidewalks, colored pipes, tanks and meters, all protected from the elements by a metal roof. The tanks and pipes allow active experimentation with real sewage sucked from the Stanford sewage outlet.
Any materials resulting from the experiments are then fed back into the regular Stanford sewage stream, which flows to the Palo Alto sewage treatment plant, to be treated as normal sewage. Although everything CR2C currently produces in its tanks is for research purposes only, the ultimate goal would be to recycle purified wastewater into the drinking water system.
The research done at CR2C varies, but the shining star of the program is a project that tests new anaerobic biological wastewater treatment methods. At present, such biological treatment is usually carried out aerobically, using types of bacteria that constantly require oxygen. This process uses a tremendous amount of energy and produces undesirable by-products, including carbon dioxide.
Anaerobic treatment, which does not require oxygen, is typically considered too slow for large-scale commercial use. But the tested anaerobic system CR2C, called Staged Anaerobic Fluidized Membrane Bioreactor (SAF-MBR), not only does not require pumping of oxygen, but even produces methane, which can then be used to generate energy.
In contrast to today’s electricity-guzzling wastewater treatment plants, according to Tilmans, the modeled energy yield from the combustion of the methane produced in a SAF-MBR plant is greater than the energy that is required to operate the system in full.
“You could see a future in which these wastewater treatment plants could be converted into green power plants,” said Tilmans. “So you not only produce clean water, but also renewable energy.”
As an extension of SAF-MBR testing, CR2C recently partnered with Silicon Valley Clean Water, a Bay Area wastewater treatment group, to build a secondary test treatment facility in Redwood City. This second location is essentially a larger version of the Stanford campus location that was built to conduct further experiments on a larger scale.
This Redwood City system went online earlier this year and the SAF-MBR has seen promising results. Operated at full capacity since last month, the resulting water quality has reached the target level.
Currently, wastewater is only recovered to a point where it is safe to release into the environment. The next phase of research is to test technologies that CR2C hopes can bring the wastewater to potable water quality.
The current drought in the west is uniquely accelerating the urgency of the kind of work CR2C is doing. Although drought is common in the area, this time around traditional water reserves like snow cover, aquifers and reservoirs have had no chance to recover between droughts as they usually do, according to the Ajami of the Water in the West program.
“Because we were in a drought, got out, and then came back in a few years later, our system hasn’t fully recovered,” Ajami said. “It definitely tests the resilience of our environment, our system as a whole.”
Testing this resilience is where wastewater recovery comes in, and CR2C hopes to show its potential. “We’re trying to change people’s view of wastewater so that it’s not hazardous waste that needs to be reduced to an ore that needs to be cleaned,” said Tilmans.
“I see water recycling as critical to our strategy in California, and I think it’s not about if we recycle the water, but when and how,” he added.
The university is also not immune to the drought and is thinking critically about these questions of water saving and management – especially since the university is to be expanded further. Water use has decreased from 2.5 million gallons per day in 2000 to 1.5 million gallons per day now, thanks in part to newer buildings being built with toilets that use gray water (wastewater from sources other than toilets such as sinks and Washing machines) and adjustments in irrigation.
But, as Tilmans said of communities across California, “the ‘simple’ savings have been made,” said Tom Zierterman, Stanford’s senior director of water resources and civil infrastructure, in an email. “But there is more we can do,” he added, listing plans ranging from harvesting rainwater to using non-potable lake water for irrigation as avenues the university is pursuing to further mitigate drought conditions.
Tilmans and CR2C hope they will make this list; there were discussions with the university about a partnership to build a complete water recycling facility on campus. But so far the university has not made any commitments.
Tilmans hopes Stanford will make the leap at some point.
“In today’s world it’s kind of necessary – it’s the smart one,” he said of implementing robust water recycling programs. “We think that this is without question the way to go and that it would fundamentally allow Stanford to continue to lead the way on sustainability issues by showing a way forward.”
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