By Evan Peng on September 22, 2021

As the American West faces unprecedented drought, one promising solution is the expansion of water recycling programs and technology. Stanford’s William and Cloy Codiga Resource Recovery Center (CR2C) has been buoyed by the demand for solutions, and continues to expand as it carries out its mission of researching water and energy resource recovery and recycling.

In recent years, water systems in the American West have come under more and more strain, culminating in today’s severe drought. Water resources are scarce in the West, and yet the population continues to grow, leading to an urgent search for sustainable solutions.

“The fact that we are back in a drought a couple of years after we were in a severe drought — it is problematic, and it’s a real issue,” Newsha Ajami, director of Urban Water Policy at Stanford’s Water in the West program, said. “It is a really problematic issue, especially because we are experiencing drier and hotter droughts than we used to.”

But because of the history of drought, most jurisdictions in California have addressed “the lowest hanging fruit” in terms of water conservation, CR2C Executive Director Sebastien Tilmans M.S. ’10 Ph.D. ’15 said. So the solution is not simply cutting more water use, as much of the current water demand is fairly rigid; instead, water recycling, Tilmans said, is critical for a sustainable water system in the long-run.

But funding and regulations are lagging. Many current water recycling systems in California, including many which were built around the passage of the Clean Water Act in 1972, are nearing or exceeding the end of their life cycles. More importantly, they use technology that consumes a significant amount of electricity to run. And this shortcoming is where CR2C’s research initiatives come in.

CR2C is an active research facility on Stanford’s campus, tucked away behind a police station and a bank. It consists of an unassuming collection of walkways, colored pipes, tanks and meters all shielded from the elements by a metal canopy. The tanks and pipes allow for active experimentation on real wastewater that is siphoned from Stanford’s wastewater output.

Any resulting material from the experiments is then inserted back into Stanford’s regular wastewater stream, which flows to Palo Alto’s wastewater treatment plant to be treated as normal sewage. Although everything CR2C currently produces in its tanks is strictly for research purposes, the eventual goal would be for wastewater treated using the processes CR2C is testing to be reused in actual water systems.

The research conducted at CR2C varies, but the shining star of the program is a project testing new anaerobic biological wastewater treatment methods. Currently, such biological treatment is commonly aerobic, done using types of bacteria that require oxygen to be pumped in constantly. This process uses a massive amount of energy and produces undesirable byproducts, including carbon dioxide.

Anaerobic treatment, which does not require oxygen, is typically viewed as being too slow for commercial, large-scale use. But the anaerobic system CR2C is testing, called the Staged Anaerobic Fluidized Membrane Bioreactor (SAF-MBR), not only requires no oxygen pumping, but it even produces methane, which can then be used to produce energy.

According to Tilmans, in contrast to today’s common electricity-guzzling treatment plants, the modeled energy output from burning the produced methane in a SAF-MBR facility is greater than the energy that is needed to run the system at full scale.

“You could see a future in which these treatment plants could be converted into green power plants,” Tilmans said. “So not only are you producing clean water, but you’re also producing renewable energy.”

As an extension of the SAF-MBR testing, CR2C recently partnered with Silicon Valley Clean Water, a wastewater treatment group in the Bay Area, to build a secondary test treatment site in Redwood City. This second site is essentially a larger version of the one on Stanford’s campus, built to run further experiments at a larger scale.

That Redwood City system came online earlier this year, and the SAF-MBR has had promising results. Running at full capacity since last month, resulting water quality has hit target level.

Right now, the wastewater is recovered only to a point where it is safe to release into the environment. The next phase in research is to test technologies that CR2C hopes will be able to bring the wastewater all the way to drinking-quality.

The current drought in the West is uniquely accelerating the urgency of the type of work CR2C is doing. Though drought is a common occurrence in the region, this time around traditional water reserves such as snowpack, groundwater basins and reservoirs did not have a chance to recover between droughts as they normally do, according to Ajami of the Water in the West program.

“Because we were in a drought, got out and then a couple years later we’re back in it again, our system hasn’t recovered fully,” Ajami said. “It’s definitely testing the resiliency of our environment, our system as a whole.”

Testing that resiliency is where wastewater recovery comes in, and CR2C is hoping to show its potential. “We’re trying to sort of transform people’s perspectives on wastewater away from it being a hazardous waste that needs to be mitigated toward thinking of it as an ore that needs to be purified,” Tilmans said.

“I view water recycling as critical to our strategy in California, and I think it’s not a question of if we’re going to recycle the water, but when and how,” he added.

The University, too, is not immune to the drought, and is thinking critically about these questions of water conservation and management — especially as the University has plans to expand. Water use has decreased from 2.5 million gallons per day in 2000 to 1.5 million gallons per day now.

But like Tilmans said of municipalities across California, “the ‘easy’ savings have been achieved,” as Tom Zigterman, the senior director of Water Resources and Civil Infrastructure at Stanford, wrote in an email. “But we can do even more,” he added, listing plans ranging from stormwater capture to using non-potable lake water for irrigation as paths the University is pursuing to further mitigate drought conditions.

Tilmans and CR2C hope they can make it onto that list; there have been discussions with the University about a partnership to construct a full-scale water recycling facility on campus. But so far, the University has not made any commitments.

Tilmans is hopeful that Stanford will make the leap eventually.

“In today’s world, it’s kind of necessary — it’s the prudent thing to do,” he said of implementing robust water recycling programs. “We think that this is without question the right way to go, and would basically allow Stanford to continue to lead on questions of sustainability by demonstrating a path forward.”

This article has been corrected to clarify that CR2C’s eventual goal of reinserting treated water back into water supplies is not specifically in relation to Stanford’s water system and to reflect that, while the University’s water use has decreased, no campus buildings use graywater for toilets or any other use.

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