Article courtesy of Glen Martin | June 11, 2015 | Cal Alumni Association UC Berkeley | Shared as educational material
It’s the kind of subject that lends itself to the lowest of low humor, but we’ll try to resist that temptation. Because at bottom (sorry), it’s among the most serious of subjects, speaking as it does to basic survival. We’re talking about water (again), of course. But more specifically, we’re talking about blackwater: Sewage. And even more particularly, recycling sewage, treating it to the potable level and–gulp–drinking it again.
And don’t think this is a desperate, ad hoc, futuristic proposal engendered by the drought. Blackwater reclamation is happening now, right here in California, and on a significant scale. Orange County? It’s been recycling sewage for a while. Each and every day, the OC is injecting 70 million gallons of erstwhile effluent (that is, sewage treated to potable standards) into local aquifers; from there, much of it is pumped back up to local taps and consumed. Whittier? They’re recycling about 44 million gallons a day. Around Chino, it’s about 18 million gallons a day, and near LAX, they’re injecting 12 million gallons of transmuted sewage (i.e., pure water) underground.
And don’t feel smug if you’re reading this in NorCal. The Santa Clara County Water District is seriously considering blackwater recycling.
Still, the basic concept of repurposing sewage is nothing new, says David Sedlak, a UC Berkeley professor of environmental science and engineering, the co-director of the Berkeley Water Center, and the director of the Institute for Environmental Science and Engineering.
“Back in the 1920s, before the widespread availability of inexpensive fertilizers, sewage was viewed as an asset because the solids were rich in nitrogen and phosphorous,” says Sedlak. “The value wasn’t in the water.”
That changed by the 1970s, says Sedlak, when wastewater reclamation “took a great leap forward. Wastewater was treated to a high but not potable degree in conventional treatment plants and then used on golf courses, commercial building landscaping and highway medians, and in commercial boilers and refineries.”
That policy was well-received, says Sedlak; a lot of wastewater treatment plants were built around the state to accommodate the trend. But the approach only worked well for properties that were relatively close to the plants—properties that didn’t require a lot of new pipes and valves for distributing the treated water. And by the 1990s, the low-hanging fruit had been plucked; or rather, nearby properties already had been serviced. Outlying tracts required new infrastructure to deliver the treated wastewater, and that was costly.
“San Jose looked at an ambitious recycling project for South Bay office parks,” says Sedlak, “but they soon realized that the plan would be prohibitively expensive. That’s because it required a distribution network separate from the potable water network—a “purple pipe” system, so called because the pipes for reclaimed wastewater systems are usually purple. So they lost interest. And as the costs of expansion became clear, that waning enthusiasm was replicated” elsewhere.
For landscaping purposes, wastewater typically was treated by extensive filtration and large volumes of chlorine. It was “safe,” but not truly “potable.” Even if you wanted to drink it, you’d gag on the chlorine, says Sedlak. But significant progress in reverse osmosis—a purification process that uses sophisticated membranes with minute pores to remove salt, toxic compounds and pathogens—changed the whole approach to blackwater reclamation. It is now possible to purify large volumes of wastewater to the sweet, pellucid, potable stage quickly and efficiently. These advances, coupled with a growing recognition that drought and subsequent water shortages in California are anything but anomalous, have made the toilet-to-teacup-option more attractive—to water district managers, if not consumers.
Orange County, in fact, got with the program way back in 1976 (the year that marked California’s last major drought, excluding the current crisis).
“It started out as a project to create a barrier against seawater intruding into the county’s aquifers due to overpumping,” says Sedlak. “They used a process that involved microfiltration, ultraviolet light, hydrogen peroxide and reverse osmosis, then injected the water underground. (The treated water) stopped the saltwater intrusion, but it also—as managers knew it would—flowed back into the aquifer, where it was pumped up for consumption.”
After producing about 30 million gallons daily for many years, Orange County built an expanded treatment plant in 2008 and ramped up production to its current 70 million gallon quotidian level. Half the water is used mainly to stop saltwater intrusion, and half goes to recharge basins, where it percolates into the aquifer and eventually flows to the homes of district customers.
But Orange County’s experience isn’t necessarily replicable everywhere, observes Sedlak. First, Orange County had little choice but to recycle what it sullied. It grew at a dizzying pace through the last half of the 20th Century, and it had junior water rights. Too, the county has good aquifers. They are permeable, capacious and stable, and they hold a lot of water. Finally, residents trusted the Orange County Water District and Sanitation District; the agencies were widely viewed as competent, leaders in innovation, and responsive to customers.
That isn’t the case in other areas, where local government officials may have rockier relations with their constituents.
“A wastewater reclamation project for the Dublin/San Ramon area failed because the wastewater district didn’t have a great reputation with the public,” observes Sedlak.
Of course, it’s also true that many consumers remain deeply uncomfortable with the notion of drinking reclaimed sewage, says Sedlak, the co-author of a paper on the subject that appeared recently in the journal Environmental Science and Technology.
“Proposed projects for San Diego, the San Fernando Valley and the San Gabriel River (in southern Los Angeles) fell through largely because of the toilet-to-tap stigma,” says Sedlak. “It’s often the case that someone writes a letter to the editor, or makes a joke on late night TV, or a group of people show up at city council meetings, and then the whole thing goes up in flames.”
Given the unrelenting nature of the drought, Californians may not have the luxury of foregoing reclaimed sewage forever. And in researching their paper for Environmental Science and Technology, Sedlak and his co-authors (Sasha Harris-Lovett, Christopher Binz, Michael Kiparsky and Bernhard Truffer) determined that the “yuck factor” is actually just a small part of the problem. Rather, he says, three other elements must be addressed to gain community acceptance.
“First, consumers have to believe the project is in their best interests,” says Sedlak. “Second, they have to trust the agencies treating and delivering the water, and the government regulators that are monitoring the process. They have to believe that the local agencies are reliable and up to the job, and that regulators are rigorous in their oversight. If people think that the regulators are too cozy with the agencies, there can be a problem. Finally, people need to be comfortable with the technology. Singapore treats its sewage to potability, and they have a fancy visitor’s center at their treatment plant. They give tours, and at the end of it you get a bottle of treated water to drink—if you want to. That shows the government has nothing to hide, it strips the mystery from process, and it helps people take it for granted rather than view it with dread and foreboding.”