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COMMENTARY | To ‘futureproof’ wastewater treatment against the rising threats of climate change, sewage should go local.
Call it the summer of sewage.
In July, Los Angeles’ Hyperion Water Reclamation Plant, the city’s largest municipal wastewater treatment facility, spilled 17 million gallons of raw sewage into Santa Monica Bay after an unexpected surge of debris overwhelmed the plant, resulting in beach closures during the height of beach season. Weeks later, The Los Angeles Times revealed that the still-damaged plant was continuing to release partially-treated wastewater into the Pacific Ocean.
Earlier in the month, England’s Southern Water, a privatized utility, was fined 90 million pounds (roughly $125 million) for intentionally releasing untreated sewage between 2010 and 2015, apparently in order to save money. And The New York Times reported on the growing, climate-change-exacerbated problem of sewer overflows in Chicago, where backups disproportionately burden poor, non-White communities.
The takeaway from reports like these is often that more investment and regulation are needed to prevent sewage spills, be they a result of accident, negligence, or plain old bad behavior. That’s true.
But there’s only one surefire way to end big sewage spills, and that’s to end big sewage.
Modern urban wastewater infrastructure started with the Victorians, who in the 19th century confronted the messy consequences of piping water to homes and businesses for drinking, bathing, cleaning, and, above all, toilet flushing. In London, this used water washed haphazardly out of homes into cesspools, streets, and ditches, fueling disease outbreaks and ultimately polluting the River Thames. When that became untenable, the city built a remarkable comprehensive system of sewers to pump all the wastewater downriver.
In the early 20th century, British engineers invented a microbe-driven wastewater treatment process to clean the sewage before releasing the effluent, but it wasn’t until the second half of the century that most high-income cities implemented the technology in large-scale treatment plants. (Unfortunately, many middle- and low-income cities worldwide lack these systems, leaving huge quantities of sewage untreated.)
The public health and environmental gains from the successful centralized management of sewage have been remarkable. But massive, centralized facilities make for massive, centralized catastrophes—and the risk of public health and ecological disasters.
One way to reduce the impact of sewage spills is to reduce the amount of sewage available to spill, but conservation can only go so far in the face of urban growth. According to a 2020 paper in the journal Natural Resources Forum, global wastewater production was set to increase 24 percent by 2030 and 51 percent by 2050. In the United States, the American Society of Civil Engineers estimated in 2017 that 56 million new users would need to be connected to centralized wastewater treatment systems over the following two decades.
Cities can also incorporate more green infrastructure, such as green roofs and bioswales to absorb stormwater and reduce the load on wastewater systems. Constructed wetlands can also mitigate pollution from sewer overflows. Massive underground reservoirs can hold storm flows until plants have capacity to handle them again.
One problem is that centralized treatment plants tend to be located in low-lying areas, to take advantage of gravity, and near bodies of water, to release their effluent. So storm surges and flooding can easily bring them down — and sometimes it takes weeks to get them working again. Drought also affects their operations: Too little water can cause a sewage flow to stagnate, and thirsty tree roots can penetrate underground pipes in search of a drink. What’s more, if power goes out, pumping stations and wastewater treatment plants can go offline too. And since centralized systems are practically invisible to users, people just keep showering and flushing even during announced failures, when the wastewater they’re creating will just flow directly out to rivers, lakes, and the sea. (And, anyway, what choice do they really have?)
Instead, sewage should go local. New residential and commercial developments, in particular, can take advantage of innovations for buildings and neighborhoods that allow wastewater to be recycled for immediate use, its nutrients and energy used onsite. In my reporting on sanitation and the environment, I’ve come across increasing numbers of such projects, many of them pilot-scale, ranging from high- to low-tech.
In Portland, Oregon, a luxury residential and commercial complex with 657 housing units received a nearly $1.5 million refund from the city for incorporating an off-grid system in order to avoid further straining the city’s century-old sewers. A series of tanks, filters, and constructed wetlands, which takes pride of place on the main plaza, recycles the community’s wastewater for cooling, irrigation, and toilet flushing, reducing water use by more than 50 percent. (In an emergency, the complex can discharge to the city’s sanitary sewer.) Solid residue gets taken offsite for reuse as fertilizer and energy.
When it comes to urban infrastructure, it’s “probably the largest and most advanced on-site wastewater treatment facility in the United States,” says sustainability consultant Lynn Broaddus, an advocate for distributed water infrastructure who is currently the president of the Water Environment Federation, an association of water quality professionals.
Local systems such as these can—depending on the circumstances—use less energy and emit less greenhouse gas than centralized ones. Some can be installed in a corner of a parking garage, or feed lush greenhouse gardens. They can create local, green jobs.
On a city scale, a network of distributed systems, or a combination of centralized and distributed systems would be less concentrated in flood zones, could have more built-in redundancies, and would be more nimble in recovery. That would make it more resilient to extreme weather events and other shocks like the surge in Los Angeles.
Finally, distributed systems can make wastewater management more flexible and modular, allowing them to shrink and grow with cities and making them additionally “future-proof.”
If this approach sounds strange, consider that there’s a trend to localize almost every other type of infrastructure system, from agriculture to energy grids. Local sewage makes sense, too, for many of the same reasons. While more research and pilot projects will be helpful in both evaluating and raising awareness of decentralized systems, the shift also requires a change in incentives and regulations, which in most places currently favor traditional, centralized approaches.
To be sure, distributed systems could and would at times fail like centralized ones do. They would also need investment, maintenance, and regulation like centralized systems. But small-scale facilities embedded in communities would be more visible to their users than big sewage treatment plants on the outskirts of town, meaning that people would be more likely to make the connection between their water use and pollution. Community members could also spot failures more quickly and demand accountability.
And then they could go swim at the beach.
Chelsea Wald is a contributing writer at Undark.