There is a sure-fire way to stop big sewage spills: stop big sewage discharges


VSall that the summer sewage.

In July, the Los Angeles Hyperion Water Reclamation Plant, the city’s largest municipal wastewater treatment facility, dumped 17 million gallons of raw sewage into Santa Monica Bay after an unexpected wave of debris overwhelmed the plant, causing beaches to close during the height of beach season. . Weeks later, the Los Angeles Times revealed that the still damaged plant continued to discharge partially treated sewage into the Pacific Ocean.

Earlier this month, Southern Water, a privatized utility, was fined 90 million pounds (around $ 125 million) for intentionally dumping untreated wastewater between 2010 and 2015, apparently for the purpose of to save money. And The New York Times reported on the growing and climate change exacerbated problem of sewer overflows in Chicago, where safeguards disproportionately burden poor, non-white communities.

The takeaway from reports like these is often that more investment and regulation is needed to prevent wastewater spills, whether the result of an accident, old neglect or bad behavior. It’s true.

But there is only one surefire way to stop big sewage spills, and that’s to end big sewage water.

Modern urban wastewater infrastructure began with the Victorians, who in the 19th century faced the messy consequences of providing water to homes and businesses for drinking, bathing, cleaning and, most importantly, drawing water. toilet flush. In London, this wastewater washed up haphazardly from homes in sumps, streets and ditches, fueling epidemics and eventually polluting the Thames. When this became untenable, the city built a remarkable comprehensive sewerage system to pump all sewage downstream.

At the start of the 20th century, British engineers invented a microbe-based wastewater treatment process to clean the wastewater before discharging the effluent, but it was not until the second half of the century that most cities high income earners have implemented the technology on a large scale. processing plants. (Unfortunately, many middle and low-income cities around the world do not have these systems, leaving huge amounts of wastewater untreated.)

The public health and environmental gains from successful centralized wastewater management have been remarkable. But massive, centralized facilities lead to massive, centralized disasters – and the risk of health and ecological disasters.

One way to reduce the impact of wastewater discharges is to reduce the amount of wastewater that can be discharged, but conservation cannot go further in the face of urban growth. According to an article published in 2020 in the journal Natural Resources Forum, global wastewater production is expected to increase by 24% by 2030 and 51% 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 next two decades.

Cities can also integrate more green infrastructure, such as green roofs and biological ditches to absorb stormwater and reduce the load on sanitation systems. Man-made wetlands can also mitigate pollution caused by sewer overflows. Massive underground reservoirs can hold back storm runoff until plants have the capacity to handle it again.

Massive, centralized facilities lead to massive, centralized disasters – and the risk of disasters to public health and ecology.

But as governments allocate new infrastructure investments – such as those in the bipartisan infrastructure plan being developed by the U.S. Congress – they should also question whether it even makes sense to expand the centralized processing of people. wastewater in the future. Large, centralized systems can benefit from economies of scale, but that scale itself can be a handicap in the face of climate change and other threats such as terrorism.

One problem is that centralized treatment plants tend to be located in low areas, to take advantage of gravity, and close to bodies of water, to discharge their effluent. So storm surges and flooding can easily bring them down – and sometimes it takes weeks for them to work again. Drought also affects their operations: too little water can cause a stagnant sewage flow, and thirsty tree roots can enter underground pipes in search of a drink. In addition, in the event of a power failure, pumping stations and wastewater treatment plants can also become disconnected. And since centralized systems are virtually invisible to users, people continue to shower and flush even during announced blackouts, when the sewage they create will flow directly into rivers, lakes. and the sea. (And, anyway, what choice do they really have?)

Instead, the wastewater should go to the local level. New residential and commercial developments, in particular, can take advantage of innovations for buildings and neighborhoods that recycle wastewater for immediate use, its nutrients and energy used on-site. In my reporting on sanitation and the environment, I have come across a growing number of such projects, many of which are on a pilot scale, ranging from high tech to low tech.

In Portland, Oregon, a 657-unit luxury residential and commercial complex received a reimbursement of nearly $ 1.5 million from the city for integrating an off-grid system to avoid overloading more the century-old sewers of the city. A series of reservoirs, filters and man-made wetlands, which take pride of place in the main plaza, recycle the community’s wastewater for cooling, irrigation and flushing, reducing water consumption. more than 50% water. (In an emergency, the complex may flow into the city’s sanitary sewers.) Solid residues are transported off-site for reuse as fertilizer and energy.

When it comes to urban infrastructure, it is “possibly the largest and most advanced on-site wastewater treatment facility in the United States,” says Lynn Broaddus, sustainability consultant, infrastructure advocate distributed water supply company and currently President of the Water Environment Federation, an association of water quality professionals.

Large, centralized systems can benefit from economies of scale, but that scale itself can be a handicap in the face of climate change and other threats such as terrorism.

In Europe, a multi-country research project funded by the European Union, Run4Life – Recovery and Utilization of Nutrients for Low Impact Fertilizer – optimizes a more radical modular treatment concept that treats waste from vacuum toilets and water crushers saving water to produce biogas. and nutrients for fertilizers. Other wastewater, collected separately, can be cleaned, extracted for heat, and then reused.

Such local systems may, depending on the circumstances, consume less energy and emit less greenhouse gases than centralized systems. Some can be set up in a corner of a parking garage, or feed into lush greenhouse gardens. They can create local and 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-prone areas, could have more built-in redundancies, and be more agile in recovery. This would make it more resistant to extreme weather events and other shocks like the Los Angeles surge.

Finally, distributed systems can make wastewater management more flexible and modular, allowing them to shrink and grow with cities and further make them ‘future proof’.

If this approach sounds odd, consider that there is a tendency to locate almost every other type of infrastructure system, from agriculture to energy grids. Local wastewater also makes sense, for many of the same reasons. While more research and pilot projects will be useful in both assessing and raising awareness of decentralized systems, the change also requires a shift in incentives and regulations, which in most places currently favor traditional and centralized approaches.

Granted, distributed systems could and sometimes fail as centralized systems do. They would also need investment, maintenance and regulation like centralized systems. But small-scale facilities integrated into communities would be more visible to their users than large wastewater treatment plants on the outskirts of town, meaning people would be more likely to make the connection between their use of water. water and pollution. Community members could also spot failures faster and demand accountability.

And then they could go swimming at the beach.

Chelsea Wald, an award-winning science and environment journalist based in the Netherlands, is the author of “Pipe Dreams: The Urgent Global Quest to Transform the Toilet”. She received a 2018 grant from the European Journalism Center for Innovation in Development Reporting, funded by the Bill and Melinda Gates Foundation, and will receive honoraria to speak about her book at an upcoming Plumbing Manufacturers conference. International.


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