Earlier this year, an obscure United Nations document, the World Water Development Report, unexpectedly made headlines around the world. The report made the startling claim that the world would face a 40 percent shortfall in freshwater in as soon as 15 years. Crops would fail. Businesses dependent on water would fail. Illness would spread. A financial crash was likely, as was deepening poverty for those just getting by.
The UN also concluded that the forces destroying the world’s freshwater supply were not strictly meteorological, but largely the result of human activity. That means that with some changes in how water is managed, there is still time—very little, but enough—for children born this year to graduate from high school with the same access to clean water their parents enjoyed.
Though the UN looked at the issue across the globe, the solutions it recommended—capturing rainwater, recycling wastewater, improving sewage and plumbing, and more—need to be implemented locally. Some of the greatest challenges will come in cities, where bursting populations strain systems designed to supply far fewer people and much of the clean water available is lost to waste and shoddy, centuries-old infrastructure.
We’ve looked at eight cities facing different though representative challenges. The amount of water in the Earth’s atmosphere is more or less fixed, meaning that as populations and economies grow, what we have needs to be clean, available, and conserved. Economies, infrastructure, river systems and climates vary from place to place, and the solutions will have to as well. Here is how eight of the world’s major cities are running out of water, and trying to save it.
Tokyo shouldn’t have a water problem: Japan’s capital enjoys average precipitation similar to that of Seattle or London. But all that rainfall is compressed into just four months of the year, in two short seasons of monsoon and typhoon. Capturing and storing so much water in such a short period in an area four times as dense as California would be a challenge anywhere. One weak rainy season means droughts—and those are now coming about once every decade.
Betting on the rain will be a precarious strategy for the world’s most populous city and its suburbs, home to more than 30 million people. When the four rivers feeding Tokyo run low, crisis conditions arrive fast. Though efficient, 70 percent of Tokyo’s 16,000-mile-long plumbing system depends on surface water (rivers, lakes, and distant snowpack). With only 30 percent of the city’s water coming from underground aquifers and wells, there are not enough alternative sources to tap during these new cyclical droughts.
The Japanese government has so far proved forward-thinking, developing one of the world’s most aggressive programs for capturing rainwater. In Sumida, a Tokyo district that often faces water shortages, the 90,000-square-foot roof of Ryogoku Kokugikan arena is designed to channel rainfall to a tank, where it’s pumped inside the stadium for nonpotable use.
Somewhat more desperate-seeming is a plan to seed clouds, prodding the environment to do what it isn’t doing naturally. Though tested in 2013 with success, the geo-engineering hack is a source of controversy; scientists debate whether the technique could produce enough rain to make much of a difference for such a large population.
Though most Americans’ concern with water shortage in the U.S. is firmly focused on California at the moment, a crisis is brewing in the last place you’d figure: South Florida, which annually gets four times as much rain, on average, as Los Angeles and about three times as much as San Francisco.
But according to the U.S. Geological Survey, the essential Biscayne Aquifer, which provides water to the Miami–Dade County area, is falling victim to saltwater intrusion from the Atlantic Ocean. Despite the heavy rains replenishing the aquifer year-round, if enough saltwater enters, all of it will become unusable.
The problem arose in the early 20th century, after swamps surrounding the city were drained. Osmosis essentially created a giant sucking effect, drawing the Atlantic into the coastal soils. Measures to hold the ocean back began as early as the 1930s, but seawater is now bypassing the control structures that were installed and leaking into the aquifer. The USGS has made progress mapping the sea water intrusion, but ameliorating it seems a ways off. “As sea level continues to rise and the demand for freshwater increases, the measures required to prevent this intrusion may become more difficult [to implement],” the USGS noted in a press release.
London faces a rapidly growing population wringing every last drop out of centuries-old plumbing. Water managers estimate they can meet the city’s needs for the next decade but must find new sources by 2025—even sooner than the rest of the world, by the U.N.’s measure. London’s utility, Thames Water, looked into recycled water—aka “toilet-to-tap”—but, being English, found it necessary first to politely ask people if they’d mind.
At least four urban districts in California use recycled water, which is treated, re-treated, and treated again to be cleaner than conventional supplies before being pumped into groundwater or other supply sources. The so-called “yuck factor” could be an impediment to this solution spreading to London and elsewhere.
Five thousand years ago, an ample water supply and a fertile delta at the mouth of the Nile supported the growth of one of the world’s great civilizations. Today, while 97 percent of Egypt’s water comes from the great river, Cairo finds itself downstream from at least 50 poorly regulated factories, agricultural waste, and municipal sewage systems that drain into it.
Though Cairo gets most of the attention, a UNICEF-World Health Organization study released earlier this year found that rural areas to the city’s south, where more than half of Egyptians live, depend on the river not just for irrigation and drinking water but also for waste disposal. Engineer Ayman Ramadan Mohamed Ayad has noted that while most wastewater discharged into the Nile upriver from Cairo is untreated, the river’s enormous size has historically been sufficient to dilute the waste to safe levels (and Cairo’s municipal system treats the water it draws from the river). Ayad argues, however, that as the load increases—with 20 million people now discharging their wastes to the Nile—this will no longer be possible. The African Development Bank recently funded programs to chlorinate wastewater before it’s dumped in the river, but more will need to be done.
On the demand side, more than 80 percent of the water taken from the Nile each year is used for irrigation, mostly the inefficient method of just flooding fields, which loses significant amounts to evaporation. Two years ago, initial steps were taken to modernize irrigation techniques upriver. Those programs have yet to show much progress, however.
When it rains in Brazil, it pours. In São Paulo, where in an average year it rains more than it does in the U.S. Pacific Northwest, drains can’t handle the onslaught, and what could be the source of desperately needed drinking water becomes instead the menace of urban floodwater.
With the worst drought in a century now in its second year, São Paulo’s reservoirs are at barely a quarter of capacity, down from 40 percent a year ago. Yet the city still sees heavy rainstorms. But reservoirs outside the city are often polluted and are too small even at capacity to supply the metropolitan area of 20 million. Asphalt covering the city and poor drainage lead to heavy floods on city streets after as little as a quarter-inch of rain. It’s hard to believe a drought is under way if your house is ankle-deep in water, so consumers haven’t been strident about conservation. The apparent paradox of flooded streets and empty reservoirs will likely fuel an ongoing debate over proposed rationing.
Poor air quality isn’t the only thing impinging Beijing citizens’ ability to enjoy a safe environment. The city’s second-largest reservoir, shut down in 1997 because of pollution from factories and agriculture, has not been returned to use.
Ensuring the cleanliness of its water is even more crucial in China than elsewhere, as there is little it can afford to lose: With 21 percent of the world’s population, China has only 6 percent of its freshwater—a situation that’s only going to get worse, as it’s raining less in northern China than it was a century ago, and glaciers in Tibet, once the largest system outside the Antarctic and Greenland and a key source of drinking water in the country’s south and west, are receding even faster than predicted. The UN Environment Programme estimates that nationally, Chinese citizens can rely on getting just one-quarter to one-third of the amount of clean water the rest of the world uses daily.
Hope emerged, however, from a 2013 study from Montreal’s McGill University, which found that an experimental program targeting farmers outside the capital showed promising results over nearly two decades. The vast Miyun reservoir, 100 miles outside Beijing, had seen its reserves reduced by nearly two-thirds because of increasing irrigation demands—while becoming polluted by agricultural runoff. Revenue from a tax on major water users in Beijing was spent paying farmers upstream from Miyun to grow corn instead of rice, which requires more water and creates more runoff.
Over the following 15 years, the study authors wrote, “fertilizer runoff declined sharply while the quantity of water available to downstream users in Beijing and surrounding areas increased.” Farmer income was not significantly affected, and cleaner water downstream led to higher earnings for consumers in the city despite the tax.
Earlier this year, a report by India’s comptroller and auditor general found that the southern city was losing more than half its drinking water to waste through antiquated plumbing systems. Big losses from leaks aren’t uncommon—Los Angeles loses between 15 and 20 percent—but the situation in Bangalore is more complicated. A technology boom has attracted new residents, leading to new housing construction. Entire apartment blocks are going up faster than local officials can update the plumbing to handle additional strain on the water and sewage systems.
Photo credit: Shutterstock
Bangalore’s clean-water challenges illustrate a dynamic that’s repeating itself across the world’s second-largest nation. India’s urban population will grow from 340 million to 590 million by 2030, according to a 2010 McKinsey study. To meet the clean-water needs of all the new city dwellers, the global consulting firm found, the government will have to spend $196 billion—more than 10 percent of the nation’s annual GDP. (McKinsey has a potential financial interest in India’s infrastructure, so its numbers may be inflated).
In Bangalore, they’re already behind schedule. The newspaper The Hindu reported in March that a 2002 plan to repair the existing system and recover the missing half of Bangalore’s freshwater had yet to be implemented.
Gravity always wins. At more than 7,000 feet above sea level, Mexico City gets nearly all its drinking water by pumping it laboriously uphill from aquifers as far as 150 miles away. The engineering challenge of hauling that much water into the sky adds to the difficulty of supplying more than 20 million residents through an aging system. Mexico City’s public works loses enough water every second—an estimated 260 gallons—to supply a family of four for a day, according to CONAGUA, Mexico’s national water commission. CONAGUA estimates that between 30 and 40 percent of the capital’s potable water is lost to leaks and spills. The good news is that leaks can be fixed.
Photo credit: Shutterstock
Water quality remains a worry, however. Unsurprisingly, companies selling bottled water have done very well in Mexico. The economy growing around the lack of potable water has attracted companies such as Coca-Cola and France’s Danone, whose Bonafont (“good spring”) brand is advertised in Mexico as a weight-loss aid. (Toting a bottle will help you “feel thinner anywhere,” according to a popular television ad).
Meanwhile, disputes over who will get access to underground supplies have turned violent: In February 2014, residents of the town of San Bartolo Atepehuacan, on Mexico City’s outskirts, clashed with police over a waterworks project they feared would divert local springs to the city’s business district. At least 100 people were injured and five arrested as the disturbances continued for more than three months.
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By Frank La Sorte and Kyle Horton
Millions of birds travel between their breeding and wintering grounds during spring and autumn migration, creating one of the greatest spectacles of the natural world. These journeys often span incredible distances. For example, the Blackpoll warbler, which weighs less than half an ounce, may travel up to 1,500 miles between its nesting grounds in Canada and its wintering grounds in the Caribbean and South America.
Blackpoll warbler. PJTurgeon / Wikipedia<p>We used this information to determine how the number of migratory bird species varies based on each city's level of <a href="https://www.britannica.com/science/light-pollution" target="_blank" rel="noopener noreferrer">light pollution</a> – brightening of the night sky caused by artificial light sources, such as buildings and streetlights. We also explored how species numbers vary based on the quantity of tree canopy cover and impervious surface, such as concrete and asphalt, within each city. Our findings show that cities can help migrating birds by planting more trees and reducing light pollution, especially during spring and autumn migration.</p>
Declining Bird Populations<p>Urban areas contain numerous dangers for migratory birds. The biggest threat is the risk of <a href="https://doi.org/10.1650/CONDOR-13-090.1" target="_blank">colliding with buildings or communication towers</a>. Many migratory bird populations have <a href="http://dx.doi.org/10.1126/science.aaw1313" target="_blank">declined over the past 50 years</a>, and it is possible that light pollution from cities is contributing to these losses.</p><p>Scientists widely agree that light pollution can <a href="https://doi.org/10.1073/pnas.1708574114" target="_blank">severely disorient migratory birds</a> and make it hard for them to navigate. Studies have shown that birds will cluster around brightly lit structures, much like insects flying around a porch light at night. Cities are the <a href="https://doi.org/10.1002/fee.2029" target="_blank" rel="noopener noreferrer">primary source of light pollution for migratory birds</a>, and these species tend to be more abundant within cities <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13792" target="_blank" rel="noopener noreferrer">during migration</a>, especially in <a href="https://doi.org/10.1016/j.landurbplan.2020.103892" target="_blank" rel="noopener noreferrer">city parks</a>.</p>
Composite image of the continental U.S. at night from satellite photos. NASA Earth Observatory images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA's Goddard Space Flight Center
The Power of Citizen Science<p>It's not easy to observe and document bird migration, especially for species that migrate at night. The main challenge is that many of these species are very small, which limits scientists' ability to use electronic tracking devices.</p><p>With the growth of the internet and other information technologies, new data resources are becoming available that are making it possible to overcome some of these challenges. <a href="https://doi.org/10.1038/d41586-018-07106-5" target="_blank">Citizen science initiatives</a> in which volunteers use online portals to enter their observations of the natural world have become an important resource for researchers.</p><p>One such initiative, <a href="https://ebird.org/home" target="_blank" rel="noopener noreferrer">eBird</a>, allows bird-watchers around the globe to share their observations from any location and time. This has produced one of the <a href="https://doi.org/10.1111/ecog.04632" target="_blank" rel="noopener noreferrer">largest ecological citizen-science databases in the world</a>. To date, eBird contains over 922 million bird observations compiled by over 617,000 participants.</p>
Light Pollution Both Attracts and Repels Migratory Birds<p>Migratory bird species have evolved to use certain migration routes and types of habitat, such as forests, grasslands or marshes. While humans may enjoy seeing migratory birds appear in urban areas, it's generally not good for bird populations. In addition to the many hazards that exist in urban areas, cities typically lack the food resources and cover that birds need during migration or when raising their young. As scientists, we're concerned when we see evidence that migratory birds are being drawn away from their traditional migration routes and natural habitats.</p><p>Through our analysis of eBird data, we found that cities contained the greatest numbers of migratory bird species during spring and autumn migration. Higher levels of light pollution were associated with more species during migration – evidence that light pollution attracts migratory birds to cities across the U.S. This is cause for concern, as it shows that the influence of light pollution on migratory behavior is strong enough to increase the number of species that would normally be found in urban areas.</p><p>In contrast, we found that higher levels of light pollution were associated with fewer migratory bird species during the summer and winter. This is likely due to the scarcity of suitable habitat in cities, such as large forest patches, in combination with the adverse affects of light pollution on bird behavior and health. In addition, during these seasons, migratory birds are active only during the day and their populations are largely stationary, creating few opportunities for light pollution to attract them to urban areas.</p>
Trees and Pavement<p>We found that tree canopy cover was associated with more migratory bird species during spring migration and the summer. Trees provide important habitat for migratory birds during migration and the breeding season, so the presence of trees can have a strong effect on the number of migratory bird species that occur in cities.</p><p>Finally, we found that higher levels of impervious surface were associated with more migratory bird species during the winter. This result is somewhat surprising. It could be a product of the <a href="https://www.epa.gov/heatislands" target="_blank">urban heat island effect</a> – the fact that structures and paved surfaces in cities absorb and reemit more of the sun's heat than natural surfaces. Replacing vegetation with buildings, roads and parking lots can therefore make cities significantly warmer than surrounding lands. This effect could reduce cold stress on birds and increase food resources, such as insect populations, during the winter.</p><p>Our research adds to our understanding of how conditions in cities can both help and hurt migratory bird populations. We hope that our findings will inform urban planning initiatives and strategies to reduce the harmful effects of cities on migratory birds through such measures as <a href="https://www.arborday.org/programs/treecityusa/index.cfm" target="_blank" rel="noopener noreferrer">planting more trees</a> and initiating <a href="https://aeroecolab.com/uslights" target="_blank" rel="noopener noreferrer">lights-out programs</a>. Efforts to make it easier for migratory birds to complete their incredible journeys will help maintain their populations into the future.</p><p><em><span style="background-color: initial;"><a href="https://theconversation.com/profiles/frank-la-sorte-1191494" target="_blank">Frank La Sorte</a> is a r</span>esearch associate at the </em><em>Cornell Lab of Ornithology, Cornell University. <a href="https://theconversation.com/profiles/kyle-horton-1191498" target="_blank">Kyle Horton</a> is an assistant professor of Fish, Wildlife, and Conservation Biology at the Colorado State University.</em></p><p><em></em><em>Disclosure statement: Frank La Sorte receives funding from The Wolf Creek Charitable Foundation and the National Science Foundation (DBI-1939187). K</em><em>yle Horton does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</em></p><p><em>Reposted with permission from <a href="https://theconversation.com/cities-can-help-migrating-birds-on-their-way-by-planting-more-trees-and-turning-lights-off-at-night-152573" target="_blank">The Conversation</a>. </em></p>
EcoWatch Daily Newsletter
By Lynne Peeples
Editor's note: This story is part of a nine-month investigation of drinking water contamination across the U.S. The series is supported by funding from the Park Foundation and Water Foundation. Read the launch story, "Thirsting for Solutions," here.
In late September 2020, officials in Wrangell, Alaska, warned residents who were elderly, pregnant or had health problems to avoid drinking the city's tap water — unless they could filter it on their own.
Unintended Consequences<p>Chemists first discovered disinfection by-products in treated drinking water in the 1970s. The trihalomethanes they found, they determined, had resulted from the reaction of chlorine with natural organic matter. Since then, scientists have identified more than 700 additional disinfection by-products. "And those only represent a portion. We still don't know half of them," says Richardson, whose lab has identified hundreds of disinfection by-products. </p>
What’s Regulated and What’s Not?<p>The U.S. Environmental Protection Agency (EPA) currently regulates 11 disinfection by-products — including a handful of trihalomethanes (THM) and haloacetic acids (HAA). While these represent only a small fraction of all disinfection by-products, EPA aims to use their presence to indicate the presence of other disinfection by-products. "The general idea is if you control THMs and HAAs, you implicitly or by default control everything else as well," says Korshin.</p><p>EPA also requires drinking water facilities to use techniques to reduce the concentration of organic materials before applying disinfectants, and regulates the quantity of disinfectants that systems use. These rules ultimately can help control levels of disinfection by-products in drinking water.</p>
Click the image for an interactive version of this chart on the Environmental Working Group website.<p>Still, some scientists and advocates argue that current regulations do not go far enough to protect the public. Many question whether the government is regulating the right disinfection by-products, and if water systems are doing enough to reduce disinfection by-products. EPA is now seeking public input as it considers potential revisions to regulations, including the possibility of regulating additional by-products. The agency held a <a href="https://www.epa.gov/dwsixyearreview/potential-revisions-microbial-and-disinfection-byproducts-rules" target="_blank">two-day public meeting</a> in October 2020 and plans to hold additional public meetings throughout 2021.</p><p>When EPA set regulations on disinfection by-products between the 1970s and early 2000s, the agency, as well as the scientific community, was primarily focused on by-products of reactions between organics and chlorine — historically the most common drinking water disinfectant. But the science has become increasingly clear that these chlorinated chemicals represent a fraction of the by-product problem.</p><p>For example, bromide or iodide can get caught up in the reaction, too. This is common where seawater penetrates a drinking water source. By itself, bromide is innocuous, says Korshin. "But it is extremely [reactive] with organics," he says. "As bromide levels increase with normal treatment, then concentrations of brominated disinfection by-products will increase quite rapidly."</p><p><a href="https://pubmed.ncbi.nlm.nih.gov/15487777/" target="_blank">Emerging</a> <a href="https://pubs.acs.org/doi/10.1021/acs.est.7b05440" target="_blank" rel="noopener noreferrer">data</a> indicate that brominated and iodinated by-products are potentially more harmful than the regulated by-products.</p><p>Almost half of the U.S. population lives within 50 miles of either the Atlantic or Pacific coasts, where saltwater intrusion can be a problem for drinking water supplies. "In the U.S., the rule of thumb is the closer to the sea, the more bromide you have," says Korshin, noting there are also places where bromide naturally leaches out from the soil. Still, some coastal areas tend to be spared. For example, the city of Seattle's water comes from the mountains, never making contact with seawater and tending to pick up minimal organic matter.</p><p>Hazardous disinfection by-products can also be an issue with desalination for drinking water. "As <a href="https://ensia.com/features/can-saltwater-quench-our-growing-thirst/" target="_blank" rel="noopener noreferrer">desalination</a> practices become more economical, then the issue of controlling bromide becomes quite important," adds Korshin.</p>
Other Hot Spots<p>Coastal areas represent just one type of hot spot for disinfection by-products. Agricultural regions tend to send organic matter — such as fertilizer and animal waste — into waterways. Areas with warmer climates generally have higher levels of natural organic matter. And nearly any urban area can be prone to stormwater runoff or combined sewer overflows, which can contain rainwater as well as untreated human waste, industrial wastewater, hazardous materials and organic debris. These events are especially common along the East Coast, notes Sydney Evans, a science analyst with the nonprofit Environmental Working Group (EWG, a collaborator on <a href="https://ensia.com/ensia-collections/troubled-waters/" target="_blank">this reporting project</a>).</p><p>The only drinking water sources that might be altogether free of disinfection by-products, suggests Richardson, are private wells that are not treated with disinfectants. She used to drink water from her own well. "It was always cold, coming from great depth through clay and granite," she says. "It was fabulous."</p><p>Today, Richardson gets her water from a city system that uses chloramine.</p>
Toxic Treadmill<p>Most community water systems in the U.S. use chlorine for disinfection in their treatment plant. Because disinfectants are needed to prevent bacteria growth as the water travels to the homes at the ends of the distribution lines, sometimes a second round of disinfection is also added in the pipes.</p><p>Here, systems usually opt for either chlorine or chloramine. "Chloramination is more long-lasting and does not form as many disinfection by-products through the system," says Steve Via, director of federal relations at the American Water Works Association. "Some studies show that chloramination may be more protective against organisms that inhabit biofilms such as Legionella."</p>
Alternative Approaches<p>When he moved to the U.S. from Germany, Prasse says he immediately noticed the bad taste of the water. "You can taste the chlorine here. That's not the case in Germany," he says.</p><p>In his home country, water systems use chlorine — if at all — at lower concentrations and at the very end of treatment. In the Netherlands, <a href="https://dwes.copernicus.org/articles/2/1/2009/dwes-2-1-2009.pdf" target="_blank">chlorine isn't used at all</a> as the risks are considered to outweigh the benefits, says Prasse. He notes the challenge in making a convincing connection between exposure to low concentrations of disinfection by-products and health effects, such as cancer, that can occur decades later. In contrast, exposure to a pathogen can make someone sick very quickly.</p><p>But many countries in Europe have not waited for proof and have taken a precautionary approach to reduce potential risk. The emphasis there is on alternative approaches for primary disinfection such as ozone or <a href="https://www.pbs.org/wgbh/nova/article/eco-friendly-way-disinfect-water-using-light/" target="_blank" rel="noopener noreferrer">ultraviolet light</a>. Reverse osmosis is among the "high-end" options, used to remove organic and inorganics from the water. While expensive, says Prasse, the method of forcing water through a semipermeable membrane is growing in popularity for systems that want to reuse wastewater for drinking water purposes.</p><p>Remucal notes that some treatment technologies may be good at removing a particular type of contaminant while being ineffective at removing another. "We need to think about the whole soup when we think about treatment," she says. What's more, Remucal explains, the mixture of contaminants may impact the body differently than any one chemical on its own. </p><p>Richardson's preferred treatment method is filtering the water with granulated activated carbon, followed by a low dose of chlorine.</p><p>Granulated activated carbon is essentially the same stuff that's in a household filter. (EWG recommends that consumers use a <a href="https://www.ewg.org/tapwater/reviewed-disinfection-byproducts.php#:~:text=EWG%20recommends%20using%20a%20home,as%20trihalomethanes%20and%20haloacetic%20acids." target="_blank" rel="noopener noreferrer">countertop carbon filter</a> to reduce levels of disinfection by-products.) While such a filter "would remove disinfection by-products after they're formed, in the plant they remove precursors before they form by-products," explains Richardson. She coauthored a <a href="https://pubs.acs.org/doi/10.1021/acs.est.9b00023" target="_blank" rel="noopener noreferrer">2019 paper</a> that concluded the treatment method is effective in reducing a wide range of regulated and unregulated disinfection by-products.</p><br>
Greater Cincinnati Water Works installed a granulated activated carbon system in 1992, and is still one of relatively few full-scale plants that uses the technology. Courtesy of Greater Cincinnati Water Works.<p>Despite the technology and its benefits being known for decades, relatively few full-scale plants use granulated active carbon. They often cite its high cost, Richardson says. "They say that, but the city of Cincinnati [Ohio] has not gone bankrupt using it," she says. "So, I'm not buying that argument anymore."</p><p>Greater Cincinnati Water Works installed a granulated activated carbon system in 1992. On a video call in December, Jeff Swertfeger, the superintendent of Greater Cincinnati Water Works, poured grains of what looks like black sand out of a glass tube and into his hand. It was actually crushed coal that has been baked in a furnace. Under a microscope, each grain looks like a sponge, said Swertfeger. When water passes over the carbon grains, he explained, open tunnels and pores provide extensive surface area to absorb contaminants.</p><p>While the granulated activated carbon initially was installed to address chemical spills and other industrial contamination concerns in the Ohio River, Cincinnati's main drinking water source, Swertfeger notes that the substance has turned out to "remove a lot of other stuff, too," including <a href="https://ensia.com/features/drinking-water-contamination-pfas-health/" target="_blank" rel="noopener noreferrer">PFAS</a> and disinfection by-product precursors.</p><p>"We use about one-third the amount of chlorine as we did before. It smells and tastes a lot better," he says. "The use of granulated activated carbon has resulted in lower disinfection by-products across the board."</p><p>Richardson is optimistic about being able to reduce risks from disinfection by-products in the future. "If we're smart, we can still kill those pathogens and lower our chemical disinfection by-product exposure at the same time," she says.</p><p><em>Reposted with permission from </em><em><a href="https://ensia.com/features/drinking-water-disinfection-byproducts-pathogens/" target="_blank">Ensia</a>. </em><a href="https://www.ecowatch.com/r/entryeditor/2649953730#/" target="_self"></a></p>
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