Households received ceramic filters that fit on tables, or larger sand filters cemented outside their doors. Volunteers promoted water-boiling, handed out bottles of chlorine and educated people about threats lurking in even the clearest-looking untreated water. Then, in , came the bucket of cold water. A newly published review argued that there was little solid evidence that household water treatment in poor rural regions was working: Placebo-controlled trials in Ghana, Gambia and Brazil found no effect on incidence of diarrhea.
Brown recalls that he was giving a talk at the World Bank in Washington, DC, about the benefits of treating water at the household level when, even as he spoke, someone in the audience was circulating copies of the paper. More criticism followed. They used treatment tools incorrectly or inconsistently, and usage dropped sharply over time.
On site visits, when asked if they had treated their water in the last day, more than 70 percent said no. For public health workers and researchers, it was a huge conundrum.
They knew the technologies could make water safe—the methods worked well in laboratory settings—so what was stopping these simple solutions from taking hold in the real world, with the people who needed them most? That puzzle has spurred a sea change in research around water development. Questions of engineering and chemistry have given way to quite different questions about policy, maintenance—and the realities of human behavior. I don't think that solution exists. In , member states of the United Nations set a package of development goals including universal safe water by the end of the next decade, with the ideal being safe, piped water delivered to homes and communities.
The world is nowhere near on track. Most researchers, public health officials and development workers agree that household water treatment options can be crucial as interim solutions in emergencies or where no other resources are available—but experts are still divided on the role household water treatment should play in filling the gaps long-term.
An abundance of cheap solutions can mimic the process that water goes through at a modern large-scale municipal utility. Chlorination, filtering and disinfection by heating water in the sun can kill or remove more than 90 percent of microbial pathogens in laboratory settings, while boiling, when done properly, kills percent of the microbes causing diarrheal diseases. Durability is one of them. A study that evaluated use of ceramic filters in 13 villages in rural Cambodia found that filter use declined at a rate of two percent each month , due mostly to breakage of spigots, containers and ceramic filter elements.
Four years out, filtering had practically ceased. And a study of ceramic candle filters in a village in South Africa found that the filters stopped working properly months earlier than expected due to higher-than-expected levels of use. This water is cleaned through several steps, the first of these being screening. Here the water flows through a pipe with a screen, which acts as a sifter to remove the larger objects in it.
Then there is the flocculation or clarification, where chemicals are added which separate the smaller particles that were not eliminated during the screening process. The third process is filtration, wherein the water passes through fine sand which traps whatever remains of the chemicals used in the second step. The last and final step is the chlorination. Chlorine is added to the water to protect against any bacteria or other pollutants that may still be in the water.
At all stages in this process, samples of the water are taken and tested to assess whether the procedure is effective and the water is getting cleaned in a proper manner. The natural cleaning of water takes place as it moves from the ground, lakes, oceans and plants and gets transformed into clouds. As water travels through the ground, it gets filtered in a natural way, much like how it is in the filtration process where it is passed through sand. Water also gets naturally purified as it flows through some kinds of ecosystems, especially in the wetlands.
Edwards and Virginia Tech colleague Kelsey Pieper collected water-quality data from more than 2, wells across Virginia in and Some were fine. Others had lead levels of more than parts per billion. Homeowners are unlikely to ever realize they have such a problem with their own well.
The researchers reported those findings in in the Journal of Water and Health. To remove lead and other contaminants, well users often rely on point-of-use treatments. This is usually some type of filter. Some people may spring for the gold-standard treatment at home: a costly reverse osmosis system. By Laurel Hamers November 29, at am. The steps of water treatment The first step is usually to add coagulants Koh-AG-yu-lunts. Caring for your pet while caring for the planet is about more than buying recycled toys and organic dog food.
The California garbage dump project would have desecrated sacred tribal lands, destroyed vital wildlife habitat, and put local waters at risk. For drinking water, flood control, climate defense, habitat protection, fishing, swimming, and, of course, craft beer. We will keep you informed with the latest alerts and progress reports.
Learn the Truth About Tap. Trashing the Gregory Canyon Landfill. An Uphill Battle, and Persistence, in Flint. Thanks for signing up. You'll receive your first NRDC action alert and update email soon.
0コメント