How Nature Does It
Water Pollution: Sun-Powered Cleanup Crews
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Wetlands contain a variety of plants, animals, and bacteria. These help clean the water that runs through, giving wetlands a natural ability to filter out many pollutants |
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To clean water naturally, a series of tanks are set up to create mini-ecosystems. Each tank contains plants, animals, and microorganisms that can clean the water of specific pollutants. |
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Photo courtesy of Worrell Water Technologies The Emmen Zoo, in the Netherlands, uses an indoor Living Machine ® system to clean 832,790.6 L (220,000 gal) of wastewater each day. The water is then reused for the toilet flushing, among other things. The zoo now uses 84% less water than it used before installing the Living Machine. |
Although nearly three-fourths of the Earth is covered in water, only 3% of that is fresh water. The rest is either frozen or too salty for humans to drink. That relatively small amount of water moves continuously through the Earth’s water cycle (for more information see Drinking Water from the Sea). There, it is made ready for reuse by the more than 6 billion people on this planet. This human/nature partnership works as long as we don’t overload the water supply with pollutants such as toxic chemicals and other nonbiodegradable wastes.
However, we are exploiting water at an alarming rate, and the consequences are often tragic. Several million people die each year from waterborne diseases, and a wide variety of animal species are harmed by polluted water.
The good news is that nature knows how to clean water. Wetlands—land that is either saturated or covered in water for a part of the year—are water-cleaning machines. They not only hold water like a sponge, which helps prevent flooding, but they also act as a kind of natural filter. The plants and bacteria that live in wetlands are able to break down or absorb damaging pollutants before the water enters our lakes, rivers, and streams.
What can we learn from how nature cleans its water? A growing number of scientists have asked the same question.
How Nature Cleans Water
To find out how nature cleans water, marine biologist John Todd studied the wetlands and tide pools near his home in Cape Cod, Massachusetts. He also looked at the fish ponds and aquatic systems used for thousands of years by farmers in China and other parts of Asia.
Todd learned that species in different ecosystems—such as those in streams, ponds, marshes, and tide pools—have remarkable capacities to self-clean and self-repair. He found that plants such as rushes filter out suspended materials in the water. Others absorb toxic metals such as mercury and lead, and still others produce antibodies that kill organisms capable of causing disease.
As we all know, wastes from most modern buildings flow out into the environment, either through a municipal treatment system, or a septic system or, in the worst cases, into nearby waterways. These solid and liquid wastes must be treated to prevent damage to surrounding ecosystems. What if, instead of these wastes being piped to wastewater treatment plants, a system could be designed to mimic the self-cleansing cycles of wetlands, bogs, and tide pools?
Thus, John Todd and his colleagues at the New Alchemy Institute invented Living Machines to do the same job as nature. Using a collection of tanks that hold different aquatic ecosystems, Living Machines (also known as Eco-Machines) take black water, or sewage, and return it to its natural state, unpolluted by human waste.
So how do Living Machines work? The tanks are teeming with grasses, algae, live plants, goldfish, freshwater shrimp, and snails, as well as a wide variety of microorganisms and bacteria. Each tank forms a separate mini-ecosystem that is designed to break down the inorganic matter in the water. The primary source of energy for these machines is sunlight.
Wastewater progresses through the different tanks, which are linked through connector tubes. Wastes generated by the residents of one tank flow through the connector tubes and become food for the residents of another. After about a week of filtering, the waste is broken down into nutrients and food for algae, bugs, snails, and aquatic plants. The formerly mucky water is now considered gray water. You can’t drink it, but it can be used for irrigation and to flush toilets.
Living Machines can be small enough to fit in a classroom or large enough to process the wastewater for an entire village. They can even be part of a large city’s water-treatment system.
Learn more about Living Machines, at the following Web sites:
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Watershed • Watersheds play an important role in our everyday lives. • Some Schlumberger sites are recycling water.
Wastewater
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