How Is Water Purified in Nature?
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Riparian Zones
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One of nature's many ways of purifying water is through riparian zones. These stream-side forests are living water filters that soak up sediments and store and transport nutrients, as well as absorb pollutants carried in runoff from adjacent lands. As water moves through a riparian forest, the trees and plants interact with traveling sediments in the runoff. Metals and other pollutants are filtered from the water and deposited along the stream's banks. This settling process can reduce nitrogen concentration by up to 90 percent and can lower phosphorus by as much as 50 percent. The loss of riparian zones to industrialization and paved surfaces can reduce the ability of streams to cleanse themselves. Without these sponge-like ecosystems, stream levels and lake flows would become irrevocably contaminated, killing all plant and animal life nearby.
Microorganisms
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Certain bacteria can break down nutrients, metals and chemical contaminants found in water. Like chemical engineers, microorganisms such as lactic acid bacteria, photosynthetic bacteria and yeast transform pollutants into more usable forms. For example, Japan has become a forerunner in using Effective Microorganisms, or EMs, to purify public water sources. More than 600 cities and towns in Japan use Effective Microorganisms to reduce waste from marine industrialization and improve the quality of household water. Countries such as Egypt that depend heavily on a single water source can benefit greatly from microorganisms in the water. Many cities in Egypt are using Effective Microorganisms to transform city waste to fertilizer and recycled water for irrigation.
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Constructed Wetlands
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Low-lying wetlands remove 20 percent to 60 percent of metals from water, retain 80 percent to 90 percent of runoff sediment and prevent 70 percent to 90 percent of nitrogen from entering waterways. Wetlands also support a diverse collection of plants and animals, many of which are imperiled. The advance of industrialization not only threatens these species but endangers the natural purification cycle of water. To combat this threat, organizations such as the Ecological Society of America support the idea of artificial wetlands. Constructed wetlands come from a branch of science known as biomimicry, which borrows principles from nature to improve human interaction with our world. These carefully constructed ecosystems can takes several years to reach their full maturity. In Arizona, artificial wetlands are being used to treat waste water. The state has gone from four constructed wetlands in 1990 to 26 in recent years. Although artificial wetlands are less effective than riparian zones and natural wetlands, the ingenuity of their design can help restore natural environments and purify water in habitats damaged by industrialization.
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- Photo Credit Image Courtesy of Jay DeLong and NANFA
