purify

river water quality purification

to make the air clean, you have to use a purifier; to make river water clean, you must not use a purifier. as the Chinese saying goes: when the water is extremely clean to the extent of purification, there would be no fish. I guess if we just cleanse the river water, we might get rid of those rubbish and dirt.

some fellow worker suggests that cleansing is not feasible for the cleaning of water; so I worked out another term. since the river water might be polluted by household garbage and chemicals, the depollution process could be undertaken.

http://www.treesearch.fs.fed.us/pubs/9158

Title: Water decontamination

Author: Rowell, Roger

Date: 2004

Source: McGraw-Hill yearbook of science and technology, 2004. New York : McGraw-Hill, 2004: pages 372-373

Description: For 1.5 to 2.5 billion people in the world, lack of clean water is a critical issue. It is estimated that by the year 2025 there will be an additional 2.5 billion people who will live in regions already lacking sufficient clean water. In the United States today, it is estimated that 90% of citizens live within 10 mi of a body of contaminated water. Large numbers of point (single, identifiable) and nonpoint sources having low flow volume [50 gal (190 L) per minute or less] contribute significantly to these water contamination problems. These sites pose a major unsolved problem because they also can be intermittent, reducing the cost effectiveness of many current mitigation technologies. The northeastern United States–-with its large population, concentrated residential areas, industrial sites, livestock confinement operations, and the like-has many such sites where low volume-flow water runoff and discharges need to be treated. In addition, it is estimated that there are approximately 500,000 abandoned hard-rock mine sites in the United States, many of them located in or near watersheds where acid mine drainage may release heavy metals into thousands of public drinking water systems.