Citation

-http://www.buzzle.com/articles/different-types-of-water-pollution.html
-http://greenliving.lovetoknow.com/Types_of_Water_Pollution
-www.google.com.sa
-www.water-pollution.org.uk
-http://en.wikipedia.org/wiki/Water_treatment
-http://www.buzzle.com/articles/ways-to-prevent-water-pollution.html
-http://eschooltoday.com/pollution/water-pollution/prevention-of-water- pollution.html
-http://www.nrdc.org/water