Water Quality Characteristic: Physical-Chemical-Biological

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• Scientists have devised a method of determining if water has been contaminated with sewage by identifying and measuring certain bacteria called fecal coliforms.
  

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• These bacteria are known to live in the intestines of mammals. The presence of fecal coliforms in water indicates that sewage is present and that other disease causing organisms may also be in the water.
  

12.Biological Indicators

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• Species that provide an indication as to the quality of the water based upon whether or not they can survive in it are referred to as biological indicators.
  
• Aquatic insects and other macroinvertebrates are often sampled in lakes and streams to assess the overall water quality. Other species, such as fish and algae are also used as biological indicators.