Source :

Micro-organisms of diverse aquatic life such as bacteria, fungi, and algae to higher organisms such as fish live in natural waters. In pure water, the density of these organisms are comparatively less when compared to the polluted water. The polluted waters, especially those of eutrophic (rich in minerals) waters contain a variety of micro-organisms. Eutrophic waters that are rich in nutrients can promote the growth of most of the aquatic organisms to large extend, similarly moderately polluted waters can develop the aquatic vegetation, fish and other organisms. But the contaminated waters from domestic sewage contain various pathogenic organisms most of the human intestinal pathogens cannot survive in the other environment except that of aquatic polluted water or sewage environment. The leakages in the drinking water sources and sewage systems can pollute the drinking water systems. The pathogenic organisms can easily enter the human system through the drinking water. These waters having pathogenic organisms can infect the human system with the water borne diseases.

Effects :

1.      Pathogenic organisms

         The pathogenic micro-organisms, especially water-borne type can survive in any kind of aquatic systems and can be carried away through the rivers also. Some of the water-borne disease spreading bacteria and the disease caused are given below.

Bacteria                                          Disease

Salmonella typhi                           Typhoid

Salmonella Paratyphoid             Paratyphoid

Vibrio cholerae                             Cholera

Escherichia coli                           Diarrhoea (children)

Shigella                                        Bacillary dysentery

One of the dreadful water-borne disease is jaundice which is caused by the Hepatitis virus .The parasite protozoan known by the name Entamoeba-histolytica causes amoebic dysentery (amoeabiasis) in human beings. It infects the large intestine of human being which produce a kind mucous and blood which comes out through the faeces. Through a cyclic process, the protozoa can get into the liver and affect it.

2.      Nuisance causing organisms

Nuisance causing organisms are mainly micro-organisms that can indirectly affect the water quality and affecting human health. This include algae, bacteria, protozoans etc. which can produce toxic secretions that are harmful for & spoils water . Some of the nuisance algal species are Microcystis, Euglena, Spirulina etc. Some of the micro-organisms the affects the taste and odour are given by their common names : blue-green algae, Non-motile green algae, Diatoms and Flagellates.

 Control measures

1. The use of algicides can prevent the growth of algae to a considerable amount. The algicides are organic or inorganic compounds such as

         Quaternary ammonium compounds (organic)

         Amide derivatives (organic)

         Quinines (organic)

         Substituted hydrocarbons (organic)

         Copper sulphate (Inorganic)

         Potassium permanganate (inorganic)

         Chlorine water (Inorganic)

Copper sulphate in minimum optimum dosage is the most efficient way for the control of algae-population.

   2.  Besides this , mechanical way of removing algae is through the filtration by rapid sand filters

  3.   Pathogenic & Virulent organisms can be killed by proper sewage treatment. The secondary and tertiary sewage treatments can control the harmful organisms present in it.

• Written by rashmi.
• In category General.
• 14 years ago.

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