Two cause of water pollution

Pathogens

One of the most severe pollutants is the disease-causing microorganisms called pathogens. Pathogens are mostly bacteria, virus, and protozoa. Although bacteria are considered harmless if not beneficial, there are a few of pathogenic bacteria as well which enter the water bodies through sewers and sanitation systems. The water-borne pathogens cause several diseases such as diarrhea, gastrointestinal illness, etc.

  Organic Wastes

Organic water pollutants include food waste, detergents, leaves, grass, etc. They originate from domestic sewage, discharge from food processing factories and farm wastes which reach the water sources through runoff and pollute them. It is a fact that the bacteria decompose the complex organic matter into the simple organic matter. They consume oxygen which is dissolved in water. As the organic waste content in the water increases so does the count of decomposers. They use up a lot of oxygen which results in the depletion of oxygen content in water. This adversely affects the aquatic life.