Category: Micro Biology
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The water people use in their homes and factories gets dirty. Sewers carry much of the domestic waste water away. Many factories get rid of their waste water in a similar way. Most of this waste water ends up in natural water bodies,such as rivers, lakes and oceans. If it is not cleaned first, it can pollute the water and cause harmful effects.

• This waste water contains large amounts of organic waste from food and other materials and includes Carbohydrates, Fats, Proteins and micro organisms

Now lets ask some questions to ourselves...

  1. 1. Dis semination of pathogenic micro organisms
  2. 2.Water pollution due to accumulation of biodegradable material and their decomposition products
  3. 3.Decomposition which may consume large amounts of oxygen in water affecting aquatic organisms (high BOD – biological oxygen demand)
  4. 4.Anaerobic decomposition leading to bad smells
  5. 5.Natural water bodies are polluted and become useless for human needs.
  6. 6.When the nutrients in the waste water reach the natural water bodies, it may result in eutrophication and large algal blooms, which may result in serious damage to animal and plant life.

• It is a legal requirement in most countries that such waste waters are properly treated to a required standard before being discharged into natural waters



Now lets see the principles and main steps in purification of industrial waste water.

            1.Primary treatment

            2.Secondary treatment

 Primary treatment



 Secondary treatment


™ The liquid flowing out of primary treatment enters the secondary treatment stage


  1. 1.Activated sludge
  2. 2.Trickling filter.


  secondary treatment in purification of industrial waste water

 secondary treatment in purification of industrial waste water


™ In secondary treatment 75-95 % of organic material is oxidized.



™ The liquid flowing through these systems are then disinfected using Chlorine or Ozone and allowed to flow into natural waters

™ Sludge remaining from both treatments is sent to an anaerobic sludge digester where anaerobic decomposition convert the organic material in the sludge finally to methane and CO2 ( bio-gas)

Typical bio-gas contains CH4, CO2, H2S, N2, H2

™ Digested sludge can be used as fertilizer


A mind map for this section will make it easy for sure!!

 purification of industrial waste water



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