What is wastewater treatment?

Water pollution is caused by domestic sewage and industrial sewage. The term sullage is applied to waste water which does not contain human excreta. The basic objectives of treatment of waste water is Industrial or municipal to bring the quality of water to an allowable level as prescribed by environmental laws.

Water Pollution Project | HCDE 333

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Aims of Wastewater Treatment:

  1. Removal the suspended particulars matter.
  2. Reduce the organic matter through decomposition y bacteria into inorganic compounds.
  3. Produce an effluent free from pathogens and which can be disposed of without any rise to environment and health.

Primary Treatment:

It includes physical separation of suspended materials by screening flocculation, sedimentation flotation and filtration. The water is first treated with alum FeCl3, to precipitate suspended particles.


Secondary Treatment:

It involves biological process like removal of biodegradable organics colloidal or dissolved biological method or removal of certain class of compounds whereby biochemical or biological oxygen demand (BOD) is reduces tricking filter process and the activated sludge process are the more important techniques of secondary of waste water .

Tertiary Treatment:

It involves physical chemical and biological process for the removal of nitrogenous, phosphatic and other inorganic pollutants, removal of color, odor and removal of the remaining organic pollutants.


Purification of water: Water is called otable or acceptable for drinking when it is free from pathogens and harmful chemical substances. All the three harmful chemical substances. All the three sources of water via rain; surface water and ground water contain imparities which have to be purified before use for drinking and other domestic purposes.

Purification of Water:


Storage in natural or artificial reservoirs, purification can be done. It allows the suspended particles to settle down penetration of light helps in photosynthesis by small plank tonic plants and the oxygen content in water increases. However storage for longer period will result in growth of algae.



Filtration is done by the biological or slows and filter and the rapid sand or mechanical filter. Supernatural or raw water flows downward through the sand bed and during such percolation of water, a number of purification processes such as mechanical screening, sedimentation, adsorption, oxidation and bacterial action takes place. During filtration a biological lay and develops with sand containing algae and bacteria which remove organic matter in the sand.


Chlorination the addition of chlorine to water and a supplement to sand filtration kills pathogenic bacteria. Chlorine also oxidizes iron, manganese and hydrogen sulfides destroys some odor producing constituents and control algae.


Boiling of water kills all bacteria spores, cysts and ova. It also removes the temporary hardness of water by precipitating calcium carbonate.

Chemical disinfection:

The water can be disinfected with many chemicals like lodine, potassium permanganate and chlorine. Chlorination of water can be done using bleaching power iodine may be used for emergency disinfection…

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