Areation is essentially a physical or mechanical method by which water is brought in close contact with air so by as to absorb oxygen for the reduction of taste odour etc.By virtue of oxidation and explusion.
The specific objectives of areation are listed below:
1.To reduce late sand odour caused by volatile compound and dissloved gases like hydrogen,sulphide,carbon dioxide and ammonia etc.
2.To oxidise organic matter
3.To convert dissloved iron and managese into insoluble and setteable from by oxidation,so that they can be removed afterwards in sedimentation thanks and filter beds.
4.To remove corrosive nature of water by releasing gases like carbon dioxide and hydrogen, sulphide.
5.To increase dissloved oxygen content of water and makes fresh.
The effectiveness of areation depend a on number of parameters as like a.Ph value b. Temparatur c.Degree saturation deficit d.Time of areation etc.
What are the types of areation
1.casecade areation:
Water is made to fall in the form of thin sheet,over a series of steps.During the fall water mixes throughly with atmosphere air and get areated head requriment vary from 0.005 to 0.03 N/mm and space requriment vary from 0.5 to 0.65 meter per 100 litres per day.
2.Spray bottles:
Water is sprayed under pressure through special nozzles in this method water is made in the form of line droplets in this foundation, increasing the contact area of water with air and thus effecting areation.Nozzles usally have diameter varying from 10 to 40mm spaces in the pipe at internals of 0.5 to 1.0m or more.
3.Multilp pan areators:
The water is made to trickle through successive perforated pans arranged one below the other and thus areated.
4.Diffusion areators:
It consists of bubbing the water from bottom through compressed by air by using prouos plates.Water contained in the tank is thus areated.
What are the limitations of areation
However the areation methods are not found to be so much effective as claimed.The obvious reasion are that most of the odour producing substance are not really volatile substance.Further the oil is produced by alga blooms are not removed by areation.Also it requries much head of water hence advanced techniques like adsorption by activated carbon etc.,are replacing the conventional areation method.