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Sewage contains minerals, inorganic matters and living organisms. Therefore, sewage which is collected from residential areas, public places, industries shall be treated properly for the following reasons :
All the above processes are not always be required. The type of treatment to be given depends upon the quality of effluent required. If the water is used for drinking purposes on the downstream, complete treatment is necessary.
This practice of purifying the water is feasible for large quantity of sewage water. This type of treatments are feasible only when the total drainage network is provided in a town or city.
In some of the cities, if the total networking of drainage is not available due to some constraints; it is necessary to provide septic tanks for smaller townships. But the effluent water from such septic tanks can not be recycled economically by the conventional treatment methods.
But the water from such septic tanks can be treated to a better extent to make it useful for domestic purposes other than drinking.
It has become necessary to recycle the available water by all means, because of the increasing scarcity of good quality water.
The water collected in a septic tank gets partially treated and hence is not much useful. It is required to treat this water by various means to bring it to the portability level.
The norms for deciding the purity of water are based on following criteria:-
The standard values for the above criteria for water to be portable are as follows :
|3.||Total Suspended particles|
The conventional methods of water treatment are not feasible practically and economically. The conventional plants require more area , space and more time for the treatment. Taking into consideration these limitations new compact and economical ‘Sewage Treatment Plants’ are made available by new techniques.
To attain this level of purity of water, various means are used conventionally. But in the highly populated cities more compact plants with faster purification capacity are required. Therefore the process of removing the organic wastes from the sewage water is achieved with the help of bacterias.
A special compartment with a plastic media is provided in a vessel with the necessary arrangement for aeration. The plastic media, because of its size and shape provides more surface area for increasing the bacterial growth. This helps to treat more quality of water in shorter time. The bacterias eat the organic material from the seepage and thus help to purify the water. This partially purified water is collected inside the conical vessel at center and is collected outside this rector in a storage tank. The water collected in this tank is treated by chlorination.
The quality of this water is not 100% near to the potability but this water can be recycled for many other domestic purposes except drinking.
This recycling process helps indirectly to economize on the purchase cost of water and helps to maintain theenvironment.