DISPOSAL OF EFFLUENT FROM THE SEPTIC TANK :-- The effluent may be disposed of in a seepage pit and the seepage pit or cesspool should be built 15 mt away (minimum) from the building. It is a small circular chamber built below to ground level. Depth is kept five feet from the effluent pipe inlet to bottom .It may be built of brick or the stone , with joints without mortar towards the bottom . For large flows two or more cesspools can be made at distances of not less than 3 diameters of cesspools apart from each other. IS 2470 recommends minimum size of one metre depth and 0.9 mt diameter. A cesspool is lined with bricks or stones with open joints below the inlet pipe level and the pit may be filled with gravel or brick bats for about 30 cm .The bottom of the cesspool should not be less than 60 cm above the sub soil water . A soak pit should not be less than thirty metre away from a well or any source of water supply. Under these conditions and circumstances of the recommendations for the quantity of sewage to be treated in the urban development areas , in the Towns sewered on the separate system the full treatment to be provided and the degree of dilution are to be calculated on the average rate of flow through out the 24 hours. Due allowance must be made for the future expansion and increase of the population for which a town may be divided into separate high and low level zones in a sump and pump it to the high level zone site for treatment and disposal , however an ideal site would be ,to which all the sewer will flow by gravitation with self - cleaning velocities and where the last sewer will still have fall enough to discharge itself at such a level as will allow the water to pass through all the operations required for the purification
This means that the site of purification should be roughly 3to 5.5 mt below the Lowest level in the town end , according to the length and the magnitude of the works , and it should also be below the level of the sorrounding properties.
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