Quality of Sanitary Sewage
Sanitary sewage includes the domestic sewage and the industrial wastes along with any infiltration due to ground water flow.
The dry sanitary sewage is also called the dry weather flow (D.W.F). the dry weather flow is the total average discharge of sanitary sewage and is the normal flow in a sewer during the summer season. This is usually expressed in litres per capita per day.
Generally quantity of sanitary sewage is taken as:
Quantity of sanitary sewage = (Total quantity of water supplied) +
(Addition due to industries, private water supplies etc.,) - (Subtractions due to leakages, sprinkling etc.,)
The quantity of sanitary sewage depends on the following factors.
(i) Population
(ii) Type of area served
(iii) Rate of water supply
(iv) Groundwater infiltration
Importance of quantity of sewage: Before designing the sewage system, it is necessary to know the quantity of sewage, which will flow in it after the completion of the project.