written 5.1 years ago by |
Given
Population = 200 persons
Sewage/capita/day = 100 litres
- Quantity of sewage produced= population X per capita
= 200 X 100
= 20000 lit/day
Assuming 80% of water becomes sewage.
Therefore, Quantity of sewage= 20000 X 80/100
= 16000 lit/day
- Assuming detention period = 24 hours.
Therefore, quantity of sewage = 16000 X 24/24
During detention period
= 16000 litres
- Assuming rate of sludge deposited = 30lit/capita/day & sludge periods =1year.
Therefore, volume of sludge
= rate of sludge deposited X population X sludge period
= 30 X 200 X 1
= 6000 litres.
Therefore, required capacity of tank = 16000 + 6000 = 22000 litres.
Or = 22m^3
Assuming depth of tank = 1.5m (Range= 1.5 to 2.5m)
Therefore, surface area available = 22/1.5
= 14.667 m^2
Assuming length & width ratio i.e. (L: B = 4:1)
Therefore, surface area of tank = L X B
14.667 = 4B X B
B = 1.917m
Therefore, L = 4B
L = 4X1.914
L = 7.65m
Area of cross-section = L X B
= 7.65X1.914
= 14.66 m^2 ok
Therefore surface area of tank calculated above or equal to the 14.667 m^2 which is satisfy by length width ratio.
Assuming free board surface 0.3m.
Therefore, depth (d) = 1.8m
Therefore, a septic tank of size 7.65mX1.917mX1.8m