#### Waste water Engineering

1

The settling velocity of a spherical particle of diameter less than 0.1 mm as per Stock's law, is

A. V_S = 418 (G_S - G_W) d [(3T + 70)/(100)]
B. V_S = 418 (G_S - G_W) d^2 [(3T + 70)/(100)]
C. V_S = 218 (G_S - G_W) d^2 [(3T + 70)/(100)]
D. V_S = 218 (G_S - G_W) d [(3T + 70)/(100)]

2

For having central angle alpha, the area of cross-section of sewers running partially full, is

A.  A = D^2/2 [ (pi alpha)/(180^circ) - sin alpha /2]
B.  A = D^2/4 [ (pi alpha)/(180^circ) - sin alpha /2]
C.  A = D^2/4[ (pi alpha)/(180^circ) - cos alpha /2]
D.  A = D^2/2 [ (pi alpha)/(180^circ) - cos alpha /2]

3

Boussinesq's equation for ascertaining unit pressure at a depth H on sewers due to traffic loads, is

A. rho_t = (3H^3 P)/(2 pi Z^5 )
B. rho_t = (2H^3 P)/(3 pi Z^5 )
C. rho_t = (3H^3 P)/(2 Z^5 )
D. rho_t = (2 pi H^3 P)/(3Z^5 )
E. none of these.

4

In a sludge digestion tank if the moisture content of sludge V1 litres is reduced from p1 % to p2 % the volume V2 is

A. (100 + P_1)/(100 - P_2) V_1
B. ((100 - P_1)/(100 + P_2)) V_1
C. ((100 - P_1)/(100 - P_2)) V_1
D. ((100 + P_2)/(100 - P_1)) V_1

5

Hazin's formula V_S = 418 (G_S - G_W) d [(2T + 70)/(100)]  is used for the settlement velocity of the particles of diameter

A. less than 0.01 mm
B. less than 0.05 mm
C. less than 0.1 mm
D. greater than 0.1 mm.