GATE CE 2020 Environmental Engg. Quiz 2 (App update required to attempt this test)

A completely mixed dilute suspension of sand particles having diameters 0.25, 0.35, 0.40, 0.45 and 0.50mm are filled in a transparent glass column of diameter 10 cm and height 2.50 m. The suspension is allowed to settle without any disturbance. It is observed that all particles of diameter 0.35 mm settle to the bottom of the column in 30 s. For the same period of 30s, the percentage removal (round off to integer value) of particles of diameters 0.45 and 0.50 mm from the suspension is _____________.

Chlorine is used as the disinfectant in a municipal water treatment plant. It achieves 50 percent of disinfection efficiency measured in terms of killing the indicator microorganisms (E-Coli) in 3 minutes. The minimum time required to achieve 99 percent disinfection efficiency would be

A water sample has following properties with respect to the particle distribution:-

Total suspended solids = 1000 gms.

Overflow rate of tank = 30.24 m/day

Size (mm)        0.2    0.3    0.4    0.5

% by weight      15     25     40     20

Setting            0.25   0.30  0.35  0.40
velocity(mm/sec)

When the above sample is subjected to sedimentation in a designated tank, the total weight of the suspended solids available in the subsequent filtration process is.

A water treatment plant treats 6000 m³ of water per day. As a part of the treatment process, discrete particles are required to be settled in a clarifier. A column test indicates that an overflow rate of 1.5 m per hour would produce the desired removal of particles through settling in the clarifier having a depth of 3.0 m. The volume of the required clarifier, (in m³, round off to 1 decimal place) would be

What will be the efficiency (%) of a 20m diameter and 1m deep single state high rate trickling filter having sewage low as 4.5MLD, recirculation rate = 1.4 and BOD influent is about 185mg/l?