SECTION 1MID-TERM EXAM MAX. GRADE 20 TIME 1

1. (3.0 pts) This problem is related to the schematic below which shows a flow

diagram of a domestic wastewater treatment plant. Select the correct answer

TS PS AT

SS

Wastewater BS GC

Chlorine

Treated

CT

wastewater

F AC

BS=bar screen TS= traveling screen GC= grit chamber PS=primary settling tank

AT=aeration tank SS= secondary settling tank F= filtration AC= activated carbon

CT= contact tank

a. The type of particle settling encountered in the grit chamber is (are)

(i) Type I settling (ii) Type II settling

(iii) Type III settling (iv) Type III and IV settling

b. The type of particle settling encountered in the primary settling tank is (are)

c. The type of particle settling encountered in the secondary settling tank is (are)

d. The objective of aeration in the aeration tank is to

(i) increase dissolved oxygen (ii) reduce the pH

(iii) remove undesirable gases (iv) increase the pH

e. The activated carbon reactor shown is designed as a

(i) batch reactor (ii) plug flow reactor

(iii) continuous-stirred tank reactor (iv) packed bed reactor

f. If the primary settling tank of this treatment plant is 12-ft deep and the tank receives

a flow rate of 2 million gallon per day. The minimum weir length that should be

provided for this tank is:

(i) 10000 ft (ii) 100 ft (iii) 12 ft (iv) 0.01 ft