Page 220 - Water and wastewater engineering

CHEMICAL HANDLING AND STORAGE 5-23

chlorine gas cylinders. These are housed in a room that is 11.5 m 7 m 3.3 m.
Assume that the chlorine gas is 100% pure and that commercial NaOCl will provide
12% available chlorine. Specify the dimensions of the tank(s) and the materials for
constructing an equivalent sodium hypochlorite storage system. Provide a dimensioned
drawing of the tank(s) with recommended appurtenances and show how they will fit in
3
the existing chlorine room. Assume the density of 12% NaOCl is 1,210 kg/m and that
a 1.0 m clearance between the top of the tank and the ceiling is required.
3
5-5. Determine the size (in m /hour) and number of diaphragm pumps to feed ferric chlo-
3
ride for a 3,800 m /d water treatment plant. The optimum dose selected is 50 mg/L.
Ferric chloride may be obtained in a liquid form that is 40% pure. The density of this
solution is 1.415 kg/L.
5-6. Black Gold is to expand their water treatment plant because of a major increase in
population due to the discovery of oil in the county. Lime is used to adjust the pH of
their coagulation process. The estimated dosage range from the opening of the plant
until it reaches its design life is 3 to 150 kg/h. The bulk density of lime is approxi-
3
mately 960 kg/m . Select an appropriate type of feeder or combination of feeders
from the list below.

Capacity Turn-down
3
Feeder type Model m /h ratio
Loss-in-weight A-1 0.06 100:1
A-2 2.0 100:1
Continuous belt B-1 0.03 10:1
B-2 0.06 10:1

5-7. A chlorinator needs to be selected to complete the design of the disinfection facili-
ties for Camp Verde. The average chlorine dose required is estimated to be 2.0 mg/L.
The maximum dose required is estimated to be 10 mg/L. The average flow rate is
3
0.23 m /s. The available chlorinators are listed below. Each rotameter has a turn-
down ratio of 20:1. Select the appropriate model and rotameter(s).

Capacity, Rotameter
Model kg/d rating, kg/d
V-1 225 45
90
135
180
225
V-2 900 45
115
225
450