Question

. A storm sewer is carrying snow melt containing 1.200 g/L of sodium chloride into a small stream. The stream has a naturally occurring sodium chloride concentration of 20 mg/L. If the storm sewer flow rate is 2,000 L/min and the stream flow rate is 2.0 m3 /s, what is the concentration of salt in the stream after the discharge point? Assume that the sewer flow and the stream flow are completely mixed, that the salt is a conservative substance (it does not react), and that the system is at steady state.

Answer 1

Step-by-step explanation:

In the steady state total volume going out will be equal to total volume coming in , and

total salt coming in = total salt going out

Total volume coming in per minute = 2000 + 2 x 10³ x 60

= 122000 L .

Total salt coming in per minute = 1200 x 2000 + 20 x 2 x 10³ x 60

= 2400000 + 2400000 mg

= 4800000 mg

volume of water going out per minute = 122000 L

Total salt going out per minute = 4800000 mg

concentration of water going out = 4800000 / 122000

= 39.344 mg / L