Question

A 1.1 m^3/s industrial discharge into a stream flowing at 55.2 m^3/s contains a critical pollutant at a concentration of 955 mg/L. What is the pollutant concentration (again in mg/L) downstream of the discharge, when the pollutant has been well-mixed into the stream?

Answer 1

so, for 1 second 1.1m^3 + 55.2m^3 flows now as it is discharged into the stream.

so, now for 1 sec, there is a flow of 56.3m^3. (1.1m^3 is industrial).

1 lit = 1 m^3

pollutant concentration = 955 mg/L

so, 1 m^3 industrial discharge contains 955 mg of pollutants

hence, 1.1 m^3 industrial discharge contains 955 x 1.1=1050.5mg

since 55.2 m^3 has no pollutants, so ;

for the total of 56.3 m^3 i.e 56.3 L, the pollutant content is 1050.5 mg

so, the pollutant concentration (again in mg/L) downstream of the discharge, when the pollutant has been well-mixed into the stream is 1050.5 mg / 56.3 L =18.6589 mg/L

hope, the process is aptitudinal and understandable.

in case of doubt, please comment.