# Environmental Engineering

1. Aug 9, 2011

### Myung

1. The problem statement, all variables and given/known data

Hi I need help on my Environmental Engineering subject!

Here is the problem:

An industry, on the banks of a lake, discharges a pollutant into the lake. The river flow is 10 m3/s, the waste flow is 0.1 m3/s, the pollutant’s concentration in the river is 20 mg/l and in the waste flow it is 3000 mg/l.

What is the flow rate out and what is the concentration of the pollutant in the outflow?

HERE is the Graph!
http://img263.imageshack.us/img263/1844/screenshot20110809at511.png [Broken]

2. Relevant equations

*The effectiveness of an environmental process in removing a contaminant can be determined using the mass balance technique:

d/dt (M) = d/dt(in) - d/dt(out)

*The mass of contaminant per unit of time may be calculated as :

mass/time = (concentration)(flowrate)

*The mass flow rate is given by the equation:

d/dt M = CinQin - CoutQout

3. The attempt at a solution

My attempt was to get the flow rate out first with simply adding Q(in flow) and Q(wasteflow)

10 m3/s + 0.1 m3/s = Q(out flow)
= 10.1 m3/s

Now I'm confused with the concentration part I dont know how to apply the said equation above to this problem

Last edited by a moderator: May 5, 2017