Question

A stream has flow of 25 cumec and BOD concentration of 15 mg/L receives the industrial wastewater having flow of 1.5 cumecs and BOD concentration of 245 mg/L. What is the BOD concentration (mg/L) of stream at downstream point of meeting of stream with industrial waste?

• A. $11.45$
• B. $28.01$
• C. $2.51$
• D. $16$

Answer 1

The correct option is B $28.01$

$\text{Given: Stream flow}\left(Q_R\right)=25m^3/sec$

$BOD\text{concentration of stream}BO{D}_5\left(C_R\right)=15mg/L$

$\text{Sewage flow}\left(Q_S\right)=1.5m^3/sec$

$BO{D}_5\text{concentration of sewage}\left(CS\right)=245mg/L$

$BOD\text{concentration of mix}C=\frac{C_S{Q}_S+C_R{Q}_R}{Q_S+Q_R}$

$C=\frac{245\times 1.5+15\times 25}{25+1.5}$

$C=28.01mg/L$