SSC JE Civil Engineering 2012 Solved Paper

BOD is the rate at which the oxygen is consumed is directly proportional to the concentration of degradable organic matter remaining at any time. The kinetics of BOD reaction can be formulated in accordance with first order reaction kinetics as:
$\frac{\mathit{d}{\mathit{L}}_{\mathit{t}}}{\mathit{d}\mathit{t}}=-\mathit{K}{\mathit{L}}_{\mathit{t}}$
Where, ${\mathit{L}}_{\mathit{t}}$ = amount of first order BOD remaining in waste water at time t
K = BOD reaction rate constant