WATER-QUALITY MODELING FOR A SINUSOIDALLY VARYING WASTE DISCHARGE CONCENTRATION

Biochemical oxygen demand modeling in a river involves derivation and solution of the governing partial differential equation which describe s concentration change with time and space brought on by convective, d ispersive, and decay processes and the loading function. In this study , a sinusoidal variation in waste discharge concentration is considere d. The governing partial differential equation is solved analytically by a transform method and by assuming that the solution varies periodi cally in time. The concepts of memory length and memory time are used to indicate when the solution becomes quasi-steady (periodic). The ana lytical solution is compared with two other solutions. The three solut ions produce comparable results. However, the analytical solution is m uch easier to apply. The analytical solution extends the number of bou ndary conditions which a modeler can apply to describe real engineerin g problems.