Numerical Modeling of Biological Oxygen Demand (BOD5) Load in Apa Mmini Stream

Abstract

Aim: The study aimed at utilizing finite element modeling approach for extrapolation of BOD5 along the longitudinal length of the stream. Study Design: The linear element method was used for analyzing the Biological Oxygen Demand (BOD) transport along the longitudinal length of the stream using the Advective dispersive equation (ADE) as the governing equation.  In this study, it was assumed that dispersion was negligible. Methodology: The BOD5 transport within the stream was modeled using finite element approach. The equation for the stream water pollution modeling was used and the descriptive variables are described as; D is the dispersion coefficient, C is the unknown or state variable (concentration of pollutant or dissolved salt), V is the velocity or convection parameter, k is the applied source or sink and t is the time coordinates. Results: Prediction results of the finite element model showed that BOD5 decreased downstream from the point of slaughterhouse effluent expulsion. It was observed that both the observed and predicted values of BOD5 correlated strongly with a correlation coefficient of 0.9686. The decrease in BOD5 downstream proves that there is a low rate of re-aeration of the stream; hence the effluent still exceeds the FMEnv recommended standard of 50 mg/l as it travels downstream along the stream profile. The prediction discloses that the river is highly polluted for long stretch of the watercourse, thus implying that selected system of treatment method must be put in place. Conclusion: Finite element modeling approach was utilized for the extrapolation of BOD5 in Apa Mmini stream. The outcomes of the simulation showed that the Apa Mmini stream is highly polluted with BOD5 of 111.8 mg/l which is far above the FMEnv recommended standard of 50 mg/l.