The influence of hydrodynamics on the spread of pollutants in the confluence of two rivers

In a river system, confluence is a very important issue. This is due to the confluence can affect the morphology and hydraulics in upstream and downstream. The aim of this study is to determine the effect of hydrodynamics on the spread of pollutants in the confluence of two rivers. The model is built based on partial differential equations in two-dimensional depth-averaged surface-water flow and the Continuum Principle. Furthermore it is solved using an implicit finite difference methods namely Alternating Direction Implicit (ADI) method because it has the accuracy and numerical stability relatively good. These results are then simulated using MATLAB 7.1 software. The Parameter used are COD, BOD, DO, discharge and velocity water flow obtained from The public company of Jasa Tirta I. Running the model performed on location Karangpilang through Sepanjang bridge, with discharge from the paper industry PT. S.Wijaya and oil industry PT Sarimas Permai and stream flow velocity 0.5 m / sec at a distance of 15 m from the confluence of two rivers. The results showed that the spread of pollutants followed in the longitudinal direction and the spread of pollutant was changed in the value of the velocity and concentration because of differences in location (before and after confluence).