A STUDY ON POLLUTANT TRANSPORT IN A STREAM

Abstract

Most of the pollutants entering to the river system are bio-degradable in nature. Due to this characteristic, the pollutants get decayed while being transported downstream. Considering first order decay at a specific rate, advection and dispersion, using HCIS model, the pollutant transport has been simulated. It is found that the concentration time profile derived from the hybrid cells in series model that incorporates decay (HCIS-D) matches with the analytical solution of advection dispersion decay equation model. While a non-conservative pollutant enters a water course, depletion of dissolved oxygen (DO) takes place due to the consumption of oxygen by microbes to digest the bio-degradable pollutants. At the same time, depending on the deficit of DO, re-aeration process takes place in a specific rate. Considering, decay of pollutant, re-aeration of oxygen and advection dispersion transport in the HCIS model, an analytical solution has been derived for DO deficit. The response of the hybrid cells in series model that incorporate re-aeration (HCIS-R) closely matches with the numerical solution of Streeter-Phelps dispersion model. The Rinaldi (1979) approach very much over estimates the oxygen deficit.