A MODIFIED WATER-QUALITY MODEL FOR PREDICTING BOD AND DO VARIATIONS IN A SHALLOW POLLUTED CHANNEL

This study developed a new water quality model by taking into consider ation the effects of flow conditions and biofilm metabolism on the BOD and DO changes in a shallow polluted channel. Experimental tests were performed in a model channel under various flow conditions. The test results showed that the organic matter deoxygenation rate coefficient (k(1)) varies significantly with the water velocities instead of being a constant as previously believed. The influences of organic concentr ation on the deoxygenation rate of biofilms was found to decrease with an increase in the Reynolds number. The present model along with a si mplified version and the conventional Streeter-Phelps model were utili zed to compare of experimental data obtained from test runs under vari ous flow conditions. The test results revealed that the residual BOD a nd DO concentrations predicted by the present study agree very well wi th the measured values while the predicted values using the two other models deviate significantly from the observed data.