Determination of Deoxygenation Rate Coefficient as Component in Water Quality Modeling of Middle Segment of Citarum River, Indonesia

Citarum River is a river that passes in the Purwakarta City at its middle segment. The riverbank is overflowing with people's houses with its wastewater outlet leading directly to the river. Various efforts can be implemented in order to improve the environmental conditions of the Citarum River. One of the activities that can be conducted is the prediction of water quality through the modeling of river quality. This domestic waste polluted river model generally uses BOD and DO equations which require the coefficient of deoxygenation rate in its calculations. This study aims to determine the value of the coefficient of deoxygenation rate using the method of laboratory experiment and using the empirical formula. The coefficient will gives more accurate result of urban river quality modeling. Samplings were carried out at two locations that are considered to represent river condition. The laboratory analysis method used in the calculation of deoxygenation rate is using Winkler Method and Slope Method, while Empirical Formula is used in calculating deoxygenation rate using Hydroscience Equation. The results of the analysis and calculations show that the value of the deoxygenation rate range (K1) in the middle segment of Citarum River ranges from 0.10 to 0.17 per day and the BOD Ultimate (La) concentration ranges from 18.46 to 24.43 mg/L. As for the value of deoxygenation rate range (K1) on Citarum River using empirical formula ranged from 0.270 to 0.278 per day. The difference in value can be attributed to the actual deoxygenation rate in the Citarum River is hampered by the factors that disrupt the process of decomposition of organic matter and its capability on self purification process.