Abstract:
This study evaluated Total Maximum Daily Load (TMDL) for the lower Phong River which runs downstream for 140kilometers from Ubolrat Dam in Ubolrat district of Khonkaen province to the Shee River in Muang district of Khonkaen province. Mathematical model QUAL2K was applied to evaluate TMDL for Biochemical Oxygen Demand (BOD) and Nitrate Nitrogen (NO[subscript 3] –N) in rainy and dry seasons. Only recent BOD and NO[subscript 3]–N at both point sources (domestic and industrial waste) and non-point sources (discharge and runoff) was analysed to evaluate TMDL in this study. TMDL for the lower Phong River was also evaluated according to the standard quality of runoff water issued by the Pollution Control Department which classified the lower Phong River as Type 3 runoff source with a maximum BOD value of 2 mg/liter, a miximum NO[subscript 3]–N content of 5 mg/liter. The results of this study showed that recently the average BOD value and the average concentration NO[subscript 3]–N of the lower Phong River in the rainy season were 39,184 kilograms/day and 3.008 kilograms/day respectively, and in the dry season were 20,652 kilograms/day and 383 kilograms/day respectively. However, TMDL for BOD and NO[subscript 3] –N of the lower Phong River estimated in this study for the rainy season were 62,905 kilograms/day and 40,581 kilograms/day respectively while the estimation for the dry season were 37,880 kilograms/day and 36,728 kilograms/day respectively.