Determination of waste assimilative capacity (WAC) of rivers located within the Desaru Region, Joho

Desaru is a popular tourist destination located on the east coast of the state of Johor. The area has been identified for further development to enhance tourism. This presents a pollution risk to its surrounding watercourses. The purpose of this study was to assess the potential risk of contamination towards rivers located in the crux of the development region, namely the Terumpah, Che Minah, Semangar, Beluntu, Penawar Besar, and Mertang Besar Rivers. Water quality and hydraulic measurements were made at these rivers, with the intention of developing a numerical model. The model results showed deterioration in BOD5 and NH3-N in the Semangar River, up to 4.0 mg/dm3 and 0.34 mg/dm3, respectively. The Beluntu River experienced the highest degradation, to about 14.0 mg/dm3 of BOD5 and 0.8 mg/dm3 of NH3-N. The waste assimilative capacity (WAC) for the Matang Besar, Che Minah and Beluntu Rivers were very limited, with a class III BOD5 limit of 15, 43, and 10 kg/day, respectively, whereas the Terumpah River is not able to accept any BOD load without breaching the same threshold.