Rapid development in sectors namely industry, agriculture, plantation, township, land clearing, logging, mining and other human activities all contribute to the entry of pollutants into the river beyond the river’s carrying capacity which in turn causes river pollution. The results of previous river studies have shown that only 20% to 30% of pollution sources in a river basin are under the jurisdiction of the Department of Environment (DOE) while the remaining 70% to 80% of pollution sources are under jurisdiction of other agencies. Enforcement on the sources covered under the DOE alone is not able to improve the quality of polluted river water. Control methods based on the concentration of effluent pollutants or wastewater from individual sources entering the river are no longer able to control the pollution entering the river as this method cannot take into account the cumulative impact of various sources of pollution whether point sources and non-point sources such as livestock activities plantations and mining. Therefore, the application of TMDL is seen as the best option at this point as a holistic water pollution control measure.

Total Maximum Daily Load (TMDL)

Maximum Total Daily Load (TMDL) is the maximum total daily load that can be accommodated by a body of water (river) based on its carrying capacity without affecting the beneficial use of the body of water. The TMDL control concept is a new approach that takes into account all the sources of pollution that contribute to the entry of pollutants into rivers. This includes point sources and non-point sources that are controlled under the jurisdiction of various agencies. The implementation of effluent and wastewater pollution load control on each source can predict the cumulative impact and as such, control measures can be taken to conserve river carrying capacity and achieve the water quality targets that have been set.

Implementation of TMDL by the Department of Environment

In an effort by DOE which is committed to addressing the issue of river pollution, DOE has taken steps to conduct a pilot study entitled ‘Development and Implementation of the Maximum Total Daily Load (TMDL) Program’ for Sg. Semenyih under the project ‘Strengthening Environmental Sustainability’ in the Four Thrusts ‘Pursuing Green Growth for Sustainability and Resilience’, Plan Eleventh Malaysia (RMKe11). ERE Consulting Group Sdn. Bhd. was appointed to conduct this study for a period of 24 months and the study was completed in 2018.