INGENIEUR
practice of sourcing raw water from upstream to identifying new raw water sources downstream , such as unused mining ponds [ 2 ]. The shift from dams to ponds was made as there was a greater yield of water downstream which could be treated for consumption purposes . However , extracting water from downstream sources is challenging in terms of managing water quality issues .
The water quality issues are mainly due to Malaysian rivers having high turbidity levels caused by high sediment load and high pollutant load from numerous discharge points along the rivers , triggered by rapid urbanisation . This resulted in the Selangor State Government ’ s decision to repurpose old mining ponds into Off-River Storage ( ORS ) which do not only serve as a new source of water but also as a Natural Pre-Treatment System ( NPTS ) utilising impounded water extracted from fresh river water .
ORS has also proved to be an effective risk mitigation option during dry weather and river pollution incidents [ 4 ], which sometimes cause plants to shut down and services disrupted . For the state of Selangor , the functionality of
ORS is similar to conventional dams except the ORS is located downstream whilst dams are built upstream . This new philosophy enabled the Selangor State Government to build a treated water reserve margin and meet future water demand considerably due to its costeffective , climate-resilient , and innovative characteristics .
The ORS adoption contributes to value creation in terms of :
● Environmental – water quality , reduced residuals from Water Treatment Plant ( WTP )
● Economic and Operational – cost efficiency , supply resilience , provide additional water resources
● Social – circular economy , sustainability .
Environmental
Water Quality ORS helps to manage the issue of poor water quality downstream . The average levels of ammonia , iron and manganese in raw water are
Figure 2 : Semenyih 2 Water Treatment Plant ( 100 MLD 1 ) commissioned in 2018
1 Million Litre Per Day ( MLD )
66 VOL 89 JANUARY-MARCH 2022