Sg Selangor Phase 2 Water Supply Scheme (SSP2) was implemented on a Build-Operate-Transfer (BOT) basis. The construction Cum Operation Agreement (CCOA) to design, finance, construct, operate, maintain and manage a new Water Treatment Plant (WTP) was signed between the Selangor State Government and Puncak Niaga (M) Sdn Bhd on 22 March 1995 and the concession period is up to 31 December 2020.

The construction of the SSP2 was carried out in two stages, with a full design capacity of 950 million litres per day (mld). Construction of Stage 1 with design capacity of 450 mld commenced in March 1996 and was originally scheduled for completion in December 1998. However, the construction of the WTP was accelerated for partial commissioning on 14 July 1998 as one of the measures taken to alleviate the water crisis experienced in the Klang Valley during the month of March to July 1998. Construction of the Stage 2 WTP Works commenced in 1998 and completed in December 2000. With this completion, the SSP2 WTP is officially completed and capable of producing 950 mld commencing on January 2001.

In meeting its obligation to successfully complete the project, Puncak Niaga has raised the single largest water supply infrastructure project financing totaling RM1.28 billion on a non-resources basis by domestic financial institutions.

The Sungai Selangor Phase 2 WTPabstracts water from the Sungai Selangor. The raw water Intake is located near the town of Batang Berjuntai.

On the whole the raw water are treatable and this is despite occasional high turbidity spikes experienced after heavy downpour.

The Sungai Selangor at the point of intake near Batang Berjuntai has a big open catchment upstream, and inevitably there are industrial and development activities within the vast catchment upstream of intake point.

Raw Water Monitoring System (RWMS) has been installed upstream of the Intake to continuously monitor raw water quality.

The RWMS works by transmitting selected raw water quality parameters to the WTP. Any severe violation of raw water quality will be detected and early preventive measures can be taken.

Once the water leave the Raw Water Pumping Station (RWPS), it travels over 4 Km through a 2100mm dia pipes where it enters the plant at the aerator. The aerator provided at the plant is the horizontal cascaded typed and it’s function is to :

i. Remove Taste and Odor
Tastes and odors in raw water evaporate readily and are released into the atmosphere by exposing as much water surface to the atmosphere as possible and introducing turbulence via the cascaded aerator.

ii. Oxidise Iron and Manganese
Completely dissolved iron and manganese, when exposed to air will be oxidised and become particles which can easily be removed via coagulation / flocculation / settling.

By gravity, water leaves the aerator and travels to the flow splitter through two separate pipes. In the splitter, water is divided equally into five (5) separate flows by means of simple weirs.

At each overflow weir, lime is added for pH control and alum as coagulant. Polymer is also added as a coagulant aid to bind the floc. Apart from making it larger and heavier, it makes the floc more durable and less likely to break during the flocculation process. Microsand is added in the coagulation/ flocculation process to hasten the settling of flocs which requires a small sedimentation basin.

Chlorine is dosed at the filtered water as a disinfectant to control any pathogenic organisms in the water before it is supplied to consumers. Fluoride is also dosed at the treated water to prevent tooth decay. Finaly the treated water pH is adjusted at the outlet of contact tank by adding lime.

The water clarification process is by means of Actiflo-Settler, a compact unit with a high degree of operating flexibility.

It uses microsand as the catalyst to expedite the clarification process with facilities to recover the sand used. This system enables the clarification process to be reduced to 21 minutes from point of coagulation to outlet of the settling tank.

The purpose of coagulation/flocculation/settling is to remove particulate impurities, especially non-settleable solids (colloids). This process is carried out in 4 steps.

i. Flash Mixing/Coagulation Tank
Raw water with added lime and alum coagulant enters the coagulation tanks and rapid mixing is introduced to ensure that the chemicals are evenly dispersed in the water as quickly as possible. Chemical reaction takes place and flocs are formed. However, the flocs formed are relatively light and small.

ii. Injection Tank
Microsand with an average particle size of 85 µm and a specific gravity of 2.3, is continuously injected along with polymer and becomes entrapped in the floc making the floc substantially heavier as well as more resistant to breaking up in the flocculation process.

iii. Flocculation Tank
Gentle mixing is introduced in this tank to increase the frequency of collision between floc particles, making them attach to one another thereby becoming larger and heavier. This will allow them to settle out at a much faster rate thereby requiring a much smaller settling tank. The water then leaves the flocculation basin and enters the sedimentation basin to undergo further treatment

iv. Sedimentation
After the floc has been developed to an acceptable level, it is allowed to settle out. To improve the efficiency of the sedimentation process, lamella settlers are incorporated. As the water leaves the flocculation basin, it is directed to the sedimentation basin and underneath the lamella settlers which are placed at an inclination of 60 degrees. The heavier floc settles to the bottom while the lighter floc is carried with the upward flow of the water through the lamellas.

The rising floc becomes attached to the walls of the lamellas and this build up eventually becomes heavy enough to slide down the lamellas and settles to the bottom of the sedimentation tank.

Sand filtration is the last stage of clarification.The filter media is composed of 100 mm gravel with an effective size of 2 - 4 mm at the bottom layer whilst the upper layer is 900 mm of sand with an effective size of 0.8 - 0.95 mm.

From the settling basin, settled water is fed to the rapid gravity filters. The water flows downward through the sand and gravel, removing much of the remaining turbidity in the process and it eventually ends up in the filter underdrain and subsequently flows into the clear water tank.

Filters are back washed by reversing the flow of air and water. A computer automatically regulates the order in which filters are washed based on a head loss of 2.4m or per set runtime.

Filtered water is then transferred to the holding tank before being pumped to Balancing Reservoirs through 2.1 m diameter pipeline for distribution to consumers.