The water treatment function incorporates treatment plant and untreated supply operations. Our programme involves water quality monitoring and maintenance services to ensure the delivery of healthy and efficient systems.
Water that passes through our system originates from groundwater sources and dam and reservoir catchments.
The Team's commitment is:
There are four Water Treatment Works (WTW) situated around the island. The largest is the Red Hill WTW which supplies water to Half Tree Hollow, St Pauls and surrounding areas. The second largest is the Hutts Gate WTW which supplies the Longwood, Bottom Woods and Alarm Forest areas. The Levelwood WTW supply Levelwood and the Chubbs Spring WTW supply Jamestown, the Briars and Rupert’s Valley.
Method of Treatment
The method of treatment is the same across all of the Water Treatment Works. It is a two stage system that starts when raw / untreated water is pumped through a series of sand filter vessels, with their function being to filter out any debris or small suspended particles found in the raw water. This process is known as rapid sand filtration, which is the most recognised and widely used water treatment process worldwide. The filters consist of multiple layers of sand of varying grain size in order to ensure that most of the suspended solids in the raw water get removed. These filtration systems are entirely automated.
The second stage of the process is to chemically treat the water and kill any bacteria that may be present. It should be noted though, that when treated water appears to be discoloured, it does not mean that the water is now unsafe to drink, as all treated water supplied have been disinfected and tested prior to its distribution. The water is treated at all of the WTW with an antibacterial agent, namely Chlorine. This is done in accordance with the World Health Organisation (WHO) standards, as well as complying with Water Quality Standards agreed with the Environmental & Health Services and the St Helena Utilities Regulatory Authority. In order to maintain a minimum of 1% of Free Chlorine in the water throughout the treated water distribution network, dosing at the WTW is done to counter Chlorine decay along the various pipelines, which might result in consumers closer to the WTW experiencing the upper threshold of Chlorine dosed.
As the Chlorine in the water distribution system decays quickly in the heat, sometimes we have to spike the Chlorine levels further down the line so that it is safe for consumption. This can sometimes cause the water coming out of your tap to have an unusually high Chlorine level, which generally affects the smell and taste of the water, which you can overcome by merely allowing the water to settle a bit before use.