Water Quality

Intakes and Water Quality
The type of water source, treatment options and distribution system all affect the quality of water supplied to the consumer. The quality of water supplied is determined by the physical, chemical, and biological characteristics of water. In St. Vincent and the Grenadines, rivers are the main sources of water sources and these are also augmented by springs.

The quality of water flowing in rivers is usually affected by both human and natural activities. There is also the consideration of the geology or soil type within the catchments and river banks and the potential for landslides and erosion. Landslides and erosion causes increased turbidity or “muddy” water.

The Treatment Process
Different treatment processes are used depending on the source of water. Because CWSA’s water is predominantly Surface Water, the treatment process comprises three main phases: sedimentation, filtration and disinfection by chlorination.

Intake: When water is extracted from the rivers, there may be logs, twigs, leaves, fish and plants that need to be screened out at the intake. This is accomplished by the use of trash-racks, grills and screens from which the water is drawn into the treatment plant. If the source is from a spring or groundwater, the "screening" process would have already been accomplished through natural means.

Sedimentation: The second phase of treatment involves the detention of water for a long enough period of time to allow heavier particles or sediment to settle to the bottom of the sedimentation basin. The cleaner effluent is then channeled into the next phase of treatment.

Filtration: From the sedimentation basin, the water flows through a series of slow sand filters. These filters are made of layers of sand and gravel. The layers of sand are used to remove any remaining fine particles left in the water as well as aiding some form of biological treatment bacteria.

Disinfection/Chlorination: This is accomplished by the application of a granular chlorine mix or by gas chlorine application. This eliminates any disease-causing organisms and bacteria. The entire water system if checked consistently for the detection of a small residual of chlorine in the water. Once this residual is present then there is a guarantee that all bacteria and harmful substances have been removed. If the residual is not present then the dosage of chlorine at the source is increased.

Storage: The water is next channeled into a closed tank or reservoir called a clear well. This allows time for the chlorine to mix throughout the water in order for complete disinfection to take place. The water is then allowed to flow into the distribution system and on to the customers.

The water is sampled and tested throughout the treatment plant. Sampling is performed to make sure the processes are working and that the water is safe before it leaves the plant.

Is your water safe to drink?
The CWSA guarantees its customers that the quality of water it delivers meets international drinking water quality statistics. Since 1970, CWSA has worked to provide St. Vincent and the Grenadines with an abundant supply of safe potable drinking water.

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