Wed | Aug 22, 2018

Getting it clean! - The water-treatment process

Published:Tuesday | March 14, 2017 | 12:00 AM
Debris is trapped and removed at the collection source at the Negro River in St Thomas.
Debris is trapped and removed at the collection source at the Negro River in St Thomas.

Untreated water in natural sources such as rivers, springs and aquifers is usually clean enough for a number of purposes such as washing clothes but definitely not good enough to drink. Although the water may look clean, it is not safe for drinking.

Untreated water contains bacteria and a host of other micro-organisms and chemicals. If this waste is used, a number of water-borne diseases such as cholera, typhoid, dysentery and other illnesses may result.

This and other information is contained in the brochure titled 'Water Treatment' produced by the National Water Commission to inform Jamaicans about the processes involved in its treatment of water, to ensure it is safe for consumption by the public after it is collected.

Water is taken through pipes to a treatment plant, which is specially constructed and equipped for this purpose. At the treatment plant, expensive equipment and chemicals are then utilised to treat the water, which is later distributed to customers. Although the specific details may vary depending on the type of treatment system available, the water-treatment process usually involves five distinct stages:

- Screening and aeration - The water is usually taken from a source and passed through screens for the removal of debris, sticks, stones and other solids. Oxygen is introduced into the water to improve the treatment process and remove odours.

- Coagulation and flocculation - Because there are still small, invisible particles contained in the water before it is treated, chemicals such as aluminium sulphate are usually added to form 'flocs', which bring these particles together. This is coagulation or flocculation. These flocs either float to the surface and are skimmed or become heavy and settle to the bottom of the settling tank and are later removed.

- Sedimentation - This is the settling of dirt particles.

- Filtration - During the filtration stage, the water is passed through strainer-like filters, made of layers of sand, gravel, charcoal or synthetic material that remove remaining small particles and germs.

- Disinfection - The final stage of the treatment process is disinfection. Here, chlorine is added to kill any bacteria or other germ. Enough chlorine is used to ensure that as the treated water is transported to homes and offices, it remains protected against any germs it may come in contact with.

- Courtesy of the National Water Commission