Water is used for drinking to showering, in washing machines and toilets, and Singapore’s water is no different. Singapore’s water supply is diverse and known as the “Four National Taps” consisting of water from, Local Catchments (Reservoirs), Imported Water, NEWater and Desalinated Water.

To ensure our water supply is “clean” from whichever channel, raw water is chemically treated, filtered and disinfected. This then poses the question of - what chemicals are used to treat our water?

According to the PUB, the process of Singapore’s raw water treatment is similar throughout the different channels, and example can be seen below:

Image source: https://www.pub.gov.sg/PublishingImages/WaterTreatmentProcess.png 

Focusing on steps 2, 5 and 7, Coagulation and Flocculation, Disinfection and, Residual Treatment, this is where chemicals are implemented to treat our water including aluminium sulphate (step 2), chlorine/ozone (step 5), chlorine/ammonia, lime and fluoride (step 7). 

This brings about another question - in achieving clean water from chemical treatments, how do these chemicals, in turn, affect our health and bodies?

Benefits vs Harms

Aluminium Sulphate

It is the most commonly used aluminium coagulant, and they help bind smaller particles into larger clumps for easier filtration - benefitting the water treatment process to produce cleaner water. 

However, Science Direct points out how the presence of aluminium in drinking water can harm people with renal dialysis - a treatment related to kidneys. 

Hydrated Lime 

It is also known as limewater (calcium hydroxide) and is used to adjust the pH of raw water, neutralising acidic water therefore also reducing any corrosion from rusted pipes. Graymont elaborates further illustrating how there is excess carbon dioxide present in these waters, and by adding lime, precipitation occurs producing calcium carbonate creating a protective layer inside water mains.

However, if there is no proper regulation of hydrated lime, it would create highly alkaline water which could cause severe injuries to one’s body and health. Other than that, as long as it is highly regulated, it poses no risks, as so far seen. 

Chlorine/Ozone/Ammonia

Benefits of chlorine or ozone include being used to kill harmful bacteria and viruses (step 5), and chlorine and ammonia (step 7) being used to maintain the water quality in the distribution system. 

However, the harms of each vary:

Harms of chlorine in water include increased risks of cancer and asthma, especially in children for the latter - when orally consumed. Chlorine can also affect our body’s moisture and elasticity resulting in dry and wrinkling skin - typically seen in wrinkly fingertips when you shower or swim for long periods of time. 

Harms of ozone in water can appear dependent on factors like solubility of ozone and water temperature to ensure ozone effectively treats the water - otherwise, it could pose issues. Additionally, if there are by-products present that will cause reactions harmful to one’s health. 

According to PUB, ammonia is typically added in the treated water containing free chlorine to form a stable chlorine residual. However, harms of ammonia include increased risk of damaging internal organs if there is an excess or due to long-term ingestion as it could be toxic to our bodies. 

Fluoride

The sole benefit of fluoride is mainly used to prevent tooth decay. The harms of fluoride in water as the World Health Organisation (WHO) identifies are really only caused by high concentrations and possible effects include mild dental fluorosis and serious skeletal issues (elevated fluoride intakes). However, if fluoride concentration and content are low, like in Singapore public water supplies contain only 0.7mg/litre of fluoride, which is low enough as Levitise emphasises. 

Singapore's water content is generally safe for consumption and application, but if you want to reduce any possible harmful effects from our chemically treated water - water filters are your best solution for now.