Potable Water

Our planet, the Earth, contains around 75% of water. Our planet has high percentages of water in the liquid state, hence appears blue when seen from space. That is why it is also known as the blue planet.

Indeed it is the presence of water that separates our planet from the rest. Water is the crucial element of our very existence without which we could not survive for long. We come back from a jog, or a good workout and quickly grab a bottle of water to quench our thirst. But can we drink any water?

Of course, not! We can only drink water that has been filtered and treated chemically to remove impurities and harmful microbes so that it is safe to drink. Such water which is safe for human consumption is called potable water.

Fig. 1. Glass of water, Public domain, Wikimedia Commons

• We will first introduce you to the definition of potable water by discussing what potable water contains.

• Then, we will go over the sources from which potable water can be obtained.

• We will then discuss the characteristics of potable water.

• We will give you some examples of potable water.

• Then, we will look into the characteristics that potable water must possess.

• Then, we will conclude by understanding the differences between pure water and potable water.

What is Potable Water?

Remember that potable water is not the same as pure water and hence it is not completely devoid of all impurities, but it is ensured that the concentration of said impurities is low enough so that it won't affect public health. Potable water actually should contain some minerals which are important for our health. Such nutrients and minerals should be present in water so that we don’t suffer from deficiency disorders. Hence, these micronutrients are deliberately added to the water supplies.

Potable Water Sources

The most common sources of potable water in many countries (including the UK) are:

• Surface water.

• Groundwater.

• Harvested/collected rainwater.

Rainwater gets accumulated in water bodies like rivers, lakes and reservoirs. These water bodies have exposed surfaces, i.e. they have surface water. The water that seeps into the ground, passing through beds of rocks inside the ground is called groundwater. Groundwater is purer and cleaner than surface water as the surface water is often contaminated with impurities because of exposure.

Fig. 2. Depending on the conditions of the surrounding habitats, you might think that river water looks pretty healthy to drink. However, regardless of its colour and odour, the water of a river carries microorganisms present in the animals that live in or around it.

The surface water or groundwater is then treated in water treatment plants. The treatment of water to make it potable has several phases:

1. The water is passed through filters to filter out any visible debris/suspended/insoluble impurities.
2. The filtered water is passed through a bed of sand and gravel to filter out the invisible contaminants.
3. This water is now sterilized by treating it with chlorine, ozone or UV light. This sterilization process kills the disease-causing microbes present in the water.

Additionally, in some countries where fresh surface water is scarce, seawater is desalinated to remove salts producing potable water.

Fig. 3. Drinking seawater will accomplish the opposite of hydration. The amount of salt present in seawater will dehydrate you.

In countries where surface water is scarce, a water treatment technique called reverse osmosis (RO) is employed. Reverse osmosis uses a semipermeable membrane which filters out the impurities and salt, giving out water that is fit for drinking.

Fig. 4. Reverse Osmosis, Image by Tirtamakmur, CC BY-SA 4.0, via Wikimedia Commons[1]

Characteristics of Potable Water

For water to be potable, i.e. suitable for human consumption, it should possess the following characteristics:

• The water should be colourless and transparent, not cloudy

• The water should be odourless - a mild level of chlorine odour is fine

• There should be only low levels of suspended/insoluble solid impurities

• Potable water should have minerals, micronutrients and salts

• Potable water should be devoid of microbes like Escherichia coli. This is an absolute must because microbes are harmful and might cause some dangerous diseases. So, potable water shouldn’t contain any microbes.

Potable Water Examples

Any water that is safe to drink is an example of potable water, but let's list some common examples:

• Pipe-borne water from your domestic pipelines.

• Water in wells that are protected to avoid contamination.

• Collected rainwater.

• Protected spring water (this form of potable water comes from groundwater).

• Packaged mineral water (but the quality of the plastic used to pack it matters: it might be harmful if good quality plastic is not used).

Fig. 5. To know if the water from a fountain is potable, you should always look for signs surrounding it that will state if it's fit for drinking or not.