Most of us know that our water does not just magically appear in our pipes, ready for bathing, washing or drinking, but few of us truly understand the complex process that brings us clean water conveniently into our homes, ready and waiting for when we need it.
The Truth About ‘Fresh’ Water
One amazing fact that is widely known but often not properly appreciated is that there is no such thing as ‘new’ water. The water that exists all over the earth today is the same water drunk by dinosaurs, swum in by primordial single-celled organisms and used by cave men to wash off the grisly result of their latest hunt!
Bearing all this usage in mind, nature does an amazing job of purifying the water within the water cycle; that of evaporation, condensation, precipitation and collection, with transpiration playing its part too. Transpiration is the process by which leaves and plants lose their water.
Where Does It Come From?
Despite the sterling job that nature does to keep water clean and safe to drink, sometimes people need to treat drinking water in order to render it even safer for consumption. The processes used depend on the source of the water. There are, broadly speaking, two sources for drinking water: underground sources, such as wells, springs and aquifers, and over ground sources such as reservoirs, rivers, lakes and dams.
Underground sources tend to be fairly pure, especially in those areas of the UK rich in sandstone and limestone. These forms of rock readily allow water to flow through them and act as a trap for even very tiny particles and pieces of matter. Also, the very fact of being contained within rock means that the water is harder to contaminate, meaning that it stays purer without needing any human intervention.
Over ground sources of water are subject to vagaries of climate, with lakes and dams often trapping particles and pollutants out of the air. Factories and industrial processes often vent waste into rivers (although this unsavoury practise is slowly being phased out as ever more stringent regulation of waste processing comes into effect) which obviously introduces a great number of undesirable substances into the water cycle. Animals often introduce waste into water collection points too, and bacteria can thrive, especially in standing or stagnant bodies of water.
The Cleansing Process
Once water is collected for use by humans, the first step is often a very simple one. It is allowed to stand in clean, protected reservoirs as this allows gravity to work: encouraging particles and sediments to settle on the bottom of the tank. Next, the water is run through a series of fine mesh screens to remove larger particles and floating debris like twigs and leaves. Other, more complex processes involve the use of ozone gas and a form of iron, which together form particles known as ‘floc’, which attract and trap impurities. When the floc is stirred or agitated, it sinks to the bottom of the tank and can be safely removed, along with all the trapped impurities.
Other processes used include filtration (through fine sand which can encourage the growth of bacteria that can break down organic particles), aeration (which removes hydrogen sulphide and carbon dioxide as well as oxidising dissolved metals).
More advanced treatment involves the use of granular activated carbon (GAC) and ozone gas to disinfect the water and remove any pesticide residues. Finally, water is often treated with chlorine to kill off any harmful bacteria and other micro-organisms.
Any waste products of the treatment process are then treated themselves, with solid matter being made into fertiliser and any water being purified, diluted with clean water and reintroduced to the water cycle.
In The Pipeline
Having been treated and now suitable for drinking and household use, the water is introduced to the water pipes that run to every home in the country. Once the water has been used for drinking, washing or whatever domestic purpose it was required for, it generally ends up in yet more pipes. Unsavoury waste, such as that from toilets (known as black water) is kept separate from bath and kitchen water (called grey water). Grey water is generally treated and recycled, while black water tends to be processed as waste and kept well away from the water due to be reintroduced to the domestic water system.