The marvel of drinking water

UV treatment unit

I visited a local Bristol water treatment works a few weeks ago and, as always, marvelled at the technological miracle that is ‘drinking water’. Most people have no idea what goes into making water taken from the natural environment clean and fit for distribution through the pipes that run everywhere under our feet and into our homes, offices, etc.

The first few steps are fairly obvious, involving straining out plant life and sediment from ‘raw’ water, but after that it becomes much more sophisticated. Typically, water is then injected with ozone which accelerates oxidation of harmful organic and chemical residues, after which water is clarified using coagulants such as poly-aluminium chloride. Then water is further cleaned through slow sand filtration (literally letting water settle through a fine sand ‘filter’) and/or granulated activated charcoal. Water is then pH adjusted and, as of January 2012, subjected to UV light treatment (see picture) to ensure all micro-organisms – especially cryptosporidium – are destroyed. Then, in a few areas of Britain, a tiny amount of fluoride is added (at the request of public health authorities) to improve dental health, before the treated water is pumped out into the distribution network.

Next time you draw a bath or fill the kettle, spare a thought to the marvel that is our drinking water system!