My brother went hiking recently. Besides energy bars, a first aid kit, and a sleeping bag, the biggest thing he packed into his backpack was water. And not just one or two bottles. He had to take nine litres of the stuff. Nine litres might sound like a lot, especially when you have to carry it around with you on your back, but he’s a strong lad, and he managed just fine. And then again, nine litres isn’t actually a lot of water, in relation to how much we use every day.
And having to carry his water around probably gave my brother an invaluable lesson. I don’t think we always realise just how much we take piped water for granted. Having a tap is something that we’re all used to. It’s how things have always been. Our homes have several taps, both hot and cold. We turn on the tap, and we have water. It sounds amazingly simple, and it is, until you start taking a closer look at those taps, and what comes out of them.
Every year, 900 people in the USA die due to contaminated tap water. That’s nearly three every day, although it’s a relatively small percentage of the 900 000 who get sick for the same reason. Besides these concrete statistics, there is also an unmeasured impact of the quality of tap water, with various alimentary cancers being ascribed to the water. The figures may be for the USA, but where purification techniques are essentially the same, the figures can be used as a rough guide. It doesn’t make for particularly reassuring reading then, does it?
But it’s not as bad as all that. There are various ways of purifying water. One of the most common is the carbon filter, which, as the name suggests, uses carbon granules to filter the water passing through it. A carbon filter is useful in that it removes chlorine, some lead, and pesticides from the water, but there are a lot of things that slip through it. The same applies to water softeners. Hard water, which is caused by a high concentration of calcium and magnesium ions, is “softened” by the softener, but the softener won’t remove contaminants. (Generally speaking, the magnesium and calcium have no adverse health effects, although they are damaging to some industrial equipment and piping, and they make the water taste strange.)
This brings us to the oldest method of water purification – distillation. You may think that distillation would leave you with 100% pure water, but this is not the case. The pesticides and herbicides which are so common in modern agriculture remain in the water, even after it has been distilled, making it unsafe to drink. These chemicals enter the water via surface run-off from contaminated land. They are very pervasive, but they are essential to modern farming. Either way, distillation on an industrial scale would not be practically efficient.
Which leaves us with the question – what are the authorities doing to purify the water?
The answer to this question depends on where the water is coming from. Ground water, taken from deep below the surface of the earth, does not usually require any treatment at all. But most tap water is taken from surface sources, and requires treatment. This treatment may involve sedimentation, or flocculation, which is what happens when solid particles in the water settle out of the water. Filtration is also a common process, using various types of filters. Getting rid of harmful chemicals can be done by ion exchange, which removes inorganic pollutants.
Most water treatment facilities also disinfect the water, usually by means of chlorination. Chlorination involves adding chlorine or chloramines to the water, in order to kill off micro-organisms that cause disease. The chlorine also keeps the water clean as it travels through the pipes to your home. This is why tap water tastes different if you leave it to stand for a day – the chlorine, which is a gas at room temperature, vapourises out of the water.
Once the water reaches your home, there are various devices on the market which can further filter and purify it. Manufacturers of these devices typically claim that they remove heavy metals and other inorganic pollutants, which is a good thing. Then there is bottled water, which is usually advertised as being “bottled as source”. This is not a good thing, because there is no way of knowing if the bottling process included purification.
So, next time you turn on a tap, you may pause to consider what comes out of it. But don’t be too alarmed. At least you are living in a country where the tap water is drinkable. In China, the most populous nation on earth, the tap water always has to be boiled before drinking. At least you have been saved that inconvenience.
