BOREHOLE - a deep, narrow hole made in the ground, especially to locate water or oil.

Providing people with clean drinking water is a major issue all over the world.

Water that comes from boreholes is usually fairly clean It is filtered as it passes through the rocks around the boreholeNormally all we need to do is sterilise this water with chlorine to

make it safe enough to drink. Chlorine kills microbes in the water

However water that we take from rivers and reservoirs needs more treatment than this.

This treatment involves several physical and chemical processes

The water source is chosen so that it contains as few dissolves chemicals as possible.

The water than passes through 5 stages.

RESERVOIRFILTER (made of fine sand; removes mud and grit)

SCREEN (metal bars close together) catches large leave and twigs

SETTLEMENT TANK – sand and soil settle out

ALUMINIUM SULPHATE AND LIME ADDED – small particles of dirt clump together and sink to the bottom. Sludge is dumped into landfill.

CHLORNE ADDED – kills bacteria

pH OF WATER CHECKED – water must be neutral. The water is then stored in large tanks.

FILTER JUGS IN YOUR HOMESAs water trickles through the top part of your jug it then passes a water filterThe water filter contains activated carbonan ion exchange resin and silver

The carbon reduces levels of chlorine as well as other pesticides and other organic impurities

The ion exchange resin removes calcium, magnesium, lead, copper and aluminium ions

Silver particles discourages growth of bacteria kills bacteriaEvery few weeks the filter need changing

PURE – OR JUST FIT TO DRINK

Eventhough water goes through a water jug it is NOT pure as it still contains dissolved substances.

But despite this it is still fit to drinkWe can get pure water by distilling itDistillation involves boiling the impure water; the liquid

water turns to steamThen it cools down and condenses into pure liquid water

HOWEVER,

Distilling large volumes of water uses lot of energy and would make the process expensive

WATER ISSUES

TO SOFTEN OR NOT SOFTEN?People in hard water regions want to soften their water The money they spend on water softeners and filters for

their jugs and repair costs to get rid of limescale cost a lot of money

However, some people disagree since hard water is beneficial to health

Ion exchange columns replace Mg2+ and Ca2+ ions, which make water hard with Na+ ions.

Na+ ions are not good for the heart and have been linked with high blood pressure

CHLORINE IN WATER

Chlorine kills bacteria in waterBut the amount of chlorine in water must be monitored

as chlorine compounds are toxic Ozone (a gas) can be used as an alternative to using

chlorine to kill microbes in water

FLUORINE IN WATERFluoride ions (F-) can protect against tooth decay It is added to water for exactly that reasonHowever there are advantages and disadvantages:

ADVANTAGES It has not been proved for 50 years that fluoridated water causes harmful

affects The effect of fluoridation as shown 30% reduction in cavities on teeth It has been shown that you are 5x more likely to have tooth decay in

areas where there is no fluoride ions in water We need fluoridation to protect teeth as many people in areas of poor

dental hygiene do not visit the dentist regularly The bacteria associated with tooth decay also cause some types of heart

disease so fluoridation protects us from that Fluoride ions are only added in very small amounts

DISADVANTAGES

Fluorosis is a condition caused when children have too much fluoride.

White streaks or tips appear on their teeth These are deposits of Calcium fluoride This could be a sign of other changes in the bones Some studies have shown that excess fluoride can weaken bone,

increasing the number of fractures and bone cancer It is ethically wrong to give people fluoride treatments that they

have not consented to. People have the right to choose. Some studies show that excess fluoride affects the brain. Producing

learning difficulties You can`t set safe limits of fluoride because you cant control

peoples intake.

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