Hard Water

Hard Water

1. What is hard water?

   • Hard water contains dissolved compounds, usually calcium or magnesium compounds. For example, limestone contains calcium carbonate, CaCO3.

2. How Hard Water forms

   • When the rain falls, it flows over rocks or soaks into the ground and then passes through layers of rock. Compounds from the rocks dissolve into the water.

3. How hard water wastes soap

   • It is more difficult to form lather with hard water. The dissolved calcium ions and magnesium ions in hard water react with the soap to form scum, so more soap is needed. Soapless detergents do not form scum with hard water.

4. How is Limescale formed

   • Limescale (a solid containing calcium carbonate) is produced when the water is heated. It coats the heating element in kettles, and the inside of boilers and hot water pipes. This means more energy is needed to heat the water, again increasing costs. Pipes may become blocked by limescale - causing the heating system to break down.

5. Temporary and permanent hardness

   • Temporary hard water can be softened by boiling it. Permanent hard water stays hard, even when it is boiled.

6. softening hard water.

   • Sodium carbonate, Na2CO3, is also known as washing soda. It can remove temporary and permanent hardness from water. Sodium carbonate is soluble but calcium carbonate and magnesium carbonate are insoluble. The carbonate ions from sodium carbonate react with the calcium and magnesium ions in the water to produce insoluble precipitates. The water is softened because it no longer contains dissolved calcium ions and magnesium ions. It will form lather more easily with soap.
   • Commercial water softeners often use ion exchange resins. These substances are usually made into beads, which are packed into cylinders called ion exchange columns. These can be built into machines, such as dishwashers, or plumbed into water systems to continuously soften the water. The resin beads have sodium ions attached to them.
     • As the hard water passes through the column, the calcium and magnesium ions swap places with the sodium ions. The calcium and magnesium ions are left attached to the beads, while the water leaving the column contains more sodium ions. The hard water is softened because it no longer contains calcium or magnesium ions. Some ion exchange resins use hydrogen ions instead of sodium ions.

7. How do we make water safe to drink

   • First the water is passed through huge sieves that catch and remove large bits of debris such as leaves, twigs and other floating rubbish. Then the smaller particles such as dirt, bacteria and metals are removed by adding carefully controlled amounts of chemicals to the water. This causes the small particles in the water to stick together, forming a dense layer (called floc) that sinks to the bottom, carrying with it the unwanted particles. The floc is now separated from the cleaned water by either: allowing it to settle as sludge in the bottom of a tank, where it is removed, or by injecting air into the bottom of the tank. Millions of minute bubbles then carry the floc to the top of the tank, where it is scraped off by brushes. The clear water then flows down through layers of gravel and carbon, which filters the water still further, removing any remaining traces of floc or other fine particles. In addition, the carbon removes traces of organic materials such as pesticides.

8. pure water can contain harmful bacteria whereas water fit to drink has been tested for safety

9. ADDING FLUORINE AND CHLORINE

   • Pros
     • Chlorine is a highly efficient disinfectant, and it is added to public water supplies to kill disease-causing bacteria that the water or its transport pipes might contain.
   • Cons
     • • Chlorine and flourine introduced into the water supply reacts with other naturally-occurring elements to form toxins called trihalomethanes (THMs), • THMs have been linked to a wide range of human health maladies ranging from asthma and eczema to bladder cancer and heart disease. •moderate to heavy consumption of chlorinated tap water by pregnant women with higher miscarriage and birth defect rates.