Water Quality

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  • Created by: Jo Wells
  • Created on: 18-04-13 20:28
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  • Water Quality
    • drinking water needs to be good quality
      • must be free of poisonous salts (e.g. nitrates) and harmful microbes
        • microbes can cause disease - e.g. cholera and dysentery
      • most of our drinking water comes from reservoirs (flows from rivers and groundwater)
        • water companies choose to build reservoirs where there's a good supply of clean water
          • government agencies keep an eye of pollution in reservoirs
        • water goes to water treatment works
          • water passes through a mesh screen
            • to remove larger things  - twigs etc
            • chemicals are added, to make solids and microbes stick together and fall to the bottom
              • water is filtered through gravel beds to remove all solids
                • water is chlorinated to kill off any harmful microbes left
          • some people aren't satisfied & buy filters
            • contain carbon/silver to remove substances from their tap water
              • carbon removes the chlorine taste
              • silver is supposed to kill bugs
            • some people in hard water areas buy water softeners (contain ion exchange resins)
          • totally pure water can be produced by distillation
            • boiling water to make steam, then condensing the steam
            • process = too expensive to produce tap water
              • is used in chemistry labs
    • adding fluoride and chlorine has disadvantages
      • fluoride is added in some parts of country - helps reduce tooth decay
      • chlorine is added to prevent disease
      • some studies have linked adding chlorine to an increase in certain cancers
        • chlorine can react with other natural substances in water to produce toxic by-products - some think could cause cancer
      • in high doses fluoride can cause cancer and bone problems
      • also a concern whether it's right to 'mass medicate' - can choose to have fluoride toothpaste, but not if it is in tap water
      • levels of chemicals added to water need to be monitored - e.g. some areas may have enough chlorine already

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