Clean Water vs.

Polluted Water

Hard WaterWhen washing with soap, do you find that the

soap does not lather or leaves a floating scum on the surface of the water?

This is HARD WATERIt does not pose a health risk

How does hard water form?Some rocks, such as limestone contain

minerals that will dissolve in waterThese minerals include ions of: calcium,

magnesium, iron and manganeseWhen slightly acidic water flows through

limestone, more of these ions dissolve in the water

What is soap scum?When soap mixes with soft water, it forms a cloudy solution with a layer of suds on topIn hard water, soap reacts with calcium and magnesium ions to form a precipitateThis is the “scum”

What is scale?If your home water contains the ion hydrogen

carbonate, HCO3-, it can form calcium hydrogen carbonate Ca(HCO3)

When you boil water with calcium hydrogen carbonate, you get scale

This prevents heat to be transferred in the water

How to ‘soften’ hard waterWe used to add washing soda (sodium

carbonate), which would precipitate the calcium and magnesium

Water softening tanks contain resin that has Na ions, to create a precipitate

Soda-lime process use washing soda and lime (Ca(OH)2) to precipitate out calcium and magnesium

Dissolved OxygenGases also dissolve in waterAeration when turning water absorbs

oxygen from the airThe proper amount of oxygen needs to be

present in water in order for aquatic organisms to survive

Polluted WaterThere are 3 types of contaminants the

contribute to water pollutionPhysicalBiologicalChemical

Physical ContaminantsDo not dissolve in waterEx. Oil, garbage, tree branchesTo remove:

Coarse screensSkimmersFilters

Physical Contaminants

Biological ContaminantsBacteria and virusesEx. E. ColiEx. Walteron, Ontario- Runoff from cattle

manureTo remove

Chlorination systems: use chlorine to bleach water

Chemical ContaminantsDo dissolve in waterEx. Man-made chemicals, metals ions,

fertilizers, pesticidesTo remove:

The environment can break down some?????

The SolutionDo not pour chemicals down the drain

Paint, medication, batteries, cleanersWater-treatment plants

Test water samples to ensure safe drinking water