1. Lesson 8

2. C11-4-16 Describe examples of situations where solutions of known concentration are important. C11-4-17 Describe the process of treating a water supply, identifying the allowable concentrations of metallic and organic species in water suitable for consumption.

3. Chemical and physical process Clean & maintain the quality of our water supplies through the following processes: Aeration Coagulation/flocculation Sedimentation Filtration Disinfection

4. The addition of oxygen to wastewater or water Oxygen helps speed up bacterial growth Bacteria digest many waste products

5. The process by which dirt and other small suspended solid particles are chemically bound, forming flocs Requires the use of a coagulant or flocculant This allows for the collection of such particles

6. Process of letting heavy particles in water settle out into holding ponds or basins before filtration

7. Process of passing a liquid or gas through a porous article or mass to separate matter out into suspension Examples of a porous articles include sand and paper membranes

8. The use of chemicals to kill potentially harmful microorganisms in the water This is typically accomplished by chlorination, ozone or UV radiation

9. 97% of the world’s water is salt water, leaving 3% usable or fresh water ~70% of this is frozen ~30% ground water ~0.3% surface water Ground & surface water  our drinking water Water from lakes, rivers and swamps contain impurities that make it smell and look dirty May contain harmful chemicals or bacteria that cause disease

10. May be natural or man-made Common issues: Odour Taste Colour Turbidity Suspended solids Organic & inorganic pollutants (pesticides, insecticides, etc.) Heavy metals Domestic & industrial wastes Bacteria & viruses

11. Major public health concern in many areas 1993 Milwaukee 400 000 people became sick and over 100 died

12. Since 1919 Winnipeg has used Shoal Lake for its water supply No outbreaks yet... Metal and organic pollution are the primary concerns

13. Metals Arsenic: 0.01 mg/L Lead: 0.01 mg/L Mercury: 0.001 mg/L Chromium: 0.05 mg/L Organics Benzene: 0.005 mg/L Malathion: 0.19 mg/L 1,2-dichlorobenzene: 0.2 mg/L

14. Granular activated carbon Chemicals adsorb to the porous carbon surface Works quite well for large organics Pesticides, ringed or branched organics Not so well for small organics Simple alcohols & formaldehyde

15. Hydroxide precipitation Many metals ions are insoluble with the -OH ion  precipitate out Works quite well----but can be tricky due to the different pH requirements of various metals

16. Keeping drinking water clean is a joint effort Federal, provincial & municipal responsibility Manitoba Drinking Water Safety Act Sets the standards for public drinking water supplies Health Canada Ensures that these standards are met Water Technicians Conduct thousands of tests each year to ensure that our water is free of disease-causing bacteria & pathogens Test results are passed on to provincial and municipal governments