1. Water Treatment

2. Surface Water Quality Contaminants: Suspended solids, soil (turbidity)
Pathogens (coliform indicator)
Color (decaying vegetation, algae)
Taste & odor
Other SDWA contaminants

3. Water Treatment Water Sedimentation Flocculation Filtration
Chlorination
Fluoridation
pH Adjustment

4. Sedimentation
The water is pumped into the bottom of the sedimentation tanks, so as not to disturb the clearer water at the top. The suspended particles settle to the bottom.

5. Filtration
Remaining suspended particles are removed by filtration. The water is allowed to pass through beds of graded sand and gravel. The sand in the filter bed acts as a filter and removes the tiny suspended particles from the water

6. Chlorination
This is the addition of chlorine or chlorine compounds to kill microorganisms in the water and to prevent reinfection. Both chlorine and sodium hypochlorite are added to the water to form an active disinfecting agent in the water

7. Fluoridation
This is the addition of fluoride compounds to drinking water to prevent tooth decay. Sodium fluorosilicate is usually the fluoridating agent.

8. pH adjustment
It may be necessary to adjust the pH of the water before it leaves the treatment plant. Tap water should have a pH in the range of 6 – 8. If the water is too acidic, lime is added to raise the pH and if the pH is too high, sulfuric acid is added.

9. Sewage Treatment Primary Treatment Secondary Treatment
Physical Process
Secondary Treatment
Biological Process
Tertiary Treatment
Chemical Process

10. Primary Treatment
Solids and large floating debris are screened from the waste water
 Remaining solids are removed by allowing the waste to settle in sedimentation tanks

11. Secondary Treatment Activated Sludge Method
The activated sludge method operates aerobically. The sewage is fed continuously into aerated tanks that is kept oxygenated by mechanical agitators.
Aerobic Microorganisms break down organic waste in the sewage by oxidation in air to carbon dioxide and water

12. Tertiary Treatment Removal of nitrates and phosphates
 Phosphates are removed by precipitation with Aluminium Phosphate
 Nitrates are removed by biological nitrification.
Tertiary treatment is a costly process

13. Eutrophication of Water
Eutrophication is caused by the overenrichment of water by nutrients such as phosphates and nitrates.

14. Eutrophication of Water
In effect, the nutrients behave as fertilisers that increase the growth of plants such as algae in lakes and rivers
The algae are short lived. As they decay, much of the dissolved oxygen in the water is used up, leading to the death of many forms of animal life.

15. Nitrate Fertilisers
Waterways can also be polluted by the run-off of excess fertiliser from farmland. Excess nitrate in the fertiliser may be washed into rivers or lakes by rainwater. Eutrophication will result.

16. Pollution of Heavy Metals
Metals with high relative atomic masses such as mercury, cadmium and lead are known as heavy metals.
When recycling is inadequate, quantities of these elements are dumped e.g. Car batteries containing lead
or dry batteries containing
cadmium.

17. Pollution of Heavy Metals
Dipositive ions of these metals
e.g. Hg2+ , Cd2+ , and Pb2+ sometimes get into waterways from industrial effluent and consequently into drinking water.
These elements are cumulative poisons in that frequent exposure causes build up in the body, resulting in serious health damage.
Lead ions can be removed from the effluent by precipitation

18. EU Legislation on Water Quality
There are limits to the quantities of Hg2+ , Cd2+ , and Pb2+ ions that can be tolerated in waterways because of their toxic effects.
Limits on phosphates and nitrates help to reduce the occurrence of eutrophication in waterways.
Limits are also set for chemical species dissolve in drinking water.