1. Sewage Treatment

2. The goal
The major goal of wastewater treatment is to prevent bacteria and viruses in human waste from infecting the public.
Sewage also contains undesirable materials.
Think about what goes into toilets & storm drains.
Are they both going to the same place?

3. Sewage treatment
Post-use cleaning of municipal water occurs at a sewage treatment plant.
Ideally all undesirable materials that enters our sewage should be removed before “used” water is returned to rivers and streams.

4. Six step process Screening and grit removal Primary settling Aeration
Final settling
Disinfection
PH adjustment & removal of ions

5. Screening and grit removal

6. Screening and grit removal

7. Primary Settling
Floating grease and scum are skimmed off and solids are allowed to settle as sludge.

8. Settling tank

9. Close up of a settling tank

11. Aeration
Air circulation and exposure to aerobic bacteria digest complex substances

12. Final settling
More sludge settles out. Most sludge is aerated, chlorinated, dried, and sent to a landfill.

13. Disinfection
Chlorine added to kill germs

14. Iron ion removal

15. Iron ion removal

16. Prior to discharge into the reservoir

17. Sludge Gas Gas is produced during sludge aeration and digestion.
This slug gas usually contains about 65% methane and 25% carbon dioxide.
Methane is a good fuel
Natural gas supply