2. Welcome To ENV-103 Presentation Wastewater Treatment System On

3. Presented to: Moushumi Zahur Assistant-Professor Mathematics and Natural Science Department BRAC University Presented By: 1.Naimur Rahman Sharnav – 13209017 2.Saima Ishraque – 14226003 3.Kabirul Islam Kanon - 12236002 Section 01, Group-6

4. Wastewater – Its Journey to Treatment and Return to the Environment

5. What is wastewater? Wastewater is water that has been used and must be treated before it is released into another body of water, so that it does not cause further pollution of water sources. The process of converting the used or dirty water to make them to reusable is known as wastewater treatment system.

6. Wastewater comes from a variety of sources :  Everything that you flush down your toilet or rinse down the drain  Rainwater and runoff, along with various pollutants  Wastewater can also come from agriculture or industry

7. Where does it all go! Where does the water from the washer go? When you flush the toilet where does the contents go? By gravity flow, the waste is on its way to your local wastewater treatment plant!

8. Why treat wastewater? Protect public health Protect surface-water quality To prevent water pollution Recycling of water Specific concerns: Pathogenic organisms Pathogen: specific agent causing disease Pathogenic: capable of causing disease

10. Steps of Wastewater treatment:  Preliminary treatment  Primary treatment  Secondary treatment  Sludge (biosolids) disposal

11. Preliminary Treatment - removes large objects and non- degradable materials - protects pumps and equipment from damage - bar screen and grit chamber

12. Preliminary Treatment Bar Screen - catches large objects that have gotten into sewer system such as bricks, bottles, pieces of wood, etc.

13. Preliminary Treatment Grit Chamber  - removes rocks, gravel, broken glass, etc. Mesh Screen  - removes diapers, combs, towels, plastic bags, syringes, etc.

14. Primary Treatment  It is also a physical method of treatment  Water from preliminary treatment step enters the settling tanks( Primary clarifier)  Water settles for several hours, solid particles deposit at the bottom (sludge)  Sludge is removed from the bottom  Water from top( effluent) enters secondary treatment

15. Primary settling tank:

16. Primary Treatment  Primary treatment reduces the suspended solids and the B.O.D. of the wastewater.  From the primary treatment tanks water is pumped for secondary treatment.  Secondary treatment will further reduce the suspended solids and B.O.D. of the wastewater.

17. Secondary Treatment  Secondary treatment is a biological process  Utilizes bacteria and algae to metabolize organic matter in the wastewater in presence of oxygen  Oxygen helps to faster the rate of breaking down pollutants (up to 90-95% pollutant free)  water then moves to the secondary clarifier tank for sedimentation

18. Secondary treatment: The final clarifiers remove additional sludge and further reduce suspended solids and B.O.D.

19. Sludge digester or Anaerobic digester: Sludge separated throughout the process are taken into sludge digester Temperature of 30-35ºC is maintained, optimum anaerobic growth The whole digestion process takes 20-30 days, Continuous addition of sludge should be maintained and only well digested sludge are removed

20. Anaerobic Digester:

21. When the treatment is done… Effluent back to stream after – a final carbon filtration and – chlorination Sludge – very nutrient rich – applied directly to land as fertilizer – incinerated (good fuel after drying) – composted

23. Any question??