(Waste Water Treatment) Lagoon

Aerated lagoon shortly known as lagoon is widely used to the purpose of waste water treatment. It is a biological treatment process. No extra chemical is required for this process.

1. Lagoon Presented by: Abdullah al masud (1018022034)

2. Lagoon

3. Lagoons system for Waste Water treatment

4. Lagoons system for Waste Water treatment Lagoons are designed to treat waste water by the interaction of sunlight, algae and bacteria Lagoons are used to treat wastewater before it is discharged to a receiving water The wastewater is stabilized by active bacteria through a biological treatment process Similar to Activated sludge and trickling filter processes

5. Types of Bacteria works in most Lagoon system Aerobic bacteria need dissolved oxygen to live and grow Anaerobic bacteria live only where no dissolved oxygen Facultative bacteria can adapt to either condition

6. Algae to supply DO In presence of Sunlight Algae grow and produce oxygen which dissolves in the water Algae takes CO2 for food produce by the Bacteria during the decomposition of wastes Bacteria can use the oxygen generated by the Algae

7. Designing Lagoons

8. Design Parameter BOD removal Effluent characteristics Temperature effect Oxygen requirement Energy requirement for mixing Solids separation

9. Design of Lagoons Definition of the symbol Q = flow rate (m 3 /d) S o = influent BOD (mg/L) S = effluent BOD (mg/L) k = reaction rate coefficient (d -1 ) V = volume of the lagoon Aerobic Facultative Anaerobic Q, S o Q, S

10. Material Balance Across the Lagoon BOD in = BOD consumed + BOD out QS = V ( kS ) + QS = = For several lagoons in series =  

11. Material Balance Across the Lagoon Reaction coefficient is temperature dependent. It varies according to following equation: k T = k 20 T-20 Where K 20 = reaction rate at 20 C (ranges from 0.2 to 0.1) and = temperature coefficient varies from 1.03 to 1.12  

12. Solution

13. Solution

14. Lagoon Configuration Parallel Series

15. Lagoons in Series Disadvantages Heavy load on the first lagoons sometimes force it to act like anaerobic and create odor Shutdown required for maintenance Advantages Final effluent contains low algae and bacteria Reduce short circuiting

16. Lagoons in parallel Disadvantages Effluent quality may not be as good as series configuration Advantages Can take heavier load Maintenance can be easily done without complete shutdown

17. Physical Component of Lagoons Dikes/Berms Outer boundary of lagoons Prevent inflow from surroundings Should be greater than 3m wide Freeboard Extra height of lagoons that handle the excess flow and large waves Minimum height 0.3m (1ft )

18. Physical Component of Lagoons Slope Slope with freeboard help to protect the lagoons from erosion Include erosion-resistant soil/vegetation, revetments ( stone or rock covering), or wave dissipating implements Horizontal distance 3-5ft and vertical about 1ft Flooring Bottom must be level and compact to avoid seepage of waste to soil For aerated lagoon bottom must lined with cement, chemical sealant or rubber

19. Physical Component of Lagoons Inlet Should be design in a way to provide with good distribution with less erosion Located above the 0.3m (1ft) from the bottom Usually there are multiple inlet with diffuser Outlet Outlet structure should design in a way to provide an acceptable flow rate Outlet should be baffled to allow only the water from top layer Surface baffle should provide to remove floating solids

20. Some important terms related to lagoons Loading Lagoons efficiency Detention time Method of Aeration Lagoon Turnover

21. Safety Lagoons can be hazardous Fences should be constructed to keep people, livestock, animal away Swimming, walking and fishing is not allowed Mechanical Equipment should be properly locked out and panel should be tagged properly. Operator should use life line while walking in slippery areas Operator should use life jacket while boat out onto lagoon

22. The End