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
Facultative
Anaerobic
• Aerobic bacteria need dissolved
oxygen to live and grow
• Anaerobic bacteria live only where
no dissolved oxygen
• Facultative bacteria can adapt to
either condition

7. 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

8. DESIGNING LAGOONS

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

10. Design of Lagoons
Definition of the symbol
Q = flow rate (m3/d)
So = influent BOD (mg/L)
S = effluent BOD (mg/L)
k = reaction rate coefficient (d-1)
V = volume of the lagoon
Aerobic
Facultative
Anaerobic
Q, So
Q, S

11. Material Balance Across the Lagoon
BODin = BODconsumed + BODout
QS0 = V (kS) + QS
𝑆
𝑆0
=
1
1+𝑘(
𝑉
𝑄
)
=
1
1+𝑘𝜃
For several lagoons in series
𝑆
𝑆0
=
1
1+
𝑘𝜃
𝑛
𝑛

12. Material Balance Across the Lagoon
Reaction coefficient is temperature dependent. It varies according to following
equation:
kT = k20 𝜑T-20
Where K20 = reaction rate at 200C (ranges from 0.2 to 0.1) and 𝜑 = temperature
coefficient varies from 1.03 to 1.12

14. Solution

15. Solution

16. Lagoon Configuration
• Parallel• Series

17. 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

18. 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

19. 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)

20. 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

21. 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

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

23. 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

24. The End