The activated sludge process is a biological wastewater treatment process that uses microorganisms to convert dissolved organic matter into biological flocs. It consists of an aeration tank where microbes break down organic matter, and a secondary sedimentation tank where the flocs settle and are removed. Key factors that affect the process include temperature, oxygen levels, sludge retention time, and biological loading rates.

1. Activated Sludge Process
Anuj Baghel (200202002)
Chemical Engineering Department

2. Content :
• About Activated Sludge Process
• Component of activated sludge process
• Mechanism of activated sludge process and diagram
• Factor affecting activated sludge process
• Design criteria

4. Most commonly used secondary treatment process
• Microbes, are involved
Designed to remove (soluble ) biodegradable organic matter
• Removal of nutrients, pathogens and heavy metals is co-identical
Usually clarified sewage (primary effluents) is treated
Treatment involves conversion of soluble organic matter into
biological flocs and their removal as secondary sludge
Include an aeration tank and a secondary sedimentation tank
Activated sludge process

5. Components of Activated Sludge Process
Aeration basins
• wastewater comes in contact with active microbial biomass for
treatment
• Organic matter is transformed into biological flocs
Aeration and mixing
• Aeration supplies enough oxygen for aerobic bio –oxidation of
organic matter
• Mixing keeps biological flocs suspended and ensure contact
between wastewater and microorganism

6. Activated sludge wasting
• Sludge wasting is either as mixed liquor or as thickened
sludge
Chemical feed systems
• Addition of nutrients and alkalinity may be required if the
wastewater is deficient in them – sewage is usually not
deficient

7. Secondary sedimentation tank
• To clarify the out-flowing aeration tank (mixed liquor)
• To separate and thicken the biological flocs from mixed liquor
for recycling or washing
Sludge recycling
• Thickened sludge is returned back from secondary clarifier to
the aeration tank to maintain desired concentration of
biological solids
• Includes pumps and necessary piping and fittings

8. Aeration mixing

9. • ASP is a type of suspended growth system.
Aeration tank
Aerobic
condition
In suspension of sewage
Organic matter
SST
Active micro organism
Mechanism of Activated Sludge
Process and diagram
Sewage
entering
Air/oxygen for aeration
and mixing
Nutrients and alkalinity
If needed

10. • Sewage entering in aeration tank
• Organic matter is present in sewage comes in
contact with micro organism
• Micro organism will use organic matter as food
• Organic matter is oxidised
• After oxidation effluent from aeration tank go to SST
and here sedimentation will take place
• Sludge will form base of sedimentary tank

11. • It will consist organic matter and will also have active
microorganism
• These active microorganism can further help in the
treatment of sewage
• Sludge recycle back to aeration tank that sludge is
known as Activated sludge

12. Factor affecting activated sludge process
• Temperature
• Return rate
• Amount of oxygen available
• pH
• Aeration time
• Wastewater toxicity

13. Design criteria
1. HRT (Hydraulic Retention Time)
2. Food to microorganism ratio (F/M)
3. Volumetric BOD loading
4. Sludge age or Sludge retention time (SRT)

14. 1. HRT (Hydraulic Retention Time)
• The ratio volume of aeration basin to the flow rate
• HRT in hrs = [v/Q] x 24
• V = volume in m3
• Q = flow rate in m3/day

15. 2.Food to microorganism ratio (F/M)
• The “food” in the ratio is the BOD entering the process
(BOD load)
• The “microorganisms” are the activated sludge solids in
the aeration tanks, which are measured as ppm or mg/L
of MLSS

16. 3.Volumetric BOD loading
• It is ratio of the BOD5 applied per unit volume of aeration
tank
• Volumetric load = (Q x La) / V
La =Influent BOD5 to aeration tank

17. 4.Sludge age or Sludge retention time (SRT)
• SRT is denoted by 0c and is defined by the equation
0c = X /( X / t )
X = total microbial mass in the reactor
( X / t ) = total quantity of solids withdrawn daily, including
solids deliberated wasted and those in the effluent