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
3.
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
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
