1. GUIDE BY
Prof. A. B. SANER
PRESENT BY
PACHPUTE AJAY L.
NERKAR JITENDRA R.
VALVI BHASKAR

2. INTRODUCTION TO THE ACTIVATED-SLUDGE
PROCESS
 The process deals with the treatment of sewage (and industrial wastewater) and
was developed around 1912-1914
 Activated sludge is a biochemical process for treating sewage and industrial
wastewater that uses air (or oxygen) and microorganisms to biologically oxidize
organic pollutants, producing a waste sludge (or floc) containing the oxidized
material
 Atmospheric air or pure oxygen is bubbled through primary treated sewage (or
industrial wastewater) and combined with organisms to develop a biological floc
which reduces the organic content of the sewage
 The combination of raw sewage and biological mass is commonly known as
Mixed Liquor.
 In all activated sludge plants, once the sewage (or industrial wastewater) has
received sufficient treatment, excess mixed liquor is discharged into settling tanks
and the treated supernatent is run off to undergo further treatment before
discharge.
 Mixed Liquor is a mixture of raw or settled wastewater and activiated sludge
within an aeration tank in the activated sludge process
 Mixed Liquor Suspended Solids (MLSS) is the concentration of suspended solids

3. TYPICAL TREATMENT PLANT
Mixed Liquor
Suspended
Solids
Returned
Activated
Sludge
Surplus
Activate
d
Sludge

4. Sludge Production
Sludge will accumulate in the activated-
sludge process if it cannot be processed
fast enough by an undersized sludge-
handling facility.
The observed yield decreases as the SRT
is increased due to biomass loss by more
endogenous respiration. The yield is
higher when no primary treatment is used,
as more nbVSS remains in the influent

5. WHY MEASURE MLSS
If MLSS content is too high
 The process is prone to bulking and the treatment system
becomes overloaded
 This can cause the dissolved oxygen content to drop with the
effect that organic matters are not fully degraded and biological
'die off‘
 Excessive aeration required which wastes electricity
If MLSS content is too low
 The process is not operating efficiently and is wasting energy
Typcial Control band

6. To maintain high levels of treatment
performance
The principal approaches to process
control are (1) maintaining dissolved
oxygen levels in the aeration tanks, (2)
regulating the amount of return activated
sludge (RAS), and (3) controlling the
waste-activated sludge (WAS).
The parameter used most commonly for
controlling the activated-sludge process is
SRT.

7. Dissolved Oxygen Control.
When oxygen limits the growth of microorganisms,
filamentous organisms may predominate and the
settleability and quality of the activated sludge may
be poor.
In general, the dissolved oxygen concentration in the
aeration tank should be maintained at about 1.5 to 2
mg/L in all areas of the aeration tank.

10. • Wastewater normally contains soap,
detergents, and other surfactants that
produce foam when the wastewater is
aerated.
• ( fig – Tapovan S.T.P. )

11. THANK YOU !