Troubleshooting Activated Sludge Problems Jim Winslade Adjunct Instructor ERTC SIUE Aeration Tank Problems Surface Turbulence should be even over entire surface of aeration tank Dead spot would indicate plugged diffuser ID: 203374
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Slide1
Operator Observations
Troubleshooting Activated Sludge
Problems
Jim
Winslade
– Adjunct Instructor ERTC -SIUESlide2
Aeration Tank Problems
Surface Turbulence should be even over entire surface of aeration tank
- Dead spot would indicate plugged diffuser
- Violent turbulence in one spot indicates broken air header or missing diffuserSlide3
Aerator PatternSlide4
Change in Aeration PatternSlide5
Aeration Basin Foaming
Stiff White, billowing foam indicates an overloaded plant – Young sludge
- Decrease wasting – Build Mixed Liquor
Excessive Brown Foam – thick and greasy in appearance
- Plant is under-loaded or sludge is too old – Nocardia Foam
- Increase wasting – reduce mixed liquorSlide6
Stiff White FoamSlide7
Thick Brown Greasy FoamSlide8
Crisp Brown or White Foam
A small amount of crisp brown or white foam on the aeration basin surface is an indicator of normal conditionsSlide9
Clarifier Problems
Solids Washout – sludge solids being carried over the weirs of clarifier
- Hydraulic Overload
- Solids Overload
- Equipment Malfunction – return sludge pump or collector
- Temperature currentsSlide10
Solids WashoutSlide11
Bulking Sludge
True Bulking – Sludge fills clarifier and overflows weirs into effluent – plant is overloaded and sludge is young – overaeration may aggravate
Filamentous Bulking – Very clear layer of water over sludge filling clarifier and overflowing weirs – caused by filamentous bacteriaSlide12
Filamentous Bulking
Filamentous bulking results from filamentous bacteria preventing the proper settling and compaction of sludge floc
-Low DO
-low nutrients in influent
-low pH
-warm temperatureSlide13
Bulking SludgeSlide14
Sludge Clumping
Clumps of sludge rise up through clear supernatant in clarifier and burst at the surface
- Sludge is sitting too long in the clarifier and denitrification is starting
Nitrogen gas builds up in sludge and carries it to the surfaceSlide15
Sludge Clumping
Sludge sitting in clarifier too long – sludge return rate is too low – increase pumping rate slightly
Sludge is too old – increase wastingSlide16
Sludge ClumpingSlide17
Solids in Effluent (Cloudy)
Ashing –small ash-like particles on surface of clarifier
- Start of denitrification
- High grease content
Pin Floc – small dense particles of floc
- Old sludge breaking down
Straggler Floc – Light fluffy sludge particles
- Young sludge, low mixed liquorSlide18
AshingSlide19
Pin FlocSlide20
Straggler FlocSlide21
Settling Test
1000 ml graduated cylinder(wall effect)
Glass Jar
2 Liter Beaker
Settleometer
Clarifier ProblemsSlide22
Settleability
Aeration Tank, but may be done on return sludge from the clarifier
Use only a fresh sample
Don’t take sample from dead spot, corner or
wall
If filamentous bulking is suspected, two
settleometers
may be set up. One
settleometer
sample is diluted 50% with effluent. If both
settleometers
settle at same rate or do not settle, filamentous bulking is likelySlide23
SettleometerSlide24
Well Operating Plant
Aeration Tank
Sludge settles and stays down for at least an hour
5min-50 to 70%, 30min-34 to 50%, and 60min-30 to 40%
Supernatant clear
Clarifier-as clear and solids free as possibleSlide25
Poor Operating Plant
Aeration Tank
Sludge settles slowly or not at all-5 min reading is above 80%
Sludge settles too fast-5 min reading below 40%
Poor color-black(septic),red(overaerated)
Settled sludge rises in less than hour
Supernatant is murky or turbidSlide26
Slow SettlingSlide27
Oxygen Uptake Rate
Measure of the uptake of oxygen by the mixed liquor
Rapid rate indicates Young Sludge or High F/M
Low rate indicates Old Sludge or Low F/M
Zero Rate indicates Toxic substance has harmed or killed microbesSlide28
OUR Procedure
Obtain fresh mixed liquor sample
Saturate sample with air by shaking in closed partially filled container
Pour sample into BOD bottle and insert DO probe (BOD bottle probe)
Record decrease in DO in mg/l over 10 min.
Calculate oxygen uptake Slide29
O2 Uptake Rate Calculation
Subtract Ending DO (10 min) from initial DO (0 min)
Divide by 10 for 10 min time period
Multiply by 60 to determine uptake rate per hour
To determine
Specific Oxygen Uptake Rate
or respiration rate divide rate by MLSS concentration in
grams(SOUR)Slide30
Specific Oxygen Uptake Rate
Process Control Levels
Activated Sludge
20-30 mg/L/hr
Aerobically digested sludge
1.5 mg/L/hr or less indicates that the sludge has stabilized