1. Operator Observations
Troubleshooting Activated Sludge Problems
Jim Winslade – Adjunct Instructor ERTC -SIUE

2. 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 diffuser

3. Aerator Pattern

4. Change in Aeration Pattern

5. 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 liquor

6. Stiff White Foam

7. Thick Brown Greasy Foam

8. Crisp Brown or White Foam
A small amount of crisp brown or white foam on the aeration basin surface is an indicator of normal conditions

9. 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 currents

10. Solids Washout

11. 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 bacteria

12. 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 temperature

13. Bulking Sludge

14. 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 surface

15. Sludge Clumping
Sludge sitting in clarifier too long – sludge return rate is too low – increase pumping rate slightly
Sludge is too old – increase wasting

16. Sludge Clumping

17. 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 liquor

18. Ashing

19. Pin Floc

20. Straggler Floc

21. Settling Test 1000 ml graduated cylinder(wall effect) Glass Jar
2 Liter Beaker
Settleometer
Clarifier Problems

22. 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 likely

23. Settleometer

24. 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 possible

25. 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 turbid

26. Slow Settling

27. 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 microbes

28. 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

29. 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)

30. 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