Operator Observations 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 - Violent turbulence in one spot indicates broken air header or missing diffuser

Aerator Pattern

Change in Aeration Pattern

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

Stiff White Foam

Thick Brown Greasy Foam

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

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

Solids Washout

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

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

Bulking Sludge

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

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

Sludge Clumping

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

Ashing

Pin Floc

Straggler Floc

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

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

Settleometer

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

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

Slow Settling

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

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

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)

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