Troubleshooting Center
Start from the symptom. Each guide walks through what to check, likely causes and what to do next.
Settling and floc
High SVI
Sludge settles slowly and the blanket climbs. SVI above 150 mL/g and rising.
Pin Floc
Tiny, dense floc particles that settle fast but leave a hazy supernatant.
Straggler Floc
Large, fluffy, light floc particles floating in the supernatant and over the weirs.
Filamentous Bulking
Filaments extend from floc and bridge between particles. SVI high, blanket fluffy.
Rising Sludge (Denitrification in the Clarifier)
Clumps of sludge float to the clarifier surface with small gas bubbles.
Aeration and DO
Low DO in the Aeration Basin
DO below setpoint, especially at peak load or in the first zone.
Excessive DO and High Blower Demand
DO well above need and blower power higher than it should be.
Poor Oxygen Transfer
Lots of air, little DO. Coarse bubbling or rising header pressure.
Nitrification and chemistry
High Effluent Ammonia (Loss of Nitrification)
Effluent ammonia above normal or above the permit limit.
Low Alkalinity
Effluent alkalinity below about 50 to 70 mg/L, pH drifting down.
Temperature Effects
Seasonal changes in nitrification, settling, DO and foaming.
Toxic Upset Recognition
Sudden loss of treatment, dead protozoa, odd color or foam, OUR collapse.
Clarifiers and RAS
Increasing Clarifier Blanket
Blanket depth growing day by day or during peak flow.
Solids Washout and Hydraulic Overload
Storm flows carry blanket solids over the weirs.
RAS Problems
Thin RAS, plugged lines, uneven pump flows or flow meter errors.