Troubleshooting Guide
A comprehensive list of common process control problems, their probable causes, and step-by-step troubleshooting.
Filamentous Bulking
Filamentous organisms overgrow the floc, causing slow settling and clarifier solids carryover.
Foaming (Nocardia / Microthrix)
Thick, brown, greasy foam accumulates on aeration basins and clarifiers, often clinging to structures.
Rising Sludge in Clarifier
Clumps of sludge float to the clarifier surface hours after settling well.
Pin Floc / Deflocculation
Small, weak floc particles fail to settle, leaving a cloudy, turbid effluent.
Ammonia Breakthrough / Poor Nitrification
Effluent ammonia rises unexpectedly even though the system has nitrified reliably before.
High Effluent Turbidity / TSS
Effluent clarity degrades even though the settling test in the lab looks acceptable.
Septic Conditions & Odor
Rotten-egg (H2S) odor develops in the collection system, headworks, or basins.
Chronic Low Dissolved Oxygen
DO consistently reads below setpoint despite blowers running at or near capacity.
Over-Aeration / Excess DO
DO consistently runs well above setpoint, wasting energy and potentially harming floc structure.
Grease & Scum Accumulation
Floating grease and scum build up on basin surfaces, clarifiers, and skimmer mechanisms.
Toxic / Industrial Shock Load
A sudden, unexplained process upset across multiple parameters at once.
pH Excursions
Aeration basin or effluent pH drifts outside the normal 6.5–8.5 operating range.
Clarifier Short-Circuiting
Flow bypasses the intended settling path, reducing effective detention time.
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