Solids Carryover
Solids Escaping Over the Weirs
Solids carryover is the visible escape of settleable material over the outlet weirs — almost always a hydraulic or distribution problem.
Understanding the Problem
Carryover happens when the local upflow velocity exceeds the particle settling velocity, lifting solids out of the settling zone and over the weirs. It is frequently localised to part of the unit.
Uneven weir levels, a blocked inlet distributor or excess flow concentrate velocity in one area. Rapid desludging or gas bubbles can also disturb settled solids.
Because carryover is often intermittent, correlate it with flow, desludge cycles and dosing to find the trigger.
Common Symptoms
- ›Solids visible flowing over weirs
- ›Effluent TSS spikes
- ›Worse at peak flow or after desludge
- ›Uneven flow across the weir length
Causes & Corrective Actions
Cause
Hydraulic overload / peak flow surge
Corrective Action
Cap flow at design; add equalization upstream to shave peaks.
Cause
Unlevel or fouled outlet weirs
Corrective Action
Re-level weirs and clean; ensure uniform overflow along their length.
Cause
Blocked or uneven inlet distribution
Corrective Action
Clear the distributor so flow enters the pack evenly.
Cause
Gas bubbles lifting solids (septicity)
Corrective Action
Address septic conditions; improve upstream aeration or reduce retention.
Prevention
Still seeing the problem?
Send us your operating data and effluent results. Our process engineers will diagnose the issue and recommend a corrective plan.