Visible floc in the mixing tank does not always mean the screw press will produce a dry cake. Before increasing polymer, separate the problem into feed conditions, polymer conditioning and press operation.
Record cake dry-solids content, filtrate appearance or solids capture, sludge feed flow and feed dry-solids content over the same operating period. A change in cake moisture alone cannot identify whether the polymer grade, preparation system or press caused it. Compare results with the equipment supplier's operating range and your own plant history.
Check feed flow, dry-solids concentration and changes in the primary/secondary sludge blend. Loading and sludge composition can change dewatering even when the polymer setting is unchanged.
Confirm the actual product, make-down water, solution preparation, aging and metering-pump calibration. A controller setpoint is not proof of the amount delivered to the sludge.
Review the injection point, contact time and floc condition immediately before the press. Floc that looks stable upstream may behave differently after transfer and mixing.
Compare feed rate, screw speed, outlet restriction or backpressure, screen condition and wash cycle with the manufacturer's instructions. Drainage and compression can limit cake dryness even when conditioning is adequate.
Record filtrate clarity or measured suspended solids alongside cake dry solids. Evaluate both outcomes together instead of optimizing cake appearance alone.
Change one controlled variable at a time and log the result. If feed or polymer preparation has changed, restore a reliable baseline before interpreting a new trial. If the cake remains wet while solids capture is acceptable, review press loading and operation with the equipment supplier before concluding that more polymer is needed.
If feed conditions and equipment operation are stable but conditioning remains inconsistent, compare candidate polymers using representative sludge and the same preparation and test method. For sludge-dewatering applications, cationic polyacrylamide may be among the candidates, but the right grade depends on the actual sludge and equipment. Review the exact grade's current TDS and SDS and confirm performance in a monitored plant trial; a generic product name is not a dose recommendation.
Planning a comparison test? See Tairan's cationic polyacrylamide (CPAM) product page for product information.
When making an inquiry, include sludge type, feed dry solids, press model, current polymer grade, preparation method, dose basis, filtrate observations and target cake dry solids.
Technical references: US EPA, Emerging Technologies for Biosolids Management; US EPA, Design Manual: Dewatering Municipal Wastewater Sludges.
This is general troubleshooting information, not an operating instruction for a specific facility. Follow the equipment manufacturer's instructions and verify any polymer choice against plant testing.
