Municipal sludge changes with primary-to-secondary ratio, biological loading, digestion, return streams and seasonal operation. Cationic PAM selection must follow the current feed and the installed separator rather than a fixed municipal grade.
Identify the solids mixture
Primary sludge may contain more settleable solids and grease; waste activated sludge contains hydrated biological floc and extracellular material; mixed and digested sludge combine different charge and water-release behavior. Record blend ratios and digestion condition during every trial.
Build a three-part sample screen
Compare adjacent charge levels, then refine molecular range within the strongest family. Maintain equal active dose, solution age and mixing. Measure drainage or centrate response and include an overdose point. Reject candidates that create narrow, unstable operating windows.
Use machine-specific acceptance
For belts, prioritize gravity drainage, capture, cake release and belt cleanliness. For centrifuges, balance centrate solids, cake, torque and throughput. For screw presses, track filtrate, ring fouling and discharge. Review the appropriate equipment path before plant confirmation.
Prepare a purchasing record
Retain sample code, lot, test water, solution concentration, active dose and performance data. The final purchase specification should reference the validated grade and agreed incoming checks, not a broad cationicity description alone.