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Sludge Dewatering with C-PAM: Filter Press, Belt Press & Decanter Centrifuge Selection

Selection of cationic polymer (C-PAM) suitable for the mechanical shear forces of filter press, belt press and decanter centrifuge in the dewatering of treatment sludge.

Biological (activated sludge) or chemical-biological mixed sewage sludges contain highly bound water and negative surface charge. Cationic polyelectrolytes (C-PAM) aim to neutralize and bring together sludge flocs, allowing free water to drain quickly and forming solid flocs that do not disperse under mechanical pressure / centrifugation.

C-PAM on Elif Çevre Kimya's product page; It is defined as powder and emulsion polymers with different cationic charge densities from low to very high (10%-80%+) and linear/cross-linked chain structures, used in filter presses, belt presses and decanter centrifuges. The aim is not only to obtain a drier cake; It is also a clear filtrate (filtrate/centrate) and clean cloth/tape operation.

Each dewatering machine applies a different mechanical force to the sludge floc. In belt presses, water must drain rapidly in the gravity drainage area and the flock must be compressed between the rollers without overflowing the cloth. In plate filter presses, a permeable cake structure that does not clog the plate cloths under high pressure is required.

Since decanter centrifuges have high G force and shear effect, shear resistant, high molecular weight or branched/emulsion cationic polymers may come to the fore. In addition, the point where the polymer is injected into the sludge line (pre-pump vs. decanter inlet) directly determines the flock quality.

The volatile solids (organic/inorganic) ratio of the sludge, inlet dry matter percentage, pH, septicization status and the amount of coagulant used in the previous stage change the behavior of C-PAM. For this reason, polymer selection must be verified by dewatering/sieve drainage test and machine trial with the facility's own sludge. Without field testing there is no guarantee of constant dosage, cake dryness or disposal savings.

What Does C-PAM Try to Improve in Sludge Dewatering?

Biological (activated sludge) or chemical-biological mixed sewage sludges contain highly bound water and negative surface charge. Cationic polyelectrolytes (C-PAM) aim to neutralize and bring together sludge flocs, allowing free water to drain quickly and forming solid flocs that do not disperse under mechanical pressure / centrifugation. C-PAM on Elif Çevre Kimya's product page; It is defined as powder and emulsion polymers with different cationic charge densities from low to very high (10%-80%+) and linear/cross-linked chain structures, used in filter presses, belt presses and decanter centrifuges. The aim is not only to obtain a drier cake; It is also a clear filtrate (filtrate/centrate) and clean cloth/tape operation.

Flock Expectation of Filter Press, Belt Press and Decanter is Different

Each dewatering machine applies a different mechanical force to the sludge floc. In belt presses, water must drain rapidly in the gravity drainage area and the flock must be compressed between the rollers without overflowing the cloth. In plate filter presses, a permeable cake structure that does not clog the plate cloths under high pressure is required. Since decanter centrifuges have high G force and shear effect, shear resistant, high molecular weight or branched/emulsion cationic polymers may come to the fore. In addition, the point where the polymer is injected into the sludge line (pre-pump vs. decanter inlet) directly determines the flock quality.

Selection Doesn't Just Depend on Polymer

The volatile solids (organic/inorganic) ratio of the sludge, inlet dry matter percentage, pH, septicization status and the amount of coagulant used in the previous stage change the behavior of C-PAM. For this reason, polymer selection must be verified by dewatering/sieve drainage test and machine trial with the facility's own sludge. Without field testing there is no guarantee of constant dosage, cake dryness or disposal savings.

Field Control and Monitoring List

Chemical dosage and system capacity decisions should be determined by analysis and facility conditions; There is no guarantee of fixed dosage or performance.

  • Measurement of dry matter (% DM), organic/inorganic ratio and pH value of inlet sludge
  • Flock strength test suitable for machine type (decanter high shear etc. belt press gravity drainage)
  • Field control of polymer dosing point and static mixer/flocculation time
  • Monitoring of effluent sludge cake dryness (% DM) and suspended solids (SS) in filtrate/centrate water
  • Regular control of filter cloth or belt washing water pressure and nozzles

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