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Sedimentation & Clarification with A-PAM: Polymer, Water Characteristics & Mixing

Rapid precipitation of micro-flocs by bridging with anionic polyacrylamide (A-PAM); Effect of anionic charge density, molecular weight and mixing energy.

Anionic polyelectrolytes (A-PAM) transform charge-neutralized micro-flocs or inorganic particles with naturally positive/mineral surface properties through the coagulation step into large macrocomponents that rapidly collapse by bridging each other along long polymer chains.

Elif Çevre Kimya; A-PAM offers different anionic charge (10%–40%) and high/ultra high molecular weight powder and emulsion options used in mineral ore preparation, marble/sand washing, iron-steel rolling mill scale pits and chemical treatment lamellar settlers.

Same A-PAM product; It may not show the same floc behavior in the presence of different suspended solids (SS) concentration, particle size, pH, water temperature, salinity (conductivity) or free oil. For example, in hot process waters above 60°C or in high shear pumps, the chain structure of standard molecular weight polymers may weaken.

Therefore, the selection should not be made only by looking at the molecular weight in the catalogue. If the flow rate and pollutant load vary during the day, comparative testing should be performed on representative samples taken from different shifts; precipitator surface load and residence time must be taken into account.

It is critical that powder A-PAM products are dissolved at the appropriate concentration (0.1%–0.25%) without clumping (“fish eyes”) and that sufficient maturation (aging) time is allowed before dosage. In the flocculation tank, sufficient contact must be ensured to distribute the polymer homogeneously into the water, but excessive turbulence and high-speed mixing that will break the newly formed flocs must be avoided. Exact dosing and settling performance are not guaranteed without water analysis and field verification.

A-PAM Selection Begins with Knowing Water and Solid

Anionic polyelectrolytes (A-PAM) transform charge-neutralized micro-flocs or inorganic particles with naturally positive/mineral surface properties through the coagulation step into large macrocomponents that rapidly collapse by bridging each other along long polymer chains. Elif Çevre Kimya; A-PAM offers different anionic charge (10%–40%) and high/ultra high molecular weight powder and emulsion options used in mine ore preparation, marble/sand washing, iron-steel rolling mill scale pits and chemical treatment lamellar settlers.

Why are Water Character and Inter-Shift Variability Determinants?

Same A-PAM product; It may not show the same floc behavior in the presence of different suspended solids (SS) concentration, particle size, pH, water temperature, salinity (conductivity) or free oil. For example, in hot process waters above 60°C or in high shear pumps, the chain structure of standard molecular weight polymers may weaken. Therefore, the selection should not be made only by looking at the molecular weight in the catalogue. If the flow rate and pollutant load vary during the day, comparative testing should be performed on representative samples taken from different shifts; precipitator surface load and residence time must be taken into account.

Solution Maturation Time and Mixing Energy Change the Fate of the Floc

It is critical that powder A-PAM products are dissolved at the appropriate concentration (0.1%–0.25%) without clumping (“fish eyes”) and that sufficient maturation (aging) time is allowed before dosage. In the flocculation tank, sufficient contact must be ensured to distribute the polymer homogeneously into the water, but excessive turbulence and high-speed mixing that will break the newly formed flocs must be avoided. Exact dosing and settling performance are not guaranteed without water analysis and field verification.

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.

  • Examination of pH, temperature, conductivity and inorganic/organic solid ratio of the sample
  • Comparison of sedimentation rate of A-PAM candidates with different anionic charge percentages using Jar-Test
  • Control of solution concentration (0.1–0.2%) and ripening time in the polymer preparation unit
  • Adjusting the flocculation tank mixer speed (low shear slow mixing) so as not to break the floc
  • TCM and turbidity monitoring in lamellar settler or thickener effluent

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