Papermaking and pulp mills operate with complex water circuits, high suspended solids, high COD, pitch/stickies, and changing fiber/filler loads. Stable water and wastewater treatment is critical to protect product quality, improve machine runnability, and meet discharge limits. Onschem provides coagulants and flocculants for papermaking & pulp industry to improve solid-liquid separation, reduce sludge volume, and optimize overall treatment cost.
Our main products include Polyacrylamide (PAM) flocculants, Polyaluminium Chloride (PAC), Polyferric Sulfate (PFS) and Polyaluminium Ferric Chloride (PAFC) for clarification, DAF systems, and sludge dewatering.
Common Pain Points (Why Treatment Becomes Unstable)
Poor DAF performance or clarifier upsets
Microflocs and low-density solids can pass through, creating high effluent TSS and COD. Air flotation can become unstable when chemistry is not matched to fiber/filler and colloidal load.
Solution direction: optimize the coagulant to neutralize colloids and emulsions, then use the right PAM to build strong, floatable/settleable flocs.
High polymer consumption and variable dewatering results
Sludge from paper mills can contain fibers, fillers (CaCO₃/kaolin), and organics that respond differently to polymers. Incorrect PAM type or make-down control leads to overdosing, poor cake solids, and higher cost.
Solution direction: match PAM charge density and molecular weight to sludge characteristics and equipment (belt press/centrifuge/screw press).
Stickies and pitch interfere with separation
Adhesives, latex, resins, and surfactants can inhibit floc formation and destabilize DAF.
Solution direction: stronger coagulation and improved floc structure to capture hydrophobic contaminants and reduce carryover.
Color and COD reduction requirements
Some mills need improved removal of colored organics or better front-end solids removal to protect biological systems.
Solution direction: improve primary treatment efficiency (coagulation/flocculation) to reduce load to secondary treatment and stabilize compliance.
Recommended Chemicals
✔ Cationic Polyacrylamide (CPAM)
Retention aid; improves fiber and filler retention.
✔ Anionic PAM
For wastewater flocculation.
✔ PAC / PAFC
For white water recycling and coagulation.
✔ Activated Carbon
Removes color and organic load in effluents.
Benefits for Paper Mills
Higher retention of fibers and fillers
Improved drainage rate
Better sheet formation and paper strength
Lower chemical consumption
Stable performance even with variable pulp quality
Application Areas
Paper machines
Coating base paper
White water treatment
Fiber recovery
Paper mill wastewater
FAQ?
Which coagulant is better for paper mill wastewater—PAC, PFS or PAFC?
It depends on your wastewater composition (fiber/filler ratio, COD, stickies, color), pH and whether you use DAF or sedimentation. PAC is commonly used for general coagulation, PFS is strong in high-solids cases, and PAFC can provide a wider operating window for complex or higher-color wastewater.
How do I choose PAM for paper sludge dewatering?
Selection depends on sludge composition (fiber vs. filler vs. biological), equipment type (belt press/centrifuge/screw press), and target cake solids/filtrate clarity. Correct charge density and molecular weight typically reduce overdosing and improve cake dryness.
Can better primary treatment reduce overall COD discharge?
Yes. Capturing more fine solids and colloidal organics in primary treatment reduces COD loading to secondary treatment and improves overall compliance stability.
Why does DAF carryover increase after chemical adjustment?
Common causes include incorrect coagulant/PAM pairing, overdosing, insufficient mixing, or changes in surfactants/stickies load. Optimizing dose point, reaction time and polymer type often restores stable flotation.