Polyacrylamide for Paper Mills

Characteristics of Water Quality at Paper Mills: Paper mill wastewater is characterized by high levels of COD and suspended solids (SS), as well as severe color. The concentrations of SS and COD in paper mill wastewater are relatively high. Typically, non-dissolved COD accounts for the majority of the total COD. When SS is removed from the wastewater, the vast majority of non-dissolved COD is simultaneously removed. Therefore, the primary challenges in treating paper mill wastewater are the removal of SS and COD.

Solution: Anionic polyacrylamide with a molecular weight of 15 million or higher yields relatively ideal results. If a combination of physical-chemical and biological treatment is employed, the typical process flow is as follows: wastewater → screening → equalization → sedimentation or dissolved air flotation (DAF) → A/O or contact oxidation → secondary clarifier → discharge. In this treatment process, cationic polyacrylamide is generally used.

Precautions:

Dissolution Temperature: A certain temperature is required to accelerate the dissolution rate. However, excessively high temperatures can cause the polymer molecular chains to break, reducing effectiveness. The appropriate temperature range is 50–60°C.

Agitation Conditions: Avoid agitation with excessive shear forces during dissolution, as this can cause molecular chains to break, thereby reducing effectiveness. Use a low-speed paddle impeller with a speed of approximately 60 rpm. When transferring the solution, avoid high-speed centrifugal pumps; piston pumps or diaphragm pumps are more suitable.

Ensure uniform and dispersed feeding. Uniform and dispersed feeding is a critical step in the dissolution of polyacrylamide; try to avoid the formation of "large clumps" or "fish-eye-like" insoluble particles.

Avoid contact with iron.

Product selection: Since the raw materials used in the papermaking process and wastewater treatment processes vary among paper mills, resulting in significant differences in water quality, wastewater or sludge samples should be provided whenever possible for polyacrylamide product selection testing.