Cationic Polyacrylamide for Wastewater Dewatering: From Beginner to Expert (I)

In the modern wastewater treatment field, cationic polyacrylamide (CPAM) is widely used as an efficient flocculant in sludge dewatering processes. Its strong flocculating ability can significantly improve the dewatering performance of sludge, increase treatment efficiency, and reduce operating costs. However, to fully leverage the advantages of CPAM and ensure safe, environmentally friendly, and efficient treatment effects, one must master a series of precautions from dissolution, dosing to monitoring, and adjustment. This article will comprehensively explain the key points of cationic polyacrylamide wastewater dewatering from beginner to advanced.

Dissolving Cationic Polyacrylamide: Laying a Good Foundation

Water Quality Selection

When dissolving cationic polyacrylamide, the choice of water quality is crucial. It is recommended to use low-hardness water with a neutral pH, avoiding sewage, strong acidic or alkaline water, high salinity, and high-temperature water. Poor water quality can affect the dissolution effect and stability of cationic polyacrylamide and may even cause product degradation. Room temperature tap water is an ideal choice, and it should not be heated to above 60°C during dissolution, as high temperatures will accelerate the degradation of PAM, affecting its flocculating effect.

Stirring Techniques

Stirring speed should be moderate to avoid product degradation due to prolonged vigorous stirring. Observe the solution status during stirring to ensure uniform dissolution of PAM. Stirring should be done slowly and continuously to prevent clumping. The dissolution time generally ranges from 30 minutes to 2 hours, which can be adjusted based on the particle size of PAM and the characteristics of the solvent. It is best to use powder products one hour after dissolution for optimal performance. The prepared solution is best used on the same day to avoid degradation of cationic polyacrylamide due to long-term storage, affecting its effectiveness.

Configuration Concentration

The concentration in preparing the solution is also a critical step. The normal dissolution concentration of cationic products is0.1% to 0.3%. Too high a concentration might lead to material waste and difficulty in uniform dosing, while too low a concentration might affect the treatment effect. The configuration concentration of high molecular weight cationic polyacrylamide should be slightly lower to avoid excessive stirring load. The concentration should be flexibly adjusted according tothe type, purpose, and onsite conditions of cationic polyacrylamide to ensure the best use effect.

Dosing of Cationic Polyacrylamide: Precise Control to Ensure Effectiveness

Dosing Method

Cationic polyacrylamide can be dosed using a metering pump, with the dosage adjusted according to the actual treatment process and water quality situation. During dosing, avoid impacts and shearing to maintain the solution's stability and effectiveness. Before dosing, PAM should be fully mixed with water to ensure uniform dispersion. Additionally, pay attention to the proper use with other agents to achieve the best treatment effects. For example, when used with coagulating agents like polyaluminum chloride, they should be dissolved and mixed separately, added in a specific sequence, and the dosing ratio and speed should be strictly controlled.

Dosing Amount Adjustment

The determination of the dosing amount requires experiments and monitoring. Before actual application, small-scale tests can be conducted to determine the optimal cationic polyacrylamide model and dosage to achieve the best flocculating effect and reduce operating costs. After dosing, regularly monitor water quality changes, such as COD, BOD, and other indicators, to adjust the dosage and treatment process in time. Based on the water quality monitoring results, evaluate the effectiveness of PAM, and make corresponding adjustments. If the water purification effect is not ideal, do not blindly increase the PAM dosage; instead, scientifically determine the optimal dosing amount.