Polyacrylamide (PAM) is widely used as a Flocculant in municipal, industrial, and wastewater treatment to improve the separation of suspended solids and other contaminants. However, choosing the right PAM type and dosage is not simply a matter of adding more chemical. Factors such as wastewater characteristics, charge type, molecular weight, pH, and mixing conditions can significantly affect flocculation performance.
This guide explains how to use PAM effectively, from selecting the appropriate polyacrylamide type and preparing the solution to conducting a jar test and determining the optimal dosage. By following these steps, water treatment operators can improve floc formation, reduce chemical consumption, and achieve more consistent treatment results.
What is Polyacrylamide (PAM) Flocculant?
How Does It Work?
Cationic polyacrylamide: The molecular chains carry a positive charge. Based on the principle that opposite charges attract, it neutralizes the negative charges on the surfaces of suspended particles, thereby eliminating the repulsive forces between particles (charge neutralization); at the same time, its long molecular chains facilitate bridging and flocculation.
Anionic polyacrylamide: The molecular chains carry a negative charge and rely on polar groups on the chains to adsorb suspended solid particles in water. Through bridging, multiple small particles are connected into large “flocs,” accelerating sedimentation.
Nonionic polyacrylamide: Nonionic polyacrylamide carries no charge, but its surface contains a large number of polar groups—amide groups. It primarily relies on hydrogen bonding and adsorption-bridging to adsorb dispersed particles, forming large flocs.
How To Use PAM?
Since the properties of different wastewater streams vary greatly, we need to conduct Jar tests to identify the PAM that is best suited for the current water quality and to determine the optimal dosing conditions. Before conducting the Jar tests, we must first determine the specific PAM grade.
Determine The Type Of Polyacrylamide
To achieve the desired results, it is necessary to comprehensively consider all factors that influence the performance of polyacrylamide.
Factor 01
pH
Anionic polyacrylamide is suitable for alkaline conditions; cationic polyacrylamide is suitable for a pH range of 2–9 and is most active under weakly acidic conditions; Non-ionic polyacrylamide is suitable for a wide range of pH values and can be used in both acidic and alkaline environments.
Factor 02
Ionic
There are three different types of polyacrylamide: cationic polyacrylamide, anionic polyacrylamide, and nonionic polyacrylamide. Different types are suitable for different applications.
Cationic polyacrylamide is suitable for treating wastewater with high organic content and negatively charged suspended particles; anionic polyacrylamide is suitable for treating wastewater with high inorganic content and positively charged suspended particles. Nonionic polyacrylamide is suitable for acidic and slightly acidic environments.
Factor 03
Ionicity
Ionicity refers to the positive or negative charge of the chemical reagent’s ions, as well as their charge density. Higher ionicity corresponds to lower molecular weight, higher cost, and better flocculation performance. Ionicity generally refers specifically to cationic polyacrylamide. Anionic polyacrylamide is typically characterized by its degree of hydrolysis.
Factor 04
Molecular Weight
Different types have different molecular weights. Generally speaking, the higher the molecular weight, the higher the viscosity is. However, this does not necessarily mean better performance.
PAM Jar Test Steps
To ensure compliance with various treatment standards, small-scale trials must be conducted based on actual application industries, water quality, and treatment equipment to preliminarily determine suitable parameters. Subsequently, full-scale testing should be performed to determine the optimal dosage, achieving the goal of minimal usage and low costs. Here are the steps for the Jar test.
Sample Collection
Sampling: To prevent sedimentation of suspended solids, take samples after stirring. Mix wastewater from different time periods to ensure uniformity, with a minimum volume of 5 L.
Preparing The Solution
Dissolving polyacrylamide:
- Use plastic or stainless steel containers whenever possible to avoid contamination by iron ions;
- Use clean soft water or tap water as the solvent whenever possible, as impurities, excessive pH levels, and hard water can affect the performance and solubility of polyacrylamide;
- The solvent temperature should ideally be maintained between 40–60°C. If the temperature is too low, the molecular chains cannot fully extend, affecting flocculation efficiency; if the temperature is too high, the molecular weight will decrease, also affecting flocculation efficiency.
Solution Concentration: Do not add dry powder directly; it must be dissolved first. Since the solution decomposes rapidly, it is recommended to prepare it immediately before use. The concentration should ideally be maintained within the range of 1%–5%.
If the concentration is too high, the solution is prone to clumping, which can clog pipes or pumps and hinder rapid, uniform dispersion in the water, thereby affecting flocculation performance. The concentration is too low, requiring large-scale mixing equipment and storage tanks, and the solution is prone to decomposition and loss of effectiveness.
Stirring Method: Slowly, evenly, and continuously add the powder to water while stirring at a speed of 200–400 rpm for 40–60 minutes, until the solution is completely transparent, viscous, and free of visible lumps.
If stirring is too fast, molecular chains are prone to breaking, causing the solution to become too thin and thereby affecting flocculation efficiency; if stirring is too slow, the dissolution rate decreases, making it easy for “fish-eye” lumps to form, which can clog pipes and reduce efficiency.
Prepare Experimental Equipment
Determine the optimal specifications and dosage through beaker experiments.
Set Dosage Gradients
Determine the dosage standards based on the concentration of the wastewater suspension.
Wastewater Allocation And Chemical Dosage
Add equal volumes of wastewater to each beaker and label them. Add the different dosage gradients to the beakers in sequence.
Stirring And Reaction (Simulating Actual Dosage Conditions)
First, stir rapidly for 1–2 minutes to ensure thorough mixing of PAM with the wastewater.
Then, stir slowly for 5–8 minutes to promote floc growth and prevent flocs from breaking apart.
Stop stirring, let the mixture stand, and start timing.
Observation And Data Recording
Record key information at different time intervals, such as 1 min, 3 min, 5 min, 7 min, and 10 min.
- Clarity of supernatant
- Sedimentation rate
- Sludge volume
- Presence of fine floating particles
Determining The Optimal Dosage
- Large, compact flocs
- Rapid sedimentation
- Clear supernatant
- Low chemical consumption
- No sticking or disintegration
Troubleshooting
Absence of flocs or small flocs may result from an incorrect product type, insufficient dosage, or unsuitable pH or temperature conditions. In such cases, adjust the parameters and repeat the experiment.
If flocs disperse, the supernatant becomes turbid, or severe stringing occurs, this indicates overdose.
Result Verification And Fine-Tuning
Repeat the experiment 2–3 times to ensure reliable results. During actual dosing, the required dosage should be slightly higher due to fluctuations in wastewater quality and equipment mixing efficiency.
Pay attention to the above issues during the actual dosing process, and after determining the optimal dosage, make fine adjustments based on on-site conditions.
Fine-tuning your PAM dosing ensures cost-effective wastewater treatment. If you need assistance in product selection or trial samples, please contact us. Send us your current PAM samples or wastewater testing reports, and our technical team will analyze them to recommend the most suitable Polyacrylamide grade at competitive factory prices.
Post time: Aug-24-2026