Polyamine for Textile Wastewater Treatment: Decolorization & Usage Guide

With the rapid development of the dyeing and printing industry, wastewater issues have become increasingly prominent.

Polyamine is widely used for decolorizing textile wastewater due to its excellent decolorizing properties and good process performance.

What is polyamine？

Polyamine is a colorless to pale yellow viscous liquid that acts as a biocide or a flocculant.

Its flocculating action is the primary mechanism for decolorizing textile wastewater. Flocculation is influenced by viscosity and charge density.

However, higher viscosity or charge density does not necessarily result in better decolorization;

the appropriate parameters must be determined based on the specific dyes and water conditions.

Below are the concentrations of our company’s six product models.

We can also customize the concentration to meet your specific needs.

The following table:

Why is it necessary to decolorize wastewater?

Textile dyeing and printing wastewater is typically characterized by its dark color, complex composition, high organic content, and difficulty in treatment.

This is particularly true for wastewater containing reactive and direct dyes, which are difficult to degrade in the natural environment.

If discharged directly without effective treatment, it will not only affect water clarity but may also disrupt ecosystems and increase the load on subsequent biological treatment processes.

Why can polyamines be used for decolorization in textile wastewater?

The primary dyes in wastewater are mostly direct dyes and reactive dyes, which typically exhibit the following characteristics:

• Anionic groups
• High stability and resistance to degradation
• High water solubility

Meanwhile, polyamines possess:

• Cationic groups
• High charge density
• Long-chain polymeric structure

Therefore, polyamines can achieve pigment precipitation through the following mechanisms:

• Charge neutralization: The cations in the polyamine neutralize the negative charges on particles of the dyes, destabilizing them.
• Flocculation bridging: The long chains link small particles together to form larger flocs.

Advantages of Polyamine

• Fast decolorization: Flocs typically form within minutes.
• Low dosage: Requires a smaller dosage than traditional inorganic flocculants, resulting in lower sludge volumes.
• Wide pH tolerance range: Effective at pH levels between 2 and 10, making it suitable for complex dyeing and printing wastewater.
• Particularly effective on reactive dyes: Reactive dyes account for a significant proportion of dyeing and printing wastewater.

For Which Types of Textile Wastewater Can Polyamine Be Used?

The following table:

How to Treat Textile Wastewater with Polyamines？

These should be used in combination: PAC + polyamine + PAM, as synergistic use is required to achieve optimal results.

When used individually, each has its own advantages and disadvantages and cannot achieve the desired effect.

PAC | Poly Aluminum Chloride

Disadvantages of using alone: Dyes are highly water-soluble, making flocculation difficult when PAC is used alone.

Increasing the dosage will not improve results; in fact, it may increase costs and the amount of sludge.

Performance: It is highly effective on suspended particles. Using PAC first can reduce SS, destabilize the dyes, and achieve preliminary flocculation.

PA | Polyamine

Disadvantages of standalone use: Relatively high cost; excessive dosing may cause the wastewater to regain color.

Performance: Reduces color and removes part of the COD through charge neutralization.

PAM | Polyacrylamide

Disadvantages of standalone use: Suspended particles are small, and long chains may fail to capture them, resulting in poor flocculation.

Performance: Through floc bridging, it enlarges small flocs for sedimentation, improving solid-liquid separation.

Usage Precautions:

1. Since wastewater is typically weakly acidic, and an alkaline environment is conducive to flocculation and sedimentation, first adjust the pH to above 9.
2. Add PAC and stir rapidly to form small flocs.
3. Add Polyamine: Dilute the product directly with water at a ratio of 10:1 to 40:1, then add it directly to the wastewater while stirring.
4. Add PAM: Determine the optimal dosage through small-scale testing, and add while stirring slowly.
5. Test the quality of the separated liquid; if the color meets the standard, the decolorization process is complete.
6. If the color does not meet the standard and the pH is < 6, adjust the pH according to step (1), then repeat steps (3) and (4) to perform decolorization and flocculation, ensuring the pH reaches 6–8, at which point the color will meet the water quality standards.
7. If the color does not meet the standards and the pH is >8, repeat steps (3) and (4) to bring the pH to 6–8, thereby achieving the required color standards.
8. If the color does not meet the standards and the pH is within the range of 6–8, repeat step (3) until the color meets the standards.

Final discharge

EU: No uniform, general color limit is established. Regulations primarily rely on BAT (Best Available Techniques) reference documents, imposing strict restrictions and total emission controls on specific enterprises based on discharge permits (IPPC/IED Directives).

These require maximum color removal, typically necessitating compliance with relatively clear visual standards.

United States: Standards are established by the U.S. Environmental Protection Agency (EPA) and individual states, requiring the measurement of “True Color.”

Some states and regions strictly enforce ADMI standards, generally requiring effluent color to be controlled within 200–400 units (depending on the water quality requirements of the receiving body of water).

Southeast Asian Countries (e.g., Vietnam, Indonesia): Generally adhere to stricter industrial discharge standards, with color index requirements typically set within the range of 80–200 Pt-Co (platinum-cobalt units), depending on the discharge destination (e.g., sewer systems or surface water bodies).

Discharge is permitted once the applicable national standards are met.