Treatment and reuse of wastewater in the textile industry

It is estimated that the textile industry consumes between 80 and 150 liters per kilogram of fabric processed. The amount of water used in making clothes varies depending on the type of fiber (cotton, wool, nylon, polyester, etc.) and the machines used in each process.

Wastewater from the textile industry is characterized by a large amount of chemicals applied in production processes, most of which are non-biodegradable reagents and are fixed in the medium, especially aqueous media.

The pigments used are highly polluting agents as they are manufactured to provide great durability and resistance to biological degradation.

In the manufacturing process, up to 200,000 tons of dyes and pigments can be lost annually if water is not treated efficiently. Hence the importance of applying wastewater treatment solutions in the textile industry. This allows the reuse of wastewater and the recovery of raw materials dissolved in the effluent.

Importance of correct design of wastewater treatment system in the textile industry

The correct design of a wastewater treatment system for the textile industry should achieve the following objectives:

• Adapt wastewater to discharge limits.
• Reuse of water in various textile product manufacturing processes (washing, dyeing, heat treatment), as well as in
• cleaning, irrigation, etc. processes.
• Recovery of raw materials dissolved in wastewater, such as dyes.
• Reducing operating costs of the production process.
• Reducing the environmental impact resulting from the company’s activity.

What are the most efficient processes for treating wastewater in the textile industry?

Textile wastewater treatment plants use different technologies, as the diversity of pollutants present in effluents cannot be treated with a single technology.

The most common processes that are combined to treat effluent generated in the textile industry are screening, homogenization, neutralization, physical and chemical processes, and biological treatment, as well as filtration or evaporation techniques in cases where you want to reuse the treated water. To be reintegrated into the production process.

The effect of dyes present in wastewater produced from textile factories

Dyes are considered one of the most polluting elements because they have a significant impact on the environment. Its effect is:

• They reduce oxygen in water bodies by blocking light, causing septic conditions.
• They are mutagenic and carcinogenic agents for animals and humans.
• It is toxic to plants because it inhibits photosynthesis.
• High levels of SDT increase salinity, altering the natural pH of the water.

The importance of the typical installation of a wastewater treatment plant resulting from the textile industry

Textile products are manufactured in different stages, each stage discharging wastewater with specific characteristics. In order to treat all wastewater generated in the industry, the wastewater coming from all treatment lines is homogenized.

The characteristics of wastewater depend on the type of fibers treated, the treatment stages, and the machines used.

The main goal of treating and reusing wastewater generated from the textile industry

The two main objectives in treating textile industry wastewater, whether for discharge or reuse, are:

• Eliminate organic materials.
• Color removal (such as dyes and other polluting agents).

Installing an on-site treatment plant, or decentralized treatment, is an investment that ensures the operation and sustainability of the plant in the medium and long term.

The main advantages of decentralized treatment

• It allows wastewater to be treated at the point of manufacture, saving wastewater system transportation costs and associated taxes.
• It allows the reuse of treated water in the same production plant.
• Overexploitation of water resources has been significantly reduced
• Promotes savings in surface water collection infrastructure.

Stages of wastewater treatment in textile factories

Although each case requires consideration to choose the necessary technologies, the most common stages in the treatment of textile wastewater are as follows:

screening

To remove large solids (fibers, fluff, hard pieces, etc.).

Eliminate oils and grease, especially in effluents generated by the wool processing industry.

Homogeneity

It is necessary to eliminate fluctuations in flow rate and concentration of pollutants present among the effluent generated at different stages of the production process. It also allows the cooling of remaining water when received at high temperatures.

Neutralization

Which consists of adjusting the pH for the correct functioning of the subsequent stages.

Physical and chemical treatment

To remove colors, solids, and fats. Coagulation, flocculation, oxidation, and filtration techniques are applied.

Biological treatment

To get rid of organic materials. Active sludge techniques are applied.

Triple processing

For intense removal of colors and rebellious organic compounds. Allows water reuse. Membrane, filtration or evaporation techniques are applied.

Physical and chemical pre-treatment

Removal of color, solids, and fats

The main goals of pretreatment are the following:

• Homogenization of flows and lowering of temperature.
• Reducing the concentration of suspended solids.
• Removal of fats and oils.
• pH adjustment.

Types of wastewater treatment techniques in the textile industry

Two types of techniques are generally applied:

• Chemical oxidation and advanced oxidation.
• Physical and chemical processes.