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Textile wastewater treatment

In textile factories, sewage is produced in the primary washing sector, dyeing, bleaching and fabrication. In the treatment of textile and dyeing waste, the presence of minerals, colored compounds, highly degradable compounds, turbidity and TSS makes it difficult and hard to process.
Wastewater produced in textile and dyeing industries lack the necessary materials for the growth of organisms such as nitrogen and phosphorus, and because of colored compounds, they require several methods of purification. Textile and dyeing wastewater treatment uses chemical, physical, electrochemical and biological methods to produce agricultural water and obtain environmental certification.

textile industry

How to produce sewage in textile and dyeing factories

Wastewater in textile industry is produced in the primary washing, dyeing, bleaching and fabricating segments. The most important raw materials in the textile industry are wool, cotton and synthetic fibers. Types of dyes used in the dyeing process include acid dyes, azoic, alkali, disperse, and sulfur. These colors have a lot of mineral compounds, and their BOD (biological oxygen content) is low, but they are very high in terms of COD (chemical oxygen demand).

In the dyeing department of a textile factory, there are a number of paintings at the beginning of the work, brightly colored fibers that will be ready, and gradually dyed with a thickening of the color of the cobalt solution, with the dark colors of black and navy blue. At the end of the work, the remaining water in the dust is disposed as sewage, which is highly acidic and rich in minerals and colors.

Of the other sewage production sites in textile factories, washing fibers, wool or cotton are the primary areas, which in turn are very large and contain fats, suspended particles and detergent. In general, for dyeing 1 kg of fiber, about 51 liters of water is consumed.

Nature and type of wastewater treatment in textile and dyeing sewage

The use of colored materials in the textile and dyeing process makes the amount of sewage paint extremely high. In addition, the presence of toxic compounds and highly degradable chemical compounds is one of the most important factors that should be considered in the design and implementation of a textile and dye wastewater treatment system.
Textile and dyeing sewage lack nitrogen and phosphorus to grow bacteria and enzymes. Therefore, the addition of these substances is necessary.

In the various parts of the dyeing and textile process, there is a large amount of suspended solid particles including natural and synthetic fibers, insoluble pigment particles that increase TSS and turbidity of the sewage.

The following analysis can be applied to the treatment of sewage from textile and dyeing industries:
Parameter Value (mg/L)
COD 2000-4000
BOD 500
TSS 750
pH 3-4

Wastewater treatment process of textile and dyeing industries

Like most industrial wastewater treatment packages, textile and dyeing filtration of wastewater are two major areas of chemical, physical and biological purification.

In the physical and chemical treatment of textile and dyeing sewage, according to TSS, and very high turbidity, methods such as electrical coagulation or chemical coagulation are used to remove paint and suspended particles. In these methods, wastewater is prepared for biological purification. It should be noted that the removal of dyes and toxic substances in aerobic and anaerobic units is difficult, and therefore, it is necessary to use chemical and physical methods in the treatment of textile wastewater and dyeing.
Textile wastewater treatment package 

Dyeing sewage is due to the use of acidic and alkaline compounds with variable pH ranges. Therefore, the use of a unitary unit and pH adjustment is very necessary. It should be noted that biological industrial purification units will work well in a neutral pH range.

One of the main differences between textile and dyeing waste with other industrial wastewater is the presence of hard materials degradable. These materials severely disrupt biological purification units. The use of oxidizing compounds, such as ozone and UV, is one of the most effective ways to break down degradable solids in the treatment of textile and dyeing wastewater.

The last step in the treatment of dyeing and textile wastewater, is the biological units which include anaerobic and aerobic units. At this stage, adding nitrogen, phosphate and methanol to the sewage is necessary in order to provide the necessary compounds for bio-enzymes and bacteria. Typical anaerobic treatments for textile and dyeing wastewater treatment include: UABR. UAFBR, UASB and common aerobic methods include: MBBR, IFAS and EAAS which are based on the active sludge method.

Applications of Textile wastewater treatment

The most important reasons for using a textile and dyeing wastewater treatment package are the use of refined wastewater in the agricultural industry and obtaining environmental certification in this regard. But if necessary, it can be recycled to surface water or absorbent wells.
Textile wastewater treatment process

In some factories, due to lack of water, refined wastewater is used in the production line. For this purpose, additional treatment of wastewater is necessary in ways such as using reverse osmosis (UF) (ultrafiltration) or RO (RO). It should be noted that the input water to the dyeing unit at a textile factory should have a salinity or low electrical conductivity, so that dyeing operations without the disturbing ions can be carried out with the best possible efficiency, so if you want to use the refined wastewater in the dyeing unit, attention to this issue is a must.