With the development of textile technology in Inner Mongolia wastewater treatment , in recent years, solvent dyeing technology systems using organic solvents as media have been established on traditional water-based dyeing systems, and gas-phase dyeing using dye sublimation as a gas. Because the solvent dyeing method is dry matter dyeing, the dyeing matter is still dry, and many post-processing steps are omitted. These printing and dyeing methods can minimize the discharge of waste liquid and avoid serious pollution of the water environment by the textile printing and dyeing industry. Wastewater from the cotton textile industry mainly comes from the dyeing and finishing section, including desizing, cooking, bleaching, mercerizing, dyeing, printing and finishing. Wastewater Discharge in Weaving Section
(1) Desizing wastewater Cotton fabric and some impurities of the fiber itself must be removed before bleaching. Desizing wastewater generally accounts for about 15% of the total wastewater, and pollutants account for about half of the total. Desizing wastewater is alkaline organic wastewater, containing various pollutants such as pulp decomposition products, fiber shavings, acids and enzymes. The wastewater is pale yellow.
(2) In order to ensure the processing quality of bleaching and dyeing, the impurities such as cotton wax, oil, pectin-containing nitrogen compounds in the fiber should be removed. The cooking process generally uses water solvents such as caustic soda, soap, and surfactants to cook cotton fibers at 1200C and a pH value of 10-13. The cooking wastewater has a large amount and is strongly alkaline, with an alkali concentration of about 0.3%. The wastewater is dark brown, and BOD and COD are up to several thousand milligrams per liter.
(3) Bleaching wastewater The bleaching process generally uses sodium hypochlorite, hydrogen peroxide (hydrogen peroxide), sodium chlorite and other oxidants to remove colored impurities on the surface and inside of the fiber to bleach the fabric. Inner Mongolia wastewater treatment. Because hydrogen peroxide is almost completely decomposed in bleaching wastewater, and most of the chlorine in chlorine-containing bleaching agents such as sodium hypochlorite and sodium chlorite is decomposed during bleaching. Small, BOD5 and CODcr are both low, basically belong to clean wastewater, which can be directly discharged or recycled.
(4) Mercerizing wastewater Mercerizing treatment is to soak the fabric in concentrated sodium hydroxide solution, the purpose is to improve the tensile strength of the fiber, increase the surface gloss of the fiber, reduce the potential shrinkage of the fabric, and increase the affinity with the dye. Mercerizing wastewater contains 3% to 5% of sodium hydroxide. Generally, it is recovered by multi-effect evaporation and evaporation, and is first used for mercerizing applications, and then used for the preparation of refining liquid, waste alkali liquid and desizing.
(5) Dyeing wastewater Dyeing wastewater is characterized by large changes in water quality and deep color. The main sources of pollution are dyes and auxiliaries. Different fiber raw materials require different dyes, auxiliaries and dyeing methods, plus the dyeing rate of dyes, the concentration of dyeing liquor, the dyeing equipment and scale, and the quality of wastewater varies greatly.
(6) Printing wastewater The pollutants of printing wastewater mainly come from the washing water of color mixing, printing drum and printing screen, as well as the waste water of soaping, washing and washing of printed interlining after treatment. The pollution degree of Inner Mongolia wastewater treatment printing wastewater is very high. In addition, a large amount of urea is used in reactive dyes to increase the ammonia nitrogen content of printing wastewater.
(7) Finishing Wastewater In addition to woolen clothes, finishing wastewater contains various resins, formaldehyde, and surfactants, but the amount of wastewater is small.