Textile and leather industry
Textile and leather industry
Products made from leather are used for different purposes, for example, for making shoes, for furniture and passenger compartment upholstery and other lines of industry. For reprocessing the jackets a water solution of different compounds is needed to be added. That is why the composition of wastewater depends on the leather producing technologies, quality and amount of compounds that are used in various processes.
Textile and leather industry wastewater is considered to be much polluted. The wastewater contains a lot of organic impurities such as parts of flesh, wool, blood, and dung, decomposition products of protein, fats, surface-active material and lots of mineral matters (which include some toxic components). Textile industry makes no less pollution than the leather one, every day on such factories is used a huge amount of dyes and chemical components, and it is difficult to get rid of them because they consist of the complex organic compound with a complex structure. In wastewater fats, waxes, bleaches, dextrins, dyes, and detergents can be found. They appear in the process of washing, bleaching, fermenting, softening, dyeing and other steps.
There are different methods of the textile wastewater treatment plant. We can divide them into four main groups, which are: mechanical, physiochemical, chemical and biological.
- Mechanical treatment includes using equipment which helps to remove FOG (fats, oil, and grease) and other solids from the water. It’s common to use screenings, centrifuges, and coagulation with calcium salts or aluminum for such treatment.
- The next type of textile industry wastewater treatment, physiochemical, includes coagulation, solvent refining, and getter methods of treatment, flocculation, dissolved air flotation (DAF), sedimentation, filtration and oxidation of sulfides and chromium precipitation. As a result of physiochemical treatment, there are not any COD or suspended solids in wastewater.
- A chemical way of treatment is based on oxidation-reduction reactions, neutralization tests, sedimentation of high-density metals ions and oxidation.
- Biological textile wastewater treatment plant is carried out in activated sludge units and biological filters with the use of microorganisms.
All the mentioned methods can be united in one multi-step cleaning system, which uses activated carbon absorption, chemical oxidation, ultrafiltration, nanofiltration, and ion exchange. Of course, it has advantages and disadvantages. On one hand, such system can achieve several times the higher level of reduction of waste load. On the other hand, it consumes very much energy. That is why for decreasing all expenses it is needed to find new better processing solutions which would reduce the cost of everything.