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Textile industry of Uzbekistan: Узбекистан - Ташкент Textile industry of Uzbekistan:
Custom-designed wastewater treatment facilities
Textile industry is one of the most priority branches of economy in Uzbekistan. This becomes possible due to the availability of rich and high-quality raw material– cotton and silk. Today, Uzbekistan is ranked fifth in the export of raw cotton, and the second – in the export of textile goods. Currently, textile industry forms the 5th part of the gross domestic product of the country. Also the third part of industrial workers is engaged in this social oriented industry. If in the earlier 90s the situation was different, the volume of processing of cotton fiber did not exceed 7 %, by 2016, after getting the independence, this index has reached 40% due to the reorganization of Uzbek industry . The targeted state economic policy, oriented on diversification and modernization, improvement of the domestic industry competitiveness, support for development of its leading industries and increasing of export potential by intensification of processing the local raw materials had been implemented.
The production capacity of the industry is 450,000 tons of yarn, 296 million square meters of fabrics, 90,000 tons of knitted fabric and 270.2 million of knitted garments per year. Nowadays, the export of products has increased 120 times - up to $ 1 billion against $ 7 million in 1991. The products labeled “Made in Uzbekistan” are exported to more than 50 countries, including EU, CIS region, South American countries, Korea, China, Singapore, Iran, Israel and USA. Uzbek textile is also popular in Pakistan, Georgia, Croatia and Nigeria .
The indicators of implementation of modern technologies and development of technical equipment of production facilities have increased. More than 1.6 million of spinning spindles and 100,000 chambers were commissioned, that equal to 89.3% of existing technological equipment.
Our life dictated by and is directly connected with development of modern technologies. This evolutionary-positive influence has its risks and might have negative impact on the environment. In response to this, most of the countries, including Uzbekistan are constantly improving the environmental legislation and applying new laws and standards for business operation. One of the main requirement and standard is related to industrial water treatment facilities. In average, 2.7 thousand liters of water are required to produce only one shirt, therefore high demands in water treatment is relevant in the textile industry.
At current stage of development, the main products of textile industry are cotton, linen, wool and silk, yarn, fabrics made from natural and chemical fibers, their mixtures and its ready products. This industry includes spinning, twisting, weaving, dyeing and sewing plants, where the majority of industrial wastewater is formed in dyeing plants, and during the sizing of yarn, chemical treatment of fibrous materials and finishing of textile fabrics.
The contamination of wastewater from dyeing and finishing plants has a complex content of insoluble organic and mineral impurities, colloidal and true solutions. Therefore, it requires more specific approach to the organization of wastewater treatment process.
The technological scheme of wastewater treatment with detailed description of the main equipment and layout of its components for dyeing of knitted fabric are shown as an example of effective treatment facilities for this industry.
Description of technological solutions of proposed scheme
According to the proposed treatment scheme, the industrial wastewater is directed to receiving section of sewage pumping station once its passed the mechanical screen of fine grating. The proposed installation for mechanical wastewater treatment allows receiving the waste suitable for disposal in solid waste disposal plant. After passing through the screen, to collect and neutralize wastewater, it is directed to the neutralizing storage.
For treatment of industrial wastewater, we propose to use pressure flotation unit, which allows to achieve high efficiency of treatment of suspended substances, COD, fats and to partially remove the dissolved impurities.
The treated wastewater flows under gravity into the existing pressure collector.
For dehydration of sediment, formed during purification (floto foam and float sludge), we suggest to use mechanical dehydration system based on screw press as an option (produced by HUBER).
General technical data
The estimated costs for wastewater:
Wastewater flow rate - 1000 m3 / day;
Maximum per hour - 42 m3 / h .;
The composition of incoming wastewater is given in the Table 1.
The qualitative indicators of waste water and maximum permissible concentration
No. Indicator name Unit Indicators of incoming wastewater MPC
1 Suspended substance mg/dm3 310 500
2 Synthetic surface-active substance; mg/dm3 9,6 20
3 Chemical oxygen demand мгО2/ dm 3 840 500
4 Biological oxygen demand мгО2/ dm 3 201,3 30
5 Sulphate mg/ dm 3 269,9 500
6 Chloride mg/ dm 3 1601,7 350
7 рН Unit 10,5 6,5-7,2
Mechanical treatment of industrial wastewater
The drum screen with gap of 2.0 mm is used for mechanical treatment of wastewater of main production of coarse waste.
The installation is designed for operation in industrial wastewater treatment facilities. It is the first stage of wastewater treatment process.
Principle of screen operation
The contaminated wastewater is pumped into receiving chamber of drum screen, where the flow rate is decreased. Then, water directed to drum screen with cell size of 2.0 mm, then to the outlet branch. Mechanical inclusions, the size of which exceeds 1 mm, remain on the surface of the screen, where they are removed and director to the waste container by scraper mechanism, located at acute angle to the screen.
Node of pressure flotation of industrial wastewater
After the screen, the wastewater is directed to neutralizer, where by submersible pump with average flow of 60 m3/h it is directed to physicochemical purification - into the flocculant.
The neutralizing of wastewater is necessary to smooth irregularity of waste flow and polluted waste water to physicochemical purification, and pH leveling.
It allows to achieve the stable high efficiency of wastewater treatment during flotation treatment and to reduce the amount of introduced reagents.
In order to prevent the sedimentation of suspended substances in neutralizer, the stirring mechanism, made of stainless steel can be installed.
Physicochemical purification
The physicochemical purification is proposed to be carried out by the method of reagent pressure flotation.
Dosing of coagulant, alkali and flocculant solutions is made by high-precision dosing pumps. The adjustment of pH is performed by using of automatic pH control system that controls the alkali dosing pump. Preparation of 0.1% working solution of the flocculant is carried out by station for the preparation of flocculant solution.
Pressure flotator with chemical stage
Flotation is the process of molecular adherence of floated material particles to the interface of two phases, usually gas (more often - air) and liquid due to redundancy of free energy of surface boundary layers and surface phenomena of humidification.
A set of each installation includes automatic control panel, components necessary for its complete automatic operation, as well as chemical stage.
Operation mode of pressure flotation unit
Flotation of industrial wastewater consists of the formation of “particle-bubble” complexes, the floating of these complexes and removal of formed foam layer from the surface of treated liquid. Its particles can adhere to the surface of gas bubble only when there is no humidification or poor humidification of the particle by liquid. Saturation of wastewater with air and using of reagents can significantly improve the quality of water in the following indicators: suspended substances, fats and oils, phosphates, BOD and COD.
Before purification In mixing basin after addition of reagents
After reagent flotation
The suspended substance and impurities, contained in wastewater are removed in flotation process by the smallest bubbles (30-50 microns).
The part of wastewater coming from the flotator is supplied as the recycling water and saturated with small air bubbles for pumping by two-stage centrifugal pump. This pump led to the process of air dissolution.
The water saturated with air is directed from nozzles to the mixing zone of the flotator; in the flotator, the pressure drops sharply under the inlet of the wastewater. Due to the regular supply of pressurized water to the flotator, air bubbles are adhered to the particles of contaminants and rise to the surface. The sediment layer on the surface is removed by the scraper. The sediment is collected into special storage tanks and removed by using of pneumatic valve, which regulated by timer.
The actual flotation area, in comparison with similar installations, is increased due to design features. This provides higher capacity of removing the contaminants and compact of installation.
Flotation mud and sediment are collected from the flotator into the tank and directed to mechanical drying.
The ready to use coagulant and alkali is imported in "eurocubes": LxBxH: 1170x1260x1040 mm, the containers procured once and can be served as the replacements.
Processing of float foams and float mud
During wastewater treatment with volatile organic compound, the following types of
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