TEXTILE DYEING WASTEWATER AND TREATMENT SOLUTION

Characteristics of textile dyeing wastewater

The textile and garment industry is playing an important role in Vietnam's economy. Beside its great contribution to the development of Vietnam, the textile and garment industry have also brought some negative impacts on the environment, especially wastewater sources from the production process. Every year, the textile and garment industry discharges large amounts of wastewater with high concentrations of pollutants into environment due to untreated or treated action but not up to the permitted standards.

In the major stages of textile and garment industry, the dyeing and completing process often generate the most wastewater in which the wastewater composition is unstable and varies by types of dyeing equipment, raw dyed materials and chemicals. Textile and dyeing wastewater usually consists of three main chemical groups: (1) The dyestuff group includes direct, dispersed, reactive dyes, acids containing chromium metal, reconstituted metal and sulphur; (2) additives including colour-holding, colour-stopping chemicals which are usually heavy metal salts; (3) Other chemicals including acids, inorganic salts, caustic soda and oxidizing agents, starch, etc.

Basically, textile-dyeing wastewater often has high temperature, colour, PH, BOD and COD. On the other hand, wastewater from textile industry contains some chemicals with heavy metals, toxic components that can not only destroy aquatic organisms but also directly affect human life.

Some polluted parameters of textile wastewater

Current status of textile wastewater treatment technologies in Vietnam

Some of the technologies are applied in dyeing and weaving business including: (1) Combination of chemical-physical method (coagulation/ flocculation) and filtration, (2) Combination of chemical-physical method and aerobic biological treatment and vice versa, (3) combining chemical-physical method, aerobic biology and chemical-physical method (4) Combination of chemical-physical method, biological treatment and filtration (sand filter or activated carbon).

Due to the particularity of dyeing and weaving business using high temperature during dyeing process, wastewater is usually high temperature. In production line of some textile and dyeing enterprises, cooling tower or cooling rig is used to reduce the temperature of the wastewater before collecting into the treatment system. In general, the traditional technologies applied in the treatment of textile wastewater have many shortcomings, the effectiveness is not high , complicated and space-consuming process, the treatment of pollutant components is not thorough, especially the COD pollution parameters, the colour level that lead to the unstable output water quality.

Effective textile wastewater treatment using MBR-X biological membrane technology

The characteristic of MBR-X technology is able to operate at low membrane pressure state when submerging underwater. When MBR-X module is in operation, water penetrates through biofilms and through the water distribution holes to flow into water pipes from which it pours into two water channels along the sides of the flanks. The special flow structure of the MBR-X module helps water penetrates the membrane quickly, reducing resistance to the lowest level and keeping the pressure across the membrane when the module operates at low conductivity. With an innovative design, the MBR-X helps the flow expand gradually, reducing losses to low levels and operating with lower filter pressure. MBR-X causes less clogging for stable filtration.

At present, MBR-X technology is applied to many projects in various industries with different discharge capacities from 20 m3/day or more. Especially, this technology has been applied to treat textile dyeing wastewater at Hangzhou Zhongqiang Print & Dye Co. Ltd (Hangzhou, China). The discharge capacity is 3,000 m3/day, the MBR-X membrane basin area is 120 m2 (40 MBR-X200 modules are required), the total installation area of ​​the system is 843 m2, operating cost is equivalent to 11,823 VND/m3 of wastewater, and 80% of wastewater can be reused after treatment.

MBR-X technology can be effectively combined with other technologies such as anaerobic, aerobic, SBR or AB, etc. With the combination of the advantages of hollow fibre membrane and flat membrane, MBR-X module does not require suction pump. It has the flow distribution design, which was patented. Moreover, it also helps save energy cost and can prolong the life of the membrane. In addition, MBR-X technology can increase the microbial density by three-four times, with 4-hour water retention duration, and can reduce the operating cost of the system. This is an efficient technology for enterprises looking for alternative solution to physical and chemical technology and wanting to apply membrane technology, biotechnology in wastewater treatment to re-use water.

After treatment at MBR-X system, textile dyeing wastewater can meet the standards of column A or B according to QCVN 13-MT: 2015 / BTNMT.

References:

MSc. Nguyen Thanh Ngan (Vietnam National Textile and Garment Group) - Efficiency of wastewater treatment by microbiological technology

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