textile factories

Wastewater treatment techniques in textile factories

There are many technologies for treating wastewater in textile factories, and we have discussed many topics related to treating wastewater in textile factories in a previous article that you can review. If you want to know the effect of dyes on the resulting water and the role and importance of the correct design of the treatment plant.

Chemical oxidation and advanced oxidation

Advanced chemical and oxidation technologies are ideal for water reuse, as they provide outstanding organic matter and color removal performance. They are easy to apply and allow the decomposition of toxic agents.

Chemical oxidation processes use oxidizing agents such as ozone O 3 or hydrogen peroxide H 2 O 2 . In advanced oxidation processes, the hydroxyl radical OH, which is a strong oxidizing agent, is generated.

Physical and chemical processes

Coagulation and flocculation allow the elimination of suspended and colloidal materials (up to 95%) and the associated COD and BOD 5 (between 60 – 80%). It also removes turbidity (above 70%) and color (above 90%).

The most effective coagulants in the textile industry are aluminum salts (including polyaluminum chloride) and iron salts (generally ferric chloride).

After the coagulation and flocculation stage, dissolved air flotation (DAF) equipment is installed to separate the formed flocs.

Activated carbon filters are also used in the pre-treatment stage, as they allow dyes and toxic compounds to be retained so that they do not affect subsequent biological treatment.

Biological treatment: removal of organic materials

Biological treatment allows the removal of organic matter and nutrients through the action of microorganisms under different oxygen conditions.

There are multiple bioreactor designs. Membrane bioreactors, also known as MBR systems, provide better performance for treating textile wastewater. MBR reactors combine a biological treatment process with ultrafiltration membranes.

Membrane bioreactors provide extensive biological treatment, allowing extended cell survival and operating at very high biomass concentrations, facilitating the slow elimination of biodegradable products.

A biological process can be aerobic, anoxic, or anaerobic. In the case of wastewater generated in the textile industry, aerobic treatment is commonly applied.

The use of ultrafiltration membranes allows very high biomass concentrations to be achieved within the reactor, between 6,000 and 12,000 mg/L MLSS (mixed liquid suspended solids), much higher than the concentration obtained using a conventional activated sludge system followed by a decanter. This results in high performance of the biological process, because it allows working at high volumetric loads, while at the same time providing minimal sludge production, much lower than the production produced in conventional biological processes.

With the  MBR system, the elimination of COD and BOD 5  can exceed 90% in the textile industry, although this always depends on the resistant nature of the dyes, which can be eliminated in pre-treatment, or through a special triple treatment with filters. Or membranes.

The unique feature of MBR is that it combines biological treatment and membrane technology. Allowing for the removal of biodegradable and heat-resistant COD. Furthermore, the membranes, acting as a tertiary treatment, allow immediate reuse of water (permeate) and recovery of products (retentate) for more intense purification. MBR can be supplemented with reverse osmosis membrane technology as a tertiary treatment.

Characteristics of MBR reactors

  • Continuous discharge of liquid waste.
  • Complete separation of clay.
  • Organic load removal above 90%.
  • The biomass concentrations that can be achieved inside the reactor are very high: 6000 – 12000 mg/L.
  • Reduced plant sizes, which means saving space and energy.
  • High resistance to oxidizing agents.
  • Very high-quality treated sewage, suitable for reuse.
  • Minimize sludge generation.

CareWater designs and builds modular MBR plants, which offer the possibility of adding additional membrane modules. And compact MBR stations, which include the reaction zone and filtration zone in the same equipment.

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