Investigation of the recovery of yarn dyeing wastewater with membrane processes

The effects of environmental factors and uncontrolled water usage on the depletion of natural water resources are increasingly significant. The textile industry is one of the industries with high water usage and wastewater generation. The textile industry, which is strategically important for Turkey, uses a large amount of water in its production processes, alongside various chemical substances. Depending on the production process, the textile industry's wastewater generally contains high concentrations of COD (Chemical Oxygen Demand), BOD5 (Biochemical Oxygen Demand), colour, and other pollutants. In particular, dyeing wastewater can have toxic and highly polluting characteristics that negatively impact the natural environment. Therefore, the treatment and recovery of textile industry wastewater are of great importance for the protection of both natural resources and the environment. Conventional and advanced treatment processes are used for the treatment of textile wastewater. Membrane processes are among the advanced treatment methods commonly used for this purpose. In this thesis study, aluminum sulfate was added to dyeing wastewater from yarn dyeing processes, which contained different colors such as light brown, navy blue, and black, at various concentrations. Following the addition of aluminum sulfate, coagulation, flocculation, and sedimentation processes were carried out using a Jar Test device. With the increase in aluminum sulfate concentration, the COD removal efficiency improved, but there was also an increase in sulfate concentration and conductivity due to the added sulfate. Generally, it was observed that particulate pollutants were removed with the addition of the coagulant, although there was no significant reduction in pollutant concentrations. Molecular weight distribution studies of the water were conducted using membranes of 150 kDA, 50 kDA, 1 kDA, and 0.2 kDA. Pollutants were separated from the water based on their molecular size. It was found that the organic substances constituting COD varied in molecular weight according to the type of dye used and that molecular weights also had an effect on pollutant removal. Based on these molecular weights, it was concluded that appropriate membrane selection should be made with pre-treatment units before membrane filtration.