To reduce pollution in chemical wastewater color removal in the process color remover chemicals are used. The global climate change we experience as a result of rapid population growth and industrialization imposes some limitations on the use of our fresh water resources. Especially industrial wastewater As a result of being discharged to the receiving environment without being sufficiently treated, our already limited fresh water resources are polluted, reduced and become unusable due to the uneven distribution of the annual total precipitation between the basins, the uncontrolled concentration of the population and industry in certain basins. lately Water Pollution Control Regulation(WPCR) in order to protect the receiving environment for industries such as textile, food, paper and chemistry, the color parameter‖ has been defined as a new waste water pollutant parameter.
Color Removal of Waste Water in the World
The national and international importance of color control in industrial wastewater discharged to the receiving environment is increasing day by day, and the color parameter and limit value have been applied for a long time in countries such as the European Union (EU), England, India and China. The direct discharge of colored wastewater into the receiving environment adversely affects the photosynthetic activities due to the decrease in light transmittance in the relevant water body and decreases the dissolved oxygen concentration in the environment over time. At the same time, due to the toxic effects of dyestuffs and their by-products on nature and their mutagenic and carcinogenic effects on humans, they must be purified. For this reason, it is inevitable to accept the color parameter as a polluting parameter as well as the pollutant parameters such as dissolved organic solids (DOC), suspended solids (AKM).
Color Removal Standard
The Pt-Co color method is a color measurement method and was developed by Chemist ―Allen Hazen‖ in 1982. This method was developed to determine and evaluate the chromaticity levels in waters. Since then, it has been used to determine the color values of samples containing yellow tones. According to this method, the color and concentration of the sample is determined by visually comparing it with known colored solutions. Comparison can also be made with special, calibrated, colored glass discs. The Pt-Co method is a standardized and widely used method for color measurement. It is the color unit of 1 mg platinum/L caused by the chloroplatinate ion. Ratios from cobalt to platinum may differ to match wavelengths in special cases. The ratios given regarding color tones are generally successful in determining the colors of natural waters.
The Pt-Co color method is useful in determining the color caused by potable waters and naturally occurring substances in the water. It cannot be applied in heavily colored industrial wastewater. In the presence of heavily colored waters mixed with industrial wastes, the color tones may deviate from the platinum-cobalt standards and it may be very difficult or impossible to compare with the standard method. Different color measurement methods should be used for such waters. Color remover These measurements must be made carefully before chemicals are used.
Technologies Applied in Color Removal in Textile Industry
Many physicochemical and biological processes are used in the removal of color in textile wastewater. When these processes are examined in general, biological methods are advantageous in terms of being economical and environmentally friendly compared to physical and chemical methods. However, studies have shown that using only one of these color removal processes is often not sufficient, and it is technically and economically more convenient to use many methods together. Anaerobic microorganisms, which play a role in the anaerobic biological treatment process, which is preferred for removing color from wastewater originating from textile processes, are very sensitive to toxic shock loads. This is an effect that slows down color removal. There are many parameters such as heavy metals, sulphide, sulfur, salts and other components that adversely affect the biological treatment efficiency.
Color and Treatment of Leather Industry Wastewater
Dyestuffs discharged from the leather industry wastewater to the environment can reach from underground waters to drinking water or to vegetables and fruits by irrigation. However, it is often difficult to remove complex colored coloring matter from wastewater. Although a single process is not sufficient for color removal, a combination of several processes is used.
Color removal The by-products that emerge during the processes applied for The leather industry has worked on many different methods for the treatment of wastewater. Biological methods used for the treatment of leather industry wastewater generally include single-stage or double-stage long-aerated activated sludge processes or sequential anaerobic-aerobic treatment processes. Pressure sand filters and activated carbon filters are generally preferred as tertiary treatment processes. However, conventional treatment processes such as chemical coagulation or aerobic treatment are insufficient to remove color from leather industry wastewater.
Color and Treatment of Food and Beverage Industry Wastewater
Among the food and beverage industries, factories producing yeast and alcoholic beverages are at the forefront of the industries that produce the most colored wastewater.
- Colored Wastewater During Yeast Production and Its Treatment
Significant and high quality water is used in the cleaning, sterilization of molasses, which is used as a raw material during yeast production, at every stage of the fermentation process and after it, in the filtering, mixing, extrusion-cutting stages, and in the cleaning of production areas and equipment. Therefore, large amounts of wastewater are generated in the food and beverage industries, especially in the yeast industry, due to the consumption of large amounts of water.
Factories producing yeast produce two types of wastewater with high and low pollution load. The main pollution components in wastewater, which has a high pollution load, are COD and color. Sugar beet molasses used as raw material in this industry contains high molecular weight, melanoidin type, dark brown colored, biodegradable organics. When wastewater containing high levels of color such as molasses is discharged to receiving environments such as lakes, rivers and seas, they increase the turbidity of the receiving environments and reduce the penetration of sunlight into the water. As a result, aquatic life is damaged due to photosynthetic activity and a consequent decrease in soluble oxygen concentration. These compounds, which give high color, are very difficult to break down in purification processes. Even though COD removal has been achieved to a great extent after the combination of anaerobic-aerobic treatment from yeast industry wastewater, the color and odor of the wastewater cannot be completely removed.
- Colored Wastewater During Alcohol Beverage Production and Its Treatment
The wastewater of factories producing alcoholic beverages has a very high BOD5 (35000-60000 mg/L) and COD (60000-100000 mg/L) content, high color (180000-220000 Pt-Co) and low pH value (<4.0-4). ,5) has. Molasses, which is formed as a by-product in sugar production processes, is used as a raw material in factories producing alcoholic beverages due to its low cost. The wastewater of these factories generally contains organic substances with brown appearance. The brown color in the wastewater of factories producing alcoholic beverages is due to the high molecular weight (5000-40000 Da) biopolymers called melanoidin. Since melanoidins are highly resistant compounds, it is not possible to completely remove the color from these wastewaters with conventional biological treatment methods (anaerobic digestion, anaerobic lagoons, activated sludge process, etc.).
Therefore, microbial decolorization methods (using fungi and bacteria) and physico-chemical methods (coagulation, nanofiltration, electrocoagulation and electrofenton and activated carbon adsorption) are applied for color removal from wastewater of factories producing alcoholic beverages.