Textile effluent is a variety of waste water generated in the process of spinning and weaving. Textile industry wastewater can be mainly divided into several categories: printing and dyeing wastewater, chemical fiber textile wastewater, degumming and scouring wastewater, among which the serious pollution is mainly printing and dyeing wastewater and chemical fiber textile wastewater.
1. The textile printing and dyeing industry is one of the industrial sectors that consume a lot of water and discharge more wastewater. According to statistics, my country's printing and dyeing enterprises discharge 3 million to 4 million tons of wastewater every day. Textile industry wastewater generally contains suspended solids, grease, fiber scraps, surfactants and various dyes. For example, cotton textile wastewater often contains cotton scraps and pulp, wool textile wastewater often contains grease; printing and dyeing wastewater often contains pulp, dyes, auxiliaries, and a variety of organic substances, Industrial wastewater treatment polyacrylamide.
2. Textile wastewater mainly has the following characteristics:
(1) The amount of water is large; the pollution of wastewater is mainly organic pollution;
(2) The concentration of pollutants is high; the pollutants in wastewater are mainly the second category of harmful substances;
(3) Most of them are alkaline with high color;
(4) Water quality changes greatly, and it is difficult for general wastewater treatment facilities to meet higher discharge standards.
3. Pollution indicators. The textile processing wastewater contains a wide variety of pollutants and is extremely complex. It is impossible to check all the pollutants one by one in the analysis and testing of the wastewater. Therefore, the analysis and testing of the environmental monitoring can only be used to analyze and test the water pollution. Several items are used as wastewater quality control indicators.
(1) Water temperature. The water temperature of textile processing wastewater varies greatly. As far as the water temperature of printing and dyeing wastewater is concerned, it is usually in the range of 30-40℃, but sometimes it can exceed 40℃, which brings certain difficulties to the treatment of wastewater by biochemical methods.
(2) pH value. The pH value of textile printing and dyeing wastewater is generally high, up to 9-12, and sometimes even more than 13. If the pH value of wastewater exceeds 10, biochemical treatment generally cannot be used.
(3) Chroma. High chroma and variable color are one of the main characteristics of textile printing and dyeing wastewater. Although pigments are not harmful, colored water can easily make people feel disgusted. Therefore, chroma is one of the main indicators of water quality control.
(4) Solid matter. Wastewater often contains a large amount of solid matter, including dissolved solids and suspended solids.
(5) Toxic substances. After toxic substances reach a certain concentration, they will endanger human health, poison or inhibit the growth of aquatic organisms, and affect the normal operation of wastewater biological treatment. Generally can be divided into acute poison and chronic poison.
(6) Organic substances. In engineering, oxygen demand and carbon content are usually used.
4. Harm, the waste water produced by textile processing contains various pollutants. If the waste water is discharged directly to rivers, lakes and seas without treatment, it will cause serious pollution to the natural environment and also a serious threat to human survival. Industrial wastewater treatment polyacrylamide.
(1) Pollution to natural water bodies
When textile wastewater is discharged into a natural water body, a large amount of organic matter in it will quickly consume the dissolved oxygen in the water body under the action of aerobic microorganisms. The organic matter deposited on the bottom of the river undergoes anaerobic decomposition under the action of anaerobic microorganisms due to lack of oxygen, and the released hydrogen sulfide further consumes dissolved oxygen in the water body, resulting in a substantial drop in the dissolved oxygen concentration in the water body. Threaten the survival of aquatic life. In addition, there is a certain amount of bleaching agent in textile wastewater, and the free chlorine in it may destroy or reduce the river's self-purification ability. Certain heavy metals can also endanger the growth of aquatic animals and plants in long river sections.
Textile wastewater with dyes can color the river water, reduce the transparency of the river water, thereby slowing down the assimilation speed of aquatic plants, indirectly hindering the growth of fish, and also greatly reducing the utilization rate of water by humans.
(2) For the pollution of farmland, irrigating farmland with textile wastewater will cause soil salinization due to high alkalinity. The suspended matter in the wastewater will block the pores of the soil, hinder the inhalation of crop roots, and affect the growth of crops. The optimum growth temperature for crops and soil microorganisms is 20-25°C, but sometimes the temperature of wastewater can be as high as 30-40°C, so it will also have adverse effects on crops and soil microorganisms. Although the content of toxic substances in wastewater is very small, and although there is no direct harm to humans, animals and crops, they will continue to accumulate in the roots and fruits of crops. In addition, it will pollute groundwater.
(3) Impact on urban sewage treatment, general textile wastewater can be directly discharged into urban sewers, and together with urban sewage, it enters the urban sewage treatment plant for unified treatment. However, the concentration of desizing wastewater with high concentration and wastewater containing aniline or sulfur dyes must be controlled, otherwise, it is not conducive to the biochemical treatment of sewage plants. Wastewater containing sulfur dyes has a corrosive effect on concrete pipes, and acid-base wastewater has a certain corrosive effect on urban underground drainage pipes.
(4) Impact on human health, various pollutants in wastewater will more or less affect human health. Heavy metals such as mercury, cadmium, lead, zinc, chromium and copper plasmas are prone to change in valence after forming sulfides with sulfur. When they enter the human body, they have a strong affinity with the sulfhydryl group (-SH) on the active center of certain enzymes in human tissues, and will inhibit the enzyme activity after binding.
5. Treatment measures, in order to reduce the capital investment and operating costs of textile wastewater treatment, the basic task of textile wastewater treatment is to reduce the flow of wastewater and reduce the degree of wastewater pollution. To this end, the following basic measures can be taken:
(1) Reform process, reform process is an important method to reduce the amount of waste water and reduce the concentration of pollutants in the waste water. Usually the gap operation is changed to continuous operation, because continuous operation requires less space and uses less water and chemicals.
(2) Replace the medicament, replace the medicament, that is, use the low BOD chemical medicament to replace the traditional high BOD chemical medicament.
(3) Recycling of dyestuffs. Recycling dyestuffs is a measure that can not only receive economic benefits, but also reduce the concentration of pollutants in wastewater. Such as recovery of alkali from cotton fabric waste liquid, recovery of lanolin from wool washing liquid and recovery of PVA from desizing waste liquid.
(4) Diversion and reuse, and separate treatment of severely polluted and lightly polluted wastewater.