Textile printing and dyeing wastewater has the characteristics of large amount of water, high content of organic pollutants, large alkalinity and great changes of water quality, which is one of the most difficult industrial wastewater. The wastewater contains dyes, slurries, additives, oil, acid and alkali, fiber Impurities, sand substances, inorganic salts and so on. At present, the main methods used for the treatment of printing and dyeing wastewater are physical and chemical methods, biochemical methods, chemical methods and the combination of several processes. The pretreatment in wastewater treatment is mainly to improve the quality of wastewater, remove suspended solids and directly settle impurities , Regulating the water quality and quantity of wastewater, reducing the temperature of waste water, etc., improving the overall effect of wastewater treatment and ensuring the stability of the entire treatment system. Therefore, pretreatment plays an extremely important role in the treatment of printing and dyeing wastewater. Currently used in printing and dyeing wastewater treatment pretreatment process are: grille, screen, grit, adjust water and water quality, cooling and other technology components. According to different water quality of printing and dyeing wastewater, different pretreatment methods are adopted to remove some pollutants, improve the quality of wastewater and improve the treatment effect of subsequent treatment units. 1. Grille, screen Printing and Dyeing wastewater contains a lot of cloth, thread, fiber litter and other small suspended solids, such as woven fabrics, scouring and bleaching wastewater, denim rinse wastewater contains a lot of small fiber suspended solids, Mixed printing and dyeing wastewater often also contains a lot of relatively large suspended matter, these substances will cause damage to the pump treatment of the main impact, so before entering the pump and the main structure to intercept it, set the grid to intercept larger suspended solids, set Screen interception of small suspended solids. A, grille grille is generally used in large quantities of water and complex water quality printing and dyeing wastewater treatment, such as more than 10,000 tons of textile printing and dyeing industrial park waste water treatment, because of this large amount of wastewater water, and larger particles of suspended solids , Set the grille to effectively intercept larger suspended solids, high processing capacity, easy to plug, for the characteristics of printing and dyeing wastewater I do not set the project in practice coarse grille, generally only use fine grille, grill gap usually 1 -5mm. Grille machine mainly rotary machine grille machine, mesh chain grille machine, fixed grille machine, rotary fine grille machine and so on, my company commonly used mainly rotary fine grille Machine, Mesh chain grid machine, fixed grille machine. B, the sieve mesh is usually used in the water is relatively small, the wastewater contains a lot of small suspended solids such as: cloth hair, thread, etc., but also can remove large particles of pumice slag, suspended solids and large particulate matter removal rate Can reach more than 90%. Engineering practice shows that the screen gap is generally 30-60 mesh, the installation form using a fixed installation, the installation angle of 30-45 °, the installation angle is not easy to be too large, too large, resulting in reduced water load, reducing the processing power at the same time Increased part of the investment, too small is likely to cause the screen clogging, increase the difficulty of cleaning slag, affecting the treatment effect. 2. Dyeing and dyeing wastewater rinse wastewater (such as denim rinse wastewater) contains a large amount of sediment material such as pumice, if not the grit of its wastewater treatment, often resulting in follow-up structures of a large amount of sand, reducing the follow-up treatment structures Of the pool dissolved, reducing the hydraulic retention time, the hydraulic characteristics can not meet the design requirements, seriously affecting the wastewater treatment effect, in particular, will cause wear and tear on the pump to reduce pump life and increase operating costs. Therefore, in some printing and dyeing wastewater treatment set grit treatment is very necessary, grit chamber can be divided into general: grit chamber, aerated grit chamber, cyclone grit chamber. My company is the most widely used advection grit chamber, mainly due to denim rinse wastewater pumic slag surface does not contain large amounts of organic matter, so there is no need to use aeration or cyclone grit chamber, the use of advective grit chamber is simple Easy operation and management. In the process of grit chamber design, the water quality characteristics of rinse wastewater are fully analyzed. Considering the small size of the grit, grit chamber can be divided into two or three grit, which can make the silt particles in series Gradually subsidence, and ultimately achieve the purpose of removing silt, the total stay can be designed for 1.5 hours, sand discharge with gravity and mechanical drainage of sand, sand can be determined according to the actual situation of the project. 3. To regulate the textile printing and dyeing industry due to its unique production process, resulting in intermittent and volatile wastewater discharge, the discharge of wastewater quality and quantity of water within a day, or even within each class have a lot of changes, Waste water to be adjusted to balance the water quality, so that it can be evenly into the follow-up processing unit to improve the treatment effect. Dyeing wastewater regulation is divided into: water regulation and water quality regulation. Wastewater treatment equipment and structures are designed according to a certain amount of water standard, require uniform water, especially for biological treatment system is more important, in order to ensure the normal operation of the follow-up treatment system, the waste water before entering the treatment system, pre-adjust the water to Processing system to meet the design requirements. Printing and dyeing wastewater organic pollutants high, dark, alkaline and pH changes, water quality changes dramatically, it is necessary to adjust the water quality of wastewater, especially the wastewater pH value. Adjust the pH to 6-10 before wastewater enters biological treatment in order to meet the biological wastewater treatment requirements. Practice has proved that, according to the amount of printing and dyeing wastewater, water quality, conditioning pool residence time is also different, when the treatment of water is relatively small, the residence time can be selected larger, when the treatment of water is relatively large, the residence time can be selected according to specific circumstances Some, usually 4-10 hours. For some printing and dyeing wastewater, in order to make the pool have a certain removal efficiency and increase the uniformity of the wastewater, especially when the wastewater contains more reducing substances, consider adding a pre-aeration device in the control tank can be effectively improved Wastewater quality characteristics. Such as denim warp dyeing pulp waste water gas can make part of S-oxidation. 4. Cooling water temperature printing and dyeing wastewater are mostly high (except for sizing printing and dyeing wastewater), such as knitting cloth dyeing, knitting yarn pulp dyeing wastewater temperature is 40-45 ℃, plush, wool bleaching wastewater temperature is 40-50 ℃ , When the water temperature is too low, the waste water biochemical treatment system will not work normally, which will directly affect the discharge of sewage. Therefore, it is necessary to consider the cooling treatment of high temperature waste water, and then, And then make the cooled waste water enter the biochemical treatment system so as to meet the biochemical treatment water temperature requirements and ensure the normal operation of the entire treatment system. Meanwhile, the thermal energy in the waste water is also a reusable resource. The method of cooling waste water is usually cooling and cooling by means of heat exchange. After the waste water of different temperature is mixed and enters the heat exchanger for cooling treatment, the water temperature is generally controlled below 42 ° C, which is beneficial to the growth of the organism and the improvement of the treatment effect . Cooling water can be used fresh process water, thus using a part of the heat to preheat the production process of water, thus reducing the water temperature on the one hand, on the other hand to raise the water temperature of the production process water, saving water heating fresh process Of the steam, to achieve the purpose of saving production costs. Heat exchange program can consider the use of multiple heat exchangers in parallel design, to ensure the normal use of heat exchange system, the heat exchanger can be divided into plate heat exchanger, tube heat exchanger, etc., the most widely used by our company Is efficient plate heat exchanger. In short, printing and dyeing wastewater is a kind of refractory organic wastewater with large amount of water, high chroma, complex composition, wide range of water quality variation and high temperature. Through a large amount of engineering practice, it has been proved that the pretreatment of waste water in the comprehensive treatment process of printing and dyeing wastewater Process is very important, it is related to the stable operation of the entire system and discharge standards, but also involves the level of operating costs, wastewater pretreatment can greatly improve the quality of wastewater, dyeing and printing wastewater is conducive to further processing, and ultimately achieve the removal of pollution The purpose of things. Therefore, pretreatment of dyeing and printing wastewater treatment is an indispensable one of the key technologies.