Printing and dyeing wastewater treatment pretreatment methods

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 mainly aims 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 and improve the quality of wastewater to improve the treatment effect of subsequent treatment units.

Grille

As the printing and dyeing wastewater contains a lot of cloth, thread, fiber litter and other small suspended solids, such as woven fabric scouring and bleaching wastewater, denim rinse wastewater contain a large number of small fiber suspended solids, mixed printing and dyeing wastewater often contain Many of the relatively large suspended substances, which can cause damage to the pump, can affect the treatment of the main unit. Therefore, they intercept the pump and the main structure before it is installed. The grille intercepts the larger suspended solids and the screen is provided to intercept fine suspended solids.

A, grille

Grille is generally used in large quantities of water and water quality more complex integrated 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 and suspended solids larger particles, set the grille Can effectively intercept larger suspended solids, high processing capacity, easy to plug, for the characteristics of printing and dyeing wastewater I do not set the coarse grid in engineering practice, generally only use fine grid, grid gap is usually 1-5mm. Grating machine mainly rotary machine grille machine, chain-type rotary grid machine, fixed grille machine, rotary rotary grille machine, etc., I used the company mainly rotary rotary grinder, mesh Chain transfer grille machine, grille machine and so on.

B, screen

Screen is usually used in the water is relatively small, the wastewater contains a large number of small suspended solids such as: cloth hair, thread, etc., but also can remove large particles of pumice, suspended solids and large particulate matter removal rate of up to 90% the above. 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.

Grit

Printing and dyeing wastewater rinse wastewater (such as cowboy rinse wastewater) contains a large amount of sediment material such as pumice, if the wastewater griting treatment, often resulting in follow-up structures of a large amount of sand, reducing follow-up treatment of pool pooling, Reduce 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 rinsing wastewater are fully analyzed. Considering the fine features of the grit particles, the 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.

Adjust

As the textile printing and dyeing industry 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 great change, requiring the wastewater to carry out Regulate and balance the water quality so that it can evenly enter the subsequent 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, requiring 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-adjusted water, 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.

Cool down

Printing and dyeing wastewater temperature is mostly high (except for sizing printing and dyeing wastewater), such as knitting cloth dyeing and dyeing, knitting thread pulp dyeing wastewater temperature is 40-45 ℃, plush, wool bleaching and dyeing wastewater temperature is 40-50 ℃, woven When the water temperature is too high, it will lead to the normal operation of the wastewater biochemical treatment system, which will directly affect the discharge of wastewater. Therefore, it is necessary to consider the cooling treatment of the high-temperature wastewater, and then make the temperature decrease After the wastewater into the biochemical treatment system in order to achieve the biochemical treatment of water temperature requirements to ensure the normal operation of the entire treatment system, while the thermal energy in 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 DEG 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, the printing and dyeing wastewater is a kind of refractory organic wastewater with large amount of water, high chroma, complex composition, wide variation range of water quality 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.

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