Current Situation of Treatment of Printing and Dyeing Wastewater

The current situation and research progress of printing and dyeing wastewater treatment at home and abroad. Dyes not only have specific colors, but also complex structures, mainly composed of polymer complexes, which are difficult to break. Their biodegradability is low, and most of them have potential toxicity. Their fate in the environment depends on many unknown factors. In addition, dye production has the characteristics of multiple varieties, small batches, and fast updates, which makes it difficult to find effective treatment methods for dye wastewater. There are many treatment methods for dye wastewater, which will be briefly introduced below.

1.1 Membrane Separation Method for Printing and Dyeing Wastewater Treatment

Membrane separation method is a general term for the selective permeation of certain components in liquids using special membranes. Commonly used membrane separation methods include dialysis, electrodialysis, ultrafiltration, and reverse osmosis.

Membrane technology can separate dye wastewater into concentrate and permeate. The concentrated solution can be used for dye recovery, and the permeate can also be reused for dye production.

This approach can achieve effective treatment of wastewater and prevent dye loss with drainage, without causing water pollution.

However, membrane separation technology has high processing costs due to concentration polarization, membrane fouling, and the high cost of membrane replacement, which seriously hinders the large-scale industrial application of membrane separation technology.

1.2 Extraction Method for Printing and Dyeing Wastewater Treatment

The essence of extraction is to use an extractant that is immiscible with water but can dissolve pollutants well, so that it can be fully mixed with wastewater and separated and extracted using the different distribution ratios of pollutants in water and solvents, thereby purifying wastewater.

The commonly used extraction methods include solution extraction, electrophoresis extraction, liquid membrane method, etc.

However, the extraction method has disadvantages in practical applications, such as high consumption of extractants, difficulty in separating extracts, high cost of treating one ton of water, and inability to continuously process large amounts of water.

1.3 Radiation method for treatment of printing and dyeing wastewater

Microwave radiation is a commonly used method for treating dye wastewater in radiation methods.

Microwave radiation is a new technology that emerged in the 1980s for the elimination of organic pollutants. Microwaves are located between infrared radiation and radio waves in the electromagnetic spectrum, and only affect polar molecules in liquids. They can cause high-speed rotation and collision of polar molecules, resulting in thermal effects that change the thermodynamic functions of the system, reduce the activation energy of reactions, and decrease the chemical activity of molecules.

In addition, microwaves also have non thermal effects, that is, in the microwave field, violent polar molecular oscillations can break chemical bonds and degrade pollutants.

But the main challenges of this technology are that the equipment used to generate high-energy particles is expensive, the technical requirements are high, and the energy consumption and energy utilization efficiency of this method are high; In addition, special protective measures are required to avoid the harm of radiation to the human body. Therefore, in order to put this law into operation, a lot of research and exploration work is needed.

1.4 Oxidation Method for Printing and Dyeing Wastewater Treatment

Oxidation method is also a commonly used method for treating dye containing wastewater, currently including high-temperature deep oxidation method, chemical oxidation method, and photocatalytic oxidation method. The application of photocatalytic oxidation technology in the field of dye wastewater treatment has good market prospects and economic benefits.

1.5 Coagulation method for printing and dyeing wastewater treatment

Coagulation method is a commonly used method for wastewater treatment, mainly including coagulation sedimentation method and coagulation air flotation method.

However, the operating cost of this method is relatively high, with a large amount of sludge and difficulty in dehydration. The removal rate of hydrophilic dyes and other soluble N and P compounds in the water is poor, and new efficient coagulants need to be developed.

1.6 Biological methods for treating printing and dyeing wastewater

Generally speaking, physical and chemical treatment methods only concentrate and transfer pollutants, and the potential impact on the environment cannot be ignored. Biological methods, on the other hand, utilize pollutants as a nutrient source for microorganisms, and are an ideal means of reducing and harmless pollutants.

Biological methods are widely used in dye wastewater treatment, with advantages such as good treatment efficiency and low operating costs.

However, due to technical reasons, the operation of this law is unstable, its applicability is not wide, and it is greatly affected by external factors, which has limited its practical application to a certain extent.

1.7 Adsorption Method for Printing and Dyeing Wastewater Treatment

The adsorption method has a special position in the field of wastewater treatment due to its ability to selectively enrich certain compounds. Adsorption refers to the residual surface energy of molecules or atoms on a solid surface due to unbalanced forces. When certain substances collide with the solid surface, they are attracted by these unbalanced forces and remain on the solid surface.

The result of adsorption is the concentration of adsorbate on the adsorbent, and the surface energy of adsorption decreases.

Adsorption technology is the use of porous solids to adsorb one or several pollutants in wastewater, in order to recover or remove certain pollutants, and is also a method for purifying wastewater. Commonly used adsorbents in adsorption methods include activated carbon, resin, minerals, waste, etc.

There are two mechanisms for adsorption decolorization of dye wastewater: adsorption and ion exchange. The adsorption efficiency is influenced by many physical and chemical factors, such as the interaction between dye and adsorbent, the specific surface area of adsorbent, the particle size, temperature, pH value, and adsorption time of adsorbent.

(1) Activated carbon adsorption method

The high price of activated carbon limits its application. After use, activated carbon needs to be regenerated using two methods: high temperature and desorption treatment. Regeneration can result in a loss of 10-15% of activated carbon.

(2) Mineral and waste adsorption method

Many substances in nature have porous structures and good adsorption properties, which can be used to treat dye wastewater. Natural minerals mainly include various clays, ores, coal, etc., which are generally abundant in reserves. In China, there are also a large amount of waste such as slag, slag, coal slag, fly ash, etc., which are more cost-effective. Therefore, the application prospects of these inorganic adsorbents are relatively broad.

(3) Adsorbent adsorption method

In the late 20th century, with the successful development of structurally improved ion exchange resins, adsorption resins, and composite functional resins, resin adsorption methods were widely used in the treatment and resource utilization of chemical wastewater.

Jiangsu Haipu Functional Materials Co., Ltd. has synthesized adsorbents with different physical and chemical properties for the treatment of printing and dyeing wastewater, and achieved good treatment results. The adsorbents synthesized by the company can not only effectively remove COD in dye wastewater, but also remove indicators such as ammonia nitrogen in wastewater. The wastewater can be discharged continuously and stably in compliance with standards.

Customer demand for printing and dyeing wastewater industry

The characteristics of dye wastewater determine that it cannot meet discharge standards through traditional treatment methods. Therefore, the adsorption method developed by Haipu functional materials can be used to treat this type of wastewater, in order to optimize the treatment effect and economic cost, which is a development direction in dye wastewater treatment.

The needs of dye wastewater treatment for enterprise customers include the following three points:

(1) Efficiently and stably remove COD, chromaticity, and other pollutants from wastewater to below discharge limits;

(2) Low investment cost, low operating cost, and convenient equipment operation and maintenance;

(3) Advanced and reliable technology, with no secondary pollution.

Customized printing and dyeing wastewater treatment process using Haipu functional materials

Jiangsu Haipu Functional Materials Co., Ltd. is located in Suzhou Industrial Park. It is a national high-tech enterprise that uses special adsorbents and catalysts as its core technology, supporting the development of application processes, technical services, engineering implementation, etc., to solve related environmental problems for customers.

The principle of the Haipu adsorption process is to use the special adsorption materials developed by our company to selectively adsorb the components or substances to be removed. When the adsorption is saturated, a specific desorption agent is used to desorb the adsorption material, allowing it to regenerate. This process is continuously repeated. The conventional process diagram for treating wastewater by adsorption method is shown in Figure 4-1.

Process treatment effect

The use of adsorption technology to treat dye wastewater can effectively remove COD from the wastewater. The specific treatment data are shown in Tables 5-1 to 5-2.

Table 5-1 Wastewater Adsorption Data

A certain enterprise in Shandong requires the COD content in the treated wastewater to be less than 500mg/L. The experimental treatment effect shows that using adsorption treatment can stabilize the COD in the wastewater to be less than 500mg/L. While ensuring that the customer's requirements are met, a certain safety margin is left, which can effectively prevent the water quality fluctuation of the incoming wastewater from causing the effluent to not meet the standard. The treatment effect is shown in the following figure

The production process of this enterprise generates 100 tons of dye wastewater per day. After adsorption treatment, the COD in the wastewater can meet the discharge requirements. The enterprise has adopted the adsorbent and process package from Jiangsu Haipu Functional Materials Co., Ltd., and the adsorption system is currently running smoothly.

The wastewater generated during the production process of a printing and dyeing enterprise, after undergoing biochemical and various filtration processes, still has a COD much higher than the discharge requirements, and a high chromaticity, requiring further treatment. The use of Haipu's special adsorption material for wastewater experiments showed that it can selectively separate difficult to degrade organic matter from the wastewater, and the adsorbed effluent can meet the discharge standards.

A textile enterprise can generate~2500 tons of wastewater per day during its production process. According to policy regulations, the wastewater reuse rate in the printing and dyeing industry must reach 60%. The existing wastewater treatment process of the enterprise has excessive COD in the biochemical effluent, which does not meet the reuse standard.

According to the production needs of the enterprise, Haipu's special adsorption materials are used in combination with adsorption technology to treat the wastewater, which can meet the requirements of reuse. While solving the problem of wastewater treatment in the enterprise, it reduces the cost of outsourcing wastewater treatment and adding new water, and has significant economic value.

Core advantages of Haipu printing and dyeing wastewater treatment process

At present, the treatment methods for dye wastewater have their own shortcomings in terms of treatment efficiency and operating costs.

The membrane separation method has problems such as membrane fouling, high membrane cost, fast replacement frequency, and high processing cost.

The disadvantage of extraction method is that it consumes a large amount of extractant, and the separation of extracts is relatively difficult. The cost of treating one ton of water is high, and it cannot continuously process large amounts of water.

Radiation method is an immature technology with high energy consumption and low energy utilization efficiency; In addition, special protective measures are required to avoid the harm of radiation to the human body.

The coagulation method, oxidation method, and biological method cannot meet the prescribed emission requirements at once and cannot stably meet the emission standards.

The adsorption method can effectively remove organic matter from dye wastewater below the discharge limit, making it an economical and effective method for treating dye wastewater. The advantages of adsorption method are as follows:

(1) Stable and compliant emissions can effectively alleviate the environmental pressure on enterprises;

(2) Conduct experiments on sampling samples of wastewater generated on-site by enterprises, based on technology and experiments to design adsorption processes with high compatibility between wastewater and processes;

(3) The equipment occupies less land, has a compact structure, and requires less investment in civil engineering and equipment; The desorption agent is applied multiple times and concentrated step by step, resulting in high drug utilization and low operating costs;

(4) It can be implemented in module component form, flexibly adjusted according to production capacity, and easy to install;

(5) Advanced and mature technology, no secondary pollution, strong technical strength and rich engineering application experience.