Full membrane water reuse equipment

1、 Scope of application
Membrane separation technology has the characteristics of operating at room temperature, no phase change, high energy efficiency, and no pollution in the production process. Therefore, it has been widely used in drinking water purification, industrial water treatment, food and beverage water purification, sterilization, biologically active substance recovery, refining, and other fields. It has quickly been promoted to various fields such as textile printing and dyeing, chemical industry, power, food, metallurgy, petroleum, papermaking, biology, pharmaceuticals, fermentation, etc. Due to its unique structure and performance, separation membranes have emerged as a rising star in environmental protection and water resource regeneration. They have broad application prospects in environmental engineering, especially in meeting wastewater treatment standards and water reuse.
The double membrane method for water reuse technology is applicable to the wastewater generated in the production processes of industrial enterprises such as printing and dyeing, electroplating, and papermaking industries. The characteristics of this type of wastewater are high concentration of organic matter, significant changes in water quality, and difficulty in treatment. The sources and pollutant components of printing and dyeing wastewater are very complex, and direct discharge poses great harm to human health and the living environment.

1. Basic principles
Membrane is a material with selective separation function. The process of using membrane selective separation to separate, purify, and concentrate different components of the feed solution is called membrane separation. It differs from traditional filtration in that the membrane can separate at the molecular level, and this process is a physical process that does not require phase changes or the addition of additives. According to the different pore sizes (also known as molecular weight cut-off) of membranes, they can be divided into microfiltration membranes, ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes. According to the different materials, they can be divided into inorganic membranes and organic membranes. Inorganic membranes mainly only have microfiltration grade membranes, mainly ceramic membranes and metal membranes. Organic films are made of polymer materials such as cellulose acetate, aromatic polyamide, polyether sulfone, polyfluoropolymers, and so on.
Membrane separation technology refers to the selective separation of a mixture of molecules with different particle sizes at the molecular level through a semi permeable membrane, also known as a separation membrane or filter membrane. The membrane wall is filled with small pores and can be divided into microfiltration membrane (MF), ultrafiltration membrane (UF), nanofiltration membrane (NF), reverse osmosis membrane (RO), etc. according to the particle size. Cross flow filtration is used for membrane separation. Membrane is a material with selective separation function, and the process of separating, purifying, and concentrating different components of the feed liquid using the selective separation of the membrane is called membrane separation. This technology mainly combines ultrafiltration membrane (UF) and reverse osmosis membrane (RO).
(1) Ultrafiltration (UF)
It is a membrane process between microfiltration and nanofiltration, with membrane pore sizes ranging from 0.05um to 1nm. It is a membrane separation technology that can purify, separate, and concentrate solutions. Ultrafiltration process can usually be understood as a sieving process related to membrane pore size. Using the pressure difference on both sides of the membrane as the driving force and ultrafiltration membrane as the filtering medium, under a certain pressure, when water flows over the membrane surface, only water and small molecules with pore size smaller than the membrane are allowed to pass through, achieving the purpose of purification, separation, and concentration of the solution.

For ultrafiltration, the retention characteristics of the membrane are characterized by the molecular weight cutoff of standard organic compounds, usually ranging from 1000 to 300000. Therefore, ultrafiltration membranes can separate large molecular organic compounds (such as proteins, bacteria), colloids, suspended solids, etc., and are widely used for clarifying feed solutions, separating and purifying large molecular organic compounds, and removing heat sources.

As an effective engineering pretreatment method, UF intercepts colloidal substances and soluble macromolecular organic compounds in wastewater through micropores, achieving the effect of reducing COD and most turbidity, thereby reducing RO pollution, extending membrane service life, and reducing membrane engineering operating costs.
(2) Reverse osmosis (RO)
It is a membrane process for separating liquid mixtures that utilizes the selective permeability of reverse osmosis membranes, which can only pass through solvents (usually water) and intercept ionic or small molecule substances, with static pressure on both sides of the membrane as the driving force. Reverse osmosis is an important component of membrane separation technology, which has many advantages such as high water quality, low operating costs, no pollution, easy operation, and reliable operation. It has become a more energy-saving and convenient technology for desalination of seawater and brackish water, as well as pure water preparation At present, it has been widely used in many industries such as pharmaceuticals, electronics, chemicals, food, seawater desalination, etc. Reverse osmosis technology has become a major water treatment technology in modern industry.
The interception target of reverse osmosis is all ions, allowing only water to pass through the membrane. The rejection rate of NaCl is over 98%, and the effluent is ion free water. Reverse osmosis can remove soluble metal salts, organic matter, bacteria, colloidal particles, and heat generating substances, which means it can intercept all ions. Reverse osmosis membranes have been widely used in the production of purified water, softened water, deionized water, product concentration, and wastewater treatment, such as the treatment of leachate from garbage.
RO can intercept particles of several nanometers and hundreds of molecular weights, further removing small molecule dissolved COD from wastewater, while achieving a removal rate of over 99% for conductivity.
2. The dual membrane method for water reuse has the following advantages
1) The dual membrane printing and dyeing wastewater water reuse process can achieve the recycling of water resources and reduce emissions;
2) As a clean production process, membrane separation technology separates or intercepts different substances during operation. The membrane separation process is a pure physical process, without phase change or chemical reaction, and can achieve water resource recovery and clean production without the generation of secondary pollutants;
3) The membrane equipment device occupies a very small area, has a high degree of automation, and is easy to operate and maintain;
4) The separation efficiency of the membrane is high (retention rate of over 99%), ensuring high water resource recovery efficiency;
5) The membrane recycling equipment conforms to the operation mode of circular economy, and enterprises can achieve a harmonious unity of economic, environmental, and social benefits while saving energy and reducing consumption, providing strong guarantees for the sustainable development of enterprises.
Due to the one-step completion of COD removal, decolorization, and desalination, the effluent quality is high and can be directly reused in the printing and dyeing process. At the same time, the concentrated water can be refluxed to conventional processes for treatment, achieving zero wastewater discharge and clean production.