1. Textile printing and dyeing wastewater industry status quo Among the various industrial sectors in the country, the top 5 industries with wastewater discharge are papermaking, chemical manufacturing, electric power, ferrous metal smelting and textile printing and dyeing industries. The discharge of waste water from textile printing and dyeing industry accounts for the national statistical discharge of industrial waste water Of the total amount of wastewater discharge ranks fifth in the country's industrial sector, the total amount of 1.413 billion tons per year, of which about 1.13 billion tons of printing and dyeing wastewater (accounting for textile printing and dyeing wastewater 80%), accounting for the national industrial wastewater discharge 6% of the amount of daily emissions of 300-400 tons. Printing and dyeing pollutants are mostly refractory dyes, additives and toxic and hazardous heavy metals, formaldehyde, halides and so on. Each discharge of 1 ton of printing and dyeing wastewater, can pollute 20 tons of water. After joining the WTO, textile printing and dyeing in recent years have double-digit growth, but the pollutant treatment facilities is difficult to synchronize, the total pollutant emissions have increased. At present, the total investment in printing and dyeing wastewater treatment facilities nationwide exceeds 10 billion yuan. Among the four key COD discharge industries in China's industrial sector, the COD discharge of the textile printing and dyeing industry ranked the fourth place. The proportion of COD in papermaking and foodstuff industries dropped year by year, while the proportion of COD in textile printing and dyeing and chemical industry increased year by year, among which, the proportion of textile printing and dyeing industry increased from 4.7% to 5.6%. It can be seen that the wastewater in the textile printing and dyeing industry has large amount of water, large total amount of COD discharge and difficult wastewater treatment, and many other features. 2 dyeing and printing wastewater recycling needs Printing and dyeing wastewater is a complex organic wastewater mainly composed of organic pollutants. The main target of the treatment is BOD5, organic matter, alkalinity, dye pigments and a few toxic substances that are not easily biodegradable or biodegradable. Although the biodegradability of printing and dyeing wastewater is generally poor, it is still a biodegradable organic wastewater except for some special printing and dyeing wastewater (such as pure fabric dyeing). The treatment method to biological treatment-based, at the same time be accompanied by the necessary pre-treatment and physical and chemical depth treatment. The pretreatment process mainly includes regulation, neutralization, waste chromium liquid treatment and dye-concentrated water pretreatment, etc. The biological treatment process mainly includes aerobic method, activated sludge method, biological contact oxidation method, biological rotary disc and Tower biological filter and so on. In order to improve the biodegradability of wastewater, anoxic and anaerobic processes have also been applied to the treatment of printing and dyeing wastewater. Commonly used physical and chemical treatment process is mainly coagulation and coagulation floatation method. In addition, electrolysis, biological activated carbon and chemical oxidation and other methods are sometimes used in dyeing wastewater treatment. However, the textile printing and dyeing wastewater treated by such processes can only discharge up to the standard, and it is impossible to achieve the standard of reuse water quality as the process water for textile printing and dyeing. As the reuse of process water, the water quality indicators, especially organic matter, color, hardness and other indicators have more stringent requirements. 2) The raw water hardness is between 150-325mg / L, most of which can be used in the production, but the soluble dye should use soft water less than or equal to 17.5mg / L, the highest water hardness of soaping or lye is 150mg / L; 3) jet condenser cooling water generally use a total hardness of less than or equal to 17.5mg / L of soft water. Analysis of the actual water quality of most enterprises shows that after the treatment, the wastewater that has reached the discharge standard will be contaminated by various kinds of inorganic materials such as dyes, surfactants, colloids, water softeners, desizing wastewater, , Organic residues, salinity of water often reach more than 1000mg / L, the total hardness is much higher than 150mg / L, and the hardness of the components are hard to remove by ordinary lime permanent hardness. Therefore, even after biochemical chroma can be removed by conventional dosing most of this type of water without desalination, it is impossible to meet the quality requirements of the current printing and dyeing water. Due to the deteriorating water environment caused by the industrialization development, the growing lack of water resources has made the country increasingly pay attention to environmental protection and water conservation. At present, the printing and dyeing industry concentrated areas such as Jiangsu, Zhejiang and Guangdong and some water-scarce areas in the north have generally increased their wastewater treatment Emission standards; the printing and dyeing enterprises wastewater discharge is also strictly limited, take the water resources costs, sewage charges also began to significantly increase. Therefore, it is no exaggeration to say that the effective reuse of water resources in the future will become the lifeline of enterprise development. On this basis, how to adopt the new water treatment technology to continuously improve the safety and economy of reuse has now become the focus of most printing and dyeing enterprises. 3. Whole film process introduction In view of the existing wastewater biochemical treatment technology and actual process water consumption of printing and dyeing enterprises, under the precondition of ensuring the safety and stability of water quality and fully considering the economic efficiency of investment and operation cost, we propose to adopt advanced membrane separation technology and adopt membrane technology All or part of the wastewater discharge of enterprises after the re-use of its production of water can not only fully meet the standards of pure water to meet the needs of high-end products in the production process; the same time, taking into account the investment based on the proposed business under the actual situation, Step by step implementation; some companies such as process water hardness and conductivity less demanding, reverse osmosis water can be used in conjunction with part of pre-treatment ultrafiltration membrane effluent to maximize water conservation costs. Membrane wastewater reuse mainly includes "ultrafiltration membrane + reverse osmosis membrane" process flow, ultrafiltration is pressure-driven membrane separation process, it can separate particulate matter from the fluid and dissolved components. The typical pore size of an UF membrane is between 0.01 and 0.1 microns, with a very high removal rate for bacteria and most germs, colloids, silt and the like. Application in the reprocessing process of printing and dyeing wastewater, the ultrafiltration membrane in addition to organic matter and color have a certain degree of removal, the main role is to remove the colloidal, bacteria, viruses and other impurities that may foul reverse osmosis membrane, extend the reverse osmosis Membrane cleaning cycle and life expectancy, reducing the overall operating costs; reverse osmosis membrane can remove 98% of the salt ions, the complete removal of hardness, while COD, also has a very high removal of color, so as to ensure the water quality back. The ultimate goal of wastewater treatment using membrane technology is to: Reuse all or part of the wastewater discharged through the membrane technology for advanced treatment. Except for the capacity requirement of enterprises' own use of water economically, the remaining waste water and reuse equipment drainage Merge the efflux to control the amount of external discharge and meet the requirements of the government environmental protection department at the same time without affecting the production capacity of the enterprise. Avoid enterprises due to water problems capacity constraints, or excessive discharge of waste water due to excessive control caused by the government environmental protection departments forced to stop production or suffer severe fines measures, thus affecting the normal production of enterprises, bring unnecessary losses to the enterprise. 4. Membrane process of printing and dyeing wastewater reuse actual effect analysis Zhejiang XX Environmental Engineering Co., Ltd. uses the membrane process to treat the wastewater from dyeing and printing wastewater (dyeing and printing waste water) in a textile dyeing and finishing company of Guangzhou as process water for reuse. The treated water volume of the two projects reaches 1200 t / h and 800 t / h, respectively. Before the project put into operation, Zhejiang Europe and the United States Environmental Engineering Co., Ltd. in the plant made a 45-day pilot test. 4.1 ultrafiltration turbidity removal