Zero discharge of high salt wastewater refers to the efficient reduction of salt content and pollutant concentration in industrial wastewater after treatment, achieving over 99% of wastewater recycling and reuse without discharging any liquid to the outside world. The following is a detailed analysis of zero discharge of high salt wastewater:

      1、 The sources and water quality characteristics of high salt wastewater

      There are three main sources of high salt wastewater:

      1. Desalination of seawater: Treating high salt wastewater generated by desalination of seawater.

      2. Industrial production: There are significant differences in the inorganic salt ions contained in industrial wastewater from different fields, such as steel enterprises, coal chemical industry, petroleum and other industries with large drainage volume. In the production process, most of the water needs to be recycled for reuse, and a certain concentration of salt water will also be produced during the reuse process.

      3. Domestic sewage: Domestic sewage also contains a certain amount of inorganic salts, such as potassium ions, calcium ions, sodium ions, chloride ions, sulfate ions, etc.

      2、 Key technologies for zero discharge of high salt wastewater

      The key technology for zero discharge of high salt wastewater can be divided into three stages: pretreatment stage, membrane treatment stage, and evaporation stage.

      1. Preprocessing stage

        Objective: To remove harmful substances from wastewater and prepare for subsequent treatment.

        Method: including drug softening, filtration, ion exchange, etc. There are traditional methods of chemical softening, such as lime softening, lime gypsum softening, and lime soda ash softening, as well as biological degradation of urea to produce carbonate precipitation. Ion exchange method is mainly used to remove all or part of Mg ² ⁺ and Ca ² ⁺ from water before membrane treatment.

    2. Membrane treatment stage

        Advantages: Small footprint, simple operation, high efficiency, and easy maintenance.

        Disadvantages: High requirements for incoming water and complex pretreatment processes are needed; Membrane fouling and cleaning have been long-standing issues that have plagued membrane processes.

        Common membrane technologies: microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). Among them, the new polyvinylidene fluoride (PVDF) hollow fiber hydrophobic membrane can achieve a desalination efficiency of 99.9%.

      3. Evaporation stage

        Objective: To separate dissolved substances from water through concentrated crystallization.

        Method: including membrane distillation and multi effect evaporation. Membrane distillation combines traditional distillation and membrane separation techniques, which can efficiently separate inorganic salts and large organic molecules; Multi effect evaporation achieves energy-saving effects by compressing and reusing steam.

      3、 Example of Zero Discharge of High Salt Wastewater

      The comprehensive treatment technology transformation project for zero discharge of high salt wastewater in a certain smelting plant has achieved the goal of "treating high salt wastewater with waste heat" and achieving the dual zero discharge of "waste heat+wastewater" by recycling and utilizing the flash evaporation and exhaust steam coupling "low-temperature thermal concentration+low-temperature multi effect evaporation crystallization" technology for air discharge, and synchronously adopting measures such as valuable metal recycling in wastewater and steam condensate reuse.

      4、 The significance of zero discharge of high salt wastewater

      1. Environmental significance: Achieving zero discharge of high salt wastewater helps reduce water pollution, protect water resources and the ecological environment.

      2. Economic significance: By recycling resources such as wastewater and waste heat, enterprises can reduce production costs and improve economic efficiency.

      3. Social significance: Promoting green industrial development and facilitating the achievement of sustainable development goals.

      Zero discharge of high salt wastewater is a challenging but significant task. Through continuous technological innovation and optimization of processing procedures, we can achieve this goal and contribute to the sustainable development of enterprises and society.