Multistage crystallization and precipitation treatment method and system for wastewater desalination

Abstract

The invention provides a multistage crystallization precipitation treatment method for wastewater desalination. The method comprises the following steps: 1) adding a calcium agent, an auxiliary agentand an aluminum agent into salt-containing wastewater, carrying out precipitation reaction, and carrying out solid-liquid separation to obtain a supernatant; 2) adding a calcium agent, an auxiliary agent and an aluminum agent into the supernatant at least once to perform precipitation reaction, and performing solid-liquid separation to obtain a clarified liquid; and 3) adding a neutralizer into the clarified liquid, carrying out neutralization reaction, and carrying out solid-liquid separation to provide the desalted wastewater. The invention further provides a multistage crystallization and precipitation treatment system for wastewater desalination. According to the multistage crystallization and precipitation treatment method and system for wastewater desalination, salt in wastewater isremoved through the crystallization and precipitation effect of calcium-aluminum crystals, and the method has the advantages that energy consumption and treatment cost are reduced, the method is not affected by the content of organic matter in water, and the method can be used for pretreatment of wastewater biochemical treatment.

Description

technical field [0001] The invention belongs to the technical field of sewage treatment, and relates to a multi-stage crystallization precipitation treatment method and system for desalination of waste water. Background technique [0002] All kinds of industrial wastewater often contain high concentrations of soluble salts, such as sodium salts, potassium salts, calcium salts, magnesium salts and ammonium salts. The anions that make up these salts usually include chloride ions, sulfate ions, and nitrate ions. and carbonate ions. The total concentration (TDS) of these soluble salts can often be as high as several thousand or even tens of thousands of milligrams per liter, and in some cases even hundreds of thousands of milligrams per liter. The discharge of a large amount of salt into natural freshwater will increase the salinity of surface water and groundwater, thereby changing the physical and chemical properties of the water environment, and even affecting the stability ...

AI Technical Summary

Problems solved by technology

Although some other ions will be removed naturally during the reaction process, these methods cannot be directly used to effectively remove the total dissolved salts in water, especially for the desalination of wastewater without sulfate radicals, the above methods are not applicable

[0012] To sum up, in the current wastewater desalination technology, ion exchange, reverse osmosis, electrodialysis and other methods consume high energy consumption, and desalination is not complete, which will produce concentrated (salt) water with high salt concentration, while evaporation and crystallization can High consumption and high treatment cost; in addition, biochemical treatment is generally considered for high-salt organic wastewater, such as chemical wastewater, pharmaceutical wastewater, leather wastewater, papermaking wastewater, landfill leachate, etc., but high salt concentration will affect biochemical treatment Generally, it is hoped that desalination can be carried out before biochemical treatment, but because the organic matter contained in wastewater can easily cause resin pollution and / or membrane pore blockage, it is impossible to directly use ion exchange, reverse osmosis, and electrodialysis methods for desalination. If the wastewater is desalted by evaporation and crystallization, the energy consumption will be high, the crystals will be mixed with a large amount of impurities, and the desalted crystals cannot be used; the existing desalination methods cannot distinguish between heavy metals and non-heavy metals, causing heavy metals to be mixed in non-heavy metals, resulting in a large amount of Toxic and harmful solid waste containing heavy metals, resulting in high cost of solid waste disposal

The method of using gypsum precipitation and calcium sulfoaluminate precipitation to treat sulfate-containing wastewater is aimed at sulfate ions in wastewater, which will introduce other impurity ions. The reaction reagents, reaction steps, and pH conditions used cannot be used for a large number of sulfate-containing wastewater. Desalination treatment of salty wastewater, especially wastewater without sulfate radicals

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