How harmful is industrial waste water?
Release time：
2023-05-31
The zero-discharge desalination process of industrial wastewater will inevitably produce a large amount of concentrated brine.
The zero-discharge desalination process of industrial wastewater will inevitably produce a large amount of concentrated brine. The main components of concentrated brine are inorganic salts, heavy metals, and also contain small amounts of chemicals used in pretreatment, chlorination, dechlorination, and desalination processes, such as scale inhibitors, acids, and other reaction products. If this incompletely treated and toxin-containing water is discharged into the external environment without strict control, it will cause serious environmental pollution problems. Therefore, the treatment of concentrated brine has become a key technology to restrict the discharge of industrial wastewater.
The concentrated brine treatment technologies adopted in industry include:
1. Concentrated brine reduction treatment method for zero discharge of industrial wastewater
(1) Softening of concentrated brine
The main scaling ions in concentrated brine are: Ca2+, Mg2+, Ba2+, Sr2+. In order to ensure that the scaling components are completely removed, there are two commonly used methods: chemical softening and resin softening. Chemical softening is mainly handled by lime-soda ash softening method. There are two ways to soften the resin: sodium ion exchange method and hydrogen ion exchange method.
(2) Membrane treatment of concentrated brine
Membrane separation technology is an emerging technology that uses separation membrane as the core to separate, concentrate and purify substances. Semipermeable membrane is also called separation membrane or filter membrane. The membrane wall is covered with small pores. According to the pore size, it can be divided into: microfiltration membrane, ultrafiltration membrane, nanofiltration membrane, reverse osmosis membrane, etc. Membrane separation adopts cross-flow filtration or dead end filter. Applying membrane separation technology to the treatment process of industrial water can separate the different substances contained in the solution with the help of the pressure of the external environment.
2. Solidification treatment method of concentrated brine in zero discharge of industrial wastewater
(1) Evaporation pond
The evaporation of concentrated brine basically used evaporation ponds for natural evaporation and crystallization at the earliest. The evaporation pond is a depression dug on the ground as a storage pool for concentrated concentrated water. Under suitable climatic conditions, sufficient solar energy can be effectively used to convert the concentrated The brine is stored in evaporation ponds where it is gradually evaporated and residual solid salts are periodically removed. However, with the frequent occurrence of environmental protection accidents of various evaporation ponds, evaporation ponds have been phased out.
(2) Evaporation crystallizer
The evaporative crystallizer mainly refers to a crystallizer that uses various processes to make the solution supersaturated under production conditions, and then crystallizes out. At present, the enhanced evaporation crystallization technology mainly includes mechanical compression evaporation process, multi-effect evaporation, multi-stage flash evaporation, membrane distillation, etc. When the high-salt wastewater treated by evaporation technology is easily concentrated beyond its solubility limit during the evaporation process in the evaporator, the salt in the water is easy to crystallize and adhere to the surface of the heat exchange tube to form scaling. Affect the efficiency of the heat exchanger, and block the heat exchange tube in severe cases. The "seed method" technology solves the scaling problem of evaporator heat exchange tubes, and has been successfully applied to the treatment of various salty industrial wastewater and has been widely used.
With the introduction of various environmental protection regulations, the treatment requirements of industrial wastewater will gradually become higher, and the treatment technology of industrial waste brine will also be continuously improved to contribute to environmental protection.
