Analysis of five commonly used processes for reverse osmosis equipment pretreatment?

For the reverse osmosis system, it is customary to divide the incoming water into groundwater, tap water, surface water, seawater, waste water (reclaimed water), etc. These water bodies are affected by various factors, different geographical conditions, and different seasonal climates lead to the characteristics of water bodies And the impurities it contains are different, so the reverse osmosis pretreatment process will also be different. Reasonable preprocessing should meet the following requirements:

  1. The reverse osmosis pretreatment must be able to remove the vast majority of impurities in the raw water and meet the water inlet requirements;
  2. Reverse osmosis pretreatment must consider changes in water quality to prevent fluctuations in raw water quality from affecting the stable operation of the entire system;
  3. The reverse osmosis pretreatment process must be able to operate efficiently and stably, while simplifying the process as much as possible to reduce investment and operating costs;

Flocculation and flocculation filtration reverse osmosis equipment

The object of flocculation treatment is the small particle suspended solids and colloids in the raw water.
For raw water with turbidity less than 70 degrees, multi-media filtration is generally used, and gravity filtration or pressure filter can be used. The requirements of the filter material are different from those of the ordinary double-filter material filter tank. When using flocculation filtration, the effect of using iron salt as flocculant is better than that of aluminum salt. The designed water output of the filter should include the water consumption of the subsequent treatment process and the water consumption of the filter itself, that is, the flushing water.

The adsorption method is a method of purifying water by using porous solid substances to adsorb certain pollutants in the water on its surface. The pollutants that can be removed by adsorption method include: organic matter, colloid, residual chlorine, and can also remove color and odor.
Activated carbon adsorption
Activated carbon is a black porous particle made by carbonization and activation of various raw materials such as bituminous coal, anthracite, nut shell or wood chips. The physical properties of activated carbon mainly refer to the pore structure and its distribution. During the activation process, pores of various shapes and sizes are formed, thus forming a huge specific surface area, and the contact surface with water is very large, so the adsorption capacity is very strong. Activated carbon can not only adsorb various pollutants in water, but also adsorb pollutants such as SO2 in exhaust gas, so it has a wide range of uses in environmental protection, water treatment and other fields.

Precision filter (security filter)

Used to remove very small particles. Ordinary sand filtration can remove very small solid particles, so that the turbidity of the effluent reaches about 1, but the effluent still contains a large number of particles with a particle size of 1~5μm, which cannot be removed by sand filtration. Entering the reverse osmosis host, under the concentration of the RO membrane, the membrane elements will still be polluted. To remove these particles, precision filtration must be used. The precision filter is often set after the pressure filter, and sometimes at the end of the entire pretreatment process to prevent broken filter material, activated carbon, resin, etc. from entering the reverse osmosis system, and try not to bring the particles generated in the previous process to the to the next process. The pore size of the filter pore should be matched with the particles of impurities contained in the water, avoiding too coarse or too fine.

Oxidation

Oxidation is a chemical treatment method that uses strong oxidants to oxidize and decompose pollutants in water. For reverse osmosis system pretreatment, oxidation is typically used to remove two types of substances:

  1. Organic matter
  2. Iron, manganese

Softening refers to the use of chemical methods to remove hardness in water. It is divided into ion exchange softening and chemical softening. At present, the softening method commonly used in reverse osmosis pretreatment is ion exchange softening. Ion exchange softening refers to the use of ion exchangers to react the calcium and magnesium ions in the water body with the effective exchange groups (usually sodium ions) of the ion exchanger, so that the water quality can be softened.

RO-water Filtration with CIP system

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