The methods of water treatment include physical treatment and chemical treatment

With the continuous improvement of human life, the problem of eutrophication of water bodies with nutrients such as ammonia nitrogen and phosphorus, and the gradual improvement of sewage discharge standards by the Environmental Protection Bureau, the traditional "primary treatment" and "secondary treatment" water treatment technology and equipment that have been used for many years are no longer suitable for the treatment requirements of high turbidity and high concentration sewage today. Moreover, the treatment process is long, the system is large, and a large amount of odor is emitted. In order for operators to meet the new emission standards, they need to invest heavily in expanding the existing sewage treatment system, increasing the land occupation, high cost of sewage treatment equipment, and high post maintenance costs. However, traditional sewage deep treatment and recycling technology systems (such as activated carbon filtration, microporous filtration, permeable membrane purification, etc.) have high investment and high post maintenance and operation costs, which are difficult for too many operators to afford.

Water treatment includes two types: sewage treatment and drinking water treatment. In some places, sewage treatment is further divided into two types, namely sewage treatment and reclaimed water reuse. The commonly used water treatment agents include polyaluminum chloride, polyaluminum ferric chloride, basic aluminum chloride, polyacrylamide, activated carbon, and various filter media.

The processing process of raw water (raw water) to meet the water quality requirements of finished water (domestic water, production water, or dischargeable wastewater).

When processing wastewater, it is called wastewater treatment. The purpose of wastewater treatment is for the discharge (discharge into water bodies or land) or reuse (see wastewater treatment, wastewater reuse) of wastewater.

Impurities in water and treatment methods: Impurities in water include carried coarse substances, suspended solids, colloids, and dissolved substances. Coarse substances such as floating aquatic plants, garbage, large aquatic organisms, gravel in wastewater, and large debris in rivers. In water supply engineering, coarse impurities are removed by the facilities of the water intake structure and are not included in the scope of water treatment.

As for domestic water (or urban public water supply), raw water taken from high-quality water sources (well water or well protected water supply dedicated reservoirs) only needs to be disinfected to become finished water; Raw water from general rivers or lakes must first be removed of sediment and other impurities that can cause turbidity, and then disinfected; Raw water with severe pollution also needs to remove pollutants such as organic matter; Raw water containing iron and manganese (such as some well water) requires removal of iron and manganese. Domestic water can meet the water quality requirements of general industrial water, but industrial water sometimes requires further processing, such as softening, desalination, etc.

By adopting a reasonable water treatment process and combining it with deep water treatment, the treated water can meet the standards of GB5084-1992 and CECS61-94 for water recovery, and can be recycled for a long time, saving a lot of water resources.

The commonly used sewage treatment technologies include biochemical methods, such as Activated Sludge Process, Fixed Biofilm Processes, Combined Biological Processes, etc; Physical and chemical methods, such as Granular Media Filtration, Activated Carbon Adsorption, Chemical Precipitation, Membrane Processes, etc; Natural treatment methods, such as Stabilization Ponds, Aerated or Facultative Lagoons, Constructed Wetlands, Chemical Color Coarse Resin Treatment, and Nanofiltration Membrane Separation Principle.

The principle of dissolution and diffusion: The permeate dissolves in the membrane and diffuses and transfers along its driving force gradient, forming a chemical equilibrium between phases on the surface of the nanofiltration membrane. The transfer form is: energy=concentration o mobility o driving force, so that a substance must overcome the osmotic pressure when passing through the membrane.

The reason why the nanofiltration process has ion selectivity is that there are negative charged groups on or in the nanofiltration membrane, which interact with each other through electrostatic forces to hinder the permeation of multivalent ions. The possible charge density of nanofiltration membrane is 0.5-2meq/g.

Separation principle of nanofiltration membrane

Nanofiltration membrane is mainly used to remove solute particles with a diameter of about 1 nanometer (nm) and a cut-off molecular weight of 100-1000. It is mainly used in the field of drinking water to remove trihalomethanes intermediates, odors, chromaticity, pesticides, synthetic detergents, soluble organic matter, hardness components such as Ca and Mg, and evaporation residues.

Processing technology

The purified water treatment process depends on the quality of the raw water.

If it is ordinary surface water, it needs to be sterilized and flocculants added before entering the above process.