Water treatment mode

As far as domestic water (or urban public water supply) is concerned, raw water from high-quality water sources (well water or well-protected water supply reservoirs) only needs to be disinfected to become finished water; Raw water from general rivers or lakes should first be removed from muddy impurities such as sediment, and then disinfected; For raw water with serious pollution, organic matter and other pollutants need to be removed. Raw water containing iron and manganese (such as some well water) needs to be removed. Domestic water can meet the water quality requirements of general industrial water, but industrial water sometimes needs further processing, such as softening, desalt and so on.

When the water quality requirements of wastewater discharge or reuse are low, only coarse impurities and suspended matter need to be removed by screening and precipitation (often called primary treatment); When organic matter is required to be removed, biological treatment (often called secondary treatment) and disinfection are generally adopted after primary treatment; For the wastewater after biological treatment, the treatment process is collectively referred to as tertiary treatment or advanced treatment. For example, when the water body into which the wastewater is discharged needs to prevent eutrophication, the nitrogen and phosphorus removal process is a tertiary treatment (see physicochemical treatment of water). When wastewater is used as a source of water, the quality requirements of the finished water and the corresponding processing process depend on its use. In theory, modern water treatment technology can make any high-quality finished water from any inferior water.

Related concept

Using a reasonable water treatment process, with the depth of water treatment, the treated water can reach GB5084-1992, CECS61-94 water recovery water standards, etc., can be recycled for a long time, saving a lot of water resources.

water treatment is the process of using physical, chemical, biological and other methods to improve the water quality of source water or water that does not meet the water quality requirements.

Common wastewater treatment technology Biological chemical method, such as Activated Sludge Process (Activated Sludge Process), biological stratification method (Fixed Biofilm Processes), mixed biological Processes (Combined Biological Processes) and so on; Physicochemical methods, such as Granular Media Filtration, Activated Carbon Adsorption, Chemical Precipitation, Membrane Processes etc.; Natural treatment methods, such as Stabilization Ponds method, oxidation ditch method (Aerated or Facultative Lagoons), Constructed Wetlands method (Constructed Wetlands), chemical color coxace resin treatment method. Separation principle of nanofiltration membrane

Nanofiltration membrane is also known as ultra-low pressure reverse osmosis membrane. Japanese scholar Toshiro Otani has specifically defined the separation principle of nanofiltration membrane: Membranes with operating pressure ≤1.50mPa, molecular weight 200-1000, and NaCl retention rate ≤90% can be considered as nanofiltration membranes. Nanofiltration membrane separation technology has been separated from reverse osmosis technology, and has become an independent separation technology between ultrafiltration and reverse osmosis technology, which has been widely used in seawater desalination, ultra-pure water manufacturing, food industry, environmental protection and many other fields, becoming an important branch of water treatment technology.

Principles of nanofiltration technology

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

Electrical effect: The electrostatic interaction between nanofiltration membrane and electrolyte ions is formed, and the charge strength of electrolyte salt ions is different, resulting in the membrane's ion retention rate is different. In the multi-component system containing different valence ions, due to the DONNAN effect, the membrane's selectivity for different ions is not the same, and the proportion of different ions through the membrane is not the same.

The reason why the nanofiltration process has ion selectivity is that there are negative charged groups on or in the nanofiltration membrane, which hinder the penetration of polyvalent ions through electrostatic interaction. The possible charged density of nanofiltration membrane is 0.5 ~ 2meq/g.

Separation principle of nanofiltration membrane

The nanofiltration membrane is between RO and UF membrane, and the removal rate of NaCL is below 90%. The reverse osmosis membrane has a high removal rate for almost all solutes, but the nanofiltration membrane only has a high removal rate for specific solutes.

Nanofiltration membrane mainly removes solute particles with a diameter of about 1 nanometer (nm), and retains molecular weight of 100 ~ 1000. In the field of drinking water, it is mainly used to remove trihalomethanes intermediates, odors, chroma, pesticides, synthetic detergent, soluble organic matter, Ca, Mg and other hardness components and evaporation residues.