Overview of industrial water treatment

Water treatment methods can be summarized into three ways:

① The most common method is to remove some or all impurities in raw water to obtain the required water quality.

② By adding new components to raw water, the required water quality can be obtained.

③ Raw water treatment does not involve removing impurities or adding new components.

Softened water treatment: treat with chemical resin, such as hard water softening.

Commonly used sewage treatment technologies include biochemical methods, such as activated sludge method, fixed biofilm method, combined biological method and so on. Physical and chemical methods, such as granular media filtration, activated carbon adsorption, chemical precipitation, membrane method, etc. Natural treatment methods, such as stabilization pond, oxidation pond, constructed wetland and chemical chromium resin treatment.

Water treatment refers to the purification of polluted industrial wastewater or sewage through a series of water treatment equipment to make it meet the water quality standards stipulated by the state. Because social production and life are closely related to water, the field of water treatment involves a wide range of applications, which constitutes a huge industrial application.

Simply put, "water treatment" is the process of removing some substances that are not needed for production and life in water by physical and chemical means.

Water is a process of precipitation, filtration, coagulation, flocculation, corrosion inhibition, scale inhibition and other water quality adjustment for specific purposes.

Because social production and life are closely related to water. Therefore, the field of water treatment involves a wide range of applications, which constitutes a huge industrial application.

Water treatment usually includes sewage treatment and drinking water treatment. Commonly used water treatment agents are: polyaluminum chloride, polyaluminum ferric chloride, basic aluminum chloride, polyacrylamide, activated carbon and various filter materials.

The effect of water treatment can be measured by water quality standards.

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

1. When the treated raw water is domestic water or industrial water, it is called water supply treatment;

4. When treating wastewater, it is called wastewater treatment. The purpose of wastewater treatment is to discharge wastewater (into water or land) or reuse wastewater (see wastewater treatment and wastewater reuse).

In the circulating water system and water regeneration treatment, raw water is wastewater and finished water is water, and the treatment process has the nature of water supply treatment and wastewater treatment. Water treatment also includes the treatment and final disposal of wastewater and sludge generated in the treatment process (see sludge treatment and disposal), and sometimes it also includes the treatment and discharge of waste gas. Water treatment methods can be summarized into three ways: ① The most common way is to get the required water quality by removing some or all impurities in raw water; (2) By adding new components to raw water, the required water quality can be obtained; ③ Raw water treatment does not involve removing impurities or adding new components.

Impurities in water and their treatment methods The impurities in water include coarse substances, suspended substances, colloids and dissolved substances. Rough substances such as floating aquatic plants, garbage, large aquatic organisms, gravel and large dirt in wastewater. In the water supply project, coarse impurities are removed by the facilities of water intake structures, which are not included in the water treatment scope.

In wastewater treatment, removing coarse impurities generally belongs to the pretreatment part of water. Suspended solids and colloids include sediments, algae, bacteria, viruses and insoluble substances existing in water and produced during water treatment. Dissolved substances are inorganic salts, organic compounds and gases. There are many treatment methods to remove impurities in water, and the application scope of the main methods can be roughly divided according to the particle size of impurities (Figure 1). Because the impurities contained in raw water and the impurities allowed in finished water are very different in types and concentrations, the water treatment process is also very different.

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) can become finished water only by disinfection; Raw water taken from general rivers or lakes should first remove muddy impurities such as sediment and then be disinfected; For seriously polluted raw water, it is necessary to remove pollutants such as organic matter; 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 treatment, such as softening and desalination.

When the discharge or reuse of wastewater requires low water quality, coarse impurities and suspended solids (usually called primary treatment) can only be removed by screening and precipitation. When organic matter needs to be removed, biological treatment (usually called secondary treatment) and disinfection are generally adopted after primary treatment; For the wastewater after biological treatment, the treatment process is collectively called tertiary treatment or advanced treatment. For example, when wastewater is discharged into water, the process of removing nitrogen and phosphorus to prevent eutrophication belongs to tertiary treatment (see physical and chemical treatment of water). When wastewater is used as water source, the quality requirements of finished water and the corresponding treatment process depend on its use. Theoretically, modern water treatment technology can make any inferior water into any high-quality finished water.