Zero discharge of electroplating wastewater What is the basic method of?
At present, the water crisis caused by the shortage of water resources and water environment pollution has become an important constraint to China's social and economic development. Therefore, it is necessary to adopt the water resources exploitation and utilization mode of coordinated protection and utilization, prevent water resources from being damaged and realize a virtuous circle through sewage treatment and water body protection. Without the sustainable use and protection of water, the sustainable development of social economy cannot be achieved.
Water is a special industry with the production goal of water quantity and quality to meet the needs of social and economic sustainable development. It is engaged in the sustainable use and protection of water. This is a new industry formed and improved with the commercialization and industrial production of water, a special product. Various enterprises and departments arising from water exploitation, purification, supply, protection and regeneration constitute the main body of the water industry. The water industry involves many disciplines. It is the integration of science and technology, engineering, equipment and comprehensive management technology, with strong comprehensiveness.
Water treatment is the abbreviation of water supply treatment and wastewater treatment, and is an important part of hydraulic technology. Before the 1950s, the definition of water supply treatment and wastewater treatment was very clear. The treatment of water taken from natural sources for domestic or industrial purposes (especially domestic purposes) is called water supply treatment; The treatment of used and discarded water for the purpose of safe discharge is called wastewater treatment. However, since water pollution has become increasingly serious and water sources have become increasingly scarce, the boundary between water supply treatment and wastewater treatment has gradually blurred. Now, wastewater can also be used as water source for industrial water and even domestic water after treatment. For the treatment of wastewater regeneration or reuse, its water quality is wastewater treatment, and its treatment purpose is water supply treatment. In this new situation, the general use of terms such as water treatment and water quality control may be more convenient and appropriate.
1、 Contents of zero discharge treatment of electroplating wastewater
The main contents of water treatment can be summarized as follows:
(1) The main content of water treatment is to remove impurities that affect the use of water and treat sludge;
(2) In order to meet the requirements for water use, other substances are added to the water to change the nature of the water. For example, fluoride is added to the drinking water to prevent dental caries, and corrosion inhibitors and scale inhibitors are added to the circulating cooling water to control corrosion and scaling;
(3) Change the physical properties of water, such as cooling and heating of water. This chapter only discusses methods for removing impurities from water.
2、 Classification of water treatment methods
There are many kinds of pollutants in wastewater, and it is not expected that all pollutants can be removed by one method, so water treatment methods are also diverse. According to different classification principles, wastewater treatment methods can generally be divided into the following categories.
1. Classification according to the degree of wastewater treatment
Generally, it is divided into primary treatment, secondary treatment and tertiary treatment (advanced treatment and high temperature treatment).
The primary treatment is mainly pre-treatment, which mostly uses physical and physical methods or simple chemical methods (such as initial neutralization pH) to remove suspended solids, colloids, suspended oils and other pollutants in wastewater. The level of primary treatment is low. Generally, secondary treatment is required to meet the specified emission requirements.
Secondary treatment is mainly to identify the colloidal or dissolved organic pollutants that can be decomposed or oxidized, and more economical biochemical treatment methods are used. After secondary treatment, the wastewater can generally meet the discharge standard, but there may be residual microorganisms, undegradable organics, nitrogen, phosphorus and other inorganic salts. They are small in number and usually do little harm to water bodies.
Third level governance, also known as deep governance, is only adopted when there are special requirements. The wastewater after secondary treatment is further treated by physical and chemical technology to remove soluble inorganic substances and non decomposable organic substances, and remove various viruses, pathogens, phosphorus, nitrogen and other substances, so as to reach the water quality standard close to surface water, industrial water and domestic water.
2. Classify according to whether the chemical properties of pollutants in water have changed.
Water treatment methods can be divided into separation treatment, conversion treatment and dilution treatment.
(1) Separation treatment: It is to separate pollutants from water by various forces. Generally speaking, the chemical properties of pollutants do not change during the separation process.
(2) Conversion treatment: convert pollutants into harmless substances or separable substances through chemical or biochemical action, and then conduct separation treatment. During this process, the chemical properties of pollutants change.
(3) Dilution treatment: neither separate the pollutants nor change the chemical properties of the pollutants. Reduce the concentration of pollutants through dilution and mixing to achieve harmless purposes.
3. Classification according to changes occurred in the process of treatment
It can be divided into physical treatment, chemical treatment, physical and chemical treatment and biological treatment. Physical method is to use physical action to separate the floating matter in water, and only physical changes occur in the treatment. Common physical treatment methods include: grid, screening, filtration, sedimentation and floating. Chemical method is to use chemical reaction to treat dissolved or colloidal substances in water. Chemical changes occur during the treatment. Common chemical treatment methods include neutralization, chemical precipitation, oxidation and reduction, etc. Physicochemical method is a method of purifying wastewater by using the comprehensive effect of physicochemistry. Physicochemical treatment of wastewater can be an independent treatment system or combined with other methods. The choice of process depends on the quality of wastewater, water quality requirements for discharge or recycling, treatment costs, etc. Coagulation and adsorption methods used to remove floating and dissolved pollutants are typical physical and chemical treatment methods. Common physical and chemical treatment methods include adsorption, ion exchange, membrane technology (electrodialysis, reverse osmosis, ultrafiltration, etc.). The biological law is to remove colloid and dissolved organic matter in water by the action of microorganisms. The commonly used biological treatment methods include aerobic activated sludge process, biofilm process, anaerobic digester process, etc.
