The principle of wastewater treatment is to separate or decompose the various pollutants contained in the wastewater into water, degrade it and lose the characteristics of pollutants. Therefore, in order to understand the wastewater treatment method, it is necessary to understand the form of the pollutants in the water and their physical and chemical properties. In general, pollutants can be divided into three categories: suspended substances, colloidal substances, and dissolved substances. However, it is more difficult to divide according to strict requirements, usually based on the particle size of the pollutants. Suspended pool particle size of 1 ~ 100μm, colloidal particle size of 1nm ~ 1μm, particle size of the dissolved material is less than 1nm.
In the treatment of waste water, the difference in size of the particle size of the pollutants has a great influence on the method of treatment. In general, the simplest treatment is suspended solids, and colloidal and soluble substances with smaller particle sizes are more difficult to handle. In other words, suspended solids are easily separated by sedimentation, filtration and water, and colloidal substances and dissolved substances must be condensed by a special substance or chemically reacted to increase the suspended solids. The membrane is separated by adsorption, filtration and water.
The basic method of wastewater treatment is to use various technical means to separate, remove, recycle, or convert pollutants contained in wastewater into non-hazardous materials so that the water can be purified.
Modern wastewater treatment technology can be divided into three categories: physical treatment, chemical treatment, and biochemical treatment.
Physical treatment method: The use of physical effects to separate suspended solid contaminants in sewage. Methods are: sieving, precipitation, floating method. Air floatation, filtration and reverse osmosis.
Chemical treatment: Separation and recovery of pollutants in various forms (including suspended, dissolved, colloid, etc.) in wastewater. The main methods are neutralization, coagulation, electrolysis, redox, stripping, extraction, adsorption, ion exchange and electrodialysis. The above two methods (physical treatment method and chemical treatment method) are collectively referred to as physical chemical treatment method.
Biochemical treatment method: Using the principle of microbial metabolism, the organic pollutants that are dissolved and colloidal in the wastewater are converted into stable and harmless substances. The main methods can be divided into two major categories, namely the aerobic method using aerobic microorganisms (aerobic oxidation method) and the anaerobic method using anaerobic microorganisms (anaerobic reduction method). The former is widely used for the treatment of municipal sewage and organic industrial wastewater. There are two types, activated sludge and biofilm. The latter is mostly used for the treatment of high-concentration organic wastewater and sludge generated in the sewage treatment process. It is now also being used for treatment. Low concentration organic sewage in urban sewage.
In addition to the above two types of biological treatment methods, there are natural biological treatments that use ponds and soil treatments. The natural biological treatment method is further divided into two methods: stable ponds and land treatment. The stable ponds are also called biological ponds. They are lands that have been artificially rectified and are suitable for the construction of embankments and impermeable layers. A sewage biological treatment technology that has been purified. Stable ponds are divided into aerobic ponds, anaerobic ponds, precision treatment ponds, aeration ponds, etc.; land treatment is a method of artificially controlling the sewage to be allocated to the land, and the sewage is purified through the soil-plants. A natural biological treatment technology for sewage treatment. The land treatment method can be further divided into wetlands, slow-speed infiltration, rapid Han infiltration, surface temperature over-flow, and sewage irrigation.
The pollutants in urban sewage and industrial production sewage are various, and it is often necessary to use several methods at the same time in order to treat different types of sewage and sludge to achieve the purpose of purifying water and discharge standards.
Modern urban sewage treatment technology can be divided into primary, secondary and advanced treatments according to the degree of treatment.
The primary treatment is the purification process that mainly removes floating materials and suspended matter in the sewage, and is mainly precipitated;
The secondary treatment is the first-stage treatment of the wastewater, followed by a biological process to continue the removal of precipitated fine-particle suspended solids, colloidal and dissolved organic matter, and nitrogen and phosphorus purification processes. Removal of organic matter only is referred to as ordinary secondary treatment. Removal of organic matter and simultaneous removal of nitrogen and phosphorus are called secondary treatments.
Depth 2 treatment further removes the contaminants that were not removed by the secondary treatment. Depth treatment is usually optimized by a combination of the following treatment units: coagulation and sedimentation (floatation), adsorption, ion exchange, and membrane technology.
Sewage wastewater treatment methods There are many methods for selecting wastewater treatment. It is important to select the most suitable method according to the type of wastewater and the purpose of treatment.
1, organic wastewater treatment
a When there is suspended matter, use filter paper to measure the BOD and COD of the filtrate. The BOD and COD in the bismuth filtrate are all below the required values. The biochemical method can be considered for this waste water, and a part of BOD and COD can also be removed together with the removal of suspended matter.
b If the BOD and COD in the filtrate are higher than the required values, biological treatment needs to be considered;
c Perform a biological treatment test to determine if BOD and COD can be removed together;
d When the COD cannot be reduced to the discharge standard, the advanced treatment process should be considered.
2 Inorganic wastewater treatment
a When there is suspended matter, settling test is to be carried out. If the required value is reached within the normal standing time, such waste water can be considered to be treated by natural precipitation method;
b If the required value is not reached within the specified standing time, a precipitation test shall be conducted;
c. When the suspended solids are still contained in the waste water after removal of the suspended matter, methods such as pH adjustment, addition of sulfides, redox and other chemical methods may be considered;
d. When the dissolved substances cannot be removed by the above method, adsorption and ion exchange may be considered for further removal.
e When the waste water contains oil, it is first necessary to separate the free oil by the static masturbation test. If the oil content exceeds the required value, the experiment shall be conducted.
3. Advanced treatment Regardless of organic wastewater or inorganic wastewater, when the above series still fails to meet the required values, it is necessary to consider adopting advanced treatment methods such as adsorption and ion exchange.
4, change the production process through the advanced treatment experiment, still can not find a suitable treatment method, we must consider starting from the production process, the discharge of difficult to deal with the process of pollutants to be changed.
In the treatment of waste water, the difference in size of the particle size of the pollutants has a great influence on the method of treatment. In general, the simplest treatment is suspended solids, and colloidal and soluble substances with smaller particle sizes are more difficult to handle. In other words, suspended solids are easily separated by sedimentation, filtration and water, and colloidal substances and dissolved substances must be condensed by a special substance or chemically reacted to increase the suspended solids. The membrane is separated by adsorption, filtration and water.
The basic method of wastewater treatment is to use various technical means to separate, remove, recycle, or convert pollutants contained in wastewater into non-hazardous materials so that the water can be purified.
Modern wastewater treatment technology can be divided into three categories: physical treatment, chemical treatment, and biochemical treatment.
Physical treatment method: The use of physical effects to separate suspended solid contaminants in sewage. Methods are: sieving, precipitation, floating method. Air floatation, filtration and reverse osmosis.
Chemical treatment: Separation and recovery of pollutants in various forms (including suspended, dissolved, colloid, etc.) in wastewater. The main methods are neutralization, coagulation, electrolysis, redox, stripping, extraction, adsorption, ion exchange and electrodialysis. The above two methods (physical treatment method and chemical treatment method) are collectively referred to as physical chemical treatment method.
Biochemical treatment method: Using the principle of microbial metabolism, the organic pollutants that are dissolved and colloidal in the wastewater are converted into stable and harmless substances. The main methods can be divided into two major categories, namely the aerobic method using aerobic microorganisms (aerobic oxidation method) and the anaerobic method using anaerobic microorganisms (anaerobic reduction method). The former is widely used for the treatment of municipal sewage and organic industrial wastewater. There are two types, activated sludge and biofilm. The latter is mostly used for the treatment of high-concentration organic wastewater and sludge generated in the sewage treatment process. It is now also being used for treatment. Low concentration organic sewage in urban sewage.
In addition to the above two types of biological treatment methods, there are natural biological treatments that use ponds and soil treatments. The natural biological treatment method is further divided into two methods: stable ponds and land treatment. The stable ponds are also called biological ponds. They are lands that have been artificially rectified and are suitable for the construction of embankments and impermeable layers. A sewage biological treatment technology that has been purified. Stable ponds are divided into aerobic ponds, anaerobic ponds, precision treatment ponds, aeration ponds, etc.; land treatment is a method of artificially controlling the sewage to be allocated to the land, and the sewage is purified through the soil-plants. A natural biological treatment technology for sewage treatment. The land treatment method can be further divided into wetlands, slow-speed infiltration, rapid Han infiltration, surface temperature over-flow, and sewage irrigation.
The pollutants in urban sewage and industrial production sewage are various, and it is often necessary to use several methods at the same time in order to treat different types of sewage and sludge to achieve the purpose of purifying water and discharge standards.
Modern urban sewage treatment technology can be divided into primary, secondary and advanced treatments according to the degree of treatment.
The primary treatment is the purification process that mainly removes floating materials and suspended matter in the sewage, and is mainly precipitated;
The secondary treatment is the first-stage treatment of the wastewater, followed by a biological process to continue the removal of precipitated fine-particle suspended solids, colloidal and dissolved organic matter, and nitrogen and phosphorus purification processes. Removal of organic matter only is referred to as ordinary secondary treatment. Removal of organic matter and simultaneous removal of nitrogen and phosphorus are called secondary treatments.
Depth 2 treatment further removes the contaminants that were not removed by the secondary treatment. Depth treatment is usually optimized by a combination of the following treatment units: coagulation and sedimentation (floatation), adsorption, ion exchange, and membrane technology.
Sewage wastewater treatment methods There are many methods for selecting wastewater treatment. It is important to select the most suitable method according to the type of wastewater and the purpose of treatment.
1, organic wastewater treatment
a When there is suspended matter, use filter paper to measure the BOD and COD of the filtrate. The BOD and COD in the bismuth filtrate are all below the required values. The biochemical method can be considered for this waste water, and a part of BOD and COD can also be removed together with the removal of suspended matter.
b If the BOD and COD in the filtrate are higher than the required values, biological treatment needs to be considered;
c Perform a biological treatment test to determine if BOD and COD can be removed together;
d When the COD cannot be reduced to the discharge standard, the advanced treatment process should be considered.
2 Inorganic wastewater treatment
a When there is suspended matter, settling test is to be carried out. If the required value is reached within the normal standing time, such waste water can be considered to be treated by natural precipitation method;
b If the required value is not reached within the specified standing time, a precipitation test shall be conducted;
c. When the suspended solids are still contained in the waste water after removal of the suspended matter, methods such as pH adjustment, addition of sulfides, redox and other chemical methods may be considered;
d. When the dissolved substances cannot be removed by the above method, adsorption and ion exchange may be considered for further removal.
e When the waste water contains oil, it is first necessary to separate the free oil by the static masturbation test. If the oil content exceeds the required value, the experiment shall be conducted.
3. Advanced treatment Regardless of organic wastewater or inorganic wastewater, when the above series still fails to meet the required values, it is necessary to consider adopting advanced treatment methods such as adsorption and ion exchange.
4, change the production process through the advanced treatment experiment, still can not find a suitable treatment method, we must consider starting from the production process, the discharge of difficult to deal with the process of pollutants to be changed.
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