The characteristics of chemical wastewater and the diversity of pollutants determine that the wastewater treatment process does not rely solely on one method. The specific treatment processes can be divided into pretreatment processes (physical, physical, chemical, chemical), biochemical treatment processes (anaerobic, anoxic, aerobic), and advanced treatment processes.
In the treatment of various water bodies, pretreatment becomes an essential link. Pretreatment of water treatment refers to the preliminary treatment of water before it is further treated, purified or separated. Pretreatment provides many benefits for subsequent water treatment processes, including improving treatment efficiency, enhancing water quality, and reducing treatment difficulties.
This article will explore in detail the importance and necessity of pretreatment in the water treatment process. Pretreatment is any treatment process of wastewater before primary treatment, such as grating, screening, crushing, skimming, grease removal, sand removal, pre-aeration, homogenization, pH adjustment, etc.
Avoid affecting the back-end biological treatment: During the process of microbial treatment of organic matter, salts, oils, toxic substances, etc. can affect the activity of microorganisms, and even cause the death of microorganisms, especially special strains can lead to huge losses, or cause the risk of shutdown and production restrictions.
Avoid affecting the operation of back-end equipment: Some sewage stations will be equipped with grit tanks, grilles, etc. for pretreatment, in part to prevent garbage from clogging equipment, sediment from long-term impact and wear equipment, and reduce equipment and facility maintenance costs.
Provide conditions for back-end processing: Some pretreatment facilities are matched and operated in the back-end system, such as the regulation tank, which can not only buffer incoming water, but also adjust temperature, pH, etc.
It can also perform preliminary pre-acidification reactions, and initially degrade the macromolecular carbon chain to achieve the effect of pre-acidification, providing conditions for the operation of the back-end IC and the cultivation of strains.
Why should wastewater treatment be pretreated first? Explain its function, equipment and common processes in detail
Why should wastewater treatment be pretreated first? Explain its function, equipment and common processes in detail
The role of pretreatment in wastewater treatment
The pretreatment before biochemical treatment is generally called pretreatment. The pretreatment processes used by the pretreatment unit for municipal wastewater can include: coarse sieve (grid), medium sieve, crushing, flow measurement, pump lifting, slag removal, pre-aeration, flotation, flocculation and chemical treatment.
Since the cost of biochemical treatment is relatively low and the operation is relatively stable, the general industrial wastewater is treated by biochemical method. In the treatment of wastewater, biochemical method is also used as the main treatment method. However, the wastewater will contain some organic substances that inhibit microorganisms and are harmful, so the necessary pretreatment should be carried out before the wastewater enters the biochemical tank.
Sand sedimentation, precipitation (natural precipitation, flocculation precipitation), clarification, etc. commonly used in pre-sedimentation tanks. When the suspended solids in the raw water are mostly large sand particles, a sand sedimentation tank should be used, and when the raw water contains more clay particles, coagulation precipitation, clarification, etc. should be used.
Grit chamber (swirling flocculation grit chamber, advection grit chamber, radial flow grit chamber, inclined tube grit chamber); pretreatment sedimentation chamber; pretreatment clarification chamber, etc.
Specifically, what does pretreatment do?
Removal of harmful substances: During water treatment, pretreatment can effectively remove harmful substances in water, such as heavy metal ions, organic matter, microorganisms, etc. If these harmful substances are discharged directly without pretreatment, it will pose a threat to the environment and human health.
Improve treatment efficiency: Pretreatment can reduce the concentration and toxicity of pollutants in wastewater, improve the biodegradability of wastewater in subsequent treatment, and help reduce the biological treatment load and improve the overall treatment efficiency.
Protect treatment equipment: Industrial wastewater may contain substances that are corrosive to treatment equipment, such as acids and bases. Pretreatment can remove these substances, protect equipment from damage, and prolong its service life.
Optimizing water resources: Pretreatment can remove most of the impurities and harmful substances in wastewater, allowing wastewater to be initially purified, thus optimizing water resources and realizing the effective use of water resources.
Compliance with regulations: In wastewater treatment, industrial wastewater pretreatment plays a key role. Untreated industrial wastewater may contain various harmful substances, such as heavy metals, organic matter and microorganisms, which accumulate in the environment and may pose a threat to the ecological environment and human health. Pretreatment can ensure that wastewater meets compliance standards before discharge, effectively protecting the environment and reducing pollution risks.
In the wastewater treatment process, pretreatment is essential to protect the environment, reduce the risk of pollution, and improve treatment efficiency, protect treatment equipment, and comply with relevant regulations.
Why should wastewater treatment be pretreated first? Explain its function, equipment and common processes in detail
The main stages of wastewater pretreatment include:
Suspension removal: mainly through some physical or chemical methods to remove suspended solids in wastewater, such as filtration, precipitation, etc.
Organic removal: using some chemical or biochemical methods to remove organic matter from wastewater, such as redox, activated carbon adsorption, etc.
Heavy metal ion removal: the use of some chemical or physical methods to remove heavy metal ions from wastewater, such as precipitation, ion exchange, etc.
Oil removal: the use of some physical or chemical methods to remove oil from wastewater, such as air flotation, precipitation, etc.
These links are usually combined and adjusted according to the specific nature of wastewater and the situation of the enterprise.
Equipment commonly used in the pretreatment process:
Mechanical filter: used to filter and remove suspended matter, particulate matter and other impurities in water.
Activated carbon filter: used to adsorb and remove harmful substances such as organic matter and heavy metal ions from water.
High-efficiency fiber filter: used to filter and remove fine suspended solids and organic matter in water, with high filtration efficiency and stable filtration effect.
Ultrafiltration filter: used to filter and remove macromolecular organic matter, bacteria, viruses and other substances in water, enabling efficient filtration and separation.
Microfiltration filter: used to filter and remove tiny suspended solids and organic matter in water, with high filtration accuracy and stable filtration effect.
Sodium ion softener: used to remove calcium and magnesium plasma from water, making the water softer and preventing the formation of scale.
Iron and manganese removal filter: used to remove iron and manganese plasma from water, making the water more pure.
Dosing device: used to add chemicals to water, such as coagulants, oxidants, etc., to make water quality more stable and purified.
Aeration tank: used to aeration water, increase the dissolved oxygen content in the water, promote the growth of microorganisms and the decomposition of organic matter.
Roots blower: In the precipitation process of the pretreatment process, the use of a Roots blower can increase the dissolved oxygen content in the water, which helps to precipitate suspended solids and oxidize and decompose organic matter. In addition, in some pretreatment processes, the use of a Roots blower can increase the oxygen content in the water, which helps to remove odors and improve water quality. If mixing, stirring, etc. are not involved in the pretreatment process, or the aeration tank already exists after the pretreatment process, then a Roots blower is not required.
These devices are widely used in pretreatment processes and can be selected and combined according to different water quality and treatment requirements.
Why should wastewater treatment be pretreated first? Explain its function, equipment and common processes in detail
IV. Pharmaceuticals play an important role in the pretreatment process
For different pretreatment steps and purposes, different agents are required. These agents can effectively separate stubborn substances from liquids and improve treatment efficiency.
Flocculant is one of the most commonly used agents in the pretreatment process. It can effectively gather suspended solids and colloidal substances in the liquid to form flocs, accelerate the precipitation of suspended solids, and improve the clarity of water quality. At the same time, flocculants can also remove some harmful substances such as organic matter and heavy metal ions, and play a certain role in pollution control.
Coagulants usually assist flocculants in their role, which can enhance the coagulation effect and promote the formation and precipitation of flocculants.
The conditioning agent is used to condition the remaining sludge before dewatering, change the physical and chemical properties of the sludge, and improve the dewatering performance of the sludge.
Demulsifier is mainly used in the pretreatment of oily wastewater, which can destroy the interfacial tension of oil and water, and make the water droplets in the emulsion gather and separate, so as to achieve the purpose of oil-water separation.
Defoamers are used to eliminate a large number of bubbles generated during aeration or stirring, improving the efficiency of wastewater treatment.
The pH regulator is used to adjust the acidity and alkalinity of wastewater for subsequent treatment.
Oxidative reducing agents are mainly used in wastewater treatment containing oxidizing or reducing substances to remove harmful oxidizing or reducing substances.
Disinfectants are used in the disinfection treatment of wastewater before discharge or reuse to kill or inhibit harmful microorganisms in wastewater and avoid harm to the environment and human health.
Pharmaceuticals play a key role in the pretreatment process. For different pretreatment links and purposes, appropriate pharmaceuticals need to be selected to achieve the best treatment effect.
The main function of setting up a sedimentation tank:
It uses gravity sedimentation to remove suspended particles that are denser than water from water. It can effectively remove suspended solids and impurities in wastewater and improve the clarity of wastewater. In a sedimentation tank, the suspended particles in wastewater will gradually sink to the bottom of the tank, while the water becomes relatively clear. Another function of a sedimentation tank is to remove large particle impurities in wastewater, such as stones, wood blocks, etc., through natural precipitation to protect subsequent treatment equipment.
Sedimentation tanks are one of the most widely used treatment units in wastewater treatment, which can be used for wastewater treatment, biological treatment post-treatment and advanced treatment. Efficient sedimentation tanks can not only achieve advanced treatment of micro-polluted water, but also can be used in industrial wastewater pretreatment, thereby improving water quality and environment, enhancing wastewater treatment effect, and then promoting the development of wastewater reuse and sludge incineration projects to achieve greater economic and environmental benefits.
It is important to note that the design and operation of a sedimentation tank should fully consider factors such as wastewater quality, flow rate, and treatment requirements to ensure that it can effectively remove pollutants from wastewater.
Why should wastewater treatment be pretreated first? Explain its function, equipment and common processes in detail
Sixth, the general pretreatment process of sewage treatment plants:
Grid filtration: Filter out large suspended solids in wastewater to prevent these substances from entering subsequent treatment equipment, affecting the treatment effect and the normal operation of the equipment.
Sedimentation treatment: By gravity separation method, suspended solids and sediment in wastewater are separated to make wastewater clear.
Air flotation treatment: By injecting air into wastewater, suspended solids and sediments in wastewater are allowed to float, and then separated.
Coagulation treatment: adding coagulant to wastewater to condense suspended solids and sediments into larger particles, and then separating them.
Adsorption treatment: using activated carbon and other adsorbents to adsorb harmful substances such as organic matter and heavy metal ions in wastewater to make the wastewater clear.
Oxidation treatment: Through chemical oxidation, organic pollutants in wastewater are oxidized into smaller molecules, resulting in clear wastewater.
Biological treatment: Through biological pretreatment, microorganisms are used to decompose organic pollutants in wastewater into smaller molecules, making wastewater clear.
These pretreatment processes can be used alone or in combination, depending on the nature of the wastewater and the treatment requirements.
Source: Environmental Science, Shengfulai Environmental Protection, Liyuan Environmental Protection Wastewater Treatment
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