Views: 0 Author: Site Editor Publish Time: 2026-03-09 Origin: Site
In the eyes of many people, the core mission of a sewage treatment plant is only one: to collect urban sewage (including domestic sewage of urban residents, drainage from public facilities such as government agencies, schools and hospitals, as well as industrial wastewater and initial rainwater that are allowed to be discharged into the urban sewage collection system), remove pollutants and impurities through a series of complex treatment processes, make the water quality meet the specified discharge standards again, and then discharge it into natural water bodies such as rivers and lakes, or conduct secondary utilization. Based on this intuitive understanding, a sewage treatment plant only needs to be equipped with relevant equipment for sewage treatment, and it seems unnecessary to spend additional costs on special water purification equipment for water quality purification. However, the fact is quite the opposite. Combined with the actual operation scenario of modern sewage treatment plants, water purification equipment is an indispensable core supporting facility, and its necessity stems from four practical needs: plant operation, equipment protection, water quality compliance, and reclamation and reuse.
First, the sewage treatment plant itself is a "large water consumer" with extremely high water quality requirements, which is a rigid demand derived from the actual operation of the plant. In the operation process of the sewage treatment plant, a large amount of clean water is required for production links such as equipment cooling, pipeline flushing, instrument maintenance, chemical dissolution and filter backwashing, as well as auxiliary links such as staff living, plant greening and fire fighting. Untreated sewage, or even unpurified tap water or groundwater, can never be directly used for these water needs — impurities such as sediment, suspended solids, calcium and magnesium ions in the water will cause pipeline blockage, equipment wear and chemical failure, directly affecting the stable operation of the entire treatment system. Therefore, water must be purified to the standards meeting the needs of each link through water purification equipment to provide reliable water quality guarantee for production and operation.
Second, precision equipment and monitoring instruments need water purification for "protection", which is based on the actual characteristics of equipment and the needs of operation and maintenance. Modern sewage treatment plants are highly automated, and their operation relies on online monitoring instruments such as COD, ammonia nitrogen, pH and dissolved oxygen to feed back the water quality data of each link of sewage treatment in real time, providing a basis for staff to adjust process parameters. The probes of these instruments need to be continuously immersed in sewage to accurately monitor the real indicators of sewage, and long-term immersion will cause sludge, fine suspended solids and other impurities to adhere to the surface of the probes. If not cleaned in time, it will cause data distortion, probe damage, thereby affecting the accuracy of process regulation. Therefore, the water used for cleaning instrument probes and pipelines must be purified by water purification equipment (such as precision filters) to remove fine suspended solids, colloids and other impurities in the water. This can not only completely clean the pollutants on the probe surface, but also avoid introducing new impurities during flushing, ensure the continuous and stable operation of instruments, and guarantee the accuracy of monitoring data.
Third, water purification is the "key support" for the up-to-standard discharge of sewage. Although most of the core pollutants such as organic pollutants, ammonia nitrogen and phosphorus have been removed after biochemical treatment of sewage, the water still contains residual impurities such as fine suspended solids, colloids and microorganisms, which cannot meet the discharge requirements directly. Therefore, it is necessary to further filter and purify the water through water purification equipment (such as multimedia filters and activated carbon filters) to remove these residual impurities, ensure that the effluent water quality meets the standards, and avoid polluting natural water bodies after discharge.
Fourth, water purification is the "prerequisite" for sewage reclamation and reuse. With the increasingly prominent problem of water resource shortage, sewage reclamation and reuse has become an important function of sewage treatment plants. Reclaimed water can be used in many fields such as urban greening irrigation, road cleaning, landscape water body water supplement, industrial cooling water and farmland irrigation, and the water quality requirements of these reuse scenarios are much higher than the ordinary discharge standards. These water quality requirements cannot be achieved only through sewage biochemical treatment, and the water must be deeply purified through a water purification system (such as ultrafiltration system and reverse osmosis system) to remove salts, hardness, trace organic matter, heavy metals and other substances in the water, so as to realize the transformation of sewage from "waste to wealth" and give full play to the utilization value of water resources.
After clarifying the core reasons why sewage treatment plants need water purification equipment, we will explain in detail the specific functions of various core water purification equipment in sewage treatment plants one by one.
The precision filter is one of the most widely used basic water purification equipment in sewage treatment plants. Its core function is to filter fine suspended solids and colloidal particles in water, with a filtration accuracy usually of 1-5 microns. It can effectively intercept fine impurities in sewage or ordinary water, and provide clean water for the operation of subsequent equipment and various water use links. Its core application scenarios are mainly two: first, instrument maintenance, the probes of online monitoring instruments are immersed in sewage for a long time, and sludge and fine suspended solids will adhere to their surfaces, which need to be rinsed with clean water regularly. The precision filter can purify the rinsing water and remove fine impurities in the water, avoiding the attachment of new impurities to the probes during rinsing. It can not only thoroughly clean the pollutants on the probe surface, but also keep the probes clean and sensitive, ensuring that the instruments feed back the real water quality data of sewage accurately and continuously; second, auxiliary production, in links such as chemical dissolution and equipment cooling, the precision filter can filter out impurities in the water, avoid chemical caking and pipeline blockage, and ensure the stable operation of each production link.
The core structure of the precision filter consists of a shell, a filter element, a seal, inlet and outlet pipelines and a blowdown valve. The shell is mostly made of stainless steel material, which is corrosion-resistant and easy to clean, and suitable for the complex water quality environment of sewage treatment plants. Fiberglass shells can also be selected for small scenarios, which are light and low in cost. The filter element is the core component, with materials divided into polypropylene, nylon, stainless steel, ceramics and so on. Polypropylene filter elements are low in cost and stable in filtration, which are the commonly used types in sewage treatment plants; stainless steel filter elements can be cleaned repeatedly, suitable for long-term operation scenarios; ceramic filter elements have higher precision, suitable for high-end water use needs. During operation, the filter element must be inspected regularly, and replaced in time when the inlet and outlet pressure difference reaches 0.1-0.2MPa. At the same time, regular backwashing is carried out to extend the service life of the filter element and ensure the stable filtration effect. No professional personnel are required for on-duty daily operation and maintenance, and regular patrol inspection is sufficient, which is suitable for the high-efficiency operation needs of sewage treatment plants.
The core function of the water softener is to remove calcium and magnesium ions in water through the ion exchange principle, and reduce water hardness, and its core role is to avoid scaling of pipelines and equipment. If water pumps, valves, heating systems, heat exchangers and other equipment in sewage treatment plants use hard water for a long time, calcium and magnesium ions in the water will form scale inside the pipelines and equipment, causing pipeline blockage, affecting equipment heat dissipation and operation efficiency, and even leading to equipment damage and increasing maintenance costs. For example, the winter thermal insulation and heating system in the biochemical treatment stage must use soft water, otherwise scale will adhere to the inner wall of the heating pipeline, reducing the heating effect and even damaging the heating equipment; in addition, the influent water of ultrafiltration, reverse osmosis and other membrane systems also needs to be softened to avoid calcium and magnesium ions scaling on the membrane surface, causing membrane pollution, ensuring the normal operation of the membrane system and extending the service life of membrane components.
The water softener works based on ion exchange technology, and its core component is ion exchange resin. When hard water passes through the resin layer, calcium and magnesium ions exchange with sodium ions in the resin, thereby reducing water hardness. Most sewage treatment plants use automatic regeneration water softeners, which can automatically complete four stages of work, backwashing, regeneration and positive washing according to water hardness and water consumption, without frequent manual operation and reducing operation and maintenance costs. It has a wide range of application scenarios. In addition to the softening of influent water for heating systems and membrane systems, it can also be used in links such as chemical dissolution and equipment cooling to avoid impurities affecting chemical effects and equipment service life. The key points of operation and maintenance lie in resin maintenance and regenerant supplement. The adsorption capacity of the resin is inspected regularly, and salt is supplemented in time as a regenerant to ensure the stable operation of the equipment. The service life of the resin is usually 3-5 years, and the replacement cycle can be adjusted according to the operation load.
The ultrafiltration system is a deep water purification equipment with a filtration accuracy of 0.01-0.1 microns. Its core function is to remove colloids, bacteria, viruses, macromolecular organic matter and other impurities in water, and it is a key equipment for advanced sewage treatment and reclamation and reuse. In the advanced sewage treatment link, the sewage after biochemical treatment and coagulation sedimentation still contains a large number of fine colloids and microorganisms. These impurities will affect the clarity of the effluent and also pollute the subsequent disinfection equipment and reverse osmosis membranes. The ultrafiltration system can completely intercept these impurities, make the water quality clearer, and lay a solid foundation for subsequent disinfection and reverse osmosis treatment.
The ultrafiltration system is mainly composed of ultrafiltration membrane components, pressure pumps, backwashing systems and control systems. The ultrafiltration membrane material is mostly polysulfone, polyvinylidene fluoride and other materials, with good pollution resistance and stability. Its operation modes are divided into dead-end filtration and cross-flow filtration. Most sewage treatment plants adopt cross-flow filtration, which can reduce membrane pollution and extend the service life of membrane components. In the reclaimed water reuse scenario, the ultrafiltration system is an important pretreatment system, which can effectively remove microorganisms and colloids in water, avoid pollution of subsequent reverse osmosis membranes, and can also be used for the purification of cleaning water for precision equipment. During operation, regular backwashing and chemical cleaning are required to remove impurities attached to the membrane surface and ensure filtration efficiency. The service life of membrane components is usually 3-5 years, which needs to be inspected and replaced regularly. Daily operation and maintenance need to monitor the inlet and outlet pressure difference and deal with membrane pollution problems in a timely manner.
The core function of the activated carbon filter is to use the strong adsorptivity of activated carbon to adsorb chroma, peculiar smell, trace organic matter, as well as some heavy metal ions in water, improve the sensory indicators of effluent, and further reduce the COD content in water, and it is an indispensable equipment in advanced sewage treatment. In the advanced sewage treatment link, the sewage after multimedia filtration may still have peculiar smell, chroma and trace harmful organic matter. These impurities will affect the sensory effect of the effluent and may also have potential pollution risks. The activated carbon filter can effectively adsorb and remove these impurities, make the treated water free of peculiar smell and color, meeting the discharge standards and reclamation and reuse requirements.
The activated carbon filter is composed of a shell, activated carbon filter material, water distributor and backwashing device. The filter material is mostly granular activated carbon, which has large adsorption capacity and fast adsorption speed, and is suitable for the treatment needs of sewage treatment plants. Its application scenarios include the purification of equipment cleaning water and staff domestic water in addition to advanced sewage treatment, to remove organic matter and peculiar smell in water and avoid impurities adhering to the equipment surface or affecting the water use experience. During operation, regular backwashing is required to remove impurities adsorbed on the surface of the filter material. When the activated carbon adsorption reaches saturation, the filter material must be replaced in a timely manner, usually with a replacement cycle of 6-12 months, which is specifically adjusted according to the influent water quality and operation load to ensure stable adsorption effect. Daily patrol inspection of the filter material state is required to avoid filter material caking affecting filtration efficiency.
The multimedia filter usually uses quartz sand, anthracite, magnetite and other materials as composite filter media. Its core function is to deeply remove suspended particles, colloids and organic matter in water, and reduce the turbidity and COD content of water, and it is an important pretreatment equipment after biochemical treatment and before advanced filtration. Its functions have covered those of a single quartz sand, anthracite filter, so there is no need to equip them separately, which can effectively simplify equipment configuration and reduce investment costs.
The filter media of the multimedia filter are arranged in layers according to particle size, with anthracite in the upper layer, quartz sand in the middle layer and magnetite in the lower layer. This layered structure can improve filtration efficiency and intercept impurities of different particle sizes. In the biochemical treatment stage, to ensure the growth environment of microorganisms, the heating system needs clean soft water. The multimedia filter can cooperate with the water softener to first remove suspended impurities and some organic matter in the water, and then the water softener removes calcium and magnesium ions to ensure that the quality of heating water meets the standards. In the advanced treatment link, it can pretreat sewage to remove large particle impurities and some organic matter in the water, avoid rapid blockage of filter materials or membrane components of subsequent activated carbon filters and membrane systems, extend equipment service life and reduce operation costs. During operation, regular backwashing is required to remove impurities on the surface of the filter material and ensure filtration effect. The filter material replacement cycle is usually 1-2 years, and the backwashing frequency can be adjusted according to the influent turbidity.
The reverse osmosis system is the core equipment for sewage treatment plants to realize advanced sewage purification and reclamation and reuse. As a complete deep water purification system, it takes reverse osmosis membrane components as the core and cooperates with auxiliary pretreatment equipment such as water softeners and security filters to operate together. Its filtration accuracy can reach 0.0001 microns, which can effectively intercept almost all salts, calcium and magnesium ions, trace organic matter, heavy metals and other impurities in water, and is a key support for realizing sewage reclamation and reuse and high-end pure water preparation. Due to the high cost of reverse osmosis membrane components and extremely strict requirements for influent water quality, fine impurities, colloidal particles and other substances will cause membrane pollution, blockage and even irreversible damage to membrane components. Therefore, the pre-pretreatment link is particularly important. As the core pre-pretreatment equipment of the reverse osmosis system, the security filter will be prioritized in the configuration scheme and work with the water softener to provide a clean and qualified influent environment for the reverse osmosis membrane.
The filtration accuracy of the security filter is usually controlled below 1 micron, and its core function is to accurately intercept the fine impurities and colloidal particles still remaining after pretreatment by multimedia filtration and ultrafiltration system, avoiding such impurities from entering the reverse osmosis membrane components from the source. The water softener is responsible for removing calcium and magnesium ions in water and reducing water hardness, preventing calcium and magnesium ions from scaling on the membrane surface. The two work together to not only ensure the stable operation of the reverse osmosis system, but also effectively extend the service life of membrane components. At the same time, there is no need to add other high-precision filtration links additionally, which optimizes equipment configuration and reduces operation and maintenance costs.
The core application scenarios of the reverse osmosis system are mainly two: first, reclaimed water reuse, when reclaimed water is used in scenarios such as industrial cooling and production process water, the water quality requirements are much higher than the ordinary discharge standards. The reverse osmosis system can efficiently remove salts and hardness in water, avoid pipeline scaling and equipment damage caused by long-term use, and realize the recycling of water resources; second, pure water preparation, it provides high-purity pure water for laboratory testing, instrument calibration, high-precision chemical preparation and other work in sewage treatment plants, avoiding impurities in water affecting work accuracy and chemical effects. In daily operation, the operation and maintenance of all components of the system must be done well simultaneously. The reverse osmosis membrane components and security filter elements are cleaned regularly. The membrane component replacement cycle is usually 2-3 years, and the security filter elements need to be replaced in time according to the pressure difference between the inlet and outlet. At the same time, the system operation pressure and product water quality are monitored, and the operation parameters are adjusted in a timely manner to ensure the stable and efficient operation of the entire reverse osmosis system.
Ultraviolet disinfection is the core physical disinfection method in the disinfection link of sewage treatment plants. Its core function is to kill pathogenic microorganisms such as bacteria, viruses and spores in water, guard the last pass of water quality safety, and ensure that the effluent water quality meets the discharge requirements and reclamation and reuse standards. It is especially suitable for scenarios with no secondary pollution requirements for disinfection, and is one of the mainstream disinfection methods for large-scale sewage treatment plants. Compared with chemical disinfection, ultraviolet disinfection does not need to add chemical agents, will not produce secondary pollution, and will not change the physical and chemical properties of water, which can maximize the stability of effluent water quality.
The ultraviolet disinfection equipment is mainly composed of ultraviolet lamps, reactors, quartz sleeves and control systems. The lamps are mostly low-pressure mercury lamps or medium-pressure mercury lamps, which can emit ultraviolet rays with a wavelength of 254nm. This wavelength can effectively destroy the DNA and RNA structure of microorganisms, make them lose their reproductive capacity, and thus achieve the disinfection effect. When the equipment is in operation, sewage passes through the reactor at a constant speed, and the ultraviolet rays emitted by the ultraviolet lamps penetrate the quartz sleeve to kill the microorganisms in the sewage. The disinfection effect is closely related to the sewage turbidity and flow rate. Therefore, it is necessary to ensure that the sewage is fully filtered before disinfection to reduce turbidity and avoid affecting the ultraviolet penetration effect.
The advantages of ultraviolet disinfection equipment are simple operation, high disinfection efficiency, no secondary pollution, no need to store and add chemical agents, and reduced operation and maintenance risks and costs. During operation, the dirt on the surface of the quartz sleeve must be cleaned regularly to avoid affecting ultraviolet penetration; the luminous intensity of the ultraviolet lamps is inspected regularly, and the lamps are replaced in time when the intensity drops to below 70% of the standard value, with a usual service life of 8000-10000 hours for the lamps. At the same time, the quality of the effluent after disinfection is monitored to ensure that the microbial indicators meet the standards, which is suitable for the dual needs of up-to-standard sewage discharge and reclamation and reuse.
In summary, the demand for water purification equipment in sewage treatment plants is determined by four practical needs: their own operation, equipment protection, water quality compliance, and reclamation and reuse, and it is not an unnecessary configuration. Various types of water purification equipment perform their own duties and cooperate with each other, from basic impurity filtration, water softening, to advanced membrane separation, disinfection and sterilization, from equipment guarantee in production links, to the supply of living and fire-fighting water in auxiliary links, running through the whole process of sewage treatment. It is the collaborative effect of these water purification equipment that enables sewage treatment plants to operate stably, efficiently and safely, realize the up-to-standard discharge and reclamation and reuse of sewage, truly turn "waste into wealth", protect the water environment and save precious water resources at the same time.