In today's society, as people's requirements for water quality continue to increase, water treatment equipment plays a crucial role in various fields. Multi-media filters, as a common device in the water treatment sector, are widely used in industrial water, domestic water treatment, and wastewater treatment due to their efficient filtration performance and relatively simple operation process. However, like any equipment, multi-media filters may encounter various faults during long-term operation. If these faults are not resolved promptly, they will not only affect filtration performance but may also cause equipment damage and increase operating costs. This article will provide a detailed introduction to some common faults of multi-media filters and their effective solutions, helping everyone better maintain and manage this important water treatment equipment.
During the operation of multi-media filters, issues related to filter media are key factors affecting filtration performance. Long-term water flow impact and impurity accumulation reduce the gaps between particles, increase resistance, and decrease filtration efficiency. Meanwhile, organic matter and microorganisms in water can breed on the media surface, clogging pores and further reducing filtration efficiency. These problems not only affect water quality but also increase operating costs and shorten service life.
Filter media in multi-media filters, such as quartz sand and anthracite, will gradually have reduced gaps between particles after long-term water flow impact and impurity accumulation. Under this situation, water flow resistance increases, leading to a significant decrease in filtration efficiency. For example, in some industrial water treatment systems, if media compaction is not resolved promptly, the filtered water quality may fail to meet production requirements, affecting product quality.
Solution: Backwashing is the primary method to solve media compaction. By reversing the water flow, the media is loosened and gaps are restored. During backwashing, it is necessary to control the intensity and duration to ensure that the media is effectively loosened without causing excessive impact or damage. If backwashing is ineffective, it indicates that the media may have aged or is severely damaged. At this time, partial or full replacement of the media is required. When replacing media, select high-quality and high-strength products and strictly follow the equipment design requirements to avoid future compaction.
Media contamination is also a common issue for multi-media filters. Organic matter and microorganisms in water can breed on the media surface, clogging its pores. This contamination is especially common in environments with poor water quality. For example, when treating wastewater with high organic content, the media is easily contaminated, resulting in a significant reduction in filtration efficiency.
Solution: Chemical cleaning can be used to remove organic matter and microorganisms from the media surface. Common chemical agents include oxidizers such as sodium hypochlorite. When using chemical agents, it is important to control the concentration and cleaning time to avoid damaging the media. Generally, a small-scale trial is recommended first to determine the appropriate concentration and cleaning time before performing full-scale cleaning. For cases where raw water quality is poor, pre-treatment facilities such as coagulation-sedimentation tanks or equalization tanks can be added before the multi-media filter. Pre-treatment reduces the impurity content, alleviating media contamination. For example, during the rainy season, raw water may carry a large amount of sediment. In this case, water can first enter an equalization tank for sedimentation before entering the filter, effectively preventing heavy sediment contamination and prolonging media life.
During long-term operation, media may break due to friction and water flow impact. The resulting small particles fill the gaps in the media, causing blockages. For example, activated carbon media is prone to breakage, especially when water flow changes sharply or is subjected to strong physical impact.
Solution: Regularly inspect media integrity and promptly replace broken media. When replacing media, select high-quality and high-strength media and avoid excessive impact during installation to reduce breakage. Avoid sudden changes in water flow velocity and strong physical impacts on the media. For example, when adjusting filtration flow rate, changes should be gradual to prevent impact; during backwashing, the intensity should be controlled to avoid excessive wear and breakage.
During continuous filtration, trapped impurities accumulate in the media layer. If backwashing is not timely or thorough, these impurities gradually block the pores, eventually causing filter blockage. Additionally, microorganisms can form biofilms on the media surface. When biofilms become too thick or detach, they can also block the filter.
Solution: Adjust backwashing parameters reasonably, such as increasing backwashing intensity, extending duration, and adjusting frequency. Air-water combined backwashing can more effectively remove impurities from the media pores using both compressed air and water. In practice, test and adjust parameters according to media characteristics and filter operation to ensure optimal backwashing. Appropriate disinfectants, such as chlorine or chlorine dioxide, can be added to the influent to inhibit microbial growth. Care must be taken with dosage to avoid negative effects on subsequent water treatment processes. Regular filter disinfection, such as soaking in hydrogen peroxide solution, can kill microorganisms on the media surface and prevent biofilm formation and blockage.
During normal operation, multi-media filter media is layered according to density, typically with anthracite on top and quartz sand at the bottom. If water flow or other factors disturb this layering, it affects backwash water distribution, reducing backwashing effectiveness.
Solution: Restore correct layering through slow hydraulic sorting or manual sorting. During sorting, care must be taken to avoid damaging the media. After restoration, gradually increase influent flow to prevent re-mixing. Daily operation should avoid actions that disturb layering. For example, when adjusting filtration flow or performing backwashing, control speed and intensity to prevent disruption. Regularly inspect layering and address issues promptly to ensure effective backwashing and normal filter operation.
Influent water quality directly affects multi-media filter performance. Excessive impurities or frequent water quality fluctuations can exceed the filter's design capacity, reducing efficiency. For example, during rainy seasons, raw water may carry heavy sediment loads, increasing filter burden and reducing water quality. Controlling raw water quality and adopting appropriate pre-treatment measures are key to ensuring efficient filter operation.
When the suspended solids or colloids in influent water suddenly increase and exceed the filter's design capacity, filtered water quality will deteriorate. This situation is common in special circumstances, such as changes in raw materials or process abnormalities during industrial production, which can worsen water quality.
Solution: For occasional deterioration, first divert water into equalization or sedimentation tanks for pre-treatment such as sedimentation or coagulation to reduce impurities before filtration. This can temporarily solve influent water quality issues and ensure normal filter operation. For long-term issues, consider upgrading the influent system and adding pre-treatment facilities. For example, adding coagulation-sedimentation tanks can remove most suspended solids and colloids, allowing influent water to meet the filter's design requirements and ensuring stable operation.
Fluctuations in influent water quality may also negatively affect filter operation. For example, industrial water quality may vary with production processes, causing unstable filtration performance.
Solution: Strengthen monitoring of influent water quality to track changes. Adjust operations based on water quality, such as dosing coagulants or changing pre-treatment parameters, to maintain relatively stable influent quality and reduce impact on the filter. Adjust filter operating parameters, such as flow rate and backwash cycle, according to water quality. For poorer water quality, reduce filtration flow and increase backwash frequency to maintain performance; for better water quality, increase flow and reduce backwash to improve operational efficiency.
If the filtration flow exceeds the filter's design capacity, water residence time in the media layer becomes too short. Impurities cannot be fully adsorbed or captured and pass through the media layer, affecting filtration efficiency. This commonly occurs in high water demand situations, where blindly increasing flow to meet usage can lead to insufficient filtration.
Solution: Control filtration flow by adjusting pump output or valve openings to return to the design range. This is the most direct method. Flow adjustments should be precise according to filter design parameters and operating conditions to meet water demand without affecting performance. Installing flow monitoring devices allows real-time adjustments to ensure the filter operates at optimal flow, maintaining stable and reliable filtration.
Insufficient backwash velocity or pressure cannot effectively flush impurities from media pores. Causes include underpowered pumps, blocked pipes, or partially opened valves. If backwashing is poor, impurities remain, reducing filtration efficiency and service life.
Solution: Inspect backwash pumps to ensure adequate pressure and flow. Replace underpowered pumps if necessary. Clean backwash pipelines and valves to ensure smooth flow. Adjust backwash duration according to media type and operating conditions, typically between 10–30 minutes, to thoroughly remove impurities without wasting water or energy.
As an important water treatment device, multi-media filters may experience various faults during practical application. However, as long as faults are detected in time and effective measures are taken, optimal operation and filtration performance can be maintained. Daily use should emphasize maintenance and management, with regular inspections and timely handling of potential issues. Adjust operating parameters reasonably based on actual conditions, optimize operational processes, and improve efficiency and service life. Through scientific management and maintenance, multi-media filters can fully perform their role, providing high-quality water for production, life, and environmental protection.Common faults and effective solutions for multi-media filters to ensure efficient water treatment, optimal performance, and extended media lifespan.
