Causes and Solutions Filter Media Clogging in Multi-Media Filters

 
Multi-media filters are widely used in water treatment processes, and the selection and management of filter materials directly affect the filtration efficiency. Common filter media include quartz sand, anthracite coal, and manganese sand, which play a crucial role in removing suspended impurities and reducing water turbidity. However, in practical applications, the use and maintenance of filter media also face many challenges, particularly filter media clogging. This article will discuss in detail the problems and solutions associated with filter media clogging in multi-media filters.

Analysis of Causes of Filter Media Clogging

 
Filter media clogging during the operation of multi-media filters is a common and serious issue, mainly due to the following aspects:

1. Ineffective Removal of Retained Contaminants

 
If the contaminants intercepted on the filter layer surface are not effectively removed within the specified cycle, uneven air distribution during backwashing can lead to uneven expansion of the filter media. In areas where the air agitation is insufficient, the grease and other impurities on the surface of the filter media cannot be effectively removed, leading to increased local load. The impurities sink from the surface into the interior, gradually forming clumps that extend into the depth of the filter media, eventually causing the filter to fail due to filter media clogging.

2. Fine Filter Media Particles

 
The fine particles of filter media on the surface of the filter layer have fewer opportunities to collide with each other during backwashing, resulting in less momentum and difficulty in cleaning. The attached sand particles are prone to forming small mud balls that contribute to filter media clogging. After the backwashing ends and the filter layer is re-graded, these mud balls enter the lower filter media, moving deeper as they grow.

3. Oil Content in Raw Water

 
Oil in the raw water is one of the main causes of filter media clogging, which is essentially a form of filter media clogging. Oil substances are difficult to handle in water treatment due to their viscosity and low density, making them easy to adhere to the surface of the filter media. Although the backwashing process can remove some of the oil stains, some oil will always remain in the filter media. Over time, these oils accumulate, gradually forming an oily film on the surface of the filter media. This oily film not only reduces the filtration efficiency of the filter media but also increases the friction between the particles, causing them to clump together and eventually form clogging, which is a type of filter media clogging.

Considerations for the Use of Filter Media

 
To prevent filter media clogging, the selection and configuration of filter media should pay attention to the following points:

1. Filler Height and Structure

 
Taking the common perforated plate structure as an example, the filler height is generally 1000 to 1200 millimeters above the perforated plate, and the straight section height of the cylinder is about 2000 millimeters. If it includes anthracite coal, the filler configuration is: 400 millimeters of anthracite coal height, 800 millimeters of quartz sand height (200 millimeters of cushion layer + 600 millimeters of filtration layer).

2. Quartz Sand Configuration

 
The bottom layer of quartz sand, about 200 millimeters, has a particle size of 2 to 4 millimeters, and the filtration layer of 800 millimeters has a particle size of 0.5 to 1.0 millimeters. If it contains anthracite coal, the particle size of anthracite coal is 1 to 2 millimeters. When designing the filter layer, the particle size of the lower layer filter media should be smaller than that of the upper layer to ensure the effectiveness and full utilization of the lower layer filter media. At the same time, the upper layer has a lower density to ensure that the stratification is restored after backwashing, forming a structure where the upper layer filter media acts as a coarse filter and the lower layer filter media acts as a fine filter.

Measures to Prevent Filter Media Clogging

 
To prevent filter media clogging and ensure the long-term effective operation of multi-media filters, the following specific measures should be taken.

1. Optimize Backwashing Cycle and Intensity

 
Based on actual operating conditions, optimize the backwashing cycle and intensity to ensure that the filter media can be fully regenerated and maintain high filtration efficiency. Set appropriate pressure difference and time parameters to ensure that the backwashing process can thoroughly remove contaminants and oil stains from the surface of the filter media, which helps to prevent filter media clogging.

2. Regular Inspection and Maintenance

 
Regularly inspect the condition of the filter media to ensure that there is no clumping or filter media clogging. Replace the filter media when necessary to maintain its filtration effect and the overall performance of the system. Inspections include visual inspections and sampling analysis to ensure that the filter layer is uniform and there is no obvious accumulation of oil stains, which can lead to filter media clogging.

3. Use Appropriate Filter Media

 
Choose the right filter media particle size and type to ensure that the particle size of the lower layer filter media is smaller than that of the upper layer, and the upper layer has a lower density to ensure that the filter media stratification is restored after backwashing, forming an effective filtration structure that resists filter media clogging. Use filter media with strong oil resistance, such as some special quartz sands or synthetic materials, to reduce the impact of oil stains on the filter media, thereby preventing filter media clogging.
 
Multi-media filters play an important role in the water treatment process, and the selection and maintenance of filter media directly affect their filtration efficiency. By optimizing the filter media configuration, regular backwashing and maintenance, effective prevention of filter media clogging can be achieved, improving filtration efficiency and extending the service life of the equipment. Through the discussion in this article, it is hoped to provide valuable references for the use and management of multi-media filters to prevent filter media clogging.