Design criteria for a drum filter

When choosing your filtration system, it is important to know which filter is the right one for your operation by taking into account the different parameters of a drum filter. In this section you can find all the information about the drum filter settings that need the most attention.

a. Water flow

To ensure that it performs its intended function optimally, it is important to choose the right drum filter. First of all, the requirements of your installation must be established according to the settings. Depending on the facility type (fish pond, wastewater treatment plant, TSSR, etc.). A more detailed study is also required, as water flow requirements will also vary, depending on the size of your structure. Depending on the species, this value may vary for fish farms (for more information, see the application section).

b. Organic load

Organic matter refers to the total amount of organic matter, whether in solution or in suspension, in the wastewater to be treated. You will need to choose a filtration system able to withstand and extract this organic matter. Without this, your mechanical filtration system may quickly become saturated and therefore obsolete. Drum filters represent the number one mechanical filtration system. It is indispensable for large and medium-sized installations. We strongly recommend you to choose this equipment. By fixing this organic load to its filtering mesh, it will change into more or less concentrated mud. Depending on the settings of a drum filter, this mud can be very concentrated. The purpose is to have the lowest saturation of water in the mud, in order to use as little storage space as possible.

c. Sedimentation of particles

Generally, water contains particles. Depending on their size and the flow of the current in which they are found, they can either sediment (settle on the bottom), be transported, or finally be eroded.

TSS or suspended solids are elements, which are constantly transported. These particles (found in the blue diagram) can be both feces, present in fish ponds, and colloids (negatively charged particles that cannot agglutinate and sediment). These materials will therefore be found suspended in the water. To ensure water quality, it is important to remove this TSS. This is where the drum filter is involved. Because of its filtering mesh, colloidal particles and other SS will be retained, as they will not be able to pass through and will simply sediment, on the mesh of the drum filter. The mechanism will allow you to remove it by flushing it down the drain. To ensure this sedimentation of particles, it is important to select your filter carefully. Indeed, the size of the mesh will have a direct impact on the quality of your water. If this mesh is too large, sedimentation will be only partial and you will have poor quality water. If the mesh is to small, you might exert too much effort, compared to your needs, and therefore spend more.

Hjulström diagram of 1h2o3 particles
Hjulström diagram to understand the sedimentation mechanism of particles

d. Water temperature

Water temperature is also the most important criteria for a drum filter and will impact your choice of material. This is because some materials are not particularly resistant to high temperatures.

Some sectors, such as industry, will have to choose materials that are resistant to hotter water.

For example, some plastic filters will tend to deform under the action of too much heat. This deformation can have a direct impact on the performance of your drum filter, to the point of making it obsolete. This is because with woven systems, such as those using polyethylene mesh and filter panels, separation of the two parts will occur. As the filter panel supports the screen, its destruction will cause an imbalance in the system, leading to breakage. Furthermore, such facilities tend to break down and release fine particles of micro-plastics. These particles are very harmful for the environment which will integrate them. Because of bioaccumulation phenomena (accumulation of pollutants in the food chain), these pollutants will be extremely harmful to our health.

Therefore we recommend stainless steel drums. They are welded and therefore have a higher strength. The material is also capable of withstanding higher temperatures than plastic drums. This version will be more expensive at the beginning, nevertheless, it will remain in place for a long time. This initial investment in stainless steel models is quickly returned with very low maintenance costs.

What material should be selected for filtering salt water?

As you probably know, salt water is extremely corrosive. Chloride ions are particularly aggressive for some metals. Corrosion efficiency depends on several variables.

Even if the size of your installation will play a role in the longevity of your filter, the most important factor is the material used. Choosing the right material for your filter’s environment is therefore essential.

To prevent this corrosion, there is a solution used for some boat hulls. This method involves applying a first layer that is more sensitive to corrosion. Therefore, the corrosion will attack the damaged layer first. As a result, the filter material will be less exposed.

However, this technique requires a high level of maintenance.
Another possibility is to cover the material vulnerable to corrosion (steel, stainless steel) with a material resistant to corrosion. This technique seems interesting, although not perfected. The slightest scratch on the surface layer can cause chloride ions to infiltrate and destroy the inner layer. In addition, this technique has a cost, because the coating materials are often precious and are therefore particularly expensive.

Filter material

One of the drum filter settings to consider is the type of material. To filter salt water, we recommend using polypropylene. It is extremely resistant and has good chemical resistance. As a result, the surface will last longer than other metals in such an environment. Choose a large filter to reduce the effects of pressure-related distortion. However, if this pressure is too great, it will be necessary to turn to more resistant and more expensive materials.

Titanium is a good alternative for high pressure marine installations. It is extremely resistant to corrosion from salt water and pressure, but is much more expensive than polypropylene.

Other alternatives exist, but we recommend not combining several metals in contact to avoid the formation of electrical couples. Moreover, we advise you to reduce the mechanical parts to the strict minimum.

Shopping Cart