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 must also be carried out, as water flow requirements will also vary, depending on the size of your structure.
In the case of fish farming, this value can vary even further, depending on the species being raised (for more information, please refer to the application section).
b. Organic load
Organic load is the total amount of organic matter, whether in solution or suspended 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 goal is to have the least water-saturated sludge possible, in order to use the smallest possible storage space.
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 total suspended solids, are elements that 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 suspended materials will therefore be found in the water. To guarantee water quality, it is important to get rid of these TSS. This is where the drum filter is involved. Thanks to its filter mesh, colloidal particles and other TSS will be retained, as they will not be able to pass through and will simply settle on the drum filter mesh. 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 mesh size will have a direct impact on the quality of your water. If this mesh is too large, sedimentation will only be 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.
d. Water temperature
The water temperature is also a parameter of a drum filter that will impact your choice of material used. This is because some materials are not particularly resistant to high temperatures.
Certain sectors, such as industry, will have to choose materials resistant to the hottest water they will have to treat.
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. Indeed, in woven installations using polyethylene meshes and filter panels, the two parts will detach. The filter panel serving as support for the grid, its destruction will lead to an imbalance of 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 has an extremely corrosive power. 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 counteract this corrosion, there is a solution used for certain 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.
This technique still 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 very resistant, both to salt water corrosion 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.
FAQ
How to Size a Drum Filter for a Fish Farm?
To size a drum filter in aquaculture, you must take into account the necessary water flow rate, the organic load generated by the farmed species (e.g., trout, carp, sea bass, etc.), as well as the pond volume. Species produce different amounts of suspended solids (TSS), directly influencing the drum size and the fineness of the filter mesh to be used. Precise sizing ensures clear water and good health of the livestock.
Can a Drum Filter be Used with Salt Water?
Yes, but the choice of material is crucial. Salt water is very corrosive, especially due to chloride ions. For this type of environment, filters made of polypropylene or, for the most demanding applications, titanium are recommended. Stainless steel, even if robust, can corrode in the long term in a marine environment. It is therefore not advisable to use poorly protected or combined metals, under penalty of electrochemical reactions.
Which Mesh to Choose to Optimize Filtration without Clogging the Filter?
The choice of mesh depends on the balance between the desired water quality and the particle load to be treated. A mesh that is too fine (e.g., <30 microns) offers excellent filtration but clogs quickly. A mesh that is too wide (>200 microns) allows too many impurities to pass through. For most applications, a mesh of 60 to 100 microns offers a good compromise. An on-site test or an organic load calculation is recommended to validate this choice.
What Materials should be Avoided for Filtering Hot Water?
Plastic materials such as polyethylene or certain composites can deform under the effect of heat, especially above 40 °C. This causes structural failures, microplastic release, and leaks. For industrial installations with hot water, it is preferable to opt for filters made of welded stainless steel, more expensive to purchase but much more durable and stable at high temperatures.
What are the Risks if the Drum Filter is Improperly Sized?
An improperly sized filter can cause:
- rapid saturation of the system,
- accumulation of unfiltered TSS in the water,
- increased maintenance costs,
- degradation of water quality (especially in aquaculture),
and premature wear of the drum.
It is therefore essential to consider the flow rate, organic load, temperature, and particle size to choose an effective drum filter.
