Pilot – mobile – skid-mounted

Continuous filtration means that particles are removed without interruption. In other words, the process is not interrupted by a backwash, regeneration or change of medium. In most cases, at Logisticon this involves a continuous sand filter. The filter sand is circulated and rinsed continuously. The rinsing water (approximately 10%) carries off the removed parts.

Pilot – Containerised – mobile – skid-mounted

In discontinuous filtration, the filtration is periodically interrupted by a backwash or by regeneration. These are necessary in order to rinse the dirt off the medium; a waste water flow is therefore created periodically. Different media are required for different contaminants. For example, a filter kettle can be filled with:

• Sand
• Active carbon
• Manganese dioxide
• Ion exchanger resin
• Etc.

Sand filtration

The most common application of the media filters is sand filtration.

A sand filter is a filter filled with sand in order to remove impurities from water. The water to be treated is pumped downwards through a sand bed so that the particles present are captured by the sand layer. In addition, a number of physical and biological processes occur in a sand filter that further remove various substances (Fe3+, Mn2+, NH4+, etc.) from the water. This is called iron removal, demanganisation or denitrification. The contaminants that remain in the sand bed of the filter must be washed out; this is done with a backwash.

Active carbon filtration

With active carbon filtration, contaminants are absorbed. The pores in the active carbon particles create a large active surface, which is positive for the absorption capacity. In case of saturation, active carbon must be replaced. Suspended particles in the water can block the active carbon. Sand filtration is therefore often used as a pre-treatment. Active carbon filtration is used for the removal of mineral oils, BTEX, PAHs, phenols, PFAS, chlorinated hydrocarbons/halogens, heavy metals (partly) and micro contaminants (such as medicine residues). Active carbon can also be used for decolourisation and odour/taste improvements.

Ion exchange

With ion exchange, ions present in the water are bonded by means of adsorption and resin. Ion exchange can have different applications, such as water softening (removal of calcium and magnesium ions), demineralisation, as a polishing step after reverse osmosis and to remove heavy metals.

The ions to be removed from the water can be exchanged with ions with the same charge that are present on a resin (for example, during softening calcium ions are exchanged with any sodium ions that are present), or can be completely removed by the resin through the exchange of H+ and OH- so that it is possible to make demineralised water (H+ + OH- → H2O).

When the resin in the ion exchanger is saturated with exchanged/removed ions, the resin is regenerated with a regenerating agent (acid or base). Then the process can start again.

With ion exchangers, a distinction can be made between cation and anion exchangers. The cation exchangers bind the positive ions and the anion exchangers have the capacity to bind the negative ions. These resins can be either non-specific or specific. For example, specific resins are used for the removal of heavy metals from a water flow. In addition, there can be mixed bed systems in which both cation and anion resins are present; this is often the polishing step after reverse osmosis.

Pilot – mobile – skid-mounted

For the nominal removal of suspended particles from a liquid, it is possible to use media with and without a depth effect. With surface filtration, this might include filtration with a gauze or a cloth. Here, the dirt accumulates on the surface like a cake. On the other hand, a medium with depth can be used. In this case, the dirt is captured in the medium itself. Logisticon has a number of different surface and depth filters available as bag and candle filters. Bag and candle filters are often used as pre-filtration (protection) for another purification system, such as membrane filtration.

Pilot – mobile – skid-mounted

With rotating filters, a water flow can be filtered continuously. This is because the filters are self-cleaning. Logisticon uses three types of rotary filters.

• Disc filters
• Drum filters
• Belt  filters

Rotary filters are used for the removal of suspended particles and are available with different filter sizes (pore size 10 – 100 μm). Whether or not in combination with coagulation and flocculation, rotating filters offer a wide range of options. Rotary filters are often used for large flows or applications for which a large filtration surface is required.