Water treatment with filter systems

Gravel and activated carbon filters are proven components in physical and chemical water treatment. They are used both individually and in combination with other processes – e.g. for pre-filtration, particle retention, adsorption or dechlorination.

Gravel filters – robust particle filters for heavy loads

Use and function:

Gravel filters are used where backwash or cartridge filters would quickly become clogged by coarse particles or organic loads. Typical applications are those with increased suspended solids, floc formation or adhesive components.

Design:

The filters consist of quartz gravel of varying grain sizes, which achieves effective depth filtration. The water flows through the gravel layers from top to bottom, whereby dirt particles are mechanically retained.

Typical areas of application:

• Pre-filtration in the beverage and food industry
• Process water treatment
• Swimming pool and cooling water systems
• Well and surface water filtration
  
  

Advantages:

• Long service life thanks to backwashability
• No chemical reaction – purely mechanical filtration
• Reliable protection of downstream systems (e.g. UV systems, membrane filters)
  
  

Maintenance:

Gravel filters must be backwashed regularly to flush out filter material and maintain permeability. The backwash interval must be determined individually depending on the water load.

Activated carbon filters – adsorption and fine filtration in one step

Application and function:

Activated carbon filters combine mechanical filtration with the adsorption of dissolved substances. They are particularly suitable for removing chlorine, odours and flavours, as well as organic compounds such as pesticides or medication residues.


Structure:

Like gravel filters, they consist of a container filled with bulk material – in this case, highly porous activated carbon. The pore structure of the carbon provides a large surface area to which dissolved substances can adhere.


Typical areas of application:

• Dechlorination prior to reverse osmosis or in beverage production
• Removal of organic residues in agriculture
• Drinking water treatment (subject to hygiene control)
• Adsorption of solvent residues in industry

Special features:

Certain contact times are necessary for effective adsorption – this leads to larger sizes with low throughput.

Activated carbon cannot remove heavy metals or germs – further process stages are required for this.

Maintenance:

In contrast to backwashable gravel filters, activated carbon must be replaced regularly as its adsorption capacity decreases over time. The service life depends on the water pollution and should be monitored by measurement (e.g. chlorine breakthrough).