Industrial and commercial filtration is the process by which particles (or suspended solids) larger than 0.5 micron are removed from water or wastewater. Many different types of commercial filters can be used to remove suspended solids. Sometimes only a single type of industrial filter is required to achieve the desired water quality. In other cases, several different types of filters in a specific sequence may be required.
Determining the number and types of industrial filters best suited to a particular situation depends upon:
- The volume of water to be treated
- Whether water must be filtered continuously or whether it can be filtered in batches
- The amount of suspended solids in the water
- The range of particle sizes in the water
- The desired amount of suspended solids in the water after filtration
- The smallest particle size desired in the water once filtered
The size of particles is typically measured in micrometers (commonly called “microns”). One micron is equal to .0000394”. The amount of particles is typically measured in mg/l. Mg/l are also referred to as “ppm” (parts per million). Particles larger than 20 micron are usually visible to the “naked” eye. A substantial concentration of very fine particles will give the water a cloudy appearance.
There is a wide variety of industrial and commercial filters available today. These include:
- Bag and cartridge filters
- Sand filters
- Dual-media filters
- Multi-media filters
- Centrifugal separators
- Screen filters (or strainers)
- Dissolved air flotation (DAF) units
- Dewatering screens
In order to select the most appropriate commercial filter(s), laboratory tests should be performed on a representative sample or range of samples of the water to be filtered. The most important tests are for suspended solids (TSS – Total Suspended Solids) and particle size distribution.
In addition, the client should also be able to define the characteristics (or quality) of the water once it is filtered. Filtered water quality is usually determined by how the water is to be used, once filtered.
The greater the concentration of suspended solids and the smaller the particles are, the greater the challenges in removing them. Every type of filter has a range of conditions within which it operates effectively and efficiently. Going beyond a particular filter’s capacity leads to poor filter performance, maintenance issues, and less than acceptable water quality.
The following table provides some general guidelines for the appropriate use of filters. Consult one or more filter manufacturers or engineering firms for specific recommendations for your particular application. Click here to consult with an Everfilt Applications Engineer.
In instances where there is a substantial concentration of very fine particles and where removal of these particles is required, coagulants or flocculants will typically be added to the water prior to filtration. The coagulants cause very fine particles to agglomerate into larger ones, making them easier to remove.
** Designates conditions where a coagulant, coagulant aid, or flocculant may need to be added to the water prior to filtration