Industrial water treatment equipment comes in a variety of implementations, all designed to suit particular operating needs. Filter presses, bed filters, cartridge filters and bag filters all excel in their intended applications. We’ll look at each type of filter and examine what applications it is most appropriate for below.
Where most industrial water treatment equipment is designed to remove solid material from water, filter presses are designed to remove water from the solids. Filter presses are ideal for any filtration application where enough material needs to be removed so that more conventional filtration methods would be ineffective. A filter press operates, as the name implies, by exerting physical pressure usually in the form of either air or a water-filled diaphragm on a slurry mixture and extracting the moisture. The remaining cake of material is then disposed of.
Bed Filters are filters with a bed of material (typically crushed walnut shell, sand, anthracite or activated carbon) that removes contaminants. Material is collected throughout the depth of the bed, allowing large amounts of material to be collected before a backwash cycle is initiated. Inlet water pumps through the filtration medium, which collects and suspends contaminants. Once the medium is saturated with contaminants, a backwash cycle is initiated. The filtration medium is fluidized and washed. This industrial water filtration method cleans the medium and readies the filter for use. This reuse of the filtration medium minimizes waste associated with the process.
Cartridge filters are disposable, replaceable, self-contained filtration units. They consist of a central perforated core wrapped in layers of filtration material. Inlet water is pumped in through the top of the filter core, and passes through the walls of the filter. Contaminants can be caught throught the depth of the filter cartrige, which allows individual cartridges to achieve very high filtration efficiencies. Cartridge filters are typically used where high purity water is required.
Bag filters are similar to cartridge filters in that they are also disposable and replaceable. Bag filters are shaped like a large sock, and are sometimes called sock filters or filter pots. They catch contaminants on the surface of the bag, and are typically used as a low cost option to remove particulate from wastewater streams.