A water filter removes impurities from water by means of a fine physical barrier, a chemical process or a biological process. Filters cleanse water to different extents for purposes like irrigation, drinking water, aquariums, ponds and swimming pools.
Our solutions for membrane treatment include anti-foulants to prevent biological growth and organic fouling, and scale inhibitors to increase the time between cleaning and enhance performance. Scale formation requires increased pressure to provide the same quantity of pure water.
Another option for removing dissolved iron and manganese compounds from raw water is Birm. The physical characteristics of Birm provide an excellent filter media which is easily cleaned by backwashing to remove the precipitant.
Birm is not consumed by iron removal and, therefore, offers a tremendous economic advantage over many other iron removal methods. Birm does not remove hydrogen sulfide, so if your raw water contains this component, a greensand filter will be a better option.
If your water has both iron and manganese, or iron and hydrogen sulfide, or iron bacteria, greensand is a very effective approach for removal. Using potassium permanganate, manganese and soluble iron are oxidized and precipitated by contact with higher oxides of manganese on the greensand granules.
The hydrogen sulfide is eliminated by oxidation to sulfate and an insoluble precipitate. Another option is to inject chlorine upstream of the greensand filter oxidizing the iron and/or manganese and allowing it to be removed as a colloid.
Multi-media filtration is a proven design concept of diminishing media particle size. The top layers of coarse media trap large colloidal particles and successively smaller particles are trapped in the finer layers of media deeper in the bed. The result is a highly efficient filtering system with removal taking place throughout the entire bed.
These filters may contain various types of media along with gravel under bedding for media support. Multi-media filters typically have a 10 micron removal efficiency, which can be increased greatly with the addition of a filter aid. If a multi-media filter is used prior to an RO membrane, the maximum inlet turbidity should be 10 ntu.
Microfiltration membranes have a pore size of 0.1 – 10 µm. These membranes remove all bacteria and some viral contaminants. Even though viruses are smaller than the pores of a microfiltration membrane, they attach themselves to the bacterial biofilm and are removed along with the much larger bacteria.
Microfiltration can be implemented in many different water treatment processes when particles, with a diameter greater than 0.1 µm, need to be removed from a liquid. For complete removal of viruses and color, ultrafiltration is required. The pores of ultrafiltration membranes can remove particles of 0.001 – 0.1 µm.
Sand filters are used to remove suspended solids. A filter aid is typically used with sand filters to increase colloidal particle size which allows the larger “floc” particles to be trapped by the sand. Most solids can be removed using this type of filter. Varying grades of sand are available for different applications.