Particulate reduction is achieved using mechanical filtration, the process of removing or separating suspended solids from the water. Sediment prefilters are an example of a common, particulate-reducing mechanical filter. Most foodservice prefilters have a micron rating ranging from 5 microns up to 50 microns, and are designed to remove larger particles. These are placed before other filtration systems to extend their life.
In simple terms, a mechanical filter is a barrier with a large number of tiny holes. The mixture of water and solids is pushed through the barrier by water pressure and any solid particles larger than the holes are trapped. The size of these “holes” determines the micron rating. A micron is the measurement used to describe the physical size of solid particles in any water supply. As a point of reference, one micron equals approximately 1/25,000 of an inch, and solid particles that measure less than one micron in size are occasionally referred to a “colloidal,” or sub-micron, particles.
The majority of mechanical filter products use simple, flow-through designs with Nominal Micron Ratings. Nominal means that approximately 85% of particles the size of the micron rating will be blocked by the filter. A few product designs are available with extremely high levels of particle reduction at small micron ratings. Most of these products were developed for consumer drinking water and foodservice applications, and usually carry one of the NSF / ANSI Standard 53 certifications for the reduction of cysts, turbidity, or asbestos fibers. Three features of mechanical filters need to be considered: the micron rating, the flow rate requirements for a mechanical filter product, and the total capacity of the mechanical filter.