Friday, 14 Dec 2018

AGF all plastic media filters

The Technology

Sand media filters operate by separating the suspended materials in unfiltered water as it flows through a bed of media in a pressurized tank. the recommend media, crushed basalt, quartz sand or catalytic media, have many varying aperture sizes (creating the micron rating) that cause the water to flow through a myriad of passages on it's way from the inlet to the outlet of the filter.

Sand Media

Due to the large volume and contact area between the water and the media/gravel particles, various physical forces are put into effect and act to retain the contaminating particles.

the efficiency of large particle retention is high as long as the gravel is kept clean. The catalytic media type applies an additional chemical-physical attraction between the media and particles - especially those of organic nature, giving more efficient organic material separation. In addition, the round shaped particles degrade more quickly and their cleaning requires less water in comparison with other media types.


Filtration Process

During the filtration process, unfiltered water enters the AGF media filter system via the inlet manifold and the three stage distributor plate therefore reaching the media bed with minimal disturbance. Contaminants are entrapped as the water flows through the media bed. 55 mushrooms in the under drain create uniform collection of the filtered water whilst preventing the media from being washed way.

During filtration, head loss across the filter media will increase according to the accumulation of solids within the media. When it reaches the limit set by the hydraulic conditions of the system, the media will be cleaned of the accumulated solids by way of the back flush process.

Backwash Process

Periodic back flushing is necessary to cleanse the media bed of accumulated contaminants. During the back flushing process, the flow of clean, filtered water from one or more tanks in the battery is reversed through one filter at a time via a 3-way back flush valve.

As the flow is reversed, the media bed is floated via hydraulic turbulence, and contaminants are flushed out to back flush manifold, through the back flush port of the 3-way valve. The design of the under drain system is critical to ensure uniform flotation of the media bed during the back flush process, and is critical for minimizing the amount of back flush water required to rapidly expel the contaminants from the media bed. Once the back flush is completed, the valves return to filtration mode and the next filter will back flush in turn.