FILTRATION SYSTEMS
Medium & High Capacity
Multigrade Pressure Sand Filters
Raw water driven by a pump is directed through the filter inlet port and distributor pipe work over the media.
Dirt and other particles suspended in the water will penetrate and become embedded in the media, allowing the cleaned water to pass through the underdrain collectors. The filtered water then discharges through the outlet port.
The effectiveness and efficiency of the filter is impaired by excessive build up of debris, clogging the media, which will result in pressure build up and poor circulation.
In this respect, a suitably calibrated pressure gauge is installed on the pressurized pipe work between the pump and the filter, or on to the raw water inlet manifold.
Increases in the normal running pressure of approximately 25 to 30 per cent will indicate that BACKWASHING or cleaning of the media is required.
Backwash Cycle
Backwashing or media cleaning is achieved by reversal of the water flow through the filter to waste and is activated by re-positioning the valves.
Waste pipe work should be kept as short as possible, (less than 6 meters is preferred), with a bore size the same as or greater than the filter inlet/outlet ports. Any restrictions or pipe work bends will reduce the efficiency of the back wash procedure.
The effect of backwashing can be monitored, by incorporating a clear section of pipe work on the waste discharge line.
At first, the purged water will become extremely cloudy, gradually the water will become completely clear, leaving the media free of debris, at which point the backwash procedure can be stopped and the system re-set for the normal run or RINSE cycle.
The frequency of backwashing is determined by the amount of pollution contaminating the water. In some cases backwashing maybe required daily.
Rinse Cycle
This may not be necessarily incorporated on all systems. The rinse cycle is designed to level the media bed and expel any foreign particles from inside the underdrain. The flow through the filter is in the same direction as for the normal filter cycle with water used being exhausted to waste, via the valve(s) and pipe work.
