Much of the solid build up in sand filters in recirculation systems, is from the growth of nitrifying and heterotrophic bacteria, feeding off the nutrients in the water, rather than the filtration of the water. Although sometimes thought of as beneficial, this can cause water quality problems in a system ; Firstly through the clogging of the filters and therefore a reduction in the filtration efficiency. Secondly and more importantly, if for some reason the sand filter had to be turned off, there would be a sudden loading of ammonia and BOD which the biofilters are not used to coping with. This can lead to a build up of ammonia and BOD in the culture water to toxic levels. Studies by Aqua Systems Ltd. have shown that in some systems, almost 50% of the system nitrification is occurring in sand filters!

NOTE: All flows given for mechanical filters (sand and screen) are approximate. Final flows will depend on their management and suspended solids loadings.  

The combination tank and valve units, offer a solution for small to medium flow systems (from 70 l/min to 930 l/min). The six way valve allows bypassing, backflushing and normal running. Pressure gauge and valve connection unions included, available in blue, grey or yellow. Note: All filters are available  without multiport valve. Dimensions for drawing (left) Type LSR-16 LSR-18 LSR-24 LSR-30 A 73 73 73 70 B 450 460 610 762 C 465 475 625 780 D 230 230 230 230 E 61 61 61 81 F 127 204 204 215 G 240 245 250 315 H 575 685 760 780 I 65 65 65 85 J 70 70 70 90 K 360 360 490 560 L 725 790 945 1100 X 300 350 380 400

Flow Rates for Tank & Side Mount Valve Units

                          Horizontal Tank Units

The horizontal tank units are designed for applications requiring a high filtration surface area for high flows. The filters are complete with a 6 way multiport valve (with the exception of the HZC-30) and pressure gauge they are available in blue, grey or yellow. An option for the filters is to have the access hole offset to the side for easier maintenance / access. Note: All filters are available without multiport valve.

Horizontal tank units are particularly suited to situations where there are higher solids loadings. The ratio between the cross sectional surface area of the sand bed compared to the bed volume, is greater than in "ball" type filters. This results in less frequent back flushing which can be an important factor in some systems where water conservation is important.

Dimensions for drawing (left)

Heavy Duty Commercial Sand Filter Units

These sand filters are popular for larger flows. The deep beds also ensure a high retention rate of particles 10 microns and over. Made from GRP, the filters are supplied with flanged connections for the attachment of the valve batteries and pipework. 
  
 

Multiport Valves

Manual and timer operated multiport valves come as standard on many sand filters, but are optional. They can also be retrofitted onto existing filters. Using timer operated valves can make life on the farm much easier, eliminating the need for staff to be available in the middle of the night, to flush the filters should it prove necessary.

Manual Multiport 6 Way Valves

Timer Operated Multiport 6 Way Valves

Multiple Filter Installations

With banks of filters flow rates in excess of 550m³/hr can be maintained.