NQA
Active Water Treatment

sustainable technology

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cubm hr-1 m2 
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Operating guidelines for AFM filters

Applications   Run phase  water flow-rate
cubm hr-1 m

 Air purge all filters at 95 cubm/hr at no more than 0.4 bar pressure

Back-wash water flow cubm hr-1 m
for grade 1 AFM
Back-wash water flow duration minutes (2)Back-wash  frequency
Drinking water optimum 5 - 10 2- 4 minutes 50 - 60 4 - 8 1 to 2 times per day
maximum 10 - 15       
Swimming pool optimum 10 - 15 2 - 4 minutes 50- 60 4 - 8 1  times per week or every second  week
maximum 15 - 30        
Sewage treatment and industrial effluent optimum 1 -5 4 to 8 minutes 55 - 65 2 - 4 4 to 8 times per day
maximum 5 - 15    4 - 8  
River, lake and sea water

 

optimum 5 - 10 4 to 8 minutes 50 - 60 4 - 8 2 to 4 times per day
maximum 10 - 30        
Aquaculture optimum 5 to 15 4 to 8 minutes 50 - 60 4 - 8 2 to 4 times per day
  maximum 10 to 30        
Public aquariums optimum 5 to 15 3 to 6 minutes 50 - 60 4 - 8 1  times per week or every second  week
  maximum 15 to 30        
Landfill Leachate optimum 1 to 5 8 minutes 55 - 65 4-8 6 times per day          

Notes

  1. Bed expansion should be around 150mm for a 1m deep bed.
  2. In some cases such as the removal of iron and manganese from water supplies,  it can actually be more effective to use a short back-flush and allow retained metals and solids to stay in the bed.  The retained solids can in some cases improve the performance of the filter.  For example, if there are diatoms ( algae) in the water,   the diatoms will improve filter performance,  but the pressure head will also increase. For critical applications such as swimming pools and drinking water,  the back-flush should continue until the water runs clear. On average AFM will remove around 50% more solids from the water than a sand filter, so the back-flush times end up being similar,  but almost twice as much solids are removed from the water.
  3. Air purge for 2 to 8 minutes prior to back-flushing is recommended for all applications,  however  unlike sand air scouring is not essential for AFM , although it does improve performance.