Method of Filtering Liquid Media

Abstract

A method of filtering liquid media comprises directing liquid to be filtered into a vessel under pressure and draining filtered liquid media from the filtration vessel. In backwash mode liquid is forced through filter media effecting rotating flow and fluidisation of the filter media, and in normal operation liquid present in the vessel above the filter media is caused to undergo rotating flow about the vessel. The drain arrangement includes a plurality of radially extending limbs configured to act as backwash liquid distribution means in backwash mode or filtered liquid collection means in normal filter mode. In backwash mode, liquid is distributed in a direction transverse to the longitudinal direction of the respective limbs; and/or the majority of the limbs direct water either clockwise or anticlockwise.

1 . A method of filtering liquid media, the method comprising: 
 directing liquid to be filtered into a vessel under pressure, the vessel including a bed of filter media and a drain arrangement for take-off of filtered liquid media from the filtration vessel, wherein in backwash mode liquid is forced through the filter media effecting rotating flow and fluidisation of the filter media and wherein in normal operation liquid present in the vessel above the bed of filter media is caused to undergo rotating flow about the vessel.    
     
     
         2 . A method according to  claim 1 , wherein: 
 in backwash mode backwash liquid is pumped through the drain arrangement into the vessel.    
     
     
         3 . A method according to  claim 2 , wherein: 
 the drain arrangement includes a plurality of radially extending limbs.    
     
     
         4 . A method according to  claim 3 , wherein: 
 the limbs of the drain arrangement include apertures, slots or other liquid passage means to act as backwash liquid distribution means in backwash mode or filtered liquid collection means in normal ‘filter mode’.    
     
     
         5 . A method according to  claim 1 , wherein: 
 the drain arrangement includes a plurality of radially extending limbs, backwash liquid distribution means being configured to distribute backwash liquid in a direction transverse to the longitudinal direction of the respective limbs.    
     
     
         6 . A method according to  claim 1 , wherein: 
 the drain arrangement includes a plurality of radially extending limbs, backwash outlet means of limbs in the drain arrangement being configured such that in backwash mode the majority of the limbs direct water in either a clockwise sense or alternatively an anticlockwise sense.    
     
     
         7 . A method according to  claim 1 , wherein: 
 the drain arrangement is mounted directly in sand filter media.    
     
     
         8 . A method according to  claim 1 , wherein: 
 in backwash mode bulk rotation of the filter bed occurs.