layered bed anion unit is a single vessel system  with  layers  of  two  resins, LBA-WB on top of LBA-SB with down flow service.  The  layered bed system provides the  high  chemical  efficiency  of  a two-bed weak base anion and strong base anion  system in a single vessel. Thus it saves the cost of additional vessel  and   its associate piping and valves. The layered bed   anion system  is  regenerated   always   by  the countercurrent mode  of  regeneration so that fresh caustic contacts first the LBA-SB resin at the bottom and provides  a  high  level    of   regeneration. This results in excellent treated water quality and high efficiency of regenerant utilisation in the system.