| 摘要 |
In ion exchange apparatuses for purification of aqueous liquid there is a frequent problem of suspended solids from the aqueous liquid for purification becoming trapped within the bed of ion exchange material. In the present invention this problem is overcome by the provision of a bed of filter material (4) through which the aqueous liquid is passed in a downward direction prior to entry into the ion exchange material (6,9). The filter bed (4) is cleaned during the regenerating and cleaning cycle of the ion exchange material, by upflow through the filter bed of a cleaning liquid which comprises the regenerating liquid. The filter comprises particulate material having a density greater than that of water. <IMAGE> |
