In the backflush filter (10) according to the invention, in which the flushing back of the filter inserts (15) which are received in several filter chambers takes place by means of flushing filtrate loaded by compressed air, the flush valve (35) and the mud drain valve (39) are actuated by a common drive, whereas the valves or the valve bores (45, 46) are dimensioned in such a manner that the flush valve only releases the connection to the filtrate chamber (19') of the filter inserts (15') to be flushed back, when the mud drain valve has already at least partially released the connection between the mud chamber (24') of the affected filter chamber (14') with a mud outlet (40). By this, it is ensured in a particularly simple manner that at the backflush process the pressure level in the mud chamber has already dropped before the filtrate for the backflush is loaded with compressed air (see FIG. 2).

 
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> Process for purifying contaminated soil or groundwater with iron particles

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