| 摘要 |
<p>Method for controlling a filter device for the purification of a contaminated, and in particular nitrates-containing, liquid such as industrial waste water or groundwater, which device comprises a standing vessel, the lower part of which has a downward narrowing inner wall, which vessel serves to receive a granular filter-bed, for instance in the form of a sand-bed, in addition to a pump tube standing in the filter-bed and having arranged therein a stand-pipe controllably fed with a gaseous medium such as air, a washer for the sand supported by the tube and situated above the filter-bed and a tube assembly debouching close to the bottom for supplying the liquid for filtering and cleaning, wherein the air supply in the stand-pipe is controlled such that a constant ratio is maintained between a value of the filter-bed resistance to be measured momentarily and the desired resistance thereof, wherein the desired resistance value is predetermined from the clean-bed resistance at a determined liquid flow rate.</p> |
