Filtration Behavior Research Of Uniform Media In Direct Filtration Process

Filtration is one of important operation units in water treatment operation process, and the sand granule used in the Deep Bed Filtration is the key to perform a satisfied capacity. For this reason, a proper choice of it can influence the filtration capacity greatly. In designing the Deep Bed, the empirical formula L/de=800 is used as the basis. However, it has been proved that the formula cannot precisely describe the functional relationship and the correlation degree between the nitration behavior of the Deep Bed filtration process, the depth of the Deep Bed and the diameter of the sand granule, and it is restricted greatly in the practical application of finding a suitable depth of the Deep Bed.Theoretical analysis shows that the filtration behaviors of the Deep Bed, that are the head loss and turbidity of the effluence water, have the correlation o f L/d2 with the Deep Bed When the diameter of the filtration media is changed, if the depth of the Deep Bed is designed according to the relationship of L/d2, the filtration behavior of the Deep Bed will have a closer similarity with that of the original one.Through choosing different diameter of sand granule, using FeCl3 and PAC as the coagulants, doing paralleled test through standard filtration column compared with referenced filtration columns (the coarser and the finer sand granule used as filtration media separately), the thesis investigates the correlation between the filtration behavior and the depth of the Deep Bed L, the diameter of the sand granule d. Meanwhile, the filtration capacity of the Deep Bed using the uniform media is analyzed and valuated.Research result shows that:(1) In the micro-flocculation joint direct filtration process, FeCl3is a suitable coagulant, but PAC is not.(2) FeClsused as a coagulant when the water quality after filtration has tiny difference in the direct filtration process, compared with the finer sand media, the velocity increase of the water head loss of the coarser sand media is slower, and its filtration cycle is longer.(3) The water head loss of the standard Deep Bed and that of the designed Deep Bed have less difference if the later is built according to the relationship of L/d2, but they have larger difference when it is constructed according to the relationship of L/d.(4)If using L/de=800 as a designing basis of theDeep Bed filtration when FeCl3 is usedas the coagulant, (here is space to lessen the depth of Deep Bed.