The Study On Combination Process Of Radiant-flow Filtration And Ultrafiltration To Treat Micro Contaminated Raw Water

With the deterioration of water source quality, the water treatment plants whichtake the traditional procedures can hardly stand this deteriorating situation. To ensurethe stability, safety, and reliability of water quality, appropriate methods are taken toreform the water treatment plants. The water safety has become an urgent issue forpeople and the hot spot among the professions. Facing these problems, this paperfocuses on both the designs and researches of a radiant-flow filter which combines theadvantages of interstitial flow, dugwell and biofilter.The experiment reveales that the recovery of the flow in this radiant-flow filterbenefited more from square screens than mat screens. The air-water combinedbackwash could remove the pollutant adhered to the outer sphere of the screens moreeffectively. The filter media were cleaner after air-water combined backwash processthan water backwash process.At the beginning of the experiment, the film in this radiant-flow filter wasnaturally cultured. The removal efficiency of ammonia nitrogen and CODMnreached43.0%and49.6%, and then both tend to be stable after17dats. The main reason forshort biofilm culture time is that the filter media were preliminarily acclimated. Thesefactors which influence the biofilm culturing, such as temperature, HRT (hydraulicretention time), raw water quality and etc. were analyzed and the low removalefficiency when the radiant-flow filter worked steadily was due to the thin filtrationlayers and short HRT.The effect of different initial filtration velocities at0.6m/h，0.9m/h，1.3m/hrespectively on such parameters as the purification effect of the radian-flow filter,periodical water yields, backwash time and waterhead loss along the filtration layerswas analyzed and the optimum filtration velocity in the radiant-flow filter is0.9m/haccording to BFI formula. The optimum dosage of coagulant was polymericaluminium of4mg/L by laboratory experiment. According to the determinedradiant-flow filter operating parameters, the device had been operated continuously inthe condition of normal temperature and normal turbidity, low temperature and lowturbidity, normal temperature and high turbidity. The purification effect of both themicro-flocculation direct filtration in the radiant direction and filtration in the radiantdirection on these three water qualities were investigated, which indicated that higher temperature led to the greater removal efficiency of the pollutants. Besides, thereexist a linear relationship between the inflow turbidity and the removal amount of theturbidity in this device. The removal efficiency of turbidity, CODMn, ammonianitrogen and algae was high whether the micro-flocculation process was applied priorto the radiant-low filtration or not. Therefore, the radiant-flow filter is believed canserve as either pretreatment process or be set in the sedimentation tank to alleviate theload in the following procedures.The micro-polluted source water was treated by the joint process ofultrafiltration and (micro-flocculation) radian-flow filtration. Both processes hadgood effect on the water purification and the process prior to whichmicro-flocculation was set was even better.