【正文】 ter well, was the water weir, clear ditch into the clear water reservoir.(3) back flush process:Close inlet valve, but there are still part of the water from both sides often open square hole into the filter, the V groove side to drain a side, the formation of a surface and wash. Then open drain valve will pool surface water from the who39。s vent to filter water and V groove top are flat. Back flush process often use air impact air water and recoil water impact three steps.(4) V type filter and the characteristics of the design parameters1) filter speed can reach 7 ~ and m/h, general is ~ m/h.2) the single upset graded filter material, size is generally ~ mm, will be allowed to expand to ~ mm, not uniformity coefficient between ~ or .3) to filter speed in 7 ~ and m/h between the filter, the filter layer height is ~ m choose between, for higher filter speed can also be increased accordingly.4) bottom with the long handle filter head plate of the drainage system, do not set gravel supporting layer. Filter head adopts network layout, about 55 / m2.5) back flush generally USES air impact, gas, water and recoil and water impact three process, backwash effect is good, save backwash water and power consumption.6) the whole filter material layer in the depth direction of the particle size distribution basic even, in the flushing process present not inflation, not occur hydraulic classification phenomenon, ensure that deep cut pollution, filter with high carrying capacity. Filter more depth general more than m, backwash water level down to the drain tank top, depth is only m.(5) from the actual operation situation, V type filter by gas water backwash technology and pure water back flush way in, mainly has The following advantages:1) better eliminates the filter material surface and inner mud ball, have cut corrupt capability is strong, filtration cycle is long, the backwash water small features. Can save backwash water forty to 60%, reduce the water for water, reduce the production operation cost.2) is not easy to produce filter material erosion phenomenon, filter only for micro expansion and improve the service life of filter material, reduce the filter fill sand, sand in cost.3) the coarse grain, homogeneous single quartz sand filter material, ensure filter flushing effect and make full use of filter material drainage capacity, after filter water quality good.(6) V type filter faults:1) increased air supply equipment, improve the infrastructure investment, increased maintenance workload.2) pool type is plicated in structure, especially the water distribution system accuracy is high, increase the construction difficulty. 3) the average ChanChi area than the average filter ChanChi area is large, but did not make full use of, for the middle of the rhone was occupied very big one part area, leading to the actual filtering area ratio ChanChi less area.4) back flush plex operation, especially a manual operation. (7) applicable conditionSiphon filter is suitable for small and mediumsized water treatment (usually in 4000 tons/day ~ 5000 tons/day), has the outstanding advantages. If water is less than 4000 tons/day, used the gravity valveless filter.The end, we should pay attention to several factors1, process requirements2, the requirements of the overall plan3, the reform of the traditional concepts4, prevent specialty and act as one pleases5, the importance of building design can not be ignoredThe main referenceWater supply engineering (third edition)China building industry press, 1995Water treatment theory foundation southwest jiaotong university pressTheory of water coagulationChina building industry pressWater purification new processChina building industry pressCoagulation technology China environmental science press28