Model Study On New Type Of Float-valve Filter

The construction bureau has issued Water Quality Standards for Urban Water Quality in the year of 2005, Comparing to the formal national standard, it refers to a more strictly water quality: The number of checked item has increased to 101 from 35, the turbidity standard has been changed to 1 NTU, and it adds organism index and pesticide control index and so on.In the big cities of our Country it could reach above water quality standards, but to a number of middle and small towns, the supply water can't accord with the new standard.The filter, as the most important unit of the normal water treated techniques flow for modern water supply plant, its technique reform is certainly very important, whereas the backwashing facility's improvement is the key point, because its work performance impacts directly on the filter's work..We carried out the innovation research to the washing device and gas and water supply facility of backwashing system for normal filter in the middle and small towns in this paper.On the base of absorbing in the new washing abstract of shutter filter, the new backwashing facility adopts a float-valve which is more suitable to the subsiding law of filter material. It is well known that backwashing with gas and water could get best result for filter washing. So the gas and water supply system in this paper will combine the pool type of two-valves filter and normal siphon filter which are used frequently in our country, absorb in the forming principle of washing gas-cushion layer in the V-filter and shutter filter, adopt cross-pipe structure for special open formation.We educe out a new formula for calculating drainage capability of the new float-valve facility from the theory and have it checked and modified by using much data from model experiments. It carries out water washing, gas washing and washing with both water and gas. these three kinds experiments to the facility for water and gas supple respectively. The result is as following: when only washing with water, the uniformity of water supply should satisfy the filter washing requirement, open area ratio must less than 0.466% and when it is small it mainly affects the uniformity. When only washing with gas, the diameter gas supply open has little influence on uniformity, and its open area ratio and washing intensity also have less influent than washing only with water. When washing with gas and water, the uniformity of water and gas supply will decrease as open area ratio being increased and will raise as the height of gas cushion layer being increased. Additionally, during the washing with gas and water, the flow rate of water and gas for holding stable gas cushion is 0.40m/s and 2.05m/s respectively. In the project for changing the old filter to the new one with both water and gas washing in the middle and small towns, the above technique parameter have important reference value.