| 摘要 |
Conventional filter underdrain apparatuses present many problems including non-uniform distribution of backwash water during cleaning of the filter media, inability to cope with explosive air release, designs that tend to cause channelling jetting through the media, designs that are prone to structural failure, designs that are expensive and difficult to install, designs that have no flexibility in terms of capability to operate with air scour assisted backwash or simultaneous air scour//water backwash, designs that require expensive, difficult to build, false bottom structures, or require tedious grouting procedures; designs not sufficiently corrosion resistant, designs that use relatively fragile materials; such as porous sintered plates or ceramics or clay tiles, designs that require gravel support layering as an inflexible requirement. A relatively simple underdrain apparatus includes plates defining inverted V-shaped arches, perforate grids extending across the troughs between or on top of adjacent arches near or at the top thereof for supporting filter media. Perforate grids are described so the underdrain can operate with gravel base layering or without such layering to suit the application. A row of air vent holes extending longitudinally of the arches provides spreading and harmless release of trapped air. Simple fabrication flexibility is described for the provision of air scour vents extending longitudinally of the arches under the grid, and inlets for introducing air into the arches for the air scouring of the media prior to water backwashing thereof. Fabrication flexibility is further described for operation of this underdrain in the mode of air scour simultaneous with backwash by providing air scour vents as described above and a partitioning plate inside the arch sections physically dividing those sections into an air section and a water section thus avoiding two-phase flow problems of wave action generation. The use of stainless steel as the preferred material of construction is reflected in the design which requires punching holes only with no drilling, tapping, or welding required. |
