Rapid Infiltration System Basin Design

Selection criteria to design a Rapid Infiltration System depend on the soil permeability whereby 25mm/hour are required. There are different soils whereby those that allow a specific retention time including those that allow uniform distribution is preferred. Usually coarse sand or large gravel is not a suitable selection because it will allow discharged wastewater to move too fast across the system and this will prevent biological and chemical reaction breakdown from taking place. The best acceptable soil types for development of the rapid infiltration system should be small particle grains of sand.

Other critical factor when determining whether a site is suitable or otherwise also depends on the depth issue. Based on past research development, soil depth must be greater than 3 meter starting from the soil level going to underground water but however, depths less than 2.5 meter is still applicable provided that the underdrain system is well designed and constructed. In order to ensure overall effectiveness, it is better that the use of basin is limited at near level topography rather than on an artificially constructed site. A sprinkler system can also be utilized for those sites that has slopes up to 15 percent gradient.

In order to avoid problems later part on the use of rapid infiltration basin, the design and planning stage has to be properly carried out to include field investigation on soil condition. This is to ensure that the best possible design can be developed and come up with the most effective system. Compared to standard infiltrometer, which uses vertical permeability measurement, recent new method has seen permeability test being done on a large basin instead. The testing should be conducted using actual samples whereby if the wastewater contains high amount of suspended solid or sludge, then this should be used instead in order to find out the actual condition or scenario. In other words, samples used for the testing has to match the loading wastewater quality to be as close as possible.

Other criterion that needs to be taken into consideration before field investigation is initiated is the weather condition during the test period whereby the coldest time of the year should provide the most accurate findings. Finally based on the data collected, all the information such as soil characteristic has to be compiled and then studied before the final design is concluded.

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