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Our current design eliminates the alum and chlorine doser components, as we decided to utilize a "batch" system instead. More information about this dosing system can be found below under the section entitled "Final Design Schematic." In the Point-of-Use Design Calculations for this new design, the head loss through the system is calculated. The float valve should help maintain constant flow through the unit during its run-time. However, when as the entrance tank empties, the water level in the foam column should vary. Originally, the water level in the foam column would be equivalent to the water level in the entrance tank. But as the entrance tank empties, the water level in the foam column slowly decreases until it is level with the float valve. This variable water level difference determines the flow through the unit.
It was determined earlier that the maximum allowable velocity through the column was 6 mm/s. Using this and a column diameter of 4 inches, the maximum allowable flow through the column can be determined as .049 L/s. The variable water level difference in the foam column can not be large enough that this maximum flow is surpassed. Therefore, if (as we decided originally) we want a minimum of 2-inches above the foam column maintained at all times, we merely need to determine the maximum water level height above this 2 inches that results in a flow equivalent to the maximum allowable flow. Based on the diameter orifice, the resulting max. height is variable; but generally, it remains in the range of 3 to 5 inches. Therefore, the entrance tank should be positioned such that this maximum water height is never surpassedAlso, comment on why this schematic actually works: need 2-3 inches of water above foam based on graph in file.
Final Design Schematic (as of currently)
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