Pipe Diameter

The effluent launder will span the length of the tank about 10.16cm (4") off of the center of the tank. The launder is placed 5.08cm (2") beneath the water level. This value was chosen so that enough water head would be available to allow for relativley equal flow through the lauder orifices and so that a majority of the tank height would be available for the floc blanket. The diameter of the effluent launder was calculated by iterating through pipe diameters to find the existing diameter of pipe that gave the desired flow rate and orifice holes. The diameter was selected based on the following equation:

• Qratio is assumed to be 0.92, this indicates that flow through the first orifice will be 92% of the flow through the last orifice.
  The best pipe diameter is 3.81cm (1.5") inches. The number of orifice holes was tweaked until the orifice hole diameter would match up with a drill bit size and still gave the proper amount of head. (equations for this can be seen in the following section) This head loss was defined to be about 5 cm, or the head available above the launder. If the head loss through the launder orifices exceeded the available head, we would have encountered issues because the water in the outlet system would have had less energy than the surrounding system, which would have effected the flow rate and caused air to collect in the outlet pipe. The total number of orifices was determined to be 15.