Methods
In order to determine the effect of the inner-diameter of the tube settlers on settling efficiency, a three-part experiment will be completed to vary flow rate, inner tube diameter, and tube inlet location. The experiment will consist of running a range of flow rates through tubes, with inlets both in and above the floc blanket, with a range of diameters. Table 1 below illustrates the parameters for the proposed experiment.
The diameters of the tubes were chosen to explore a range of spacings based on the current plate spacings used in plants of two inches. The flow rates were chosen to explore a range of capture velocities from 5-20 m/day.
Table 1: Tube flow rates vary due to the critical veolcity and the diameter.
As the tube diameter increases the necessary flowrate to achieve the same Vc also increases. Note the high flowrates for the 9.5 mm diameter tubes and the 12.7 mm diameter tubes. These flowrates actually represent the flow rate through the manifold holding six tubes, there for the per tube flow rate can be determined by dividing the flowrate by six. The final three tube sizes 19.5, 25, and 36.1 mm, will only be tested using one tube at the apporpriate flow rate.
The main process controller states for the experiment are floc blanket formation, two flow states for high and low floc blanket heights, a floc blanket equilibrium state, two states devoted to incrementing the flow rates. Several other states, such as drain, are used for system maintience.
Results
Priminary experiments have been conducted for the purpose of determining the appropriate time interval for the flow and increment states, as well as determining which Vc and floc blanket combinations cause failure. Based on these prelimnary findings we are modifying the experiment to produce quality results in an efficient manner.
The plot below displays the effluent turbidity vs. critical velocity graphed on a semilog plot. Each flow state was run for 6 hours, however, the floc blanket
