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.
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We expect to see failure in the lower diameter tubes with the high Vc values because the flocs have a smaller area over which they can settle. The smaller diameters are expected to with flocs more quickly, and are less likely to have flocs waste out of the tube as the flow state is running.
Results
Preliminary 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 combination cause failure. Based on these preliminary findings we are modifying the experiment to produce quality results in an efficient manner.
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The graph clearly indicates that at the first Vc, the 9.5 mm tubes performed very well, with effluent turbidities around 0.5 NTU. The next three Vc settings result in very high effluent turbidities, over 100 NTU over the influent. This high values are most likely cause by a combination of extremely high Vc and the tubes position in the floc blanket at the upper height of 60 cm.
Conclusions and Future work
From the preliminary results we were able to troubleshoot many of the errors in the system. Future work includes testing all of the parameters in the above chart at the two floc blanket heights. The results were not conclusive enough to determine the appropriate time interval for the flow states, so we will stick with the 6 hour time period.