Page History

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We observed flocculation in the demo plant in order to determine at what point in the length of the flocculator the flocs reached a maximum size before beginning to break up. These flocs were also measured in order to be able to more accurately represent in the flocculation model the maximum floc size that it is possible to achieve in the plant. Using the location of the largest flocs as an estimate of the optimum plant length, we set the maximum floc size to the size of the measured flocs and changed the value of the efficiency factor in the flocculation model until the design length of the plant model created by the Demo Plant SP08 Flocculator D&C flocculator design program was consistent with the observed occurrence of maximum floc size.

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The maximum flocs were observed at a distance of 28 cm from the flocculator inlet. After that point in the plant, they ceased to get any bigger, and eventually began to break up from too much shear. The size of the largest flocs was about 0.7 mm, so that value was set as the maximum floc size in the flocculation model. When various efficiencies were tried used in the model, the plant design program returned a design length of approximately 28 cm for a value of 0.2, and so we have determined that the flocculation efficiency is equal to this value.

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Figure 1. Maximum Floc Formation

Originally, we assumed that problems with the Fall 2007 Demo Plant were attributed to the dimensions of the channels, including channel width and baffle spacing. These properties were predetermined by the corrugated plastic material that was used. Thus, we originally planned to obtain different materials from McMasterCarr.

However, once we adjusted the efficiency to a more realistic value, we found that the channel dimensions were not that far from ideal. Therefore, we plan on using the same materials were used for the Spring 2008 Demo Plant as that were used for the Fall 2007 Demo Plant.