...
Figure 1 shows that after about five hours of operation the foam filtration system achieved a pC* of greater than 0.9, or an effluent turbidity of less than one. The performance of the foam increased almost linearly over time, suggesting that the film on top of the foam increases filter performance or that previously removed particles within the filter bed improve filter performance. In later experiments, we will determine how long performance will increase before leveling off, and how head loss through the system is affected by the film on top of the foam. 
Figure 1: pC* vs. Time
...
When the results of the 3- 1 inch foam sheets are compared with those with the 1 inch foam sheet experiment, it becomes clear that foam filtration is a function of depth. While the three inch foam experiment achieved an acceptable pC*, the one inch foam sheet experiment did not. Even after running for 24 hours, the pC* does not even reach 0.5, which is far below our goal of a pC* of 0.9 
Figure 2: pC* vs. Time