Liza Johnson's Individual Contribution Page

Spring 2015 Contributions

As a member of the Enclosed Stacked Rapid Sand Filtration team (EStaRS), I assisted in fixing several of the problems that we were having with the filter. One of the main problems that we were having with the filter was the appearance of air bubbles during backwash. I determined that the causation of the air bubbles was due to the inlet opening, where water was flowing into the entrance tank during backwash, often was above the water level in the tank once the headloss dropped far enough to have the water only going through the bottom tube. I discovered that there was a very small margin in the headloss in which the water would only flow through the bottom tube but would also not create air bubbles. As a team, we determined that the way to control the height of the headloss was to increase the height of the siphon. After experimenting with potential different siphon heights and seeing the effects on headloss, we redesigned the siphon to keep the headloss at the perfect height to get rid of the air bubbles.

Our next step in altering the filter was replacing the inlet slotted pipes with orifice pipes. We successfully took apart the filter, replaced the pipes, and rebuilt it. These orifices should prevent the problem that sites in Honduras have been having with clogged slotted pipes.