Page History

...

The hypothesis that absorbed air would be released in the apparatus was qualitatively observed by bubble formation. The adverse effects of bubble formation on floc blanket formation and effluent turbidity were supported qualitatively by the appearance of floc particles in the sedimentation tank effluent. Although it did not appear that the floc particles were attached to the air bubbles, it is likely that these air bubbles caused some of the flocs to break up. (Were the floc particles attached to air bubbles? Unclear what you mean here) Also, large particles were sparse in the sedimentation column. (Could this be because flocs were being broken up?)

Quantitatively, data collected over twenty four hours showed an increase in effluent turbidity when comparing the experiment run with saturated air to the control experiment. We ran this experiment on both high and low floc blanket formation. In the high floc blanket formation state the floc blanket level is above the plate settlers. In the low floc blanket formation the floc blanket formation level is below the plate settlers. The presence of air bubbles could break up some floc particles and force floc particles up into the clarified effluent. Floc particles attached to air bubbles could potentially travel through the tube settler when they would normally settle out. Due to the energy build-up in the sedimentation column, the top layer of the liquid in the column is more unstable. Instability causes flocs to enter to the plate settler and potentially leave with the effluent. This instability is increased when the system is exposed to water saturated with air.

Experiment 1: Low Floc Blanket Formations

...

It was expected that these bubbles would disturb floc blanket formation, permitting more floc particles to leave with the sedimentation column effluent. An increase in effluent turbidity and the appearance of bubbles in the apparatus supported this hypothesis. If AguaClara is considering to build a plant which would traverse altitude drops and climbs, results from this experiment should be considered. Future experiments relating to saturated water in the plant could include bubble removal before floc blanket formation. However, the true effects of saturated air on the experiment cannot be fully determined until the chemical drop waterfall effect is controlled. When chemicals are dropped into the system, such as alum, they create surface bubbles that disturb the system. It is not well understood whether if bubbles created from the hydraulic jump in the chemical dose controller are the potential cause of worsened performance in plate settler effluent or if worsened performance is caused more by the presence of supersaturated air in some plants. in turn, creates the addition of an unknown amount of bubbles to the amount of bubbles released by the water saturated with air.