Page History

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Introduction
Our team ran an experiment to investigate the affects of saturated air on floc blanket formation. To do this, our team paired with the Floating Floc research team, who supplied water saturated with air to the process. This experiment is meant to model the effects of having a supersaturated system and the affects i.e. the effects that change in pressure (in the transmission line to the plant) could have on sedimentation performance due to dissolved gas coming out of solution in escaping from the influent water as bubbles.

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This supersaturated water was fed to the apparatus as influent water, where it immediately experienced a pressure drop to atmospheric pressure. While a pressure drop should result in the immediate formation of escaping air bubbles in the liquid, these did not form immediately. This is due to the activation energy required for the bubble to form, which is dependent on the surface tension of the bubble. In order to test bubble formation we observed the experiment qualitatively, looking for bubbles throughout the apparatus. We also monitored effluent turbidity, a value parameter that would reflect the effect of the bubbles on tube settler performance.

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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 cloudiness of the liquid exiting the sedimentation tank effluent. It is possible that these air bubbles caused some of the flocs to break up.(State that the cloudiness could indicate the presence of small particles from breaking up of flocs. Where would flocs be broken up?) In addition, it is likely that these air bubbles disrupted the velocity gradient in the tube settler, which is assumed to be a convex velocity gradient whose peak is closest to the tube settler escape (What do you mean by tube settler escape? Also, how are these air bubbles disrupting the velocity gradient? I think more careful thought is needed here about what large air bubbles could be doing in the tube settler.) . This gradient controls the transport of flocs velocity of the sedement sediment that enters enter the tube settler, . Floc roll-up is characterized based on a force balance (Put in a citation of where this is found in your wiki.).

Quantitatively, data collected over twenty four hours showed an increase in effluent turbidity when comparing the experiment experimental run with saturated air to the control experiment. We ran this experiment on both high and low floc blanket levels. 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 causing worsened performance.

Experiment 1 & 2: Low & High Floc Blanket Formations

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It was expected that these bubbles would disturb floc blanket stability (Again note the ways that these bubbles disturb floc blanket formationstability. Perhaps, you should also define what you mean by stability here.), 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 designing additional plants undergoing elevation drops, 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 hydraulic jump produced by the current design of AguaClara linear chemical doser system is controlled ameliorated. When chemicals are dropped into the system, such as alum, they create surface bubbles. It is not well understood whether bubbles created from the falling jets 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, or if both are causing worsened performance.