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Our first experiment sought to determine whether or not alum was the sole factor in the formation of a surface foam. After dosing the water with varying alum concentrations, it was determined through photographs taken every 2 minutes and through observation that no foam was formed. Sample photos are included in Figure 1 below.
Although the foam was not formed, this data was crucial to our research. Not only did it minimize the list of potential foam formation factors, it also help build our understanding of foam formation. As a result of a foam not forming due to alum addition at the surface of the water, we also were able to rule out alum addition under the water surface as intituvely intuitively it was a solution to the form formation.
Our second experiment sought to determine whetherr whether or not the addition of Natural Organic Matter (NOM) contributed to the formation of surface foams. At all concentrations of humic acidHumic Acid, we again found there was no surface foam formed. We belived believed this was due to a lack of air bubbles which naturally are found in AguaClara plants so at this point we modified our experiment to include a filter an aerator to provide them.
In our next experiemntexperiment, we varied the concentration of NOM but included a filter an aerator to provide bubble directly into what would be the (flocculation?) tank. At concentrations below XXXX 2 g/mL we found that no foam was formed. However at higher concentrations of humic acidHumic Acid, we found that large bubbles would rise and then quickly pop in the center of the tank. In the meantime, smaller bubbles would form around the edges of the tank and were slightly more persitent persistent as seen in Figure 2 below.
Bubbles form when water molecules form bonds around airpocketsair pockets. A surfactant is generally an organic molecule that has both hydrophobic and hydrophilic. Due to this polalitypolarity, surfactants form micelles in water which helps to stabilize air bubbles and prevent them from agregatingaggregating. Humic acid is a weak surfactant, so though it did reduce the agregation aggregation of air bubbles it still occurred. This resulted in large, non persistent air bubbles that formed a foam at the surface of the water.
Although, a surface foam was formed at high concentrations of Humic Acid concentrationsgreater than 2 g/mL, it was not the foam that is found in AguaClara plants. The foam we created in lab contained large non-persisent bubbles, however the foam we sought to create contained small persistent bubbles. At this point we began searching for a stronger surfactant to further prevent the agregation aggregation of bubbles, thus replicating the foam found in Honduran AguaClara plants.
In order to support our hypothesis, we added soap to our last experiment with lactic acid Humic Acid simply to see if would createthe create the surface foam we wanted. Indeed the soap caused a persistent foam, similar to that found in AguaClara plants and can be seen in Figure 3 below.