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The two experiments gave results that were somewhat different from those produced in last semester's experiments. Because the data log shows that the system was generally working as is expected, and because the new results were more consistent than last semester's, we plan to use the new results. The first experiment indicates clogging in the sand filter, for which we are currently devising a solution.

Additionally, these experimental results may be modeled as gas removal efficiency when subjected to two different sand grain sizes. Data suggests that the sand with larger media diameter might be less effective at gas removal. Particles with larger diameter have relatively lower surface area to volume ratio and thus provide less extra surface area to which the bubbles can adhere to in the sand column. Although the media size is just one of the factors that affect the gas removal rate, the results indicate that perhaps using particles with higher surface area to volume ratio might further optimize the conditions for dissolved air removal and thus facilitate the process under certain conditions.

The unexpected results come from measuring dissolved oxygen concentrations at various points in the system. The results indicate that high pressure in the sand filter causing more bubbles to dissolve into the water. Fixing this problem requires some major rethinking of the way the system works, especially in improving aerator efficiency and pressure maintenance in the sand filter. We will replace the large aeration stone in the aerator with four smaller ones to try to improve gas dissolution in the aerator.