Page History

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Most experimentation related to floating flocs is conducted using a set-up created by members of the floating flocs teamnew sand filter setup modified from the Spring 2009 setup. A description of the set-up and the Process Controller methods used to conduct experiments can be found here.

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Research conducted in Spring 2009 suggested that gas removal increases with bed depth, but the sample was too small to make any definite conclusions about the relationship over a larger range. We predict that very small bed depths will be ineffective in less effective at gas removal. As depth increases within some yet unknown rangerange that is yet to be determined, gas removal probably will increase. At very large bed depths, we believe, the amount of gas removal will begin to taper off; as the concentration of gases in solution decreases, fewer bubbles will form, and the rate of change of gas removal will decrease.

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Our hypothesis is that if the bed expansion is too low, the gas bubbles might not be able to form properly or might be trapped inside the sand bed. On the other hand, we think that if the bed expansion is too high the gas removal rate might may begin to decrease as a result of the increased distance that the gas molecules would have to travel to diffuse.

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Because of seasonal changes in temperature, the dissolved air concentrations of influent water at AguaClara plants may not be consistent throughout the year. Because of this, we are interested in determining if there is a relationship between the dissolved gas concentration and the rate of gas removal via the sand filter.
This experiment is designed specifically to measure the changes in the gas removal rate of the sand filter as a direct consequence of changes in the dissolved gas concentration of the influent water.

For this experiment, the setup will be run on the "On" state on Process Controller described above. It will be assumed that the residence time in the new aerator will allow the dissolved gas concentration to equilibrate with the pressure maintained in the aerator. Since dissolved gas concentration is a function of pressure, the pressure in the aerator will be adjusted to achieve different dissolved gas concentrations in the influent water while keeping all other variables constant. It is likely that the range of pressures tested will be between 20 kPa - 100 kPa. The pressure is adjusted within the aerator by adjusting the "Aerator Min Air Pressure and Aerator Max Air pressure setpoints" in the process controller configuration file. Presently, we are considering using Sand 40 with a diameter of 0.42 - 0.59 mm with a bed depth of 30 cm and 50% bed expansion.

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