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In the treatment plants, water would be sent upward through a bed of sand suspended in the grit chamber. The sand filter is intended to provide some surface area on which bubbles can form. The bubbles would accumulate, forming larger bubbles that could quickly float to the surface of the water in the grit chamber. The anticipation is that enough bubbles can form and leave the water in the grit chamber so that the water flowing into the sedimentation tanks would have a lower dissolved gas content and less potential to form bubbles.

Previous research has found that smaller grain sizes are more effective in gas removal than are larger grains in the same volume of sand, since small grains provide more surface area per unit volume on which bubbles can form. Other parameters, such as optimal bed depth and bed expansion, will be determined experimentally. Additionally, since dissolved gas content fluctuates in natural bodies of water, such as the sources of water for AguaClara plants, the dissolved air content of the influent water into the experimental system will be varied to explore its effects on gas removal. The purpose of this team is to test a variety of parameters (listed below) to design an effective sand filter that can be implemented in AguaClara plants.

Parameters

Size of sand grain

Research performed last semester focused on studying the effects of sand grain size on gas removal. We found that smaller sand grains provide more surface area per unit volume than larger grains, but grains that are too small are carried to the surface with bubbles and are washed away. Grain size also affects �porosity- porosity pore size of the sand bed, which affects the distance a gas molecule must diffuse to reach a surface. This also may affect aggregation of gas molecules to form larger bubbles. Further study of optimum grain size will be explored through MathCAD modeling, or through experimentation, if that is deemed necessary.

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