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Ideas for full scale implementation that we will be investigating at Laboratory Scale:
• Add air bubbles using suction through a small hole in the side of a down-flowing pipe right before the water enters the grit chamber. The additional air in the water will increase the bubble size as it joins the preexisting air pockets. The pressure in the pipe could also be maintained at a partial vacuum to accelerate the bubble formation process.
• Add sand to the bottom of the grit chamber simulating back-wash in a sand filter. The idea is that the dissolved oxygen in the water will form bubbles on the sand particles. Once the buoyant force is greater than the connection between the bubble and the sand particle, it will rise to the surface of the water.
• Add the equivalent of lamellas to the grit chamber. Bubbles will form on the underside of the lamella and eventually become large enough that they roll across the lamella surface and float to the surface of the water.

Two contraptions will be made that we will use to simulate different situations to help us determine the best course of action. The team will also be split into two subgroups so that each experiment can have the undivided attention of different team members. The members of each subgroup were decided based on class and work schedules. Tiffany and Tanya will be working on the aeration experiments and Haley and Ling will be focusing on the backwash sand filter. Wenny will be assisting each team interpret the data, contemplating other experiments that can be performed, attending meeting and assisting on written assignments.

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Several different experiments will be conducted with this set-up. In order to simulate the water conditions in the pipes of the Honduras plants on a smaller scale, all experiments will be conducted with tap water that is supersaturated with oxygen.

Experiment 1 will be attempting to simulate what is happening in the pipe as air bubbles are being sucked into it. With the stir bar running, the dissolved oxygen level in the cylinder will be continually measured as different flow rates of air are pumped into the tube. This will be done with the lid securely attached to the top of the apparatus to make it air tight so we can add varying amounts of negative pressure in the pipe. The pressure in the pipe will depend on how high up from the outlet we put the holes through which air will be sucked into the pipe at the plants. By changing the pressure in the cylinder we are simulating different locations of the air holes.

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The length of each test run will be determined once we have the experimental device working. We currently do not know how the data will behave and thus do not know how long each test run should be. The data will be evaluated based on the level of dissolved oxygen in the water and how big the bubbles are. The goal is to determine the pressure and air flow rate that produce the biggest bubbles and lowest DO level. This should help us determine the optimum orifice size and its height above the outlet of the pipe.

Experiment 2 will model the interface between the pipe that is under negative pressure and the grit chamber that will be under atmospheric pressure. After air has been pumped into the sealed PVC pipe that is under negative pressure for a period of time (yet to be decided), we will turn off the inlet air and remove the lid to the device, exposing the water to atmospheric pressure. The dissolved oxygen level in the water will be continually measured one inch below the surface on the water as well as at the bottom of the cylinder. We hope to see more bubbles form and rise to the surface once the water is exposed to atmospheric pressure. This should help us determine the rate at which the dissolved oxygen level in the water will decrease under varying air flow rates and initial pressures. This will in turn suggest the retention time needed in the grit chamber to decrease the DO to an acceptable level.
We will measure DO levels at the top and the bottom of the water column as a function of exposure time for each pressure and flow rate tested. We will also observe bubble size, average bubble diameters, and note any changes in the behavior of the bubbles under atmospheric pressure.

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