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Tap water is sent upward through the filter column. The tap water cannot be guaranteed to be super-saturated with gases already, so the aeration apparatus previously used in the aeration method has been implemented to supersaturate the cold water before it is fed through the filter column. The aeration chamber is kept under 1 atmosphere of pressure while the water is bubbled by an aeration stone. Air is allowed to leave the aeration apparatus through a valve controlled by Process Controller ProCoDA Software and a rotameter, which restricts the air flow to maintain pressure inside the chamber.

From the bubbling chamber, the super-saturated cold water joins hot tap water and flows through 1/4" tubing into the flow accumulator, which uses a pressure sensor, temperature probe, and two valves (one for hot water, one for cold water) controlled by Process Controller ProCoDA Software to regulate the water's flow rate (which is altered to achieve the desired level of suspension of the filter media in the vertical column) and the water's temperature (which is set to 20°C, and can be changed to mimic water temperatures in Honduras).

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The bubble collector is made of a 3.8 cm- diameter PVC pipe that is sealed at both ends. Water and bubbles from the glass filter column enter the chamber through 3/8" tubing that connects the top of the glass filter column to the bottom of the bubble collector. Inside the chamber (which is initially filled with water before each experiment), bubbles float to the surface while the water flows out through 3/8" tubing attached the bottom of the bubble collector. A 1/4" tube attached to the top of the bubble collector allows air to enter and leave. This tube as well as the water outflow tube at the bottom are both controlled by valves that are opened and closed by Process Controller ProCoDA Software, which uses a pressure sensor to monitor the water level inside the chamber. The water level inside the chamber can be visually monitored through an additional 1/4" clear plastic tube that is attached to the top and bottom of the bubble collector.

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The the rate of change of the water level can be converted to an equivalent rate of change in gas volume by multiplying the trendline's slope by the cross-sectional area of the bubble collector:

{latex}
$$
\frac{\Delta Volume}{\Delta Time} = slope * \pi * r _{collector} ^2
$$
{latex}

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!Gas removal, mL-L. GB, 40, 30.png|width=300px!
h5. Figure 3:  Dissolved gas removal for various filter media. Bed Expansion: 50%
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To determine how much gas is removed per liter of water sent through the filter column, that volume rate of change is then divided by the flow rate of water in L/min.

{latex}
$$
\frac{mL\:gas\:removed}{L\:water\:treated} = \frac{\frac{\Delta Volume}{\Delta Time}}{Q_{water}}
$$
\\
{latex}

This was done for each sand, and the results are plotted in #Figure 2.

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