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Data analysis was performed in a similar way as was performed in the Experiment 1. Figure 1. depicts the initial and final water level in the bubble collector during each of the data collection period ("runs"). Each run represents a specific time period during which the water level in bubble collector gradually sinks down from its maximum to the set minimum point. This period is represented on the graph when the line slants downward. Once the minimum water level is reached, the system has to refill with water in order to continue the runs. For this reason, the water outflow valve is closed until the water level reaches the set maximum point. This period is represented on the graph by the vertical lines. During the third run we changed
Figure 1. also shows that the bubble collector didn't finish the whole cycle during the third period. The measured water level in the bubble collector governs when the bubble collector should start a new cycle by filling up with water. It is possible that the cause was occasional noise in data. Since the data averaging period from 5 seconds to 10 secondsis 10 seconds, there might have been spikes in data collected in this particular averaging period. The spikes would have caused the average to be lower than the minimum water level set point which would met the condition for the process to change to a refill state.
More detailed information on the bubble collector setup can be found here.
The initial data collection period was omitted from the analysis since because of the setup conditions the air might have been trapped inside the system. For the subsequent data collection periods, we calculated the content of gas removed per liter of water sent through the sand filter. We added fitted a line to each of the runs to see the rate of change of the water level inside the bubble collector when water runs through the sand filter. Figure 2. and Figure 3. show the linear fit line for the second data collection period, and more detailed graphs can also can be found here.
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