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From our experiments, we have found that the change in dissolved oxygen that occurs over the span of a few minutes is less than desirable. The first experiment uses water that has an initial dissolved oxygen level of — mg/L. After being put under partial vacuum for ---- minutes, we expect to see the dissolved oxygen level drop as bubbles form and rise, drawing dissolved oxygen out of solution. The change between the initial and final dissolved oxygen level is ---mg/L. For the second experiment, in which the water was pressurized and aerated for — minutes and then exposed to the atmosphere, we see that the change in dissolved oxygen is — mg/L. Contrary to our initial belief, the change in dissolved oxygen only slightly increased, indicating that aeration only slightly affects the rate of change of dissolved oxygen in the water and not to the desirable degree. Because of this, we are considering alternate solution methodsWe ran experiments that involved aerating water under a partial vacuum and compared the results to data obtained from experiments in which water was only subject to a partial vacuum with no aeration. We were expecting to see a greater change in the dissolved oxygen concentration; however, contrary to our initial belief, aerating the water had little affect on the change in dissolved oxygen. Because of this, we are doubtful that the aeration method will solve the floating flocs problem and have decided to consider alternate solution methods. While we search for other possible solutions, we will still continue to run quick experiments with the aeration method in order to verify our decision to move to an alternate solution.
Some of the major concerns about our data include discrepancies caused by erratic behavior of the dissolved oxygen probe under partial vacuum. We are still trying to understand what might be causing the discrepancies and to what degree the functionality of the probe is affected. We are concerned that after the probe is subject to negative pressure, data collected after pressurization may be faulty. In the mean time, we will be measuring dissolved oxygen before and after pressurization and aeration instead of during the process. Also, notice that the pressure gradually increases as the experiment the pressure in the contraption was initially ---- kPa and rose to about — kPA. We were initially concerned about this, so we were initially concerned about the gradual pressure increase in our system. So, we tested the apparatus to make sure that it was airtight by putting the container under positive pressure and holding it over night. It proved to be airtight enough for our purposes. We postulated that the change in pressure is mostly due to bubbles leaving the solution.
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