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The purpose of this experiment is was to observe and quantify the change in dissolved oxygen transfer out of supersaturated water that is while it was subject to slight aeration under a partial vacuum. This experiment evaluated the use of air bubbles as a catalyst to increase the rate of removal of dissolved oxygen from water. The difference in oxygen concentration between the bubbles and the supersaturated water may be used to should in theory draw excess dissolved oxygen into the bubbles and out of the solution.

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While using EasyData to monitor the pressure and dissolved oxygen, water was pumped out of the apparatus until the desired pressure was attained. The A partial vacuum was maintained while the solution was aerated . The and the flow of air into the container was regulated by a rotameter that takes either pressurized air or room air. Originally, pressurized Pressurized air was used; however, originally used to aerate the water. However for later experiments involved detaching the air inflow tube into was detached from the rotameter and allowing to allow air to be sucked into the apparatus as it rather than being forced in; this better simulated how the air would be sucked through the holes in the actual pipes. Panel Does into an actual pipe that had free falling water. Theoretically, the source of the air should affect the experiment ? Are the air bubbles that form influenced by the air source? After the water is if they have different concentrations of dissolved oxygen. Since bubble formation depends on the difference in DO between the air bubbles and the water, source air with a lower amount of DO would form larger bubbles because of the greater concentration gradient. After the water was aerated under partial vacuum for a period varied amount of time ranging from about one minute to about four minutes, the apparatus is was again exposed to atmospheric pressure and data is was recorded in the same manner as mentioned before . The period of time can be determined by finding the approximate time the water spends under partial vacuum in the transmission lines that bring water to the plantsfor two to three minutes.
Using the Tamara Plant's design values the water entering the grit chamber is going approximately 10 m/min. This is based on using four 6in diameter pipes to carry 740 L/day of water into the plant. Thus in a 1.5 meter long vertical pipe (which is the height of the entrance tank) with free falling water the water would be exposed to a partial vacuum for only 10 seconds.

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Results and Discussion

The data from this experiment shows that under partial vacuum and slight aeration there was a problem with bubbles forming on the DO probe. This is indicated by the sharp dips in the data which corresponds to a bubble rising off of the DO probe as seen in Figure 1. Overall there was not much change in the DO over time but we found the DO probe to be unreliable when it was pressurized and was further complicated by there almost constantly being bubbles on the probe.

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Figure 1. The concentration of dissolved oxygen as a function of time while the system was under negative pressure and being aerated.Image Removed