DO Removal by Partial Vacuum

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Purpose and Principle

Procedure

The purpose of this experiment is to determine the degree of dissolved oxygen removal from supersaturated water subject to a partial vacuum. Dissolved oxygen removal from the water occurs because the partial pressure of oxygen in space above the water is lowered by the partial vacuum. Thus, the dissolved oxygen will transfer out to the space above the water in order to restore equilibrium. Measuring the dissolved oxygen in the water over a period of time will allow us to observe the amount of dissolved oxygen removed and also to calculate the approximate rate of dissolved oxygen removal.

Procedure

procedure for this experiment is relatively simple. While using Easy Data to monitor the pressure, water is pumped out of the apparatus until the pressure reaches -50 to -70 kPA. The apparatus is allowed to sit for a short period of time and is then opened to atmospheric pressure and the . The dissolved oxygen is monitored and recorded for no more than two to three minutes after the chamber is opened to atmospheric pressure.

Results and Discussion

We wish to see a drop of at least 2 mg/L in that period of time.

Results and Discussion

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. We 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.

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