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The experimental results for gas removal rate using Sand 40 and Sand 30 as a filter media gave consistent results of 5.09 mL/L and 2.01 mL/L, respectively. This data has been essential in confirming that the apparatus is performing reliably. Yet the results deviate from the theoretical model, which predicts the theoretical bubble formation potential to be around 18mL/L for water that has been previously exposed to 1 atm gage pressure at temperature of 25 C. The model calculates the theoretical bubble formation potential as a function of the air pressure that the water equilibrated with prior to returning to atmospheric pressure. The discrepancy between laboratory results and theoretical predictions indicates that there could be an array of possibilities where some of the system components could be redesigned to achieve better performance in producing air saturated water and consequently removing released air using the suspended matter. For additional analysis, we measured the dissolved oxygen concentration at the effluents from the aerator, sand filter, and bubble collector. Both the model and DO measurements have been instrumental in pointing out several improvements in design of the current apparatus and optimizing the process conditions.
Based on further collaboration with the TA, the following design modifications have been advised to be made:
1. It is has been estimated that the aerator is producing the water that is not aerated enough. This could be remedied by inserting multiple aeration stones with different volume so that aerator would displace more air into the water.
2. Currently, the large headloss is occurring throughout the sand filter. As a result, it is possible that the additional release of pressure will allow the tiny bubbles to form, and thus dissolving them into the solution. One solution would be to focus on where the maximum headloss occurs and redesign the sand filter so it will effectively act as if it is open to the atmosphere. Alternatively, if the situation allows, it might be possible to experimentally find a bed expansion at which the minimum headloss takes place
, which may The DO measurements indicate that the dissolved oxygen concentration in the sand filter is higher than that in the aerator.
The unexpected results come from measuring dissolved oxygen concentrations at various points in the system. The results indicate that high pressure in the sand filter causing more bubbles to dissolve into the water. Fixing this problem requires some major rethinking of the way the system works, especially in improving aerator efficiency and pressure maintenance in the sand filter. We will replace the large aeration stone in the aerator with four smaller ones to try to improve gas dissolution in the aerator.