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Results and Discussion

Our results demostrate that our clear well design can be adapted to current AguaClara plants to further reduce the turbidity of the effluent of the water. The ratio of the height difference required is acceptable and so is the dimension of the clear well and filter beds requiredexperiments demonstrate that Okun and Schulz equation for headloss through a fluidized bed is a valid tool to use in our design. Once fluidization is achieved, headloss through an expanded bed is constant. For a 5 cm filter bed, headloss was around .7 cm irregardless of the level of bed expansion. This is a positive discovery because a constant value for expanded bed headloss means that we can estimate all the headloss in our backwash system and design the height difference between the clear well and the filter bed appropriately.

We had mixed results with regards to Weber's equation for filter bed expansion. At low levels of filter bed expansion, the Weber equation accurately predicted the fluidization velocity required to achieve the targeted bed expansion. As the target bed expansion increased, so did the degree of error. At 9% expansion, the degree of error was at 14%. At 38% expansion, the degree of error was at 37%.

We believe the following to be sources of error.
>> Human error: Despite our best attempt at being consistent, there will always be human error in observing the bed expansion visually.
>> Wall Friction: We can attribute the increase in error as flow rate increased due to the increase in wall friction on the test vial. We can minimize this by increasing the size of our bench scale experiments.
>> Sand Properties Parameters: We might have used an incorrect D60 and porosity for the filter bed in our equations.
>> Preferential flow: Despite our best attempt to keep the test tube as level as possible, we might have introduced preferential flow in our experiment causing an unbalanced backwash flow.

Plan of Action for Remainder of Spring 2010 Semester

The rest of the semester will be devoted to using the clear well technology applied to stacked filtration or other filter designsthe following objectives:

>> Repeating the Weber Fluidiation Velocity experiment with a larger scale bench model to see if error decreases.
>> Repeating the Weber Fludization Velocity experiment with multiple media.
>> Preliminary plant size design of the clear well backwash based filtration system for an actual AguaClara plant.