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ANC
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CONTROL
EXPERIMENT 3:
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Addition
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of
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sloping
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glass
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column
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above
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the
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lime
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feeder
OVERVIEW
In order to overcome the difficulties faced at the end of the second experiment, a new design was considered, which consisted of a diagonal column attached at the top of the vertical column. The design would retain small lime particles while allowing saturated lime water to exit. Since the velocity in the slanted tube is affected by the angle, its vertical component is lower than the upflow velocity of the primary column.
The angle of inclination and laminar flow regime allows lime particles to settle back into the column and thus prevent unnecessary lime loss. Thus the primary column would be used as a storage vessel for the suspended lime bed while the slanted tube above it would allow more lime particles to settle back to the column below, making the process more economical.
The detailed calculations and assumptions regarding the design of the sloped column of the lime feeder can be found here
Figure 1: Sloping Column Lime feeder
With the new apparatus, as seen in figure-1 above, four sets of trials were carried out and evaluated.
The apparatus was first tested with tap water in trial 1 and trial 2 and then with distilled water in trial 3 and 4.
It had been observed that after a few hours into any experimental run, the lime, instead of remaining in suspension as soluble particles, formed a single mass and became insoluble. It was hypothesized (by the previous research team) that this happened because some or all of the lime got converted into calcium carbonate(which is insoluble)if tap water was used since the water at Cornell is alkaline in nature. This should not be a problem in Honduras because the raw water to be treated is not as alkaline. However, under laboratory conditions, in order to get a true estimate of the lime feeder's efficiency (in dissolving lime for a longer period and thereby lasting for a longer time) distilled water was used because it has no alkalinity. In the pictures below, the ANC Control team can be seen carrying the distilled water tank on to the platform where the experiment is to be set up.
Figure 2: Apparatus for experiment 3
Each trial carried out using the sloped column lime feeder apparatus can be viewed in detail below:
Trial 2: Using tap water - increasing lime amount