Column Testing of Alternatives

The five design alternatives were all tested between layers of coarse sand. The sand was tested individually as a control to determine if it had a removal efficiency that may interfere with the removal efficiency of the materials. A summary of the results is shown in the table below.

Detailed Results of Column Tests

To see the detailed results of the column tests, click on the photograph of the design alternative. Each table of results presents the concentrations of uranium and arsenic for the effluent from the column. When the value is shown in red, this indicates a failure of the filter material to reduce the contaminant to below the maximum contaminant limit. When the value is shown in green, this indicates a success.

Sand, Tested as a Control

Ion Exchange Resin for Uranium and Arsenic Removal

Orange Peels for Uranium Removal

Zero Valent Iron Turnings for Arsenic Removal

Zero Valent Iron Filings for Arsenic Removal

Rice Husks for Arsenic Removal

Comparison of all Alternatives

Procedure for Column Testing

The testing apparatus, shown below, consists of a 1.75 inch inner diameter acrylic column with the capacity to hold at least 20 inches of sand and material. The acrylic column connects to an elevated reservoir via plastic tubing. There is a diffuser at the top of the acrylic column in order to facilitate a uniform flow through the column. The flow rate is controlled by an in-line ball valve.


The column is filled with to a total of 20 inches, composed of sand and material. The ratios of sand to material are based upon suggested values found through the literature review.

Test

Sand Volume (mL)

Material Volume (mL)

Sand Control

788.3

N/A

Ion Exchange Resin

236.5

551.8

Orange Peels

670.1

118.3

ZVI Turnings

473.0

315.3

ZVI Filings

473.0

315.3

Rice Husks

585.8

202.5

The experimental procedure consists of the following steps:

  1. Fill column with approximately 2 inches of gravel. The gravel prevents the sand and materials from clogging the outlet at the bottom of the column.
  2. Place the appropriate sand and material quantities on top of the gravel.
  3. Connect the column to the tubing and reservoir system.
  4. Place a 1 L or larger graduated cylinder under the apparatus to collect effluent.
  5. Allow approximately 1 L of DI water to flow through the column to ensure the column is operating properly and to completely saturate the materials.
  6. Use a pump to fill the reservoir with approximately 10 L of synthetic water.
  7. Allow the synthetic water to flow through the column while maintaining a constant head of water on top of the material in the column.
  8. Collect the effluent in the graduated cylinder as it exits the column. After 1 L has accumulated in the cylinder, pour the effluent into beakers.
  9. Use the effluent in the beakers to fill one centrifuge tube to send for uranium and arsenic analysis. Use the remaining effluent in the beakers to test for pH, turbidity, total dissolved solids, and dissolved oxygen.
  10. Repeat steps 7 and 8 after 3 L, 5 L, and 7 L has flowed through the column.