Spring 2005 Senior Design Project
Erica Zerfoss
Dept. of
Bioengineering
The Pennsylvania State University,
University Park, PA 16802
Sponsor: Dr. Bruce Logan, Kappe Professor of Environmental Engineering
An estimated 3.4 million deaths a year are attributable to waterborne diseases. Recently, the World Health Organization (WHO) has recognized point-of-use water treatment as an effective means of reducing illness in developing country households [1]. WHO also estimates that over one billion people do not have access to safe drinking water. A possible solution to these problems is to use activated carbon point-of-use filters in the plant and at the tap.
Activated Carbon is a highly porous granular material well known for its adsorption properties and ability to remove organic impurities from drinking water. Because of its highly porous nature, a small amount of carbon is able to adsorb a large amount of dissolved organic matter [2]. Recently, attention has been given to activated carbon for its ability to adsorb viruses and bacteria; however there has not been much research in this area.
Currently, there are methods to calculate the sticking coefficient of bacteria on activated carbon using packed activated carbon columns. This is accomplished by the radiolabeling of the bacteria and using a scintillation counter to quantify the amount adsorbed. This method cannot work with the bacteriophage MS-2 because this particular virus does not adequately take up radiolabel. Also, radiolabel is expensive and requires all lab workers to have the proper safety training. Therefore, a new column flow experiment has been developed that involves the quantification of adhesion by serial dilution plating of influent and effluent as opposed to radiolabeling.
Objectives
| ·Design and production of a new flow test apparatus and experimental methods for the calculation of the sticking coefficient of bacteriophage MS-2 to GAC. |
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·Alter the mathematical model of the MARK test to meet the constraints of the new experiment. |
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·Run column experiments with MS-2 on four variations of GAC to check that the new experiment gives reproducible results. |
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The new flow experiment column was designed to fit on top of a vacuum box that allowed for filtrate collection. The apparatus is fairly simple with a metal base that fits into the vacuum box and a circular piece of plastic with a hole for the syringe attachment glued to the top (Figure 1 and 2). The syringe fits tightly into the plastic piece but is easily removed. With a vacuum pressure of 1 psi, a flow of 5 mL/min is achieved. The flow controller is a LuerLok connector. The final product is shown in Figure 3.
Figure 3. The flow experiment apparatus. Adhesion is quantified by collection of effluent.
Design of Experimental Methods
In the new two-layer column experiment, the filtrate from the column is collected and the fraction retained in the carbon bed is quantified by serial dilution plating. The test is referred to as a two-layer experiment because the suspension effluent is collected after passing through both a GAC packed bed and a supporting filter. Because adhesion to the supporting filter must also be accounted for, column experiments are also run with the filter alone (Figure 4).
Figure 4. Two layer column experiment. The column on the left has both layers, a filter and a GAC bed. The column on the right has only the first layer, the GF/D filter.
Figure 5. Two-layer column test setup with variables. (a) Syringe with carbon supported with GF/D filter. (b) Syringe with only a GF/D Filter.
Design Performance
Figure 6. The sticking coefficients for duplicate column experiments calculated using the RT clean-bed model