Title: Fixed-Bed Adsorption Column Studies and Engineering Scale-Up Design of a Limestone-Based Metals Removal Technology for Small Water Supply Systems
Project Type: Research
Start Date: 03/01/2006
End Date: 02/28/2007
Congressional District: First
Focus Categories: Toxic Substances, Treatment, Water Supply
Keywords: Metals; metals removal; drinking water; point of entry systems
Principal Investigators: Davis, Arden D (S.D. School of Mines and Technology); Dixon, David J. (None)
Federal Funds: $12,918
Non-Federal Matching Funds: $25,836
Abstract: This project will quantify and compare the effectiveness of both unprocessed limestone chips and manufactured limestone-based granules to remove arsenic from naturally occurring arsenic-contaminated groundwater. Keystone, South Dakota, City Well No. 4 will be used as the water source. By running column studies with three columns in series, the researchers will be able to extend the amount of adsorbent used to treat the water, in comparison to previous column studies that have used only one column at a time. This will extend the length of the mass transfer zone established as the adsorbent media reacts with arsenic in the water. The length of the mass transfer zone is directly affected by contact time with the adsorbent. Longer contact time results in a shorter mass transfer zone and results in more complete utilization of the adsorbent.
A breakthrough curve will be plotted for each column in each study. Breakthrough in this study will be when the arsenic concentration goes from undetectable to 10 ppb, the future drinking water standard. Exhaustion of a column, the point at which the media must either be replaced or regenerated, is when the influent and effluent concentrations of the metal in question are equal. Empty bed contact time (EBCT) for each column study will also be calculated. The EBCT is used to represent the length of time a stream of water is in contact with the adsorbent media and is related to the system's kinetics.
Results from the column studies using Keystone well water will be used to design a scaled-up pilot project for future application at Keystone City Well No. 4. Pilot project operating variables to be determined will include: adsorbent type, column diameter, water flow rate, adsorbent bed depth, weight of adsorbent in column(s), contact time, influent and effluent impurity concentrations (ions present other than arsenic), and desired effluent impurity concentrations. More than one design method will be applied for comparison purposes. In addition, column testing of the limestone-based granules as a treatment method for cadmium removal will quantify cadmium removal capacity of the adsorbent in a fixed-bed adsorption column.
Benefits of this research will include a low-cost treatment technology that will reduce select metals to below drinking water standards. Also, this project will bring installation of a pilot arsenic treatment technology at the Keystone, South Dakota City Well No. 4 site one step closer to reality.The objectives of this work are to:
Progess/Completion Report, PDF