In many places in the world, surface water is either contaminated
to the point of being undrinkable or exists in a quantity that is potable but scarce. A popular
solution is to instead extract groundwater from deep underground. The issue
with this is that despite being cleaner, oftentimes this groundwater will be
contaminated with heavy metals such as arsenic due to its contact with the
surrounding soil.
AguaClara’s research in arsenic treatment first began in the
form of a capstone idea presented in a previous semester of our CEE 4540
course, “Small-Scale Sustainable Water Supplies.” The goal was to direct
AguaClara’s research efforts to address the problem of widespread arsenic
poisoning in communities around the world that rely on contaminated groundwater
as their primary water source. A team of students was formed the following
semester to research possible solutions to this large-scale problem.
This semester, the Arsenic Team has begun testing methods
for separating arsenic from water in order to render the water potable. One of
the team’s goals is to see if their idea of using AguaClara’s
process of water treatment as a base could, with some adjustments, work
similarly effectively for arsenic.
Flocculation, as it works in the AguaClara plant, entails
dosing pre-treated water with a coagulant so that unwanted particles will stick
to one another to form larger masses called flocs. As they become heavier than the water, these flocs are pulled to the bottom of our tank by gravity through a process called sedimentation. The water is then filtered.
In modifying this process for arsenic removal testing, the team will first
dose a sample of mock groundwater with known concentrations of arsenic and
coagulant. The samples with then be mixed at a low speed in a tumbler to
simulate flocculation. After flocs form, the container with the sample will then
be placed into a centrifuge and rotated at a high enough velocity that the flocs—hopefully
containing the arsenic—will be distinctly separated from uncontaminated water.
The sample will then be analyzed using a spectrometer to measure the remaining
concentration of arsenic in the sample.
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From left: Imtiaz, Tanapong, and Michelle preparing a sample for the spectrometer. |
Most recently, the team has been testing to see if a
combination of filtration and sedimentation by centrifuge—with varying
coagulant dosage—will aid in the removal of arsenic from mock groundwater.