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Overall Goals: - Design and improve AguaClara filtration unit to remove arsenic from influent - Evaluate the feasibility of implementation This Semester's Goals: - Fabricate a sand filtration unit for continuous flow experiment - Establish a rigid experimental procedure to ensure safety of researchers and minimize hazardous waste - Improve arsenic detection method using the graphite furnace atomic absorption spectrometer - Perform continuous flow experiment and evaluate filter capacity to removal arsenic from influent |
If this is the case, then a floc blanket consisting of precipitated coagulant could be an efficient reactor for arsenic removal.
An important first task is to develop a reliable and sensitive measure for dissolved As (atomic absorption using graphite furnace atomization may be one option if we have a suitable lamp, inductively coupled plasma may be another option if you can get free help from someone with this instrument). There are some wet chemical methods (see Hach), but their sensitivity may not be adequate. Without an analytical tool we won't be able to verify the efficacy of any treatment scheme tested. Measuring dissolved As will require a phase separation from As adsorbed to suspended solids that does not alter the dissolved As concentration. Centrifugation is a good option (filtration probably will not work well). Uptake of dissolved As (adsorption) onto solids will likely depend on pH and ionic strength (as well as the concentration of suspended solids and dissolved As). pH control will be particularly important and it will be difficult to reproduce results if this is not part of the experimental protocol.
In Spring 2013, we determined that aluminum coagulants may be just as effective as iron salts for arsenic removal. We also have researched the lab safety protocols for dealing with arsenic in the AguaClara lab, and believe we can begin testing coagulants next semester. Below is a list of questions we suggest next semester's team continue researching. We've also included a task list in our final report detailing how to get the lab arsenic ready and a potential experimental setup to test arsenic coagulation.
In Fall 2013, we began laboratory testing. The team initially began by preparing the lab area for hazardous chemicals with the proper personal protective equipment and appropriate signage. Then we went on to collect testing equipment such as the tube tumbler, test tubes, and the appropriate chemicals. We had to order tubes which had a filter insert so that we could test our small scale filtration process. There were also several chemicals which we needed to purchase to create our test groundwater. Once all of our materials were collected we were able to begin testing our process of sedimentation and filtration in a small scale reactor. Our GFAAS machine is not fully operational at the time; there are a few tubes which need repairing, but once this is complete, we are confident that we will be able to read concentrations of arsenic which are below five parts per billion.
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