| Author | Phan Sophary |
| Call Number | AIT Thesis no.EV-03-30 |
| Subject(s) | Arsenic wastes Cambodia
|
| Note | A thesis submitted in partial fulfillment of the requirements for the
degree of Master of Science. |
| Publisher | Asian Institute of Technology |
| Abstract | For a country like Cambodia with a significant groundwater arsenic problem, there is an
urgent need for the arsenic-contaminated wells to be quickly identified and appropriate
action to be taken. This will involve the testing of a large number of wells. A field testing
kit made by Hach is currently used national-wide. The field Hach kit is based upon the
Gutzeit method, which involves the reduction of arsenic to arsine gas, which reacts with
mercuric bromide to form yellow colour. The determination of arsenic concentration is
done by visual comparison of the coloured stain with a colour chart. The detection limit
of the Hach kit is about 10 μg/L. Since Hach kit is widely used it became necessary to
evaluate its effectiveness and possible made suggestions for improvement. The Hach kit
performance was evaluated in various ways including arsenic standard solution, samples
preservation using hydrochloric and nitric acid, quality of the test strip, effect of hydrogen
sulphide, colour scale reading and reaction time. Samples from 94 tube wells were tested
by kit and by a reliable laboratory technique to ascertain the reliability.
Overall the Hach kit performed well with arsenic standard solution as well as with
preserved samples. Problems were noted in proper use and storage of test strips as well as
interference from hydrogen sulphide. It was also noted that operators usually fail to
record arsenic concentration in ranges between the two-gradation values of the colour
scale. The 20-minutes reaction time recommended by the kit procedures was not
adequate; 30 minutes was necessary to give good results. The comparison of the
analytical results of 94 samples showed Hach kit usually gave higher result than either
HG AAS or SDDC methods except at arsenic concentration below 10 μg/L. The closest
agreement between Hach kits and laboratory methods were observed when arsenic
concentrations were low. There were 12 (13%) false positives found but no false
negatives. All of the finding suggest further development is needed to improve methods
of testing arsenic concentrations for less developed countries like Cambodia. |
| Year | 2003 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Visvanathan, C.; |
| Examination Committee(s) | Nguyen Thi Kim Oanh;Preeda Parkpian; |
| Scholarship Donor(s) | Swedish International Development
Agency (Sida); |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2003 |