Our experiment returned different results than we expected. Initially we were expecting the tests we performed (nitrate and copper tests) to give us sufficient evidence to classify our two water sources—the Hudson River and Sunset Lake—as non-potable. However, as we discovered, the nitrate and copper levels are sufficiently low to be below the EPA’s cut-off for potability. We were disappointed by this outcome, as we had hoped to prove, beyond a shadow of a doubt, that the water sources were dangerous to drink. In the future, given more time, we would like to have been able to perform tests to determine bacteria levels in the water, such as E. coli or other coli-form bacteria, and the levels of other organisms, such as Giardia. We would expect the levels of these bacteria and organisms to be too high to allow for safe drinking. Perhaps the spectroscopy readings suggest the presence of things other than simply water molecules, as the Hudson River and Sunset Lake had higher absorbance in the violet range of the spectrum than regular drinking water.
This experiment, while perhaps unsuccessful in terms of what we had hoped to discover, is a good example of why one or two negative tests do not necessarily account for all possible contaminants.
In conclusion, despite the negative results from our tests, we would still suggest that you choose not to drink from the Hudson or Sunset Lake.