Identication of Contaminants In Water

[Grove1996]

The purpose:
Basically I've been given a pre-contaminated sample of water, as well as a post-contaminated sample of water. I have to determine what the water is contaminated with, and the concentration of the contaminants present in the water.

My Problem:
I have determined one contaminant that is present in the water, and this is ammonium with a reading of approximately 430 mg/L. However, it's not just ammonium by itself, there are other contaminants present. I've tested for a few things (calcium/chloride/nitrate) and all is fine. I'm limiting it down to phosphate or sulfate. The pH of the water is 8, and I know that ammonium in water creates a more basic solution. So whatever the other contaminant is, I'm assuming there is not much of it. Since I'm in high school the testing equipment I can use is very limited. I can test for phosphate but I am yet to find a procedure I can use to test for sulfate ions.

Does anyone know a procedure I could use to determine the amount of sulfate ions present in a given sample of water. I've searched long and hard and unable to find anything I can do with the equipment I have at school.

Thankyou

 

[Borek]

The most obvious approach is the precipitation of barium sulfate.

 

[Grove1996]

The most obvious approach is the precipitation of barium sulfate.

I've research this a little bit. From my understanding it only can determine whether there is sulfate present in the water sample, but not the concentration.

 

[Borek]

No, it can be used for quantitative analysis as well, this is one of the most basic gravimetric methods.