Hello dear
I am working on water  analyses for using it in a input drinking water treatment plant and it's results of phosphate is in the range of eutrophic (0.035-0.1 mg/L ) and for nitrogen is in the range of (0-0.5 mg/L) . The results of chlorophyll A is in the range of <40 µg/lit.
What other factors should I verify so that I could be sure that the result of phosphate is the lab error?
With best regards