1 mg/l = 1 ppm. That is not what i meant by which scale. As I posted earlier in this thread, There are two scales used to measure things like ammonia, nitrite or nitrate. One is called the nitrogen scale and when this is used you will see one of two things- either -Nitrogen or -N. here is an example: 1.5 ppm NH3-N or 1 .5 ppm NH3-Nitrogen.
That -N or -Nitrogen means it is using the nitrogen scale. One the other hand if the test measure Total Ions, there will be no -N or -nitrogen at the end. The one exception is sometime it is outright stated "measured as nitrogen" and then the -N or -Nitrogen is omitted.
The EPA drinking water standards for nitrate are stated using the nitrogen scale not the total ion scale. However, hobby test kits almost always measure using the total ion scale.
So what I was asking you is what scale your nitrate report used. The 10 mg/l-N the government sets is the Nitrogen scale. When we test using our hobby kit that result is shown using the total ion scale. This means that 10 mg/l-N would test out in a tank as 44.3 ppm.
The EPA site does not make this clear on the link you posted above. If you go here and then scroll down to Nitrate you will see :"Nitrate (measured as Nitrogen)"
http/water.epa.gov/drink/contaminants/index.cfm
The standards for nitrite also use the nitrogen scale. However, the standards for ammonia levels which were revised in 2013 do not appear on the master list. If you are curious about these, the information is here:
http/water.epa.gov/scitech/swguidance/standards/criteria/aqlife/ammonia/upload/Aquatic-Life-Ambient-Water-Quality-Criteria-for-Ammonia-Freshwater-2013-Fact-Sheet-April.pdf And this too uses the nitrogen scale:
Table 1. Comparison of past and current EPA- recommended aquatic life water quality criteria magnitudes for ammonia. Criteria magnitudes are expressed as total ammonia nitrogen (mg TAN/L) at pH 7 and 20°C.
So, your 11 ppm of nitrate is on which scale- nitrogen or total ion?