It depends on the water use perpose and the country where these norms adopted. For Russia they are: drinking water NO3-N - 10,17 mg/l, NO2-N - 1 mg/l; fishery water NO3-N - 9,0 mg/l, NO2-N - 0,02 mg/l.

Kind regards,

Timur E. Pavluk

It depends of the water type. Each country has their own guidelines and norms. For potable water, the OMS has 50 mg/l for NO3 (as nitrate ion) and 3 mg/l for NO2 (as nitrite ion).

According to the ODWQS O.Reg 169 03 (Ontario Drinking Water Quality Standards) the level of Nitrate (nitrogen) = 10 mg/L and Nitrite (as nitrogen) = 1 mg/L

Accordingly to water purposed either for drinking or not for drinking (recreational etc). You can refer this to website of Ministries of Health, Malaysia or Environmental Quality Report at website of Department of Environment, Malaysia. The best references still at WHO.