A novel FIA configuration for the simultaneous determination of nitrate and nitrite and its use for monitoring an urban waste water treatment plant based on N/D criteria

A novel FIA configuration for the simultaneous determination of nitrate and nitrite, and its automation for monitoring an urban waste water treatment plant (WWTP) based on nitrification/denitrification criteria, are proposed. The detection range achieved is 0.25-50 mg l(-1) for nitrate and 0.05-5 mg l(-1) for nitrite (0.056-11.29 mg N-NO3- l(-1) and 0.015-1.52 mg N-NO2- l(-1)). The maximum sampling frequency is 180 samples/day and the Relative Standard Deviation (RSD, n=5) was 1.1% at 5 mg l(-1) nitrite and 2.3% at 50 mg l(-1) nitrate plus 1 mg l(-1) nitrite. The particle size of the reductant (Cd) and the use of Cu as a catalyst influencing the stability of the reduction column were examined and an electronic calibration system was developed in order to increase the capacity of the equipment to operate unattended with a view to its use at WWTP. The maximum unattended deployment time is four days. The proposed configuration was validated by analyzing real water samples at a pilot plant based on nitrification/denitrification criteria with optimal results. (C) 1998 Elsevier Science B.V.