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 nitrat e 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 n itrate and 0.05-5 mg l(-1) for nitrite (0.056-11.29 mg N-NO3- l(-1) an d 0.015-1.52 mg N-NO2- l(-1)). The maximum sampling frequency is 180 s amples/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) nit rite. The particle size of the reductant (Cd) and the use of Cu as a c atalyst influencing the stability of the reduction column were examine d and an electronic calibration system was developed in order to incre ase 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 samp les at a pilot plant based on nitrification/denitrification criteria w ith optimal results. (C) 1998 Elsevier Science B.V.