Stability Monitoring of the Nitrification Process: Multivariate Statistical Analysis

The aim of this article is to define the possibilities of applying multivariate statistical analysis (PCA and control charts) in the monitoring of the effectiveness of biological nitrification in a wastewater treatment plant working for the municipality of Sanok. The difference in oxygen affinity between ammonium and nitrite oxidizers results in a bacteria competition between AOM and NOM. A more stable nitrification process was obtained in reactor I for mean oxygen concentration of 1.13-2.05 mgO(2).dm(-3). The lowest mean concentrations of ammonia nitrogen were obtained in the range 3.43-3.62 mgN-NH4+.dm(-3). Reactor II worked at mean oxygen concentration 1.69-4.56 mgO(2).dm(-3), which caused lower stability in this study period. The mean concentration of ammonium nitrogen ranged from 4.06 to 9.08 mgN-NH4+.dm(-3). April 2016 was considered the most stable period of work of nitrification reactors. In that month, in reactor I the upper specification limit USL was not exceeded. In reactor II the USL was exceeded only 10% of the time. The index of the process capacity C-pk was higher for reactor I, and achieved a value of 1.71. The process of nitrification in both reactors was qualified as stable when oxygen concentration was between 1 and 2 mgO(2).dm(-3).