Quantification of nitrifying bacterial populations in a full-scale nitrifying trickling filter using fluorescent in situ hybridization

Fluorescent in situ hybridization (FISH) was used to quantify the ammonia-o xidizing populations within intact biofilm samples collected from a full-sc ale nitrifying trickling filter (MTF). Ammonia, nitrite, and nitrate concen trations were measured for aqueous samples taken in conjunction with biofil m samples at multiple filter depths. Correlation coefficients for individua l sampling events, calculated by simple linear regression of FISH signal ar ea and ammonia removal rates, ranged from 0.558 when using probe NEU23a to 0.982 when using probe Nso190. The improved correlations with Nso190 sugges t that genera other than Nitrosomonas are present in this system Percent bi ofilm coverage, as determined by 4 ' ,6-diamidino-2 phenylindole countersta ining and dry weight biomass measurement, did not change throughout the NTF . This indicates that biofilm growth is fairly uniform throughout the filte r even if nitrifier growth is not.