Condition Nitrifying organisms (MPN mL-1) Denitrifying organisms (MPN mL-1) Ammonium oxidizing bacteria Nitrite oxidizing bacteria Heterotrophic Autotrophic AInitial 9.2 x 1016 7.8 x 107  4.7 x 1016 1.4 x 105 1 1.6 x 1018 3.3 x 106 > 1.6 x 1018 1.7 x 105 4 2.2 x 1022 1.3 x 109 2.0 x 1016 1.6 x 107 APrevious condition described in Moraes et al, [11] in which sulfide concentration was about 20 - 25 mg TDS L-1

Table 3: MPN of nitrifying and denitrifying bacteria in FBSBR at the end of specific conditions.