In situ characterization of nitrifiers in an activated sludge plant: detection of Nitrobacter Spp.

Abstract

Aims: The purpose of this work was to investigate microbial ecology of nitrifiers at the genus level in a typical full-scale activated sludge plant. Methods and Results: Grab samples of mixed liquor were collected from a plug-flow reactor receiving domestic wastewater. Fluorescent in situ hybridization technique (FISH) was used to characterize both ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) in combination with Confocal Scanning Laser Microscope (CSLM). Fluorescently labelled, 16S rRNA-targeted oligonucleotide probes were used in this study. Both Nitrosomonas and Nitrosospira genera as AOB and Nitrobacter and Nitrospira genera as NOB were sought with genus specific probes Nsm156, Nsv443 and NIT3 and NSR1156, respectively. Conclusions: It was shown that Nitrosospira genus was dominant in the activated sludge system studied, although Nitrosomonas is usually assumed to be the dominant genus. At the same time, Nitrobacter genus was detected in activated sludge samples. Significance and Impact of the Study: Previous studies based on laboratory scale pilot plants employing synthetic wastewater suggested that only Nitrospira are found in wastewater treatment plants. We have shown that Nitrobacter genus might also be present. We think that these kinds of studies may not give a valid indication of the microbial diversity of the real fullscale plants fed with domestic wastewater.

Nitrous oxide emissions and dissolved oxygen profiling in a full-scale nitrifying activated sludge treatment plant

“…Average ammonia concentrations entering the lane were 15.3 mg/L, with most of nitrification taking place by zone 6 (Fig.2).In-lane measurements during the pre-assessment period showed the majority of the oxidised nitrogen was in nitrate form (average 12 mgN/L), with limited to undetectable nitrite in lane (average 0.3 mgN/L). This is consistent with what is expected in a full-scale nitrifying ASP (Coskuner and Curtis, 2002). The operational conditions were measured during the study and used to assess the relationship between emissions and the environmental conditions (Table 1).…”

Influence of growth manner on nitrifying bacterial communities and nitrification kinetics in three lab-scale bioreactors

“…On the other hand, Nitrobacter has a higher K S for nitrite. Therefore, in environments with high concentrations of nitrogen, Nitrobacter is frequently found to be the dominant NOB [10]. In our study, the ratio between populations of Nitrospira and Nitrobacter varied from 5.2 to 13.4; Nitrospira showed evident dominance in population concentration compared with Nitrobacter, which was identical to many result [8,31,36,37].…”

Molecular Diversity of a North Carolina Wastewater Treatment Plant as Revealed by Pyrosequencing

“…The current use of molecular techniques that do not require the isolation and cultivation of microorganisms (1,33), including 16S rRNA analysis (6,13,20) and fluorescent in situ hybridization (8), have greatly expanded our understanding of wastewater microbial communities. Researchers have identified many bacteria of importance to wastewater treatment, including the bacteria involved in biological phosphorus removal (5,16,29), nitrifiers (8,19,25), denitrifiers (3,12,17), and methanogens (18,36). Molecular techniques have also improved our understanding of fundamental processes such as nitrification and denitrification, as well as plant upsets, such as foaming (9,24), which can decrease treatment efficiency.…”