The effects of the lengths of aeration and nonaeration periods on nitrogen removal and the nitrifying bacterial community structure were assessed in intermittently aerated (IA) reactors treating digested swine wastewater. Five IA reactors were operated in parallel with different aeration-to-nonaeration time ratios (ANA). Populations of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bact...

In this work the kinetics of a number of sulfide-oxidizing nitrate-reducing (SO-NR) cultures acclimated and not acclimated to nitrite were characterized. Anoxic respirometry coupled to kinetic modeling of respirometric profiles was the methodology used to study the two-step denitrification associated to thiosulfate oxidation. Autotrophic denitritation was initially studied in a non-acclimated S...

Nitrite and nitrous oxide made up 40% of the hypolimnetic dissolved inorganic nitrogen in mesotrophic Lake Rotoiti, New Zealand, prior to hypolimnetic anoxia. Up to 120 mg of N m-3 as nitrite and 20 mg of N m-3 as nitrous oxide accumulated, whereas dissolved-oxygen concentrations remained between 1.0 and 0.2 g m-3 and were totally consumed when the hypolimnion became completely anoxic. Assays o...

Biological nitrogen removal (BNR) based on partial nitrification and denitrification via nitrite is a cost-effective alternate to conventional nitrification and denitrification (via nitrate). The goal of this study was to investigate the microbial ecology, biokinetics, and stability of partial nitrification. Stable long-term partial nitrification resulting in 82.1 +/- 17.2% ammonia oxidation, p...

A unique consortium of ammonia-oxidizing bacteria (AOB) and denitrifying bacteria was obtained via a long-term, 3-step cultivation of isolates from organically-enriched marine sediment. We developed this microbial consortium for possible applications in the remediation of degraded habitats in closed aquaculture or other aquatic environments via microbial degradation. Analysis of media component...

CEB Biofilm Group In biological denitrification of wastewater nitrate (NO3 -) or nitrite (NO2 -) are converted into nitrogen gas (N2), in the absence of dissolved oxygen (DO) or under limited DO concentrations. A rotating biological contactor (RBC) is an attached growth bioreactor, that constitutes a very unique and superior alternative technology for carbon oxidation, phosphorus removal, nitri...

We investigated the enzymatic reduction and oxidation of iron in M.magnetotacticum which synthesizes magnetite at room temperature. NADH-Fe(lI1) reductase with the molecular mass of 36kDa was purified from the bacterium. The enzyme was located in cytoplasm and utilized NADH and NADPH in the presence of FMN as reductant and showed maximum activity at pH 7.0. The Km for NADH and NADPH were about ...

Rhodobacter sphaeroides 2.4.1, which is incapable of denitrification, has been found to carry nnrR, the nor operon, and nnrS, which are utilized for denitrification in R. sphaeroides 2.4.3. The gene encoding nitrite reductase was not found in 2.4.1. Expression of beta-galactosidase activity from a norB-lacZ fusion was activated when cells of 2.4.1 were incubated with NO-producing bacteria. This...

Bacterial denitrification is expressed in response to the concurrent exogenous signals of low-oxygen tension and nitrate or one of its reduction products. The mechanism by which nitrate-dependent gene activation is effected was investigated in the denitrifying bacterium Pseudomonas stutzeri ATCC 14405. We have identified and isolated from this organism the chromosomal region encoding the two-co...