[1] We use transit time distributions calculated from tracer data together with in situ measurements of N2O to estimate the concentration of biologically produced N2O ([N2O]xs) and N2O production rates in the central North Atlantic Ocean. Our approach to estimation of N2O production rates integrates the effects of potentially varying production and decomposition mechanisms along the transport p...

The cold-adapted bacterium Pseudomonas putida Y-9 was investigated and exhibited excellent capability for nitrogen removal at 15°C. The strain capable of heterotrophic nitrification and aerobic denitrification could efficiently remove ammonium, nitrate, and nitrite at an average removal rate of 2.85 mg, 1.60 mg, and 1.83 mg NL-1 h-1, respectively. Strain Y-9 performed nitrification in preferenc...

Apseudohomogeneous model of the nitrifying activated sludge process was developed to investigate the effects ofmass-transport resistance and heterotrophic/nitrifier competition on the apparent relationship between dissolved oxygen (DO) concentration and nitrification . The kinetics of both heterotrophic carbon oxidation and autotrophic ammonia oxidation within activated sludge flocs were descri...

The microbial community composition and activity was investigated in aggregates from a lab-scale bioreactor, in which nitrification, denitrification and phosphorus removal occurred simultaneously. The biomass was highly enriched for polyphosphate accumulating organisms facilitating complete removal of phosphorus from the bulk liquid; however, some inorganic nitrogen still remained at the end of...

It is crucial to reveal the regulatory mechanism of nitrification to understand nitrogen conversion in agricultural systems and wastewater treatment. In this study, the nwiI gene of Nitrobacter winogradskyi was confirmed to be a homoserine lactone synthase by heterologous expression in Escherichia coli that synthesized several acyl-homoserine lactone signals with 7 to 11 carbon acyl groups. A n...

Simultaneous nitrification and denitrification (SND) was investigated in the single aeration tank of a municipal wastewater treatment plant. Microelectrode measurements and batch experiments were performed to test for the presence of SND. Microelectrodes recorded the presence of O(2) concentration gradients in individual activated sludge flocs. When the O(2) concentration in the bulk liquid was...

Nitric oxide production was measured during nitrification in a laboratory-scale bioreactor, operated at conditions relevant to municipal nitrifying wastewater treatment plants. This study aims to determine which type of microorganism and which metabolic pathway is responsible for nitric oxide emission during nitrification. Simulation studies were used to identify which pathway is the main sourc...