Understanding aerobic denitrification has become an important focus of environmental microbiology. Aerobic denitrification can be performed by various genera of microorganisms and describes the use of nitrate (NO
 3
 -
 ) as oxidizing agents under an aerobic atmosphere. Isolation of aerobic denitrifiers, enzymes involved in aerobic denitrifiers, phylogenetic distribution of aerobic denitrifiers, factors affecting the performance of aerobic denitrifiers, attempts of applications and possible future trends are depicted. The periplasmic nitrate reductase is vital for aerobic denitrifiers and NapA gene may be the proof of aerobic denitrification. Phylogenetic analysis revealed that aerobic denitrifiers mainly belong to α-, β- and γ-Proteobacteria. Aerobic denitrifiers tend to work efficiently at 25 ~ 37°C and pH 7 ~ 8, when dissolved oxygen concentration is 3 ~ 5 mg/L and C/N load ratio is 5 ~ 10. In addition, recent progresses and applications on aerobic denitrifiers are described, including single aerobic reactors, sequencing batch reactor and biofilm reactors. The review attempts to shed light on the fundamental understanding in aerobic denitrification.

Aerobic denitrification: A review of important advances of the last 30 years

Performance of membrane-less microbial fuel cell treating wastewater and effect of electrode distance and area on electricity production

Heterotrophic nitrification and aerobic denitrification by the bacterium Pseudomonas stutzeri YZN-001

https://ir.nctu.edu.tw:443/bitstream/11536/5264/1/000278056300001.pdf

Co-existence of anammox and denitrification for simultaneous nitrogen and carbon removal—Strategies and issues

The removal of ammonia from wastewater has become a worldwide emerging concern because ammonia is toxic to aquatic species and causes eutrophication in natural water environments (Tchobanoglous et al. 2003). Nitrogen compounds in wastewater can only be effectively removed by biological approaches (EPA 1993; Zhu et al. 2007a,b). Based on the microbial nitrogen cycle and the metabolism of inorganic nitrogen compounds (Fig. 1), many biological technologies and processes have been developed and implemented for nitrogen removal from wastewater, such as predenitrification (Anoxic/Oxic), modified Bardenpho, Bio-denitro, sequencing batch reactor (SBR), oxidation ditch (OD), step feeding, anaerobic/anoxic/ aerobic (A2/O), and University of Cape Town (UCT) processes (Wentzel et al. 1992; Ostgaard et al. 1997; Williams and Beresford 1998; Tchobanoglous et al. 2003; Pai et al. 2004). These processes have been widely employed in wastewater treatment plants for nitrification and denitrification (EPA 1993). However, with the effluent discharge standards having become more stringent (<10mg total nitrogen/L), conventional processes cannot meet the new requirements (Khin and Annachhatre 2004).

Biological Removal of Nitrogen from Wastewater

Aerobic nitrification-denitrification by heterotrophic Bacillus strains.

Characteristics of Denitrification by Mixed Active Bio-beads

The characteristics of nitrogen removal by the free cell and the immobilized cell of R. capsulatus were investigated. Denitrification by R. capsulatus cells resulted in reduction of ORP with the rapid depletion of DO and the increase of pH. Without accumulation of nitrite, the removal efficiencies of -N for the free cell and the immobilized cell were 99.1 and 99.3%, respectively. During the three-month experiment of goldfish breeding equipped with a water-purification biofilter, the average values of pH and total cell numbers present in an aquarium were not significantly different between water-purification system and the control. The average concentrations of -N and -P in water-purification system were relatively low, compared to that in the control. Goldfish died at , , , and days in the control, while goldfish died at , , and days in the water-purification system. On the days of goldfish's death, the total concentrations of nitrogenous compounds except for were higher than those on the other days of the experiment, especially with the concentrations of -N ranging from 7.4 to 13.5 mg/L. The water-purification system also showed the less turbidity of water with more active movement of goldfish than the control. PVA gel beads showed almost the full denitrifying ability even after the long-term experiment. As a result, the water-purification system was effective to remove nitrogenous compounds with better survival of goldfish.

/pdf/characteristics-of-a-water-purification-system-using-54mkrkk4w3.pdf

Characteristics Of A Water-Purification System Using Immobilized Photosynthetic Bacteria Beads

Isolation, identification and immobilized-cell characteristics of a bacterium that produces N₂ from NH₄ + under an aerobic condition

To treat wastewater efficiently by a one-step process of nitrogen removal, a new bacterial strain producing gas from under an aerobic condition was isolated and identified. The cell was motile and a Gram-negative rod, and usually occurred in pairs. By 16S-rDNA analysis, the isolated strain was identified as Enterobacter asburiae with 96% similarity. The isolate showed that the capacity of production under an oxic condition was approximately three times higher than that under an anoxic condition. Thus, the consumption of by the isolate was significantly different in the metabolism of production under the two different environmental conditions. The optimal conditions of the immobilized isolate for production were found to be pH 7.0, and C/N ratio 5, respectively. Under all the optimum reaction conditions, production by the immobilized isolate resulted in reduction of ORP with both the consumption of DO and the drop of pH. The removal efficiencies of , and TN were 56.1 and 60.9%, respectively. The removal rates of , and TN were the highest for the first 2.5 hrs with the removal ratios of 32.1, and afterwards the rates decreased as reaction proceeded. For application of the immobilized isolate to a practical process of ammonium removal, a continuous operation was executed with a synthetic medium of a low C/N ratio. The continuous bioreactor system exhibited a satisfactory performance at 12.1 hrs of HRT, in which the effluent concentrations of -N was measured to be 15.4 mg/L with its removal efficiency of 56.0%. The maximum removal rate of -N reached 1.6 mg -N/L/hr at 12.1 hrs of HRT(with N loading rate of -carrier/d). As a result, the application of the immobilized isolate appears a viable alternative to the nitrification-denitrification processes.

https://eeer.org/upload/eer-10-5-213-2.pdf

Kyoung Joo Park

Papers

Aerobic nitrification-denitrification by heterotrophic Bacillus strains.

Characteristics of Denitrification by Mixed Active Bio-beads

Characteristics Of A Water-Purification System Using Immobilized Photosynthetic Bacteria Beads

Isolation, identification and immobilized-cell characteristics of a bacterium that produces N₂ from NH₄ + under an aerobic condition

Isolation, identification and characterization of an immobilized bacterium producing n 2 from nh 4 + under an aerobic condition