Denitrification-Potential Evaluation and Nitrate-Removal-Pathway Analysis of Aerobic Denitrifier Strain Marinobacter hydrocarbonoclasticus RAD-2

An aerobic denitrifier was isolated from a long-term poly (3-hydroxybutyrate-co-3-hydroxyvalerate) PHBV-supported denitrification reactor that operated under alternate aerobic/anoxic conditions. The strain was identified as Marinobacter hydrocarbonoclasticus RAD-2 based on 16S rRNA-sequence phylogenetic analysis. Morphology was observed by scanning electron microscopy (SEM), and phylogenetic characteristics were analyzed with the API 20NE test. Strain RAD-2 showed efficient aerobic denitrification ability when using NO3−-N or NO2−-N as its only nitrogen source, while heterotrophic nitrification was not detected. The average NO3−-N and NO2−-N removal rates were 6.47 mg/(L·h)and 6.32 mg/(L·h), respectively. Single-factor experiments indicated that a 5:10 C/N ratio, 25–40 °C temperature, and 100–150 rpm rotation speed were the optimal conditions for aerobic denitrification. Furthermore, the denitrifying gene napA had the highest expression on a transcriptional level, followed by the denitrifying genes nirS and nosZ. The norB gene was found to have significantly low expression during the experiment. Overall, great aerobic denitrification ability makes the RAD-2 strain a potential alternative in enhancing nitrate management for marine recirculating aquaculture system (RAS) practices.

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Coupled anaerobic ammonium oxidation and hydrogenotrophic denitrification for simultaneous NH4-N and NO3-N removal

Water Science & Technology ◽

10.2166/wst.2018.459 ◽

2018 ◽

Vol 79 (5) ◽

pp. 975-984 ◽

Cited By ~ 4

Author(s):

Tatsuru Kamei ◽

Rawintra Eamrat ◽

Kenta Shinoda ◽

Yasuhiro Tanaka ◽

Futaba Kazama

Keyword(s):

Nitrogen Removal ◽

Inorganic Nitrogen ◽

Nitrate Removal ◽

Fixed Bed ◽

Anaerobic Ammonium Oxidation ◽

Anammox Bacteria ◽

Ammonium Oxidation ◽

N Removal ◽

Anammox Process

Abstract Nitrate removal during anaerobic ammonium oxidation (anammox) treatment is a concern for optimization of the anammox process. This study demonstrated the applicability and long-term stability of the coupled anammox and hydrogenotrophic denitrification (CAHD) process as an alternative method for nitrate removal. Laboratory-scale fixed bed anammox reactors (FBR) supplied with H2 to support denitrification were operated under two types of synthetic water. The FBRs showed simultaneous NH4-N and NO3-N removal, indicating that the CAHD process can support NO3-N removal during the anammox process. Intermittent H2 supply (e.g. 5 mL/min for a 1-L reactor, 14/6-min on/off cycle) helped maintain the CAHD process without deteriorating its performance under long-term operation and resulted in a nitrogen removal rate of 0.21 kg-N/m3/d and ammonium, nitrate, and dissolved inorganic nitrogen removal efficiencies of 73.4%, 80.4%, and 77%, respectively. The microbial community structure related to the CAHD process was not influenced by changes in influent water quality, and included the anammox bacteria ‘Candidatus Jettenia’ and a Sulfuritalea hydrogenivorans-like species as the dominant bacteria even after long-term reactor operation, suggesting that these bacteria are key to the CAHD process. These results indicate that the CAHD process is a promising method for enhancing the efficiency of anammox process.

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The Nitrogen-Removal Efficiency of a Novel High-Efficiency Salt-Tolerant Aerobic Denitrifier, Halomonas Alkaliphile HRL-9, Isolated from a Seawater Biofilter

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph16224451 ◽

2019 ◽

Vol 16 (22) ◽

pp. 4451 ◽

Cited By ~ 1

Author(s):

Jilong Ren ◽

Chenzheng Wei ◽

Hongjing Ma ◽

Mingyun Dai ◽

Jize Fan ◽

...

Keyword(s):

Removal Efficiency ◽

Nitrogen Removal ◽

Nitrogen Balance ◽

High Efficiency ◽

Aerobic Denitrification ◽

Salt Tolerant ◽

N Accumulation ◽

Recirculating Aquaculture ◽

N Removal ◽

Recirculating Aquaculture Systems

Aerobic denitrification microbes have great potential to solve the problem of NO3−-N accumulation in industrialized recirculating aquaculture systems (RASs). A novel salt-tolerant aerobic denitrifier was isolated from a marine recirculating aquaculture system (RAS) and identified as Halomonas alkaliphile HRL-9. Its aerobic denitrification performance in different dissolved oxygen concentrations, temperatures, and C/N ratios was studied. Investigations into nitrogen balance and nitrate reductase genes (napA and narG) were also carried out. The results showed that the optimal conditions for nitrate removal were temperature of 30 °C, a shaking speed of 150 rpm, and a C/N ratio of 10. For nitrate nitrogen (NO3−-N) (initial concentration 101.8 mg·L−1), the sole nitrogen source of the growth of HRL-9, the maximum NO3−-N removal efficiency reached 98.0% after 24 h and the maximum total nitrogen removal efficiency was 77.3% after 48 h. Nitrogen balance analysis showed that 21.7% of NO3−-N was converted into intracellular nitrogen, 3.3% of NO3−-N was converted into other nitrification products (i.e., nitrous nitrogen, ammonium nitrogen, and organic nitrogen), and 74.5% of NO3−-N might be converted to gaseous products. The identification of functional genes confirmed the existence of the napA gene in strain HRL-9, but no narG gene was found. These results confirm that the aerobic denitrification strain, Halomonas alkaliphile HRL-9, which has excellent aerobic denitrification abilities, can also help us understand the microbiological mechanism and transformation pathway of aerobic denitrification in RASs.

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Short and Long-Term Responses to Changes in Hydraulic Loading in a Fixed Denitrifying Biofilm

Water Science & Technology ◽

10.2166/wst.1992.0433 ◽

1992 ◽

Vol 26 (3-4) ◽

pp. 535-544

Author(s):

M. M. de Mendonca ◽

J. Silverstein ◽

N. E. Cook

Keyword(s):

Field Experiments ◽

Nitrate Removal ◽

Short Term ◽

Packed Tower ◽

Hydraulic Loading ◽

Denitrification Reactor ◽

Water Field ◽

Short And Long Term ◽

Term Response

The long- and short-term effects of hydraulic loading were investigated in a pilot packed tower bioreactor used for denitrifying a groundwater used for drinking water. Field experiments were conducted at hydraulic loading rates of 3.63 and 7.24 m3/hr/m2. The long-term (21 day average) performance of the denitrification reactor and the short-term response (48 hour) to regular air scour are reported here. In summary, an increase in hydraulic loading resulted in a long-term increase in the half-order denitrification rate constant, so that, on average, nitrate removal was maintained in the 5.2 m tower. At the lower hydraulic loading rate (3.63 m3/hr/m2) denitrification performance in the first 48 hours after air scour was maintained; however at twice the hydraulic loading, several days were required to restore the biofilm performance to long-term average levels.

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An Exploration of Seaweed Polysaccharides Stimulating Denitrifying Bacteria for Safer Nitrate Removal

Molecules ◽

10.3390/molecules26113390 ◽

2021 ◽

Vol 26 (11) ◽

pp. 3390

Author(s):

Hui Zhang ◽

Lin Song ◽

Xiaolin Chen ◽

Pengcheng Li

Keyword(s):

Growth Rate ◽

Bacillus Subtilis ◽

Nitrate Removal ◽

Denitrifying Bacteria ◽

Soil Salinization ◽

Nitrate Content ◽

Weak Efficiency ◽

N Accumulation ◽

N Removal ◽

Intensively Managed

Excessive use of nitrogen fertilizer in intensively managed agriculture has resulted in abundant accumulation of nitrate in soil, which limits agriculture sustainability. How to reduce nitrate content is the key to alleviate secondary soil salinization. However, the microorganisms used in soil remediation cause some problems such as weak efficiency and short survival time. In this study, seaweed polysaccharides were used as stimulant to promote the rapid growth and safer nitrate removal of denitrifying bacteria. Firstly, the growth rate and NO3−-N removal capacity of three kinds of denitrifying bacteria, Bacillus subtilis (BS), Pseudomonas stutzeri (PS) and Pseudomonas putida (PP), were compared. The results showed that Bacillus subtilis (BS) had a faster growth rate and stronger nitrate removal ability. We then studied the effects of Enteromorpha linza polysaccharides (EP), carrageenan (CA), and sodium alginate (AL) on growth and denitrification performance of Bacillus subtilis (BS). The results showed that seaweed polysaccharides obviously promoted the growth of Bacillus subtilis (BS), and accelerated the reduction of NO3−-N. More importantly, the increased NH4+-N content could avoid excessive loss of nitrogen, and less NO2−-N accumulation could avoid toxic effects on plants. This new strategy of using denitrifying bacteria for safely remediating secondary soil salinization has a great significance.

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Nutrient retention behind a tropical mega-dam: a case study of the Sardar Sarovar Dam, India

SN Applied Sciences ◽

10.1007/s42452-020-04118-7 ◽

2021 ◽

Vol 3 (1) ◽

Author(s):

Harish Gupta ◽

S. Kiran Kumar Reddy ◽

Mounika Chiluka ◽

Vamshikrishna Gandla

Keyword(s):

Arabian Sea ◽

Inorganic Nitrogen ◽

Nutrient Retention ◽

Significant Loss ◽

N Removal ◽

Narmada River ◽

Sardar Sarovar ◽

The Impact

AbstractIn this study, we demonstrate the impact of the construction of a mega-dam on the nutrient export regime of a large tropical river into the Arabian Sea. Long-term (11 years) fortnight nutrient parameters, upstream and downstream to Sardar Sarovar (SS) Dam, were examined to determine the periodical change in nutrient fluxes from the Narmada River, India. During this 11-year period, the average discharge of the Narmada River upstream to Rajghat (35.3 km3 year−1) was higher than that of downstream at Garudeshwar (33.9 km3 year−1). However, during the same period, the suspended sediment load was reduced by 21 million tons (MT) from 37.9 MT at Rajghat to 16.7 MT at Garudeshwar. Similarly, mean concentrations of dissolved silica (DSi) reduced from 470 (upstream) to 214 µM (downstream), dissolved inorganic phosphate (DIP) from 0.84 to 0.38 µM, and dissolved inorganic nitrogen (DIN) from 43 to 1.5 µM. It means that about 54%, 55%, and 96% flux of DSi, DIP, and DIN retained behind the dam, respectively. The estimated denitrification rate (80,000 kg N km−2 year−1) for the reservoir is significantly higher than N removal by lentic systems, globally. We hypothesize that processes such as biological uptake and denitrification under anoxic conditions could be a key reason for the significant loss of nutrients, particularly of DIN. Finally, we anticipated that a decline in DIN fluxes (by 1.13 × 109 mol year−1) from the Narmada River to the Arabian Sea might reduce the atmospheric CO2 fixation by 7.46 × 109 mol year−1.

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Quantification of anammox activity in a denitrification reactor for a recirculating aquaculture system

Aquaculture ◽

10.1016/j.aquaculture.2008.11.020 ◽

2009 ◽

Vol 288 (1-2) ◽

pp. 76-82 ◽

Cited By ~ 31

Author(s):

Ori Lahav ◽

Iris Bar Massada ◽

Dimitry Yackoubov ◽

Ruth Zelikson ◽

Noam Mozes ◽

...

Keyword(s):

Recirculating Aquaculture System ◽

Recirculating Aquaculture ◽

Aquaculture System ◽

Anammox Activity ◽

Denitrification Reactor

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Nitrite reduction and methanogenesis in a single-stage UASB reactor

Water Science & Technology ◽

10.2166/wst.2015.446 ◽

2015 ◽

Vol 72 (12) ◽

pp. 2236-2242 ◽

Cited By ~ 2

Author(s):

L. I. Borges ◽

C. M. López-Vazquez ◽

H. García ◽

J. B. van Lier

Keyword(s):

Domestic Wastewater ◽

High Strength ◽

Single Stage ◽

Nitrite Reduction ◽

Upflow Anaerobic Sludge Blanket ◽

Uasb Reactor ◽

Organic Loading Rate ◽

Anaerobic Sludge ◽

N Removal

In this study, nitrite reduction and methanogenesis in a single-stage upflow anaerobic sludge blanket (UASB) reactor was investigated, using high-strength synthetic domestic wastewater as substrate. To assess long-term effects and evaluate the mechanisms that allow successful nitrite reduction and methanogenesis in a single-stage UASB, sludge was exposed to relatively high nitrite loading rates (315 ± 13 mgNO2−-N/(l.d)), using a chemical oxygen demand (COD) to nitrogen ratio of 18 gCOD/gNO2−-N, and an organic loading rate of 5.4 ± 0.2 gCOD/(l.d). In parallel, the effects of sludge morphology on methanogenesis inhibition were studied by performing short-term batch activity tests at different COD/NO2−-N ratios with anaerobic sludge samples. In long-term tests, denitrification was practically complete and COD removal efficiency did not change significantly after nitrite addition. Furthermore, methane production only decreased by 13%, agreeing with the reducing equivalents requirement for complete NO2− reduction to N2. Apparently, the spatial separation of denitrification and methanogenesis zones inside the UASB reactor allowed nitrite reduction and methanogenesis to occur at the same moment. Batch tests showed that granules seem to protect methanogens from nitrite inhibition, probably due to transport limitations. Combined COD and N removal via nitrite in a single-stage UASB reactor could be a feasible technology to treat high-strength domestic wastewater.

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The effect of prior long-term recellularization with keratocytes of decellularized porcine corneas implanted in a rabbit anterior lamellar keratoplasty model

10.1101/2020.12.31.424936 ◽

2020 ◽

Author(s):

Julia Fernández-Pérez ◽

Peter W. Madden ◽

Robert Thomas Brady ◽

Peter F. Nowlan ◽

Mark Ahearne

Keyword(s):

Stromal Cells ◽

Scar Tissue ◽

Dendritic Morphology ◽

Lamellar Keratoplasty ◽

Human Cornea ◽

Serum Free ◽

Anterior Lamellar Keratoplasty ◽

Potential Alternative

AbstractDecellularized porcine corneal scaffolds are a potential alternative to human cornea for keratoplasty. Although clinical trials have reported promising results, there can be corneal haze or scar tissue. Here, we examined if recellularizing the scaffolds with human keratocytes would result in a better outcome. Scaffolds were prepared that retained little DNA (14.89 ± 5.56 ng/mg) and demonstrated a lack of cytotoxicity by in vitro. The scaffolds were recellularized using human corneal stromal cells and cultured for between 14 in serum-supplemented media followed by a further 14 days in either serum free or serum-supplemented media. All groups showed full-depth cell penetration after 14 days. When serum was present, staining for ALDH3A1 remained weak but after serum-free culture, staining was brighter and the keratocytes adopted a native dendritic morphology with an increase (p < 0.05) of keratocan, decorin, lumican and CD34 gene expression. A rabbit anterior lamellar keratoplasty model was used to compare implanting a 250 µm thick decellularized lenticule against one that had been recellularized with human stromal cells. In both groups, host rabbit epithelium covered the implants, but transparency was not restored after 3 months. Post-mortem histology showed under the epithelium, a less-compact collagen layer, which appeared to be a regenerating zone with some α-SMA staining, indicating fibrotic cells. In the posterior scaffold, ALDH1A1 staining was present in all the acellular scaffold, but in only one of the recellularized lenticules. We conclude that recellularization with keratocytes alone may not be sufficiently beneficial to justify introducing allogeneic cells without concurrent treatment to further manage keratocyte phenotype.

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