Science topic

Denitrification - Science topic

Nitrate reduction process generally mediated by anaerobic bacteria by which nitrogen available to plants is converted to a gaseous form and lost from the soil or water column. It is a part of the nitrogen cycle.
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What is the behavior of anaerobic bacteria in deep salty groundwater with high level of chlorine? Is the nitrate level deceasing and is denitrification controlled by excess chlorine? Thanks
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Anaerobic bacteria can reduce nitrate to nitrite under anaerobic conditions. Groundwater is affected by the contamination of both inorganic and organic compounds. Common anaerobic redox conditions in ground water are nitrate reducing, manganese reducing, iron reducing, sulphate reducing, and carbon-dioxide reducing. Most are Strict anaerobes while a few facultative anaerobes have also been reported in soils under water or sediment deep water sludge. E. coli is classified as a facultative anaerobe. In chlorinated water it can kill most bacteria in less than a minute, other germs are more chlorine-tolerant.
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Lab scaled biofilm reactor are operated for treatment of wastewater with initial pH = 7.44, the pH of effluent after treatment from reactor increased to 8.15. The percentage removal of COD is greater than 70% with nitrification rate being higher than denitrification rate. What might be the possible reasons for rise in pH contradictory to the decrease in pH that must be observed during reduction of COD and nitrification occurring in the system?
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On a root there is a principle of electrical neutrality so when a cation is taken in a cation need be released.
So, when ammonium is up taken hydrogen ions are released resulting in acidification of the rhizosphere.
In a root when an anion is up taken it must release an anion for the uptake of nitrate the balance is releasing hydroxyl which means the rhizosphere is limed from the rhizosphere release.
In a controlled situation the use of mono and dibasic phosphate can result in a 7.4 buffering and many natural substances also. A carbonate bicarbonate buffer would also be effective.
Hope some of this is useful for your purposes.
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At what cathodic potential (range) we can perform the electrocatalytic denitrification ?
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Javier Ernesto Vilaso Cadre Thank you for your answer.
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Hi All,
I wondered if anyone knows of published examples of the denitrification capacity (e.g., weakly reducing aquifers) of an aquifer being overwhelmed? I thought that weakly buffered (e.g., NO3-or MnIV-reducing) aquifers might be more easily overwhelmed by high nitrate loading rates.
Many thanks for considering my question.
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Thanks Paul, I will take a look at the Aussie examples.
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Biodenitrification was performed using Thiobacillus denitrificans in the presence of nanostructures.
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Continuous denitrification is definitely the better way than the discontinuous system. The following article might help you on this aspect:
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Basal Salt Medium culture medium was used to study the denitrification process of Thiobacillus denitrificans ATCC 23644. In this medium, potassium nitrate was added to the medium as the only source of nitrate. To create anaerobic conditions, 4 ml of bacterial suspension was added to 40 ml vials containing 36 ml of BSM medium. The flasks were heated in an incubator (30 ° C) for 24-48 hours. To investigate the nitrification process, microorganisms were inoculated in BSM medium with a concentration of 300 mg / L nitrate. Sampling was performed with an interval of 6 hours and the vials containing microorganisms were centrifuged for 20 minutes at 5000 rpm. After centrifuge, the samples were passed through filter paper and the optical absorption of soluble nitrate at 410 nm was read using a spectrophotometer and the concentration of soluble nitrate would be obtained.
Now I want to measure the growth of microorganisms by spectrophotometer at the same time as measuring nitrate, in other words, I want to conclude that as the growth of microorganisms increases, nitrate in the culture medium decreases. How should I measure the growth of a microorganism? What wavelength should I use? Is a half McFarland concentration of microorganisms necessary?
If you can help me to complete this method, I am very grateful.
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you can measure Optical density
at 600nm.
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Metal nanoparticles St-Fe0 and CQD-Fe0 were incubated in BSM medium with nitrate concentration of 300 mg / L, in three concentrations of nanoparticles equal to 0.05, 0.5, 1 g at 25, 30 and 35 ° C for 48 hours.
In order to investigate the effect of nanoparticle concentration and temperature on the denitrification rate of metal nanoparticles, sampling was performed after 48 hours and the results were evaluated through nitrate kit.
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Elahe Hamdi The correct diluent is the 'mother liquor' - the same ionic and additive make up that is in your undiluted colloidal suspension. This mother liquor could be recovered by centrifuging, dilution, or (usually) by a knowledge of the original formulation. Dilution in DI water is never to be recommended - removes and dilutes all the ions and protective additives and usually results in aggregation and agglomeration.
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Dear all,
Here is a question about the C/N ratio:
We evaluated a novel heterotrophic nitrification-anaerobic denitrification bacteria for nitrogen removal using formic acid as the sole carbon source. The treated wastewater is a biogas slurry that was generated from pig manure digestion, and it has a pH of 9.55 and NH4+-N concentration of 683±8.49 mg/L. The C/N ratios used were 10, 20, 30, 40, and 50. But the optimum one was 40 in the flask trial, which is high. So, with such a high C/N ratio, is there any justification for the economic aspect of the approach in the large-scale application?
Thanks in advance!
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It is depends upon which type of waste you are treating. The optimal parameters for nutrient removal were influent C/N ratios of 5 : 1 and 10 : 1 . Relatively low values of greenhouse gas (GHG) emission rates measured in situ were obtained at a C/N ratio of 5 : 1. The emission rates of CH4 and N2O is considerably lower than that of CO2. The C/N ratio of 5 : 1 exhibited the highest nutrient removal efficiency with the lowest GHG emission rate. The carbon to nitrogen (C/N) ratio is significant in composting because microorganisms need a good balance of carbon and nitrogen (ranging from 25 to 35) in order to remain active. High C/N ratios can lead to prolonged composting duration and low C/N ratios enhance nitrogen loss.
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the soils I am experimenting with is highly sodic (high Na) with a pH of 8.3 to 8.6. When I checked the NH4+ and NO3- concentrations in the soil compared to a reference soil from an unaffected area, NH4+ of the test soil was similar to reference soils at all times; however, NO3- is gradually decreasing. I have two assumptions,
1) Sodicity/alkalinity induce denitrification
2) Sodicity/Alkalinity inhibit nitrification
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Dear Dr Samadhi Gunathunga, see the following useful links:
•Krishnamurthy, S.L., Sharma, P.C., Sharma, D.K. et al. Identification of mega-environments and rice genotypes for general and specific adaptation to saline and alkaline stresses in India. Sci Rep 7, 7968 (2017). https://doi.org/10.1038/s41598-017-08532-7
•Hammerl, V., Kastl, EM., Schloter, M. et al. Influence of rewetting on microbial communities involved in nitrification and denitrification in a grassland soil after a prolonged drought period. Sci Rep 9, 2280 (2019). https://doi.org/10.1038/s41598-018-38147-5
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pulsator technology is used widely in water treatment, but it is an innovation to use it in a SBR process , whili it can enhance the handelling of sludge in settling and draw phase and finally an efficient denitrification.
i wanna know about the primary considerations or impediments in using this technology, of course if there is any !
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Good question. Now superpulsator are in use they are clarifier that combines the principles of a sludge blanket and solids contact system into a single, high-rate, clarification unit. Capable of removing turbidity, color, TOC and other constituents in both municipal and industrial water applications.
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I am about to start experiments on nitrogen removal by MBBR. I started some trial tests in batch mode to see if biofilms form before the main ones, and I have some questions regarding the operation.
1) First and foremost, water keeps evaporating from the reactor, and I do not know how to prevent this.
2) What is the best inoculum (seed sludge) to substrate ratio to start the experiments?
3) What is the best way to measure the filling ratio?
4) What is the optimum range for DO? I have seen several ranges, and I do not know which is the best.
Any other suggestions and references are welcomed.
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Kasra Pourrostami Niavol , Your first question about the evaporation from the reactor. I am very familiar with this problem. A long time ago I learned to use a air humidifier on the airflow that is used for the reactor.
It is essentially a bottle of water which the airflow is passed through. I have the air entering the bottle from a pipe that goes through the lid and end in the bottom of the bottle. The air make bubbles which take up water vapor and this air i take from the headspace in the top of the bottle with a tube into the reactor I work with. I'll look for a picture of a setup.
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Dear community,
I have bacteria that perform the first step of denitrification, so they reduce nitrate to nitrite.
Nitrite accumulates to 1.5 mM in my culture. Then the bacteria stop being active. I assume that there is some kind of feedback inhibition. I would like to remove nitrite from the system so that the bacteria can completely consume all the nitrate. Is there a chemical doing this, which I could use as supplement for my media?
Thanks a lot!
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Yes, you would need sufficient selectivity between the ions
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Can somebody advise of a publication that determines the nitrification and denitrification rates of mixed toilet waste (aka feces and urine only) or at least of pure urine in an MBR or CAS?
I am interested in knowing how much ammonium (nitrification) and nitrate (denitrification) nitrogen is removed per unit of time and unit mass of VSS.
Thank you!
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Dear Pompilia,
Please attached find some recent published papers may help you for determination of nitrification-denitrification rates in wastes.
Good luck.
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Hello colleagues,
We are trying to induce a liner consequences reaction of nitrification follows de nitrification processes. The main challenge is the redox potential. we need to reduce it from 250 mv by the nitrification chamber into -50 mv by the anoxic denitrification chamber. We are using a potassium carbonate to reduce the redox potential. Any new ideas how to reduce the redox potential?
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Thank you Dr. Murphy!
I just sent you an e-mail for a discussion.
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I conducted potential nitrous oxide emission assessment from soil samples following the method previously used by Zhong et al 2018. The samples were incubated for 48 hours, taking gas samples at 0, 24 and 48 hours respectively.
I have read the N2O concentrations from the gas samples collected using GC, and this data is available. Also, available is the soil-dry weight of the soil samples used in the assessment.
I feel somehow stuck at the procedure for final calculation of the potential N2O production using the available concentration readings from the GC.
Has anyone previously undertaken such, or a similar study, and can quickly unstuck me?
How do i proceed to determine the final N2O emitted from the soil samples ?
Thanks in advance
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Best wishes and interested
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I was reading about hydraulic performances and Nitrogen removal processes in bioretention cells as LID, or BMP practices, and just wondered if there would be advantages (or significant negative impacts) if a gravel layer is put on top of the media layer.
There are some aspects that I think of. Any discussions are welcome.
When putting gravel storage layer on top:
(a) we have similar water storage capacity. If we install drainage pipes or orifices in storage layers, we can better prevent overflow (runoff peak goes: gravel layer--discharge vs media layer--gravel layer--discharge)
(b) worry less about groundwater mounds, groundwater intrusion or draining too much groundwater, because the media layers have wetting-drying curves more similar to the original soil
(c) probably can be easier maintained. Consider: sedimentation happen primarily in gravel layer, and the next rain event can flush the large pores
(d) DO drops before water enters soil layer, thus soil media can be more efficient for denitrification per depth
(e) In addition, do denitrification bacteria has higher activity, because the soil layer is adjacent to original soil? Can ammonification and nitrification happen in gravel layer or the interface, and provide higher nitrate concentration to enhance denitrification?
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Our team studied the use of engineered media used in a bioretention tree system to treat stormwater runoff from roof catchments. In this study, there was gravel on top and below the filter media. the key purpose of these gravels was for different functions. The top layer was to disburse the water flow (which was flowing from a higher elevation, the adjacent classroom blocks). Whereas the gravel below is to prevent the soil particles/ smaller grains of particles from coming out of the retention tree system. The key novelty of the system is the self-containment and the relatively small footprint. Hence the control of the soil/ small particulates being washed out is crucial.
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Expecting analytical approach..
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I am performing a denitrification reaction using potassium nitrate. But before performing the experiment I want to know the approximate amount (theoretical) of intermediates formed in the reaction which will help me to compare between the theoretical and experimental amounts of intermediates formed in the denitrification reaction. So can stoichiometry be used for measuring the intermediates formed in denitrification or are there any other methods by which I can calculate the theoretical amount of intermediates formed in denitrification?
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interested
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Hello,
do You know any methods of measurement how many (in cm3 or other units) of undissolved gas (mainly nitrogen) is in activated sludge sample. For example im interested in measurement of how nitrogen bubbles behave after denitrification reactor. How many of them remains trapped in sludge.
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Take a sample with a volumetric drill. Determine the total pore volume by standard methods.
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Hi everyone,
I am designing a wastewater treatment plant for a company which Our company only uses Category III raw materials from healthy slaughtered animals and is approved and certified accordingly in accordance with the applicable regulations.
Our company only uses Category III raw materials from healthy slaughtered animals and is approved and certified accordingly in accordance with the applicable regulations.
Our company only uses Category III raw materials from healthy slaughtered animals and is approved and certified accordingly in accordance with the applicable regulations.
Our company utilized exclusively raw materials of Category III of healthy slaughtered animals and is also approved and according to current regulations for certified accordingly.
Our company utilizes exclusively raw materials of healthy slaughtered animals and produces bone fat and animal protein from it. I would like to have two activated sludge basins, first aerobic for denitrification and then aerobic for nitrification. The cod content of waste water is 3600 mg/l. How can I find out the easily degradable content of COD which can be used as carbon content for denitrification?
How can I calculate the amount of required COD for denitrification?
I would appreciate it, if someone could help me.
Zahra Alipour
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At first, I would like to tell, that I am not sure that the performance of denitrification under aerobic conditions is a good idea.
The amount of COD you need depends upon nitrate concentration to be removed. It means according to nitrate concentration you have to calculate stoichiometrically COD needed.
Regards
Vit
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Why does COD increase over time when external carbon sources are added in the denitrification process in waste water?
After 1 hour, the concentration increased from 30mg/l to 40mg/l after 20 hours.
carbon source : ethanol
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It is clear the observed COD increase over time from 1 hour to 20 hours after adding ethanol is NOT due to the ethanol itself which is readily biodegradable (fast COD/BOD) but to the previously slowly biodegradable COD adsorbed and absorbed by the bacteria which is enzymatically broken down and released in anoxic and anaerobic conditions. That's why we apply the far more efficient simultaneous bio-N-removal process via partial nitritation (NO2-) and anammox. This process does not need the addition of external carbon sources.
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Hello everyone,
In my experiment, I find that N2O emission rates from long-term warmed soils (+2.5 °C; 10 years) do not change during a four-week drought compared to pre-drought level. In control soils (no warming) emission rates decline almost 100%. I am thinking that the long-term warmed soils are better aerated due to intesified dryout dynamics after each wetting and thus soil disaggregation. I get that this may pronounce waterlogging in rewetted soils after drought and influence denitrification. But how does this look like at drought conditions? Which shift on organismal or functional level (within nitrification?) can serve as an explanation for mny observations?
I appreciate any suggestions,
best regards!
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The effects of simulated climate change on N2O emissions and the related functional genes were much more significant in phase II than in phase I in the urea treatments, mainly because of the adaption and growth of the microbial communities following urea application under the simulated conditions. The simulated warmer and drier conditions under the greenhouse gases following urea application significantly increased N2O emissions due to reduced N losses by leaching and enhanced microbial growth. Both AOB and AOA were shown to be able to grow following urea application in phase II following some exposure to urea-N in this strongly acidic soil. The simulated climate change conditions in phase II also changed the composition of AOAwith the species affiliated to marine group 1.1a-associated lineage increasing significantly. The simulated climate change decreased the abundance of all the functional denitrifier genes and the legacy effect stimulated the abundance of nirK and nosZ gene in urea-treated soil. In general, the effect of the simulated climate change was shortlived, with the denitrifier communities being able to recover once exposed to ambient conditions. As plants, which were excluded in our study, can also have significant effects on N2O emissions and related microorganisms, it would be interesting to conduct further studies where there is the presence of plants.
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My lab designed a qPCR assay for amplifying the denitrification gene nirS from DNA extracted from soil. The assay has worked perfectly in the past with almost perfect efficiency and gene copy number results. However, recently we noticed that the assay was underestimating by 2 log (Should be at least 10^5, but coming out as 10^3). This was noticed as the gene copy numbers of the external positive control, Pseudomonas aeruginosa, were 2 logs lower than they should be. We tested a number of things to explain this. We regrew and extracted fresh DNA from a new strain of P. aeruginosa, yet the results were the same. BSA was used in this assay, but was also found to not affect gene copy numbers to this extent. Standards and stocks were all re-quantified using Qubit. We are still unsure what is causing the underestimation and how we should to proceed. Does anyone have any suggestions for troubleshooting this issue? Or know of any published research that ran into similar issues? All suggestions are welcome, thank you.
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what will happen if we combined process of washing hydrogen sulfide from biogas and
denitrification on the WWTP line
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Let's not forget that the hydrogen sulfide H2S as well as the carbon dioxide CO2 in the biogas and the nitrates NO3- in the STP/WWTP are all ACID. Hence sufficient alkalinity would be needed to neutralize these. It is unlikely that the required alkalinity would be available in the sewage/wastewater after full nitrification (NH3+ > NO3-) which consumes a lot of alkalinity. Hence most likely caustic lye NaOH or lime would need to be added just for neutralisation of the wastewater.
However this does not remove/convert the H2S or NO3-.
The nitrates NO3- could in theory provide the chemical oxygen to oxidize the hydrogen sulfide H2S to sulfur S (partial oxidation) and/or to sulfate SO4-- (full oxidation). Unfortunately, the reaction rate is (very) low resulting in (very) large chemical oxidation reactors.
Instead of trying to chemically oxidizing H2S by NO3-, biological H2S oxidation would be more efficient and much faster as we apply successfully in our full scale biological biogas desulfurization units since many years (mainly in Asia).
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I collected effluent samples from a biorention column with the hopes of collecting denitrifying bacteria, following the procedure described in “Inhibition of assimilatory nitrate reductase activity in soil by glutamine and ammonium analogs” by Gregory W. McCarty and John M. Bremner.
To my knowledge, there are at least 3 microbial processes in soils which use NO3- as a substrate:
  • The assimilatory reduction of NO3- to ammonium (NH4+)
  • The dissimilatory reduction of NO3- to NH4+
  • and denitrification, the dissimilatory reaction of NO3- to dinitrogen (N2) and nitrous oxide (N2O)
In the article, L-Glutamine is used to inhibit the activity of assimilatory NO3- reductase (ANR). Might L-Glutamine affect other microbial processes related to denitrification?
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Dear Willow
Your first two reactions are technically possible but the last one is not entirely dissimilatory.
Denitrification is a respiration process (energy producing catabolic) driven mainly by respiratory reduction since denitrifying bacteria use much of the oxidized-N (i.e. NO3, NO2, NO and N2O) as substitutes for O2. The above reactions can be in the cell (membrane) or outside the cell (periplasmic). The use of NO3 for respiration is aided by respiratory nitrate reductase (in membrane) and periplasmic dissimilatory nitrate reductase respectively.
Should assimilatory reduction of NO3 occurs, it is not for the purpose of denitrification (i.e. respiration) and for the purpose of biosynthesis (anabolic) (hence aided by assimilatory nitrate reductase), which is technically a non-respiratory process. If the denitrifying bacteria are in the energy producing (i.e. respiratory) mode, they are unlikely to perform an assimilatory process which is energy taxing.
However, other bacteria might be interested in the assimilatory process hence can reduce NO3 for biosynthesis purpose. Therefore, eliminating the assimilatory nitrate reduction process by inhibition will ensure accurate assessment of the respiratory process of the denitrifying bacteria.
Once NO3 is reduced by respiratory enzymes to NO2 form, the balance of the denitrification is carried out by the remaining NO2 reductase, NO reductase and N2O reductase enzymes. It is generally accepted that the term denitrification can only be used when there is N2O and/or N2 emissions from the process.
It is well known that denitrification is one of the most complex N processes since a sole denitrifying bacteria may not be completing the entire process hence the process is referred to as modular. The main reason is except for the NO reduction (held in the membrane), other reductions can occur outside the host cell (periplasmic) and such reductions can be performed by other bacteria rather than the host bacteria.
As for your query on whether assimilatory nitrate reductase inhibitors can affect the denitrification process, I have not seen any papers/evidence supporting the above process. I hope other workers can shed any light on it.
Kind regards
Selva
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I find opposite and contradictory range for ORP which reported by various researchers who worked on denitrification. I need to reliable reference for ORP range in aerobic, anoxic and anaerobic metabolic conditions. thanks for your contribution
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There is not an accurate value of redox conditions for biological denitrification. The reason is that redox potential depends among others on groundwater chemistry and the measured value ios influenced by chemicaůl processes in water. This is the reason why the correct answer in my opinion is redox potential in the range - 100 mV to + 100 mV is suitable for denitrification.
Regards
Vit
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1 mole of lactate denitrifies 2.2 moles of nitrate (bacterial denitrification).
I need to denitrify 1L of 6000 ppm nitrate and I have 60% Sodium lactate solution. how do I proceed with the calculation?
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Please follow Dr Selva..... regards
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Hello every one,
My master's thesis focuses on the development of a decentralized wastewater treatment method with the purpose of irrigation reuse in a town in India. Based on my research, there is no guideline for irrigation reuse in India. I tried to use international guidelines like USEPA, WHO or EU. All of these guidelines have a focus on human leath risk and the requirments for pathogen removal and BOD are mentioned in them. But they did not mention the required amount of nitrification and denitrification in treatment process. O could not find any limitation for nitrate and ammonia or TN concentration in final effluent. However, I think becuse of ground water pollution risk, there should be a limitation. Otherwise, the nitrate can infiltrate into groundwater. Is there any one who could help me. I really appreciate it.
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With this article on the links below, you will find what you are looking for.
Saudi wastewater reuse standards for agricultural irrigation: Riyadh treatment plants effluent compliance
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  1. I have discovered a novel species of bacteria that belongs to Pseudomonas genus. On the basis of rpoD gene (individually) and 16sRNA+rpoD genes based (concatenated) trees,it shows close similarity to P.alcaligenes (P.aeruginosa lineage).
  2. Genome blast distance phylogeny (GBDP) tree created using Type strain genome server (TYGS), mirrors the similar results with 100 % bootstrap value. Moreover, the "type species" suggested by the TYGS platform on the bases of genome sequences are P.aeruginosa and Azomonas agilis.
My Question: Can I directly say that this soil bacterium is human pathogen? OR This bacterium holds potential for being human pathogen?
P.S: The bacterium was isolated from grassland soil to study their role in nitrogen cycle , more specifically, respiratory ammonifcation /Dissimilatory nitrate reduction/ denitrification.
Regards,
Timsy
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Hi,
Since it shows simililarity to P. alcaligenes, so more likely holds a potential for bioremediation purposes. Pseudomonases in soil are more decomposer than a pathogen.Of course underlying in P. aeruginosa lineage, it can also holds potential for being human pathogen.
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Rhizosphere microorganisms are the main drivers of turnover of organic C, N, and P and thus recycling of organically bound nutrients, for example by ammonification and nitrification, but may also increase N loss via denitrification.
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@ Bayu, Nitrates are the preferred nitrogen source under any situation except water logging conditions. Unlike ammonium, nitrate is non-volatile, so there is no need to incorporate it in the soil when applied by top- or side dressing, which makes it a convenient source for application.Nitrate is mobile in the soil , direct uptake by the plant and have highest efficiency. Plants can use ammonia as a nitrogen source. ... Plants absorb ammonium and nitrate during the assimilation process, after which they are converted into nitrogen-containing organic molecules, such as amino acids and DNA. When the plant takes up ammonium (NH4+), it releases a proton (H+) to the soil solution. Increase of protons concentration around the roots, decreases the pH around the roots. Accordingly, when the plant takes up nitrate (NO3-) it releases bicarbonate (HCO3-), which increases the pH around the roots.
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I have conducted several lab-based incubation experiments to test how estuarine sediment reacts to different nitrate loading. I have a large data set of nutrient and carbon data, as well as data such as pH, ORP, and Conductivity. I havent been able to find a way through literature review, but thought maybe someone might have some advice.
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In Appendix A: supplementary data of our paper,
we explained how we estimated denitrification rate (as well as nitritation and anammox rates) in a PN-anammox system, using nitrite, nitrate, ammonium and DOC data.
Hope it can be useful to you.
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Kindly provide detailed reactions involved in heterotrophic nitrification and aerobic denitrification and how to calculate the gibbs energy of these process
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This software will calculate the GFE for you. It comes with a gas and aqueous database. http://dudleybenton.altervista.org/software/CREST614.zip The software is described in this book https://www.amazon.com/dp/B07SLBZJK3, which is free tomorrow (1/4/2020).
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Dear all,
I was wondering how to determine the denitrification potential of water. Most references are focused on sediment or soil. Can these methods also be used in determination denitrifation of water , epiphyton or biofilm?
Really appreciate your feasible suggestions and references.
Thanks.
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Dear Zhenrong,
Indeed methods for soils and sediments (my main expertise) can also be applied to water samples. It may very well be that activities are much lower depending on the biomass you have in the sample. As Tobias suggest, isotopic methods are among the best, and have a good detection level.
Depending on the budget and analytical possibilities you may have, I'd also consider using regular acetylene blockage and N2O measurements. Selective N2O electrodes are fairly good and give you an on-line measurement (we tried them for measurements using epiphytic samples).
Good luck in your research
Lluis
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Hi, everyone, anybody know the N2O production rate of nitrifiers and denitrifiers on a single cell level, or have related work recommended? especially denitrification.
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@ Dai, production rate depends on the availability of oxygen. For more details please have a look of the attached files.
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i m working on Sulfur and nitrate removal from wastewater treatment. during reviewing papers i observe that the researchers claim that during the autotrophic denitrification of Sulfur and nitrate in the reactor, ammonium (NH4) accumulated in the reactor. but the problem is that why it is accumulated, no one explain the reason. so i want to know why it is accumulated in the reactor. For example i will give one paper as a reference i.e. " Effect of S/N ratio on sulfide removal by autotrophic denitrification". if any one want to see the paragraph, i have highlight it in the paper and have added the paper here..
Need reasonable answers...
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Thank you @ Shalini Gupta for adding a valuable reference paper, can you update me with any latest reference paper, as the one which is given by you is too old i.e. of 1977.
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Current, I am simulating the OPR for irreversible biochemical reactions. The reactions mainly include the processes of nitrification, denitrification, carbon oxidized by oxygen and so on. I noticed that lots of reference use Nernst Equation to solve the ORP, but I tired this method for about half a month and still do not get the results that are well matched with the experimental data.
It is also said that Nernst Equation is only suitable for equilibrium reactions. Does someone who familiar with the ORP calculation can provide some advices and recommend a method for irreversible kinetic reactions. If Butler-Volmer equation is suitable for my situation?
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Yes you can use“Butler-Volmer equation”. Here we argue that the Butler-Volmer equation is unsuited to PEMFC kinetics and offers no advantages over simpler empirical approaches
Redox potential is measured in volts (V), or millivolts (mV). Each species has its own intrinsic redox potential; for example, the more positive the reduction potential (reduction potential is more often used due to general formalism in electrochemistry), the greater the species' affinity for electrons and tendency to be reduced. ORP can reflect the antimicrobial potential of the water.
Empirical models, linear reversible kinetics for irreversible kinetics for the oxygen reduction reaction (ORR), avoiding superfluous parameterization in the Butler-Volmer equation. Reduction of empiricism requires more mechanistically detailed models than the Butler-Volmer equation. You can emphasize that incorrectly formulated kinetic equations risk generating incorrect data or misleading conclusions.
Mathematically, by “Butler-Volmer equation” we mean:
i=i0(exp(βfη)−exp(−αfη))
η=E−Eeq
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Hi, everyone, now I have a question about the efficiency of denitrification and nitrification in N2O production. do you know is there paper or data that talk about this question?
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thank you
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Is the denitrification process and Electric Conductivity related?
can you suggest me some paper or other documents to understand the relations.
Thank you
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The activity of soil microorganisms decreases with increase in electrical conductivity (EC). This impacts soil processes such as denitrification, and nitrification.
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Hi, everyone, here I have some question for you, in order to clarify the N2O production problem, I have done some work in four estuaries of China, focused on the abundance (DNA),activity (cDNA) and divesity of N2O releated groups using quantitive PCR and sequencing method, combined with biomarkers such as amoA(AOA/AOB),nirS/K and nosZ(I/II). however, when it comes to the explaination of the result , I found that biochemical physiology knowlege is important for understanding the reault and drawing a seasonable conclusion. so now I want to seek advice about how do you think about the relationship between oxygen and denitrification? how dose oxygen influence denitrification? on the distribution of gene or through transcriptional and metabolic regulation?
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Denitrification is typically higher in anoxic environments because facultative microbes will preferentially use oxygen as a terminal electron acceptor instead of NO3, until oxygen becomes depleted. Incomplete denitrification leads to release of N2O, as well as nitrification.
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I have to perform a potential denitrification assay on soil samples to measure the capacity of the soil to carry out denitrification under optimal conditions. To perform this assay, the soils need to be made up to 70% water holding capacity, while also having 2ml of nutrient solution added to them. To do this, I calculate the target water volume I need to add to each soil, using gravimetric water content and WHC. I then subtract the 2ml nutrient solution and I am usually left with a small volume of water I need to add to make the soils up to 70% WHC.
However, this time my soils are too damp and the calculated target water volume for each soil is just under 2ml. I do not have the option of sampling again, so I was wondering is there any way of reducing the volume of nutrient solution I add (usually 2ml) to 1ml, while keeping the concentration of the solution the same?
To make the nutrient solution:
i. 75 mM KNO3 (0.758274 g / 100 mL)
ii. 37.5 mM Na-succinate (0.45039 g / 100 mL)
iii. 25 mM glucose (0.6076875 g / 100 mL)
iv. 75 mM Na-acetate (0.61525725 g / 100 mL)
v. Sterile H2O (100 mL)
Then 2ml is added to each sample. Would I simply dissolve the reagents in 50ml water, then add 1ml to each sample? Sorry if this is a basic question, but I just can't seem to wrap my head around it...
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Very attractive discussion, following.
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We have conducted a field experiment to evaluate the effects of infiltration trenches and improved grass species on biomass productivity and soil quality. The result indicates that water conservation through infiltration increased biomass productivity while the available form of nitrogen (ammonia and nitrate) content decreased, but the total N content increased. What would be the possible explanation? The reduction in available N could be related to the increased uptake by the grass, and possible denitrification due to increased soil moisture content because of infiltration trench. The organic matter content has increased with the increased biomass- can this alone explain the increase in total N?
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The increase in organic matter content enhanced the nitrogen availability and this is might be due to additional of plant origin material.
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Hi everyone
It is well-know that most of soil N2O emissions come from N-fertilization. Leguminose perennial crops such as Medicago sativa can reduce N2O emissions, but how?
I understand that such crops do not require any N-fertilizaion (Thus, we have an indirect reduction of emission) and consuidering a life-span of 3-5 years with no soil tillage we reduce the soil areation.
Moreover leguminose are N-Fixing crops since they perfom a symbiotic fixation of atmospheric N2.
But, the things that is still not clear to are:
1) Such N2 wich is fixed by Medicago sativa is it also an intermediate of denitrifcation/nitrification and other soil process? Or is it just the one which is present in the atmosphere?
2) If the answear to the prvious one is positive, can I say that Medicago sativa reduces N2O emission by the fixation of N2 (the intermediate of denitrification/nitrification etc.)?
3) Apart from the atmospheric N2 fixed by Medicago sativa, does this plant catchs some other N from the soil via roots?
Thank you
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Please check the following RG link and PDF attachment.
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Has anyone had any success using DAF FM diacetate, for Nitric Oxide detection, on bacterial or archaeal cells? I am seeing very little literature using this.
If so, are there any specific techniques I should know about for getting it through the cell membrane of various bacterial groups?
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I wan to set up an anaerobic/oxic/anoxic (AOA) SBR for simultaneous nitrification, denitrification and phosphorus removal with aerobic granular sludge. But I'm confused how to maintain the anaerobic and anoxic phase in AOA system.
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Dear Pankaj Kumar Saha: I rocommened you learn the basics of the process and only then to start designing A/O/A SBR for SNDPR system.
Without basic knowledge of the process it is not possible perform quality designing at all.
Best regards
Vit
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Even in nitrogen fixation, both candidates (bugs) can participate but in the case of nitrification, only bacteria? Expecting a good explanation.
Regards!
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Dear Paudel,
Both archaea and bacteria can participate in nitrification. Although, the issue regarding the niche differentiation between ammonium-oxidizing bacteria (AOB) and ammonium-oxidizing archaea (AOA) is still not well settled.
I give you some suggestions to read:
I hope I have helped.
Best regards!
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I have found published research using the the acetylene inhibition technique but what is this the best method?
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I am attaching some papers that could answer your query. You can also contact Dr. MS Aulakh for some of his interesting work.
The following paper is using an incubation technique and measuring the N2O released. You will need an electron capture GC.
Smith, M.S., Tiedje, J.M., 1979. Phases of denitrification following
oxygen depletion in soil. Soil Biol. Biochem. 11, 262±267.
The above articles use N free air incubations. Lots of sophistication will be needed. In case you have a simple lab, can you try with the disappearance of the nitrate and nitrite fraction. Under aerobic conditions, if there is a rapid depletion of the oxidised forms of N, then there is high rate of denitrification.
But for accuracy purposes, you should follow the methods mentioned above.
A book by Aulakh and his co-workers summarize a number of methods available in the Advances in Soil Science 18: p. 1-57.
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Not getting 100% conversion of NO3 to N2.
feed:
CBOD5 -150mg/L
TSS -200mg/L
Ammonia N -60mg/L
TP -10mg/L
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Dear Bhavik,
Of course there are potentially many factors that I am unfamiliar with for your system. However, just on a big picture level, it would seem that there is not enough BOD for the amount of denitrification required (based on the initial BOD/ammonium-N ratio), if this is a classic nitrification/denitrification system. Could that be the problem? Good luck in any case!
- Peter
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I'm PhD candidate of hydrogeology course and interested to read the report of your project( Assessments of denitrification in a karst aquifer system), if it's possible please let me know.
Best Rigards
Majid Kazemi
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This paper may be helpfull:
Best regards
Vit
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Culture media for denitrifying bacteria promotion and isolation. 
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I think that for aerobic denitrifying bacteria you should try:
Enrichment medium (EM)
0.5 g/L (NH4)2SO4, 0.36 g/L KNO3, 4.0 g/L sodium citrate, 0.05% (ratio of volume) of the trace element solution which was composed of 6.5 g/L K2HPO4·3H2O, 2.5 g/L MgSO4·7H2O, 2.5 g/L NaCl, 0.05 g/L FeSO4·7H2O, 0.04 g/L MnSO4·H2O. The final pH was adjusted to 7.0.
Denitrifying medium (DM)
0.36 g/L KNO3, 10.55 g/L Na2HPO4·12H2O, 1.5 g/L KH2PO4, 0.1 g/L MgSO4·7H2O, 4.0 g/L sodium citrate, 0.2% (volume ratio) of trace element solution which included 50.0 g/L EDTA-Na2, 2.2 g/L ZnSO4, 5.5 g/L CaCl2, 5.06 g/L MnCl2·4H2O, 5.0 g/L FeSO4·7H2O, 1.57 g/L CuSO4·5H2O, 1.61 g/L CoCl2·6H2O. The final pH was adjusted to 7.0.
You can find some other options in the articles listed below:
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I have used activated sludge in water denitrification and would like to do denitrifying bacteria identification to infer if they are involved in the process. I don't know which analysis should be carried out and how I can remove bacteria from granular support (the microbial cells are immobilized on graphite)
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Denitrifying bacteria are fairly well known and can be identified by their 16S rRNA genes. Alternatively, you can look for nirS and nirK genes which are indicative of the denitrification pathway. For this you can amplify and sequence these genes from DNA, which will tell you who is present, or from RNA, which will tell you which organisms were actively expressing denitrification genes. If your cells are within the sludge there are several great soil DNA extraction kits out there. These typically work quite well and produce good quantities of DNA.
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I need to analyse Monod kinetics for nitrogen removal from wastewater. Can anyone provide me with alternative biomass estimation methods( instead of VSS)?
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Dear Nitish,
as already mentioned above only a small fraction of (ML)VSS will be nitrifiers/denitrifiers. Anyway, if you are just searching for an alternative method to estimate your biomass in activated sludge (since MLVSS measurement requires some time and sample volume), the following rough rules of thumb (!) so far seemed pretty reliable to me:
1) Carbon content in bacterial cells: 50% (dry weight)
2) MLVSS = 0.8 x MLSS
Therefore, if you measure the TOC (for example Hach Cuvette Test):
3) TOC x 2 = MLVSS
4) TOC x 2.5 = MLSS
Only applicable, if your DOC (dissolved organic carbon) is neglectable in comparison to biomass, otherwise you would have to subtract the DOC.
Be careful to shred your sludge flocks, and don't use pipette tips with narrow openings to avoid sludge separation by pipetting.
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A current modern trickling filter (TF) system with plastic filters has an input of BOD = 200 mg/L, COD = 350 mg/L and TN = 45 mg/L (effluent volume being 15,000 m3/d) has an output (in mg/L) of BOD = 50, TKN = 15, NO3-N = 3, NH4 = 10, TP = 5 and DRP = 3.
Given the high NH4-N in the TF effluent, aeration (by diffusers) appears to be the next obvious step to nitrify. Should such an aeration being performed can good nitrification be achieved without introducing RAS given there is already 50 BOD being present? Given nitrification requires CO2 as a C source, why would it need RAS (organic-C)? Please ignore the next steps involved in denitrification after full nitrification. If you could share any existing cases rather than laboratory studies that will be great.
Kind regards
Selva
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First, NH can not be reduced, but only oxidised ( to NOor NO3 for example).
Second, this is a biological oxidation : then it requires, besides CO2, autotrophic bacteria, which can utilize CO2, by deriving the necessary energy through the oxidation of N forms.
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I am looking for data to run Machine learning algorithms to estimate Dissolved oxygen control of the activated sludge wastewater treatment process using model predictive control.
Historical data from a SCADA system   may work.
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Thanks Carlos
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I am working on N2 production by none denitrifying bacteria. To be sure that N2 produced by these organisms actually is from the N2O route, I need to spike the culture medium with labelled N2O and trace the yield of labelled N2
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buy labeled N2O (don't know if it is possible), or produce it yourself from labeled nitrate, using a denitrifying organism that lacks nosZ. There are several methods to produce N2O chemically (see Wikipedia), but I would not trust them, because you may get a mixture of N oxides.. Good luck!
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Sexual inversion of fish.
Monosex production for intensive cultivation.
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Thanks Tomas, I'm sure the articles will help!
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The hypothesis is that the protons formed during the nitrification react immediately in the denitrification reaction (in a combined system). In a separated system the protons formed during nitrification will react with bicarbonate forming CO2 + H2O leading to a higher decrease in TIC compared with the combined system.
NH4+ + 1,5 O2 -> NO2- + H2O + 2 H+ (nitrification)
NO2- + 0,5 O2 -> NO3- (nitrification)
CH2O + 0,8 NO3- + 0,8 H+  -> 0,4 N2 + 1,75 H2O +1,25 CO2 (denitrification)
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COretention or release from water or wastewater is pH dependant with pH<7 promoting CO2 release, hence nitrification can be expected to reduce inorganic-C via two pathways, (a) nitrifiers use CO2 as a C source to fix C and (b) CO2 release by acidity. However, inorganic-C dynamics may not be entirely influenced by nitrification. Aeration to promote nitrification can also promote CO2 release by oxidation of organic-C. If we ignore the above, continuous nitrification without denitrification could rate limit nitrification since nitrification rates are lower below pH<7 with high build-up of H+, thereby self-limiting the release of CO2 by high acidity. It could be argued that triggering denitrification by ceasing aeration at this point in a 'combined system' could promote alkalinity and when aeration commences again, there is greater potential for nitrification and release and use of CO2.
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Soil fertility.
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In anaerobic fermentation the end product is methane which can be captured for cooking heating and electrical generation. Anaerobic is a condition where oxygen is very limited. In anaerobic fermentation the condition is maintained in a closed container with lots of solid saturating a slurry. Methane as such can be renewal resource from sanitary waste and manures for example.
In aerobid fermentation the end product is carbon dioxide rather than methane.  The aerobic condition is maintained in composting by turning piles of materials which have enough coarse material that they can aerate. 
Anaerobic fermentation by products can have issues with residue toxic materials. In stabilized aerobic composting these issues are taken care of by the composting process. The residues of anaerobic fermentation would be destined for aerobic composting to make them ready of amendment use for plant productions. 
Maintaining of aerobic conditions in composting prevent the anaerobic products which can be harmful for plant growth and generate foul smells not appreciated by residents surrounding the facilties.  Turning of compost piles allows the maintainence of aerobic conditions as well as combining proper ratios of C and N and materials which have the right textures for aeration. 
A simple test for maturity of aerobic compost is the saturation of test material with water and sealing it in a ziplock plastic bag if after 2 days the material generates no foul smell the compost is stabilized and ready for plant use. This simple test is called the stink bag test. Generally anything that smells bad is not good for crop or plant amendment. 
Raw manures can have issues related to their direct use with the right composting or anaerobic fermentation and composting waste with some noxious nature are transformed into valuable inputs and their issues with disposal are greatly minimized by the 80 to 90% consumption of the organic materials. This is criitical for our soil fertility and environmental issues related to synthetic nitrogen and use of raw manures which can contaminate our water systems through the eutrophication which results from excess soluble products in the water which ends in robs water of oxygen needed for fishery health and best recreational use. 
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I am looking for elaboration for measurement of nitrates and ammonium in soil through SKALAR METHODS, but the SKALAR instrument that we have in our Lab, there I have seen, mentioned only for nitrate+nitrite, ammonia and ortho phosphate, how I can calculate ammonium in this method? because I want to estimate the ammonium and nitrate to find out ammonification and nitrification? 
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Do your SKALAR equipment did have the cadmiun column? If you don´t passed through the column containing granulated copper‐cadmium you will measured only nitrite. if you pass the sample through the column you will measured nitrate+nitrite.
Amonia you do it in another channel of the equipment.
best regards
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why is nitrite reduction process associated with denitrification is the most sensitive step to dissolved oxygen concentration while nitrate reduction is the least sensitive step to DO?
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There are more than 2 Nir
Assimilatory nitrite reductase
Cu containig nitrite reductase  (NirK)
Cytochrome containing nitrite reductase 
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There are some literature which states a decline in the rate of Nitrification and increased rate of Denitrification in saline soil. But I am wondering if Sodium ion interact with Nitrate in positive or negative way and its effect mechanism in Non - saline soil. 
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Dear Niguss,
Sindhu and Cornfield (1967) studied the effect of different soil moisture contents (from near the wilting point to water-logging) combined with various levels of added sodium chloride (0.5-2.0%) on the accumulation of mineral nitrogen (ammonia plus nitrate) during incubation (30°) of a neutral clay loam soil for 3 and 6 weeks. Their findings are summarized below.
(1) The optimum moisture content (50% m.w.h.c.) for mineralisation and nitrification was not affected by addition of sodium chloride.
(2) The most pronounced effect of sodium chloride in reducing mineralisation and nitritification occurred at the lowest moisture content and was very marked even at the lowest level (0.5%) of sodium chloride. Nitrification was completely suppressed by 1-2% sodium chloride at all moisture contents but ammonification continued even with 2% sodium chloride. The presence of 1-2% sodium chloride resulted in loss of nitrate at both low and high moisture contents, whilst 0.5% sodium chloride caused loss of nitrate only at 25% m.w.h.c.
For detailed information, I suggest you to read their full paper referred below
Sindhu MA and Cornfield AH (1967) Effect of sodium chloride and moisture content on ammonification and nitrification in incubated soil. Journal of the Science of Food and Agriculture 18(11):505-6.
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Gas chamber is required for monitoring Ammonia volatilization loss and denitrification loss from Rice fields fertilized with neem coated urea and polymer coated urea. Please provide me some mail addresses,contact numbers of authentic manufactures. 
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You can contact bale plucker,bio gas chamber Address: 2 / 16-A, Sri amman nagar coimbatore Tamil Nadu India Phone: 91-422-255501 Fax: 91 Mobile: 8883697736 Contact Person
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What is the best DNDC model for River Basin?
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Dear Prof. Brian,
Thank you so much.
Regards,
Dhananjay
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Denitrification-How is actual COD/NO3 determined for denitrification? Is it ok to take the difference of COD consumed/NO3 reduced for each day
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Dear Nasir,
COD/NO3 ratio in denitrification is a smart way  to ensure your bacteria gets a right dose of electron donor (i.e COD) for reducing your nitrates (electron acceptor).  You must calculate this ratio from your initial concentrations i.e how much COD is available for reduction of say X mg of nitrates.
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The articles I follow as guidelines tend to have differences on to why they decided to use X amount of N-fertilizer to lead to nitrification and denitrification processes. I don't want to *poison my microbiota within the soil but I don't want to prohibit them to feed on a substrate either.
Any idea or any standard guideline I should be aware of when considering amounts of NH4Cl and/or KNO3 specifically for promoting these two processes?
Thank you!
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In arid soils we find that 0.5mM concentration is the best for both the case4s
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I have read many studies which use anaerobic incubation method to determine PMN. My understanding is that when soils are flooded with water,  denitrification processes are enhanced because of lack or oxygen which result in some N lost as a gas and some leached. Are results from this method of incubation in determining PMN an accurate representation of the mineralization process? Does this method then encourage waterlogging in soils?
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Portia,
The objective of this test is to determine NH4-N production after a 7-day anaerobic incubation.  As incubation is done under anaerobic conditions, all NH4+ produced during the incubation remains as NH4+ since the nitrification is restricted by anaerobic conditions.  It is true that any already existing NO3- in the soil sample can be denitrified; but, it does not matter, since the aim of the test is to measure potentially mineralizable N.  It is the biological N availability index recommended by Keeney (1982) and the purpose and usefulness of the test is well explained in Keeney, D.R., 1982. (N availability indices.  Page 711-733, Methods of Soil Analysis Part 2.Agron. Monogr. 9 ASA & SSSA).
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In fact I search a method via instrument or equipment measuring quickly, but may be otherways too
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Hi Musa,
I did the the denitrification in lab following the method (Yoshinari, 1977). You can find the attached file. Hope it might help. 
Cheers,
Xin
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I want to study treatment of  NO3.NO2 by activated carbon. We prepared the following synthetics solution ;KNO3. NH4Cl. What conservation status of NO3 ions for [NO3] in t = 0 constant (stop nitrification and denitrification).
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thank you 
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My project will focus on effects of water level on ecosystem functioning. The study area is lowland polder (clay) grassland and pasture land, so grasses will dominate the surface.
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Hi Martiijn sir,
Denitification can be worked out indirectly as follows:
Analyse initial soil Total N
Analyse Total nitrogen in soil after leaching with water in a column
Analyse leached nitrates
If it needs to be tested after addition of fert., accordingly after the treatment leaving 15 days the same may be done.
Initial Total N + added N if any = x value
Total N after leaching = Y value
Nitrate N in leachate = Z value
Denitrification value =  X - (Y+Z)  if the soil pH is acidic
Denitrification will be still less if the soil pH is alkaline where ammonia volatilization is also accounted.
Thanks
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I want to measure denitrification (only N2O) from decomposing legume cover crop residues in a controlled growth chamber incubation. In some papers, authors add acetylene to the head space. I read this is to prevent N2O from being converted to N2. Is this true? Is it critical to use acetylene for these kind of studies?
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Dear Arun,
If I have undestood well your post, you don't create anaerobic conditions in the controlled growth chamber incubation. So, the C2H2 concentration will play an important role. If you add a 0.1% of C2H2 you will inhibit the N2O production by nitrification.  If you add a 5% of C2H2 you will inhibit the nitrification and the reduction of N2O to N2 by denitrification. So you can calculate it in this way:
N2O production: N2O (incubation without C2H2)
N2O from denitrification: N2O (incubation with 0.1% C2H2)
N2O from denitrification: N2O (incubation without C2H2) - N2O (incubation with 0.1% C2H2)
Total N production from denitrification: (N2O+N2): N2O (incubation with 5% C2H2)
You can check this paper:
Best regards,
Sergio
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If I maintain field capacity, but flush columns on sampling dates, is there a method I can use to return to field capacity quickly and avoid denitrification losses? I am not sure how vacuum suction works. I also have many several replications and don't knowif suction is feasible. 
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Dear Arun,
as Selva saied, you can use tension lysimeters. The system is easy to handle and you can quickly determine and  adjust the tension  to be applied.  Be careful to   choose a sampler appropriate for the column size. In the field we use ceramic lysimeters, while, for column studies, if you need several replicates, you could consider also polymer lysimeters. Take into account that the polymer acts like a molecular cut, so if you want to determine  others parameters (e.g. DOC concentration), is not useful. Let me know if you need more detailed practical informations.
Best regards
Guia
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As  we  all  know that  In the environment soil, primer of nitrite reductase(nirk)   has  been  designed ,but  primer of  nitric oxide reductase(P450nor) has  not .So  if  I  use  the  primer of  nirk to  amplify envrionment  soil  and  the primer  of  cyp55(A1,A2,A3,A4,A5) to amplify fungal  strains(isolate from  the environment   soil ) ,the  result  whether  can  explain  the  fungal  denitrification in the  environment  soil?
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I think that it is hard to convince other people. You can try to use the cyp55 gene to identify the fungal strains in different denitrification condition. Moreover, choose denitrified genes from fungi to describe.
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 Hi,eyeryone.In  the  process of  fungal  denitrification,nitrite  reductase(nir) and  nitric oxide  reductase(P450nor) participate in it. And the  nirk  gene  encodes  the nitrite reductase,cyp55 gene  encodes  nitric  oxide reductase.now  I  have find  the  primer  of  nirk  for  PCR   of  soil  samples,but  the  question is  that  cyp55 is  a super family,different  strain  has  different  primer  of  cyp55,for  example,  primer      of Fusarium oxysporum's cyp55A1 gene has  been fund,now  my  sample from the  rice paddy  soil ,so  I  want  to  find  the  universal primer   target  cyp55 gene,do  you  konw  this  primer?I hope  anything  you  know  could  tell  me.thanks  very  much.I  need  your  help.
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Hi again, sorry for not answering earlier, I was on vacation. The problem with these genes in fungi as their variability. There are some quite degenerate primers for cyp55 genes which can be considered as universal, but from my experiences they produce more than one band after PCR of pure cultures of N2O producing fungi and after sequencing, there is no homology with known cyp55 genes. Other cyp55 primers were designed just for one or a few species so they are not universal at all.
I think it is this reference* but I am not sure if you will be able to read it. I will try to find some other later today, ok?
*Zhang and Shoun 2008. Purification and Functional analysis of fungal nitric oxide reductase cytochrome P450nor. In Poole RK (ed): Methods in Enzymology, vol 437, Globins and other Nitric oxide-reactive proteins, part B. pp 117-134
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Recently,I  search  some  papers  about  the  genes  in  the  process  of  fungal  denritriication,and  I   have  search  some  papers  about  nirk  gene  and  cyp55  gene,but  I  can   not  find  any  papers  about  the  genes  of  nitrite  reductase  in the  fungal  denritrification,such  as   dNar  and  aNar  gene.If  you  know  some  papers  about  the  genes in the  function,expecially about   dNar and aNar,please  recommend   some  related  papers   for  me.thanks  very  much.
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Dear Kamp,thank you  very  much for  your  reply. your  advise  is  very  good, most  of  fungal  are  reducing  nitrite  to  nitric oxide,but  it   still  exist  some  fungal  reduce  nrtrate  to  nitric  oxide,but  the  primer  for  nitrate  reductase(nar) is  not  designed.so  now  I  will   only  study  the  nirk and  p450nor  in  fungal  denitrification.and shoun's paper  your  recommed    is  very  good,and  I  will  follow  shoun‘team,for  shoun  is  my  idol.thanks  again.best wishes.
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Recently I  read Hirofumi Shoun‘paper “denitrification by fungi ”,in this  paper ,he said  that  some  of  fungus  lack  N2O  reductase? I don  not  konw  why ,whether  because  some  of  them  lack  p-450nor?or  depend  on  species? I can not  contact Hirofumi Shoun,so if  you konw the  reason, please  tell me  the  reseason .or  tell me  some  related  papers.thank  you  very  much!
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I think that there is a little misunderstanding between you and the review. The nitrogen cycle is very complex and hard to follow. Bacteria, for sure, are the dominant organisms responsible for the full pathway of denitrification from nitrates upto N2. On the other hand, fungal denitrification ends with N2O (lack of N2O reductases). The sentence "other fungi might show great ability to reduce N2O to N2" is to my opinion just a theory - not proven yet. As I wrote previously, there is co-denitrification pathway for N2 production from N2O by fungi as well as nitrifier denitrification pathway.
However there are some errors in this review as I can see - the N2O-reductase is not NOR but shoud be NOS or N2OR!
Try some more papers:
Ma et al., Soil Formate Regulates the Fungal Nitrous Oxide Emission Pathway. Appl. Environ. Microbiol. 74, 6690-6696 (2008); doi: 10.1128/AEM.00797-08.
Siciliano et al. Nitrifier dominance of Arctic soil nitrous oxide emissions arises due to fungal competition with denitrifiers for nitrate. Soil Biology & Biochemistry 41, 1104–1110 (2009); doi:10.1016/j.soilbio.2009.02.024
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if this organism could denitrify efficiently in the existence of DO, why do we need thiosulfate then ? 
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It is to inhibite the nitrification (enzimatic)
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Table 5.1 page 110 in IWA report No 9: Activated Sludge Models ASM1, ASM2, ASM2d and ASM3: Conservatives of Nitrogen:
I would like to know how to calculate conversion factors of SNH4, SN3 and SNOx to get 1? Because I want to calculate this value of SNO2, SN2O and SNO.
Thank you
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I would suggest having a look at our book Guidelines for using activated sludge models (IWA Scientific and Technical Report No. 22). You may also want to get a copy of Gujer and Larsen (1995, published in Water Science & Technology). Or drop me an email.