Topic
Ammonia
About: Ammonia is a research topic. Over the lifetime, 16217 publications have been published within this topic receiving 271940 citations. The topic is also known as: NH3 & azane.
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TL;DR: Growth of both AOA and AOB at high ammonium concentration is demonstrated, a hypothesis that ammonium supplied continuously at low rates is preferentially oxidised by AOA is tested, with lower N2O yield than expected for AOB-dominated processes, suggesting lower emissions when AOA dominate ammonia oxidation.
Abstract: High and low rates of ammonium supply are believed to favour ammonia-oxidising bacteria (AOB) and archaea (AOA), respectively. Although their contrasting affinities for ammonium are suggested to account for these differences, the influence of ammonia concentration on AOA and AOB has not been tested under environmental conditions. In addition, while both AOB and AOA contribute to nitrous oxide (N2O) emissions from soil, N2O yields (N2O–N produced per NO2−–N generated from ammonia oxidation) of AOA are lower, suggesting lower emissions when AOA dominate ammonia oxidation. This study tested the hypothesis that ammonium supplied continuously at low rates is preferentially oxidised by AOA, with lower N2O yield than expected for AOB-dominated processes. Soil microcosms were supplied with water, urea or a slow release, urea-based fertiliser and 1-octyne (inhibiting only AOB) was applied to distinguish AOA and AOB activity and associated N2O production. Low ammonium supply, from mineralisation of organic matter, or of the fertiliser, led to growth, ammonia oxidation and N2O production by AOA only, with low N2O yield. High ammonium supply, from free urea within the fertiliser or after urea addition, led to growth of both groups, but AOB-dominated ammonia oxidation was associated with twofold greater N2O yield than that dominated by AOA. This study therefore demonstrates growth of both AOA and AOB at high ammonium concentration, confirms AOA dominance during low ammonium supply and suggests that slow release or organic fertilisers potentially mitigate N2O emissions through differences in niche specialisation and N2O production mechanisms in AOA and AOB.
226 citations
TL;DR: An enhanced version of the widely acknowledged IWA (formerly IAWQ) activated sludge models is suggested, suggesting that inhibition and limitation by nitrous acid and unionised ammonia have often been overestimated and the bicarbonate concentration proved to be crucial for the process.
226 citations
TL;DR: In this paper, the effects of acetate and different salts present in the feeding of a SHARON reactor have been evaluated, and it was shown that concentrations up to 0.2 g TOC/L did not exert significant effect on the ammonia oxidation to nitrite.
224 citations
TL;DR: It was found out that negative effect of low ammonia nitrogen concentration on biomass is caused not only by low buffer capacity but also by insufficiency of nitrogen as nutrient.
Abstract: Ammonia increases buffer capacity of methanogenic medium in mesophilic anaerobic reactor thus increasing the stability of anaerobic digestion process. Optimal ammonia concentration ensures sufficient buffer capacity while not inhibiting the process. It was found out in this paper that this optimum depends on the quality of anaerobic sludge under investigation. The optimal concentrations for methanogens were 2.1, 2.6 and 3.1 g/L of ammonia nitrogen in dependence on inoculum origin. High ammonia nitrogen concentration (4.0 g/L) inhibited methane production, while low ammonia nitrogen concentration (0.5 g/L) caused low methane yield, loss of biomass (as VSS) and loss of the aceticlastic methanogenic activity. It was found out that negative effect of low ammonia nitrogen concentration on biomass is caused not only by low buffer capacity but also by insufficiency of nitrogen as nutrient. It was also found out that anaerobic sludge with higher ammonia nitrogen concentration (4.2 g/L) tolerates even concentration of volatile fatty acids (160 mmol/L) which causes inhibition of the process with low ammonia nitrogen concentration (0.2 g/L).
223 citations
TL;DR: In this paper, a kinetic model based on a previously proposed reaction scheme was used to describe reaction kinetics measurements for the selective catalytic reduction of nitric oxide by ammonia over a 6 wt% vanadia/titania catalyst.
223 citations