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Application of inorganic nitrogen (N) fertilizers in agriculture can increase emissions of nitrous oxide, a potent greenhouse gas, leaching of nitrate (NO 3 ), a groundwater contaminant hazardous to human health, and soil acidification. Soil amendment with biochar potentially mitigates these losses and undesirable outcomes. However, there have been considerable inconsistencies in reported impacts, likely owing to variable physiochemical characteristics of the biochar materials and/or the soil environment. This study methodically evaluated the impact of biochar soil incorporation on N transformation and underlying microbial processes using soils with varying biochar types, soil texture, soil moisture, and manure compost co- amendments. Laboratory incubations were conducted to monitor the fate of urea fertilizer N spiked in biochar amended and unamended soils by assaying soil ammonium (NH - ), a groundwater contaminant hazardous to human health, and soil acidification. Soil amendment with biochar potentially mitigates these losses and undesirable outcomes. However, there have been considerable inconsistencies in reported impacts, likely owing to variable physiochemical characteristics of the biochar materials and/or the soil environment. This study methodically evaluated the impact of biochar soil incorporation on N transformation and underlying microbial processes using soils with varying biochar types, soil texture, soil moisture, and manure compost co- amendments. Laboratory incubations were conducted to monitor the fate of urea fertilizer N spiked in biochar amended and unamended soils by assaying soil ammonium (NH 4 + concentrations, pH, and abundances of soil nitrifiers; ammonia oxidizing bacteria and archaea (AOB and AOA) and Nitrospira with the capacity to perform complete ammonia oxidation (comammox). Soil moisture was a critical factor affecting N transformation processes, more so than biochar, but biochar did result in significantly different concentrations of N species in response to urea application. Biochar enhanced nitrification, more significantly in drier conditions and in sandy soil. Biochar offered some buffering potential in the neutral-alkaline, unsaturated soils, preventing >1 unit drop in pH compared to unamended soils. Co-application of biochar with manure composts enhanced nitrification slightly, which was evidenced by higher abundances of some soil nitrifiers at 4 weeks, although increases in nitrification rates were not statistically significant. Soil nitrifier populations tended to increase in response to a pinewood biochar, but trends differed for saturated soil, in soils of differing textures, or when different biochar materials were evaluated. Thus, when evaluating implications of biochar on the fate of mineral N fertilizer, soil moisture and other environment conditions should be considered.2 - ), and NO 3 - concentrations, pH, and abundances of soil nitrifiers; ammonia oxidizing bacteria and archaea (AOB and AOA) and Nitrospira with the capacity to perform complete ammonia oxidation (comammox). Soil moisture was a critical factor affecting N transformation processes, more so than biochar, but biochar did result in significantly different concentrations of N species in response to urea application. Biochar enhanced nitrification, more significantly in drier conditions and in sandy soil. Biochar offered some buffering potential in the neutral-alkaline, unsaturated soils, preventing >1 unit drop in pH compared to unamended soils. Co-application of biochar with manure composts enhanced nitrification slightly, which was evidenced by higher abundances of some soil nitrifiers at 4 weeks, although increases in nitrification rates were not statistically significant. Soil nitrifier populations tended to increase in response to a pinewood biochar, but trends differed for saturated soil, in soils of differing textures, or when different biochar materials were evaluated. Thus, when evaluating implications of biochar on the fate of mineral N fertilizer, soil moisture and other environment conditions should be considered., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Suduan Gao reports financial support was provided by United States Department of Agriculture Agricultural Research Service., (Published by Elsevier B.V.)

Heterotrophic nitrification and aerobic denitrification (HNAD) sludge were successfully acclimated. The effects of organics and dissolved oxygen (DO) on nitrogen and phosphorus removal by the HNAD sludge were investigated. The nitrogen can be heterotrophically nitrified and denitrified in the sludge at a DO of 6 mg/L. The TOC/N (total organic carbon to nitrogen) ratio of 3 was found to result in removal efficiencies of over 88% for nitrogen and 99% for phosphorus. The use of demand-driven aeration with a TOC/N ratio of 1.7 improved nitrogen and phosphorus removal from 35.68% and 48.17% to 68% and 93%, respectively. The kinetics analysis generated an empirical formula, Ammonia oxidation rate = 0.08917·(TOC·Ammonia) 0.329 ·Biomass 0.342 . The nitrogen, carbon, glycogen, and poly-β-hydroxybutyric acid (PHB) metabolism pathways of HNAD sludge were constructed using the Kyoto Encyclopedia of Genes and Genomes (KEGG). The findings suggest that heterotrophic nitrification precedes aerobic denitrification, glycogen synthesis, and PHB synthesis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

In extent of this study, ammonium removal from wastewater through biological nitrification process was performed in upflow biofilm reactors. The effects of hydraulic retention time (HRT) and nitrogen loading rate (NLR) on the nitrification process were investigated. For the nitrification process, the optimum HRT and NLR were determined to be 80 hr and 0.044 kg/m 3 .day, respectively. It is observed that the efficiency increased from 53% to 96% along with the increase in HRT from 22 hr to 80 hr and the decrease in NLR from 0.165 kg/m 3 .day to 0.044 kg/m 3 .day.The substrate consumption kinetics were studied in the attached growth reactor, and the Monod kinetic model, first-order kinetic model, modified Stover-Kincannon and Grau second-order kinetic models were examined. For the substrate consumption kinetic study, experimental studies were performed at 125, 150, 175, 200, 225 mg NH 4 -N/L substrate concentrations and 62 hr at HRT during the nitrification process. As a result of the considering kinetic studies, it was determined that the kinetic study was suitable for the modified Stover-Kincannon kinetic model that had the highest coefficient of regression by 0.997 and when the effluent NH 4 -N concentrations and NH 4 -N removal efficiencies calculated using kinetic models were examined, it was observed that the results closest to the experimental results (4.5, 10.1, 19.7, 26.2 and 42.3 mg NH 4 -N/L) were obtained through the modified Stover-Kincannon model (4.16, 10.71, 18.92, 28.12 and 39.51 mg NH 4 -N/L).

To overcome a large amount of nitrite accumulation and poor removal rate for hydroxylamine, a simultaneous nitrification and denitrification (SND) bacterium was isolated and identified as Pseudomonas taiwanensis EN-F2 by DNA sequencing. Strain EN-F2 could remove 100% of ammonium (52.90 mg/L), 100% of hydroxylamine (23.32 mg/L), 86.99% of nitrite (56.32 mg/L) and 89.21% of nitrate (56.18 mg/L) with a maximum removal rate of 8.72, 2.12, 4.55 and 5.80 mg/L/h, respectively. Ammonium and hydroxylamine could be preferentially removed during the SND process. The nitrite removal rate and cell growth were substantially enhanced by 2.10 mg/L/h and 0.45 after supplementation of hydroxylamine. The specific activities of ammonia monooxygenase (AMO), hydroxylamine oxidoreductase (HAO), nitrate reductase (NR), nitrite reductase (NIR) were successfully detected as 0.95, 0.31, 0.42 and 0.03 U/mg protein, respectively. All results demonstrated that strain EN-F2 could perform SND to remove multiple nitrogen sources from wastewater., (Copyright © 2022. Published by Elsevier Ltd.)

Due to the diverse speciation and biochemical characteristics of nitrogen in urban runoff, excess nitrogen continues to be a major source of eutrophication in receiving waters. The performance of a nitrifying-sorptive Clinoptilolite (ZT) was examined for use in a media-based stormwater control measure (SCM) for ammonium removal. Results suggested that columns operated under continuous feed showed more nitrification as the media approached ammonium exhaustion. Influent concentrations of 2.5 and 5 mg NH 4 + N] of 1.2 and 1.7 mg/L, respectively. The performance of the media under intermittent flow regime showed lower effluent ammonium, nitrification between simulated saturated periods, and could treat an additional 70 bed volumes of simulated runoff when compared to a column receiving identical continuous feed. However, nitrification was not sufficient to prevent desorption of ammonium during drops in influent NH 3 -N concentrations. Use of Clinoptilolite for ammonium sorption/nitrification is a systematic approach for capture and transformation of incoming/mineralized ammonium to nitrate prior to reaching an anoxic/denitrifying zone within SCMs. PRACTITIONER POINTS: Clinoptilolite can accumulate stormwater ammonium, allowing it to be nitrified. Ammonium nitrification will regenerate exchange sites on the clinoptilolite. Intermittent flow conditions allowed more nitrification between stormwater events.- N] of 1.2 and 1.7 mg/L, respectively. The performance of the media under intermittent flow regime showed lower effluent ammonium, nitrification between simulated saturated periods, and could treat an additional 70 bed volumes of simulated runoff when compared to a column receiving identical continuous feed. However, nitrification was not sufficient to prevent desorption of ammonium during drops in influent NH 4 + -N concentrations. Use of Clinoptilolite for ammonium sorption/nitrification is a systematic approach for capture and transformation of incoming/mineralized ammonium to nitrate prior to reaching an anoxic/denitrifying zone within SCMs. PRACTITIONER POINTS: Clinoptilolite can accumulate stormwater ammonium, allowing it to be nitrified. Ammonium nitrification will regenerate exchange sites on the clinoptilolite. Intermittent flow conditions allowed more nitrification between stormwater events., (© 2021 Water Environment Federation.)

We studied the effects of urease/nitrification inhibitor combinations on urea hydrolysis and nitrification, aiming to screen out the effective inhibitor combinations for black soil and cinnamon soil in Northeast China. Urease inhibitor, N-butyl thiophosphate-triamine (NBPT), and its combination with nitrification inhibitor dicyandiamide (DCD), 3, 4-dimethylpyrazole phosphate (DMPP), 2-chloro-6 (trichloromethyl)-pyridine (CP), 2-amino-4-chloro-6-methylpyrimidine (AM) and 3-methylpyrazole (MP) were added to urea separately. Samples were collected 15 times in each of all the treatments during 125 days. We examined the changes of urea nitrogen, ammo-nium, nitrate, and nitrification inhibition rate in the two soils. Our results showed the hydrolysis of urea in black soil and cinnamon soil was about 7 d, and the addition of NBPT with or without diffe-rent nitrification inhibitors slowed down the hydrolysis to 21 d at least. Compared with the treatment with common urea, inhibitor addition significantly increased soil NH 4 + -N, decreased soil NO 3 -N content in soil for a longer time. In black soil, application with nitrification inhibitor inhibited soil nitrification significantly and lasted for more than 125 d. DMPP and CP combined with NBPT increased the NH - -N content in black soil by 1.6-1.8 times, while the nitrification inhibition rate was 47.9% and 24.1% at 125 d, respectively. In the cinnamon soil, the application of nitrification inhibitor could prolong the duration of ammonium oxidation from 80 d to 110 d. DCD and DMPP combined with NBPT increased the NH 4 -N content in cinnamon soil by 2.1-3.4 times, while the nitrification inhibition rates at 125 d were 25.3% and 23.2%, respectively. Therefore, NBPT+DMPP combination with urea was recommended for utilization in black soil, followed by NBPT+CP. In cinnamon soil, NBPT+DCD combination with urea was recommended, followed by NBPT+DMPP.+ -N content in soil for a longer time. In black soil, application with nitrification inhibitor inhibited soil nitrification significantly and lasted for more than 125 d. DMPP and CP combined with NBPT increased the NH 4 + -N content in black soil by 1.6-1.8 times, while the nitrification inhibition rate was 47.9% and 24.1% at 125 d, respectively. In the cinnamon soil, the application of nitrification inhibitor could prolong the duration of ammonium oxidation from 80 d to 110 d. DCD and DMPP combined with NBPT increased the NH 4 + -N content in cinnamon soil by 2.1-3.4 times, while the nitrification inhibition rates at 125 d were 25.3% and 23.2%, respectively. Therefore, NBPT+DMPP combination with urea was recommended for utilization in black soil, followed by NBPT+CP. In cinnamon soil, NBPT+DCD combination with urea was recommended, followed by NBPT+DMPP.

A heterotrophic nitrifying bacterium was isolated from the activated sludge and identified as Pseudomonas stutzeri GEP-01. Strain GEP-01 exhibited an efficient heterotrophic nitrification capability and a high nitrogen utilization rate, 48 mg/L NH 4 + -N was removed after culturing for 24 h without NO 2 - -N was removed by heterotrophic nitrification. Single-factor experiments indicated that factors such as the carbon source, temperature, NH 3 -N load, and inoculum size had significant effects on the ammonium removal efficiency of strain GEP-01. The preferred conditions for heterotrophic nitrification were sodium citrate, 30 °C, 40 mg/L NH - -N accumulation, and 64.7% of the NH 4 -N amounts were 100, 200, 500 and 1000 mg/L, the removal rates were approximately 100%, 93%, 90.4%, and 78.9%, respectively, and higher ammonium concentrations require longer culture time. Nitrogen balance demonstrated that 40% of the initial nitrogen was lost, which was probably removed in the form of gas products under optimum culture conditions, and 36.3% of NH + -N was converted to biomass. When incubated (adding a small amount of sodium citrate as carbon source and no carbon source) in swine wastewater containing 835 mg/L of ammonium, the removal ratio reached 56.3% and 24.8%. Strain GEP-01 has potential applications in the treatment of ammonium-rich wastewater.4 + -N load, and inoculum size had significant effects on the ammonium removal efficiency of strain GEP-01. The preferred conditions for heterotrophic nitrification were sodium citrate, 30 °C, 40 mg/L NH 4 + -N, and 5% inoculum size. When the initial NH 4 + -N amounts were 100, 200, 500 and 1000 mg/L, the removal rates were approximately 100%, 93%, 90.4%, and 78.9%, respectively, and higher ammonium concentrations require longer culture time. Nitrogen balance demonstrated that 40% of the initial nitrogen was lost, which was probably removed in the form of gas products under optimum culture conditions, and 36.3% of NH 4 + -N was converted to biomass. When incubated (adding a small amount of sodium citrate as carbon source and no carbon source) in swine wastewater containing 835 mg/L of ammonium, the removal ratio reached 56.3% and 24.8%. Strain GEP-01 has potential applications in the treatment of ammonium-rich wastewater.

Chronic elevated nitrogen (N) deposition has altered the N status of temperate forests, with significant implications for ecosystem function. The Bear Brook Watershed in Maine (BBWM) is a whole paired watershed manipulation experiment established to study the effects of N and sulfur (S) deposition on ecosystem function. N was added bimonthly as (NH 4 ) 2 SO 4 to one watershed from 1989 to 2016, and research at the site has studied the evolution of ecosystem response to the treatment through time. Here, we synthesize results from 27 years of research at the site and describe the temporal trend of N availability and N mineralization at BBWM in response to chronic N deposition. Our findings suggest that there was a delayed response in soil N dynamics, since labile soil N concentrations did not show increases in the treated watershed (West Bear, WB) compared to the reference watershed (East Bear, EB) until after the first 4 years of treatment. Labile N became increasingly available in WB through time, and after 25 years of manipulations, treated soils had 10× more extractable ammonium than EB soils. The WB soils had 200× more extractable nitrate than EB soils, driven by both, high nitrate concentrations in WB and low nitrate concentrations in EB. Nitrification rates increased in WB soils and accounted for ~ 50% of net N mineralization, compared to ~ 5% in EB soils. The study provides evidence of the decadal evolution in soil function at BBWM and illustrates the importance of long-term data to capture ecosystem response to chronic disturbance.

Drinking water treatment plants based on groundwater may suffer from incomplete ammonium removal, which deteriorates drinking water quality and constrains water utilities in the operation of their plants. Ammonium is normally removed through nitrification in biological granular media filters, and recent studies have demonstrated that dosing of copper can stimulate the removal of ammonium. Here, we investigated if copper dosing could generically improve ammonium removal of biofilters, at treatment plants with different characteristics. Copper was dosed at ≤1.5 μg Cu/L to biofilters at 10 groundwater treatment plants, all of which had displayed several years of incomplete nitrification. Plants exceeded the Danish national water quality standard of 0.05 mg NH 4 /L by a factor of 2-12. Within only 2-3 weeks of dosing, ammonium removal rates increased significantly (up to 150%). Nitrification was fully established, with ammonium effluent concentrations of <0.01 mg NH + -N/L at most plants, regardless of the differences in raw water chemistry, ammonium loading rates, filter design and operation, or treatment plant configuration. However, for filters without primary filtration, it took longer time to reach complete ammonium removal than for filters receiving prefiltered water, likely due to sorption of copper to iron oxides, at plants without prefiltration. With complete ammonium removal, we subjected two plants to short-term loading rate upshifts, to examine the filters' ability to cope with loading rate variations. After 2 months of dosing and an average loading rate of 1.0 g NH 4 + filter material/h, the loading rate was upshifted by 50%. Yet, a filter managed to completely remove all the influent ammonium, showing that with copper dosing the filter had extra capacity to remove ammonium even beyond its normal loading rates. Depth sampling revealed that the ammonium removal rate of the filter's upper 10 cm increased more than 7-fold from 0.67 to 4.90 g NH 4 + /h, and that nitrite produced from increased ammonium oxidation was completely oxidized further to nitrate. Hence, no problems with nitrite accumulation or breakthrough occurred. Overall, copper dosing generically enhanced nitrification efficiency and allowed a range of quite different plants to meet water quality standards, even at increased loading rates. The capacity increase is highly relevant in practice, as it makes filters more robust towards sudden ammonium loading rate variations.3 filter material/h, the loading rate was upshifted by 50%. Yet, a filter managed to completely remove all the influent ammonium, showing that with copper dosing the filter had extra capacity to remove ammonium even beyond its normal loading rates. Depth sampling revealed that the ammonium removal rate of the filter's upper 10 cm increased more than 7-fold from 0.67 to 4.90 g NH 4 + -N/m 3 /h, and that nitrite produced from increased ammonium oxidation was completely oxidized further to nitrate. Hence, no problems with nitrite accumulation or breakthrough occurred. Overall, copper dosing generically enhanced nitrification efficiency and allowed a range of quite different plants to meet water quality standards, even at increased loading rates. The capacity increase is highly relevant in practice, as it makes filters more robust towards sudden ammonium loading rate variations., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Allylthiourea (ATU) and chlorate (ClO 3 - ) are often used to selectively inhibit nitritation and nitratation. In this work we identified challenges with use of these compounds in inhibitory assays with filter material from a biological rapid sand filter for groundwater treatment. Inhibition was investigated in continuous-flow lab-scale columns, packed with filter material from a full-scale filter and supplied with NH 4 + or NO 2 - . ATU concentrations of 0.1-0.5 mM interfered with the indophenol blue method for NH 4 + quantification leading to underestimation of the measured NH 4 + concentration. Interference was stronger at higher ATU levels and resulted in no NH 4 + detection at 0.5 mM ATU. ClO 3 - at typical concentrations for inhibition assays (1-10 mM) inhibited nitratation by less than 6%, while nitritation was instead inhibited by 91% when NH 4 + was supplied. On the other hand, nitratation was inhibited by 67-71% at 10-20 mM ClO 3 - when NO 2 - was supplied, suggesting significant nitratation inhibition at higher NO 2 - concentrations. No chlorite (ClO 2 - ) was detected in the effluent, and thus we could not confirm that nitritation inhibition was caused by ClO 3 - reduction to ClO 2 - . In conclusion, ATU and ClO 3 - should be used with caution in inhibition assays, because analytical interference and poor selectivity for the targeted process may affect the experimental outcome and compromise result interpretation., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Incomplete nitrification in biological filters during drinking water treatment is problematic, as it compromises drinking water quality. Nitrification problems can be caused by a lack of nutrients for the nitrifying microorganisms. Since copper is an important element in one of the essential enzymes in nitrification, we investigated the effect of copper dosing on nitrification in different biological rapid sand filters treating groundwater. A lab-scale column assay with filter material from a water works demonstrated that addition of a trace metal mixture, including copper, increased ammonium removal compared to a control without addition. Subsequently, another water works was investigated in full-scale, where copper influent concentrations were below 0.05 μg Cu L(-1) and nitrification was incomplete. Copper dosing of less than 5 μg Cu L(-1) to a full-scale filter stimulated ammonium removal within one day, and doubled the filter's removal from 0.22 to 0.46 g NH4-N m(-3) filter material h(-1) within 20 days. The location of ammonium and nitrite oxidation shifted upwards in the filter, with an almost 14-fold increase in ammonium removal rate in the filter's top 10 cm, within 57 days of dosing. To study the persistence of the stimulation, copper was dosed to another filter at the water works for 42 days. After dosing was stopped, nitrification remained complete for at least 238 days. Filter effluent concentrations of up to 1.3 μg Cu L(-1) confirmed that copper fully penetrated the filters, and determination of copper content on filter media revealed a buildup of copper during dosing. The amount of copper stored on filter material gradually decreased after dosing stopped; however at a slower rate than it accumulated. Continuous detection of copper in the filter effluent confirmed a release of copper to the bulk phase. Overall, copper dosing to poorly performing biological rapid sand filters increased ammonium removal rates significantly, achieving effluent concentrations of below 0.01 mg NH4-N L(-1), and had a long-term effect on nitrification performance., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Agricultural activities lead excessive emission of ammonia nitrogen in the environment and can profoundly interfere the equilibrium of the natural ecosystems leading to their contamination. Actually, the biological purification of wastewaters is the most adopted technique thanks to its several advantages such as high performance and low energy consumption. For this reason, two novel strains of Alcaligenes sp. S84S3 and Proteus sp. S19 genus were isolated from an activated sludge and applied in the treatment of ammonium and nitrite in aqueous solution. Under the optimum operating conditions of temperature (30 °C), pH (7), carbon substrate (2 g/L of glucose) and duration of incubation time (69 h), the strain Alcaligenes sp. S84S3 could oxidize 65% of the ammonium as high as 272.72 mg-NH4(+)/L. Moreover, during 48 h, the nitrate reduction rate performed by the strain Proteus S19 was about 99 % without production of nitrite intermediate (negligible concentration). Moreover, the coculture of the strains Alcaligenes sp. S84S3 and Proteus sp. S19 could eliminate 65.83% of the ammonium ions without production of toxic forms of nitrogen oxides during a short time of incubation (118 h) at the same operational conditions with providing the aeration in the first treatment phase. The coculture of our isolated strains is assumed to have a good potential for nitrification and denitrification reactions applied in the treatment of wastewater containing ammonium, nitrite and nitrate. As a result, we can consider that the mixed culture is a practical method in the treatment of high-strength ammonium wastewater with reducing of sludge production.

The first step of nitrification is carried out by ammonia-oxidizing bacteria (AOB) and archaea (AOA). It is largely unknown, by which mechanisms these microbes are capable of coexistence and how their respective contribution to ammonia oxidation may differ with varying soil characteristics. To determine how different levels of ammonium availability influence the extent of archaeal and bacterial contributions to ammonia oxidation, microcosm incubations with controlled ammonium levels were conducted. Net nitrification was monitored and ammonia-oxidizer communities were quantified. Additionally, the nitrification inhibitor allylthiourea (ATU) was applied to discriminate between archaeal and bacterial contributions to soil ammonia oxidation. Thaumarchaeota, which were the only ammonia oxidizers detectable at the start of the incubation, grew in all microcosms, but AOB later became detectable in ammonium amended microcosms. Low and high additions of ammonium increasingly stimulated AOB growth, while AOA were only stimulated by the low addition. Treatment with ATU had no effect on net nitrification and sizes of ammonia-oxidizing communities suggesting that the effective concentration of ATU to discriminate between archaeal and bacterial ammonia oxidation is not the same in different soils. Our results support the niche-differentiating potential of ammonium concentration for AOA and AOB, and we conclude that ammonium limitation can be a major reason for absence of detectable AOB in soil., (© FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Mining and mineral processing of gold-bearing ores often release arsenic to the environment. Ammonium is released when N-based explosives or cyanide are used. Nitrification of simulated As-rich mining waters was investigated in batch bioassays using nitrifying cultures enriched in a fluidized-bed reactor (FBR). Nitrification was maintained at 100mg AsTOT/L. In batch assays, ammonium was totally oxidized by the FBR enrichment in 48 h. As(III) oxidation to As(V) occurred during the first 3h attenuating arsenic toxicity to nitrification. At 150 and 200mg AsTOT/L, nitrification was inhibited by 25%. Candidatus Nitrospira defluvii and other nitrifying species mainly colonized the FBR. In conclusion, the FBR enriched cultures of municipal activated sludge origins tolerated high As concentrations making nitrification a potent process for mining water treatment., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

A bench-scale assay was developed to obtain site-specific nitrification biokinetic information from biological rapid sand filters employed in groundwater treatment. The experimental set-up uses granular material subsampled from a full-scale filter, packed in a column, and operated with controlled and continuous hydraulic and ammonium loading. Flowrates and flow recirculation around the column are chosen to mimic full-scale hydrodynamic conditions, and minimize axial gradients. A reference ammonium loading rate is calculated based on the average loading experienced in the active zone of the full-scale filter. Effluent concentrations of ammonium are analyzed when the bench-scale column is subject to reference loading, from which removal rates are calculated. Subsequently, removal rates above the reference loading are measured by imposing short-term loading variations. A critical loading rate corresponding to the maximum removal rate can be inferred. The assay was successfully applied to characterize biokinetic behavior from a test rapid sand filter; removal rates at reference loading matched those observed from full-scale observations, while a maximum removal capacity of 6.9 g NH4(+)-N/m(3) packed sand/h could easily be determined at 7.5 g NH4(+)-N/m(3) packed sand/h. This assay, with conditions reflecting full-scale observations, and where the biological activity is subject to minimal physical disturbance, provides a simple and fast, yet powerful tool to gain insight in nitrification kinetics in rapid sand filters., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The unique positioning of mangrove ecosystems between land and sea makes them vital in the nitrogen cycle. The role of nitrification in the nitrogen cycle is important to provide nitrogen compounds readily absorbed by mangrove plants. Nevertheless, the nitrification process and nitrifying bacteria in mangrove areas have yet to be comprehensively understood. The primary objective of this study is to provide comprehensive analysis of nitrifying bacteria in mangrove sediments by conducting a systematic review. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses method is used as a guide to help report reviews systematically and has a flow chart to show the process of selecting relevant studies. Data collection was carried out by utilizing 6 databases and journal search engines including Scopus, PubMed, ResearchGate, Google Scholar, and Springer in order to achieve more comprehensive findings. This study employed the widely recognized and commonly used technique of defining the review's scope in a focused manner by first identifying the population, intervention, comparison, and outcome. This study identified 358 studies, and 31 studies were included in the review after screening. Based on the screening results, research on nitrifying bacteria in mangrove sediments is geographically limited to several countries such as Indonesia, Vietnam, Thailand, China, Mexico, the United States, India, and Saudi Arabia. This study vealed that there is a high level of diversity among nitrifying bacteria in mangrove sediment, with five distinct groups identified: ammonia oxidizing bacteria, nitrite oxidizing bacteria, anammox bacteria, and comammox bacteria, a recently identified group. In carrying out changes in nitrogen compounds, nitrifying bacteria use functional genes from different steps of the nitrification process, such as nitrogenase, ammonia monooxygenase subunit A, nitrite oxidoreductase alpha subunit, nitrate reductase alpha chain, nitrite reductase, nitric oxide reductase, nitrous oxide reductase, hydrazine synthase, hydrazine oxidoreductase and hydroxylamine oxidoreductase genes. Ammonia-oxidizing bacteria were the predominant group in general, but various nitrifying bacteria groups were distributed diversely across different mangrove environments. This study also indicated the vegetation type and the distribution of nitrifying bacteria in mangrove sediments. The depth of these sediments typically varies from 0 to 60 centimeters, with most samples taken at a depth of 0 to 20 centimeters. The type of vegetation at the sampling location is dominated by species of Kandelia candel, Avicennia marina, Kandelia obovata, and Rhizophora mangle. Limitations regarding research on nitrifying bacteria in mangrove sediments provide opportunities for in-depth study. This comprehensive review provides an in-depth overview of the variety and spread of nitrifying bacteria, highlighting their role in nitrogen cycling and emphasizing the potential for discovering new nitrifying bacteria in mangrove sediments.

The unique positioning of mangrove ecosystems between land and sea makes them vital in the nitrogen cycle. The role of nitrification in the nitrogen cycle is important to provide nitrogen compounds readily absorbed by mangrove plants. Nevertheless, the nitrification process and nitrifying bacteria in mangrove areas have yet to be comprehensively understood. The primary objective of this study is to provide comprehensive analysis of nitrifying bacteria in mangrove sediments by conducting a systematic review. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses method is used as a guide to help report reviews systematically and has a flow chart to show the process of selecting relevant studies. Data collection was carried out by utilizing 6 databases and journal search engines including Scopus, PubMed, ResearchGate, Google Scholar, and Springer in order to achieve more comprehensive findings. This study employed the widely recognized and commonly used technique of defining the review's scope in a focused manner by first identifying the population, intervention, comparison, and outcome. This study identified 358 studies, and 31 studies were included in the review after screening. Based on the screening results, research on nitrifying bacteria in mangrove sediments is geographically limited to several countries such as Indonesia, Vietnam, Thailand, China, Mexico, the United States, India, and Saudi Arabia. This study vealed that there is a high level of diversity among nitrifying bacteria in mangrove sediment, with five distinct groups identified: ammonia oxidizing bacteria, nitrite oxidizing bacteria, anammox bacteria, and comammox bacteria, a recently identified group. In carrying out changes in nitrogen compounds, nitrifying bacteria use functional genes from different steps of the nitrification process, such as nitrogenase, ammonia monooxygenase subunit A, nitrite oxidoreductase alpha subunit, nitrate reductase alpha chain, nitrite reductase, nitric oxide reductase, nitrous oxide reductase, hydrazine synthase, hydrazine oxidoreductase and hydroxylamine oxidoreductase genes. Ammonia-oxidizing bacteria were the predominant group in general, but various nitrifying bacteria groups were distributed diversely across different mangrove environments. This study also indicated the vegetation type and the distribution of nitrifying bacteria in mangrove sediments. The depth of these sediments typically varies from 0 to 60 centimeters, with most samples taken at a depth of 0 to 20 centimeters. The type of vegetation at the sampling location is dominated by species of Kandelia candel, Avicennia marina, Kandelia obovata, and Rhizophora mangle. Limitations regarding research on nitrifying bacteria in mangrove sediments provide opportunities for in-depth study. This comprehensive review provides an in-depth overview of the variety and spread of nitrifying bacteria, highlighting their role in nitrogen cycling and emphasizing the potential for discovering new nitrifying bacteria in mangrove sediments. [ABSTRACT FROM AUTHOR]

Biological filtration is a process that can be used for ammonium removal from water. The removal of ammonium is based on the nitrification process. Nitrification depends on many factors, such as water quality and filtration process parameters. To investigate the influence of filtration rate on the nitrification efficiency, nitrifying biofilters were formed at the pilot plant in the industry for drinking water production from surface water. The new biological filters were started under optimal conditions for biofilm formation. After the biofilm formation, the influence of the filtration rate on nitrification was examined over 3 months (from November to January). The time required for the spontaneous growth of nitrifying bacteria on the new filters was around 70 days. The operating conditions at the start-up period were the continuous flow of water containing γ(NH4+) ≈ 1mg/L, dissolved oxygen in a concentration >9 mg/L, filtration rate 12 °C and pH from 7.8 to 8. After the complete formation of the nitrifying biofilm, the percentage of NH4+ removal was greater than 95% for all tested filtration rates, from 0.5 to 8.4 m/h, at γ(NH4+) from 1 to 2.5 mg/L and raw water temperature from 13 to 7°C. HIGHLIGHTS Nitrifying biofilm was spontaneously formed on the surface of filter material at the pilot plant.; Ammonium was removed by nitrification during filtration on rapid sand filters.; Ammonium removal efficiency was higher than 95%.; The complete nitrification was achieved even at the highest filtration rate of 8.4 m/h.; Nitrification efficiency decreased at a high filtration rate when water temperature dropped below 7 °C.;

Partial nitrification and Anammox (PN/A) is a low carbon and low consumption process for autotrophic nitrogen removal from wastewater. However, how to effectively intercept the slowly growing AnAOB in the reactor and create a symbiotic habitat between AnAOB and AOB is the key to the stable operation of PN/A. In this study, iron loaded porous biological carrier PVA/PA/Fe is proposed to promote the interception of AnAOB and the symbiosis with AOB, so as to realize the rapid start-up and efficient operation of PN/A. The results showed that PVA/PA/Fe significantly promoted the retention of AnAOB and the co-symbiotic nitrogen removal with AOB, and the abundance of AnAOB increased by 5.93% in Anammox stage and 7.81% in PN/A stage compared with the control group. In the Anammox stage, the reactor with PVA/PA and PVA/PA/Fe carriers showed better impact load resistance, and the NLR could reach 1.01 kg-N/(m3d), while the control group could only stabi lize at 0.61 kg-N/(m3d). The reactor with PVA/PA/Fe carrier reached RETN>85% after 7 days of startup in PN/A phase, while the control group and the reactor with PVA/PA carrier reached this treatment effect after 12 days. The above results provide theoretical and technical guidance for the practical application of PN/A process. [ABSTRACT FROM AUTHOR]

The integrated fixed‐film activated sludge (IFAS) process is considered one of the cutting‐edge solutions to the traditional wastewater treatment challenges, allowing suspended sludge and attached biofilm to grow in the same system. In addition, the coupling of IFAS with anaerobic ammonium oxidation (Anammox) can further improve the efficiency of biological denitrification. This paper summarises the research progress of IFAS coupled with the anammox process, including partial nitrification anammox, simultaneous partial nitrification anammox and denitrification, and partial denitrification anammox technologies, and describes the factors that limit the development of related processes. The effects of dissolved oxygen, influent carbon source, sludge retention time, temperature, microbial community, and nitrite‐oxidising bacteria inhibition methods on the anammox of IFAS are presented. At the same time, this paper gives an outlook on future research focus and engineering practice direction of the process. [ABSTRACT FROM AUTHOR]

The research was conducted for 210 days on a partial nitrification/Anammox system (PN/A) using fixed bed biomass carrier to remove nitrogen in domestic wastewater. Total nitrogen and ammonium removal efficiency reached 69.8 % and 91.4 %, respectivety. In this study, we investigated three kinetic models (the first-order, Grau second-order and Stover Kincannon model) to determine which model is most suitable to describe the kinetics of the partial nitrification and anammox process. The results have shown that the Stover-Kincannon model is the most suitable and applicable for prediction the substrate concentration in the wastewater and the optimal volume of the reactor. The values of saturation constant (KB) and the max ultilizaion rate (Umax) were calculated for partial nitrification process as 15.489 and 8.038 (mg L-1 d-1). respectively. The research has also determined the values of KB and Umax for anammox process as 1.738 and 1.241 (mg L-1 d-1), respectively. [ABSTRACT FROM AUTHOR]

This study assessed the impact of the method of conducting the biofiltration process on the efficiency of ammonium nitrogen removal from water in combined sorption and nitrification processes. The research was carried out on diatomite deposits using biofiltration with gravity and counter-gravity flow. The following physicochemical water parameters were controlled during the research, including ammonium nitrogen, nitrite nitrogen, nitrate nitrogen, and dissolved oxygen. Unconventional flow turned out to be more beneficial because it allows for optimal use of the entire bed surface, natural regulation of the biofilm thickness, and maintaining constant microbiological activity of the biofilm. The automatic regulation of the biofilm thickness during water flow prevented excessive growth of dead organic matter and limited the development of heterotrophic bacteria. Biofiltration with counter-gravity flow also resulted in reduced oxygen consumption. Regardless of the flow direction used, water after the single-stage biofiltration process was characterized by an increased content of nitrite nitrogen. The introduction of the second stage of filtration made it possible to obtain water that meets the requirements for water intended for human consumption. [ABSTRACT FROM AUTHOR]

Partial nitrification is known as first and critical step for autotrophic nitrogen removal in high strength nitrogenous wastewater. Phosphorylated polyvinyl alcohol gel entrapment was used for suppressing oxygen to nitrite-oxidizing bacteria (NOB) in the gel matrix. The study investigated the effect of the size of gel matrix on partial nitrification. Results show that ammonia-oxidizing bacteria (AOB) proportion in the inoculum rather than the size of gel matrix governed ammonia oxidation. Nitrite oxidation depended on the size of gel matrix not the relative proportions of NOB and AOB in the inoculum. Larger size of gel matrix lead to less in situ oxygen penetration and available for NOB resulting in higher nitrite accumulation. This finding gains a better understanding of using suitable inoculum to control partial nitrification that is beneficial for the preparation of anaerobic ammonium oxidation-suited effluent. [ABSTRACT FROM AUTHOR]

Kinetic assays with a nitrifying consortium with whole nitrifying cells amended with 5 mg 2-CP-C/L and 100, 200, 300, or 500 mg NH4+–N/L were carried out in batch and nitrifying sequencing batch reactor (SBR) cultures. No nitrification activity was observed in batch assays with 100 mg NH4+–N/L and 5 mg 2-CP-C/L. Nevertheless, increasing the ammonium concentration from 200 to 500 mg NH4+–N/L allowed simultaneous ammonium and nitrite oxidation even in the presence of 5 mg 2-CP-C/L plus the halogenated compound consumption. Under these conditions, the ammonium monooxygenase enzyme participated in 2-CP consumption. Complete nitrification and simultaneous elimination of 5 mg 2-CP-C/L were achieved in the SBR amended with 200–500 mg NH4+–N/L. The inhibitory effect of 2-CP on the nitrite oxidation process completely disappeared under these conditions. Assays with nitrifying cell-free extracts, ammonium (100 mg NH4+–N/L), and 2-CP (5 mg 2-CP-C/L) were also conducted. In the absence of 2-CP, the nitrifying cell-free extracts maintained up to 60% of the nitrifying activity compared to whole-cells. Contrary to whole-cell assays, cell-free extracts were capable of simultaneously oxidizing ammonium and consuming 2-CP. However, the inhibitory effect of 2-CP on nitrification was still present as lower specific rates of ammonium consumption and nitrate production were obtained. Thus, these assays indicate that the presence of 2-CP affects both, the ammonium transport mechanism and the activity of nitrifying enzymes. [ABSTRACT FROM AUTHOR]

Biological filters effectively remove ammonium from drinking water via nitrification. In a pilot-scale upflow biological contact filter (U-BCF), complete ammonia oxidizers (comammox), which are capable of oxidizing ammonia to nitrate in one cell, were more abundant than ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). However, little information is available on the contribution of comammox to nitrification. In this study, we evaluated the autotrophic growth activity of comammox associated with biological activated carbon (BAC) in a U-BCF by DNA-stable isotope probing (DNA-SIP). BAC samples collected from the U-BCF were continuously fed mineral medium containing 0.14 mg N L−1 ammonium and 12C- or 13C-labeled bicarbonate for 20 days. DNA-SIP analysis revealed that comammox (clades A and B) as well as AOA assimilated bicarbonate after 10 days of incubation, proving that dominant comammox could contribute to nitrification. Contrarily, AOB remained inactive throughout the observation period. Amplicon sequencing of the 13C-labeled DNA fractions of comammox revealed that specific genotypes other than the most dominant genotype in the original sample were more enriched under the incubation condition for the DNA-SIP experiment. Thus, dominant genotypes of comammox in a U-BCF might utilize organic nitrogen to fuel nitrification in ammonia-limited environments. [ABSTRACT FROM AUTHOR]

Pseudomonas otitidis YM-01, which was isolated from swine wastewater, showed efficient simultaneous nitrification and denitrification ability by effectively using a single nitrogen source and a mixed nitrogen source. A high concentration of free ammonia (FA) can decompose EPS (extracellular polymeric substances), which makes the ammonia monooxygenase (AMO), hydroxylamine oxidase (HAO), periplasmic nitrate reductase (Nap), and nitrite reductase (NIR) lose the protective activity of EPS, resulting in the deterioration of the denitrification performance of the strain. For high-strength ammonium wastewater (500 mg/L and 1000 mg/L) with FA concentrations of 55 mg/L and 209 mg/L, the removal rates of strain YM-01 were 70.24% and 27.84%, respectively. The results indicate that strain YM-01 has the potential for application in high-strength ammonium wastewater. [ABSTRACT FROM AUTHOR]

Introduction: The production of root exudates with biological nitrification inhibition (BNI) effects is a strategy adopted by ammonium-N (NH4+ - N) tolerant plant species that occur in N-limited environments. Most knowledge on BNI comes from plant species that occur in acidic soils. Methods: Here, combining field sampling and laboratory culture, we assessed the BNI-capacity of Leymus chinensis, a dominant grass species in alkaline grasslands in eastern Asia, and explored why L. chinensis has BNI ability. Results and discussion: The results showed that L. chinensis has strong BNIcapacity. At a concentration of 1 mg mL-1, L. chinensis' root exudates inhibited nitrification in soils influenced by Puccinellia tenuiflora by 72.44%, while DCD only inhibited it by 68.29%. The nitrification potential of the soil of L. chinensis community was only 53% of the P. tenuiflora or 41% of the Suaeda salsa community. We also showed that the supply of NH4+ -N driven by L. chinensis' BNI can meet its requirements. In addition, NH4+ -N can enhance plant adaptation to alkaline stress by regulating pH, and in turn, the uptake of nitrate-N (NO3- - N). We further demonstrated that the regulatory function of NH4+ -N is greater than its nutritional function in alkaline environment. The results offer novel insights into how L. chinensis adapts to high pH and nutrient deficiency stress by secreting BNIs, and reveal, for the first time, differences in the functional roles of NH4+ -N and NO3- -N in growth and adaptation under alkaline conditions in a grass species. [ABSTRACT FROM AUTHOR]

Exploring nitrifiers in extreme environments is vital to expanding our understanding of nitrogen cycle and microbial diversity. This study presents that complete ammonia oxidation (comammox) Nitrospira, together with acidophilic ammoniaoxidizing archaea (AOA), dominate in the nitrifying guild in sediments of an acid mine lake (AML). The lake water was characterized by acidic pH below 5 with a high ammonium concentration of 175 mg-N/liter, which is rare on the earth. Nitrification was active in sediments with a maximum nitrate production potential of 70.5 μg-N/(g-dry weight [dw] day) for mixed sediments. Quantitative PCR assays determined that in AML sediments, comammox Nitrospira and AOA amoA genes had relative abundances of 52% and 41%, respectively, among the total amoA genes. Further assays with 16S rRNA and amoA gene amplicon sequencing and metagenomics confirmed their dominance and revealed that the comammox Nitrospira found in sediments belonged to comammox Nitrospira clade A.2. Metagenomic binning retrieved a metagenome-assembled genome (MAG) of the comammox Nitrospira from sediments (completeness = 96.76%), and phylogenomic analysis suggested that it was a novel comammox Nitrospira. Comparative genomic investigation revealed that this comammox Nitrospira contained diverse metal resistance genes and an acidophile-affiliated F-type ATPase. Moreover, it had a more diverse genomic characteristic on nitrogen metabolism than the AOA in sediments and canonical AOB did. The results suggest that comammox Nitrospira is a versatile nitrifier that can adapt to acidic environments even with high ammonium concentrations. IMPORTANCE Ammonia-oxidizing archaea (AOA) was previously considered the sole dominant ammonia oxidizer in acidic environments. This study, however, found that complete ammonia oxidation (comammox) Nitrospira was also a dominant ammonia oxidizer in the sediments of an acidic mine lake, which had an acidic pH < 5 and a high ammonium concentration of 175 mg-N/liter. In combination with average nucleotide identity analysis, phylogenomic analysis suggested it is a novel strain of comammox Nitrospira. Moreover, the adaption of comammox Nitrospira to the acidic lake had been comprehensively investigated based on genome-centric metagenomic approaches. The outcomes of this study significantly expand our understanding of the diversity and adaptability of ammonia oxidizers in the acidic environments. [ABSTRACT FROM AUTHOR]

Complete ammonia oxidizers (comammox) are a group of ubiquitous chemolithoautotrophic bacteria capable of deriving energy from the oxidation of ammonia to nitrate via nitrite. Here, we present a study characterizing the comammox strain Nitrospira sp. BO4 using a combination of cultivation-dependent and molecular methods. The enrichment culture BO4 was obtained from the sediment of Lake Burr Oak, a mesotrophic lake in eastern Ohio. The metagenome of the enrichment culture was sequenced, and a metagenome-assembled genome (MAG) was constructed for Nitrospira sp. BO4. The closest characterized relative of Nitrospira sp. BO4 was "Candidatus Nitrospira kreftii." All genes for ammonia and nitrite oxidation, reductive tricarboxylic acid (TCA) cycle, and other pathways of the central metabolism were detected. Nitrospira sp. BO4 used ammonia and oxidized it to nitrate with nitrite as the intermediate. The culture grew on initial ammonium concentrations between 0.01 and 3 mM with the highest rates observed at the lowest ammonium concentrations. Blue light completely inhibited the growth of Nitrospira sp. BO4, while white light reduced the growth and red light had no effect on the growth. Nitrospira sp. BO4 did not grow on nitrite as its sole substrate. When supplied with ammonium and nitrite, the culture utilized nitrite after most of the ammonium was consumed. In summary, the genomic information of Nitrospira sp. BO4 coupled with the growth experiments shows that Nitrospira sp. BO4 is a freshwater comammox species. Future research will focus on further characterization of the niches of comammox in freshwater environments. [ABSTRACT FROM AUTHOR]

Uniform incorporation of controlled-release fertilizer (CRF) is a recommended best management practice to reduce nitrogen leaching losses from container-plant production. The potential for damage to CRF prill coating when mechanically incorporated into a soilless substrate was tested. Osmocote Plus 15-9-12 was uniformly incorporated mechanically or manually at the same rate into a soilless substrate and leachate was collected over 76 days. Two experiments were conducted, with or without lavender plants planted into the soilless substrate. Leachate volume, electrical conductivity (EC), and pH were recorded and aliquots were later analyzed for inorganic nitrogen content. Electrical conductivity and leachate volume were used to calculate total salt content. Greater total salts, ammonium, and nitrate were leached from planted or unplanted mechanically incorporated soilless substrate compared to manually incorporated. Plants grown in soilless substrate with mechanically incorporated CRF did not have decreased plant shoot biomass even though leachate EC was consistently greater throughout the experiment. Mechanically incorporating CRF in soilless substrate results in greater leaching losses and is likely a result of CRF prill coating damage during incorporation. Researchers should report incorporation method when publishing results on CRF in container-plant production. Container-plant producers should ensure that their mechanical-incorporation equipment does not cause unintended damage to their CRF of choice. [ABSTRACT FROM AUTHOR]

Nitrification rates and ammonia-oxidizer functional gene abundance were measured in the water column of Lake Lacawac, Pennsylvania, USA, a freshwater lake on a nature sanctuary that allowed an investigation with minimal human impacts. Nitrification is a 2-step process consisting of ammonia oxidation followed by nitrite oxidation. Recent studies have shown that these 2 nitrification steps may be uncoupled and respond in different ways to environmental conditions. Additionally, the relative contribution of ammonia-oxidizing archea (AOA) vs ammonia-oxidizing bacteria (AOB) to nitrification rates varies widely across aquatic systems. To determine how nitrification rates are related to environmental parameters and the ammonia-oxidizing community in a nearly pristine environment, rates and gene abundance were measured over multiple seasons where in-situ environmental conditions varied. Rates of ammonia and nitrite oxidation were measured separately and summed to calculate total nitrification rates ranging from 1 to 568 nM/d. Ammonia oxidation rates generally outpaced nitrite oxidation rates, and rates of both ammonia and nitrite oxidation were higher at depth (10 m) compared with near-surface and mid water column. Ammonia oxidation, nitrite oxidation, and total nitrification rates were all strongly, positively correlated with in-situ [NH4+] (Kendall's τ > 0.35, p < 0.02). AOB ammonia monooxygenase (amoA) gene copy numbers were generally greater than AOA amoA. However, AOB gene copy numbers were not correlated with any ammonia oxidation or total nitrification rates, whereas AOA abundance was positively correlated with both ammonia oxidation and total nitrification rates (Kendall's τ > 0.41, p < 0.01). A Bayesian generalized additive model, which accounted for sampling month, indicated that total nitrification rates were best explained by AOA and [NH4+]. Thus, substrate concentration and AOA likely play key roles in regulating rates of nitrification in this small, nearly pristine freshwater lake. These reported relationships between rates of ammonia and nitrite oxidation (and, thus, total nitrification), in-situ environmental parameters, and the ammonia-oxidizer community in a protected environment establish a reference for evaluating the impact of a changing environment on mesotrophic lake water quality. [ABSTRACT FROM AUTHOR]

Synthetic nitrification inhibitors (SNI) and biological nitrification inhibitors (BNI) are promising tools to limit nitrogen (N) pollution derived from agriculture. Modern wheat cultivars lack sufficient capacity to exude BNIs, but, fortunately, the chromosome region (Lr#n-SA) controlling BNI production in Leymus racemosus, a wild relative of wheat, was introduced into two elite wheat cultivars, ROELFS and MUNAL. Using BNI-isogenic-lines could become a cost-effective, farmer-friendly, and globally scalable technology that incentivizes more sustainable and environmentally friendly agronomic practices. We studied how BNI-trait improves N-uptake, and N-use, both with ammonium and nitrate fertilization, analysing representative indicators of soil nitrification inhibition, and plant metabolism. Synthesizing BNI molecules did not mean a metabolic cost since Control and BNI-isogeniclines from ROELFS and MUNAL presented similar agronomic performance and plant development. In the soil, ROELFS-BNI and MUNAL-BNI plants decreased ammonia-oxidizing bacteria (AOB) abundance by 60% and 45% respectively, delaying ammonium oxidation without reducing the total abundance of bacteria or archaea. Interestingly, BNI-trait presented a synergistic effect with SNIs since made it also possible to decrease the AOA abundance. ROELFS-BNI and MUNAL-BNI plants showed a reduced leaf nitrate reductase (NR) activity as a consequence of lower soil NO-3 formation and a higher amino acid content compared to BNI-trait lacking lines, indicating that the transfer of Lr#-SA was able to induce a higher capacity to assimilate ammonium. Moreover, the impact of the BNI-trait in wheat cultivars was also noticeable for nitrate fertilization, with improved N absorption, and therefore, reducing soil nitrate content. [ABSTRACT FROM AUTHOR]

Peatlands are an important source of nitrous oxide (N2O) emissions, which is a potent greenhouse gas and is also involved in the depletion of stratospheric ozone. Due to the large number of N2O production and consumption processes, it is challenging to trace N2O emissions to an individual process. We investigated the effect of different water regimes (dry, intermediate and flooded) on N2O emissions via 15N tracing in a microcosm study with well-decomposed nitrogen-rich alluvial fen peat. The isotopic composition of the peat and emitted N2O gas was analysed in combination with qPCR analysis of abundances and diversity of N-cycle functional genes. Bacterial denitrification was the predominant source of N2O emission, followed by nitrification (ammonia oxidation). This was identified by a close relationship between 15N-N2O and 15N-NO3− under flooded (anoxic) and intermediate (sub-oxic) treatments and concomitant increases in nirK, nirS and nosZ after the flooding. The site preference and δ18O values fell within the previously observed range indicating multiple overlapping processes and bacterial denitrification as the dominant process. Although the combination of isotopic and microbial analyses indicates that bacterial denitrification is the primary process under intermediate and flooded treatments, the high abundance of amoA indicates that nitrification via comammox was present. High archaeal amoA and bacterial amoA gene copy numbers and second highest N2O emissions under the intermediate and flooded peats indicated that ammonia oxidation was, secondary to denitrification, also a source for N2O. The increase in emissions with nrfA gene copies also showed that dissimilatory nitrate reduction to ammonium (DNRA) potentially contributed to N2O emission under flooded treatment. [ABSTRACT FROM AUTHOR]

In this work, a UV/H2O2 system was evaluated using an experimental design 2 level I-optimal response surface design to analyze the effect of temperature, pH, UV lamp power (W), and H2O2 concentration on dye load removal and nitrification from industrial cleaning wastewater. Results showed that the optimum conditions were 80 °C, pH 4, PW-UV 60 W, and H2O2 3.1 Mol*L-1. Removal percentages of 45% for COD, 47.5% color, 87% Fe, 82% Cr and 91% ammonium oxidation to nitrate were achieved. It can be concluded that the effluents treated by this process could be promising for reuse and exploitation in biotechnological tools through microalgae and cyanobacteria. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is pivotal to crop yield, and the application of N fertilizer in crop production systems is a crucial aspect of modern crop management practices and one of the determining factors to increase crop yield and thereby keeping pace with human population increase. However, most of the N fertilizers (>60%) added to rice fields is not taken up by rice plants, but lost to the environment in forms of ammonia, nitrate, and nitrous oxide. The ‘reactive N’ causes serious environmental problems and detrimental impacts on human health. Furthermore, the N cycling in a cropping system is complicated, and solutions must be made based on an in-depth understanding of the transformation of N in soil and the biochemical processes of N in rice plants. Here, we described multiple transformations and oxidation/reduction processes of N in the paddy rice field, and then summarized the basic biological processes in N acquisition, transportation, assimilation, and metabolism in rice. We discussed various local N signals that regulate root systems. In the end, we suggested the solutions that can synchronize the supply of available N in the soil to the demands of rice plants. A portfolio solution is needed in which integrative management should be established to reduce N loss and increase N use efficiency in rice production.

BACKGROUND: The combination of partial nitrification (PN) and anaerobic ammonium oxidation has been identified as a promising technology for the removal of nitrogenous contaminants from wastewater. The inhibition or wash‐out of nitrite‐oxidizing bacteria (NOB) while keeping the ammonia oxidizing bacteria (AOB) active is key for PN. Multiple strategies, including intermittent aeration, pH shocks and sulfide addition, were investigated in this study for the start‐up of PN and stable suppression of NOB. RESULTS: Intermittent aeration with a dissolved oxygen (DO) level of <5 mg L−1 effectively suppressed NOB activity and resulted in an average nitrite accumulation (NAR) of 93%, implying that the initial DO level during the aeration phase may influence the establishment of successful PN. Likewise, when the reactor was run at a low pH (5), both AOB and NOB activity was reduced. When the pH was raised to neutral pH (7.5), there was an increase in AOB activity with an average NAR of 84%; however, NOB activity remained suppressed. Likewise, when the reactor was fed with sulfide (≤25 mg L−1) without pH control, the average NAR increased from 63% to 85%. CONCLUSIONS: This study proposes a successful approach to achieving PN by controlling DO level in the aeration phase during intermittent aeration and pH control. The findings also show that the nitrite oxidation process is more sensitive to sulfide than the ammonium oxidation process. As a result, the findings of this study may contribute to a better understanding of establishing PN in a sequential batch system. © 2022 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Due to the rapid development of medical industries, wastewater treatment plants have become sinks for residual antibiotics. However, the contribution of novel partial nitrification processes to the bioremediation of antibiotics remains unclear. In this study, the removal rate of a partial nitrification process on the biotransformation of sulfamethoxazole (SMZ) was evaluated. A biological aerated filter made from zeolite successfully achieved stable partial nitrification. A nitrite accumulation percentage (NAP) greater than 85% was obtained when the influent ammonium concentration was increased to 300 mg/L with a nitrogen loading rate of 1.24 kg/(m3 d). Batch tests were performed on support collected from different heights of the up-flow reactor at the end of the pilot monitoring experiment. The maximum ammonium oxidation rate of 5.63 mg/(g VSS·L) in one hour was recorded at a height of 0.32–0.48 m in the reactor, indicating nitrifying bacteria activity link between the free ammonia (FA) and biomass concentration was found. After the addition of SMZ (2.5 mg/L), the NAP declined to approximately 70%, and the abundance of Nitrosomonas (the main ammonia oxidizing bacteria (AOB) genus in the zeolite biological aerated filter (ZBAF)) decreased 7.24–6.10%. Lower abundance and activity of AOB oxidized ineffectively the primary amine of SMZ, which led to lower than 19% of the SMZ removal efficiency. [Display omitted] • AOB was successfully enriched in a zeolite biological aerated filter. • Stable partial nitrification achieved with influent ammonium concentration of 300 mg/L. • The effect of FA inhibition on NOB was related to dose of FA and the biomass concentration. • Microbial analysis showed that SMZ reduced the abundance of AOB in the reactor. [ABSTRACT FROM AUTHOR]

Some microorganisms with the nitrification function can carry out nitrogen conversion under oxygen-limited conditions. In this study, a continuous-flow biofilm reactor was operated to investigate the removal of ammonium nitrogen (NH4-N) under microaerobic or anoxic conditions. After more than 100 days of long-term operation, the NH4-N removal rate and removal percentage reached 2.92 mg/(L·h) and 72.3%, respectively. In the batch experiments, NH4-N removal was achieved regardless of the presence or absence of nitrite. The main microorganisms relating to nitrogen metabolism in the system were Nitrospira, Nitrosomonas, Candidatus Kuenenia, and denitrifying bacteria. The metagenomics analysis indicated that these functional microorganisms constituted the main nitrogen metabolic network in the system, and microorganisms such as Rhodanobacter, Nitrosomonas, Defluvii, and Cyanobacteria had the possible capacity for oxygen production. Without organic carbon in the synthetic wastewater, heterotrophs including denitrifying bacteria might utilize organic carbon such as extracellular polymeric substances produced by autotrophs. The removal of NH4-N under oxygen-limited conditions might be achieved through interactions among nitrifying bacteria, anammox bacteria, and heterotrophs, which deserves further investigation. [ABSTRACT FROM AUTHOR]

Microbial transformations of nitrogen (N) largely determine whether N is retained in ecosystems via net primary productivity or lost via gaseous emissions and leaching. The controls on soil N cycling are often studied at single locales, making it difficult to predict N cycling at regional to global scales. We hypothesized that contemporary soil properties exhibit consistent relationships with instantaneous gross N cycling rates across diverse biomes that create a continuum in these properties. We measured ex situ gross N cycling rates and soil properties at 33 study sites representing five biome classifications in California including deserts, grasslands, shrublands, forest, and wetlands. Desert soils had significantly lower total N, organic carbon (C), microbial biomass N, and soil moisture as well as higher pH than all other biomes, whereas forests and wetlands had significantly lower soil nitrate (NO3−) concentrations (P

Microbial transformations of nitrogen (N) largely determine whether N is retained in ecosystems via net primary productivity or lost via gaseous emissions and leaching. The controls on soil N cycling are often studied at single locales, making it difficult to predict N cycling at regional to global scales. We hypothesized that contemporary soil properties exhibit consistent relationships with instantaneous gross N cycling rates across diverse biomes that create a continuum in these properties. We measured ex situ gross N cycling rates and soil properties at 33 study sites representing five biome classifications in California including deserts, grasslands, shrublands, forest, and wetlands. Desert soils had significantly lower total N, organic carbon (C), microbial biomass N, and soil moisture as well as higher pH than all other biomes, whereas forests and wetlands had significantly lower soil nitrate (NO3−) concentrations (P < 0.001 for all). Gross mineralization rates were best predicted by the combination of soil moisture and soil C:N ratios (R2 = 0.46), which exerted positive and negative controls, respectively. Grasslands exhibited marginally higher gross mineralization than all other biomes, whereas deserts had the lowest rates due to low soil moisture (P = 0.09). Gross nitrification rates were positively correlated to soil NO3− concentrations (R2 = 0.34) and negatively correlated to soil C:N ratios (R2 = 0.31). The negative relationship between gross nitrification and soil C:N ratios was driven by forest soils, which had significantly higher C:N ratios and lower gross nitrification than all other biomes (P < 0.05). Dissimilatory NO3− reduction to NH4+ (DNRA) occurred in soils from all biomes. The strong positive correlation between DNRA rates and soil NO3− (R2 = 0.41) suggests NO3− limitation of DNRA. Predictable patterns in gross N cycling across biomes in California suggest that contemporary soil properties are important drivers of instantaneous soil N cycling rates that integrate over differences in vegetation type, atmospheric N deposition rates, and local climate.

Atmospheric nitrogen (N) deposition has a significant impact on terrestrial N cycling. However, it has not been well understood how external inorganic N addition affects the dynamics of soil organic N (SON) that supports long-term plant productivity and carbon (C) sequestration. Here, we added six levels of ammonium (NH 4 +-N) or nitrate (NO 3 −-N) to a temperate grassland soil to reveal the mechanisms of SON responses to inorganic N addition. Results showed that the SON content decreased by 7% ± 2%–15% ± 1%, which corresponded with the increase in the abundance of functional gene related to SON mineralization (i.e., chiA) by both NH 4 +-N and NO 3 −-N. The inorganic N addition stimulated gaseous losses from the native soil N, leading to at least 6% ± 2%–12% ± 1% of the initial SON lost at different N addition levels (i.e., N-priming). However, the responses of nitrification- and denitrification-related functional genes to NH 4 +-N and NO 3 −-N treatments varied remarkably. The positive responses of nitrification- and denitrification-related functional genes (i.e., hao , nirS , and narG) to NO 3 −-N addition contributed to gaseous N losses. The negative responses of some denitrification-related functional genes (i.e., nirK , narG , and napA) to NH 4 +-N addition resulted in less gaseous N losses by NH 4 +-N compared with that by NO 3 −-N addition. Additionally, the release of H+ by NH 4 +-N addition may liberate organic matter from associated minerals, showing a decrease in mineral-associated organic matter (MAOM) but an increase in extractable Fe. These findings provide direct evidence that the addition of inorganic N results in a net native SON loss through microbe-mediated mineralization and gaseous emissions. The study also emphasizes the different mechanisms of reduced and oxidized N additions in affecting SON mineralization and gaseous N losses. [Display omitted] • Inorganic nitrogen addition decreased soil organic nitrogen (SON) content by 7% ± 2%–15% ± 1%. • Both NH 4 +-N and NO 3 −-N increased the abundance of chiA , a key gene in SON mineralization. • Inorganic nitrogen addition stimulated gaseous losses, resulting in at least 6% ± 2%–12% ± 1% initial SON loss (N-priming). • Gaseous N losses caused by NH 4 +-N was less than that by NO 3 −-N addition. • The release of H+ by NH 4 +-N addition may liberate organic matter from associated minerals. [ABSTRACT FROM AUTHOR]

Uniform incorporation of controlled-release fertilizer (CRF) is a recommended best management practice to reduce nitrogen leaching losses from container-plant production. The potential for damage to CRF prill coating when mechanically incorporated into a soilless substrate was tested. Osmocote Plus 15-9-12 was uniformly incorporated mechanically or manually at the same rate into a soilless substrate and leachate was collected over 76 days. Two experiments were conducted, with or without lavender plants planted into the soilless substrate. Leachate volume, electrical conductivity (EC), and pH were recorded and aliquots were later analyzed for inorganic nitrogen content. Electrical conductivity and leachate volume were used to calculate total salt content. Greater total salts, ammonium, and nitrate were leached from planted or unplanted mechanically incorporated soilless substrate compared to manually incorporated. Plants grown in soilless substrate with mechanically incorporated CRF did not have decreased plant shoot biomass even though leachate EC was consistently greater throughout the experiment. Mechanically incorporating CRF in soilless substrate results in greater leaching losses and is likely a result of CRF prill coating damage during incorporation. Researchers should report incorporation method when publishing results on CRF in container-plant production. Container-plant producers should ensure that their mechanical-incorporation equipment does not cause unintended damage to their CRF of choice.

The performance of a mixture between L. sphaericus and E. fetida was evaluated for ammonium cycling and nitrifying bacteria stimulation during oil sludge remediation. The addition of E. fetida significantly increased ammonium concentration (p = 0.0218) and total Colony-forming units (CFU) count p = 0.02848). However, oil sludge with worms and L. sphaericus reached lower ammonium concentrations and CFU counts than sludge with worms alone. Sludge inoculated only with L. sphaericus presented higher ammonium concentration than sludge without inoculum, but the bacterial population reached a lower density during the final days. Final DNA and RNA extractions from all treatments amplified for L. sphaericus putative amoA and Gram-negative nitrifying bacteria amoA genes correlated with diminished ammonium concentrations during the final days of the experiment. Final RNA extractions for L. sphaericus amplified for Molybdenum transporter gene suggesting possible nitrogen fixation by L. sphaericus. The addition of Red Wiggler Earthworm to oil sludge remediation systems may provide better conditions for bacterial populations to carry out hydrocarbon degradation. The addition of E. fetida to a L. sphaericus crude oil biodegradation system may improve soil ammonium concentrations and nitrifying activity, and this could be crucial in oil sludge remediation because of bacterial inhibition due to high C:N ratios. The final product of this process may be used for soil enhancement due to its richness in nutrients and beneficial bacterial populations.

This paper includes the results of laboratory modeling of ethyl and methyl alcohol and sulfide ions impact on the biochemical process of ammonium ions nitrification in water from the Dniester River, Palanca village, Stefan Voda district (august 2019). An insignificant influence of ethyl and methyl alcohol (0,5 ml/L) was established in both stages of the process. In the comparison test, the stage NH4 + → NO2 - lasted 12 days, and in the presence of ethyl alcohol - 14 days and in the presence of methyl alcohol - 16 days. The NO2 - → NO3 - stage in the comparison test lasted 16 days and in the presence of ethyl alcohol 2 days less (14 days) and in the presence of methyl alcohol - 16 days, so without any influence. The study showed a significant influence of sulfur ion in both stages at a concentration of 0.1 mg/L with and without the presence of ethyl and methyl alcohol. In the comparison test, the NH4 + → NO2 - stage lasted 12 days, in the presence of the S2- ion it lasted 18 days, and in the presence of alcohols and sulfur ion - more than 20 days, the synergism of the impact being obvious. In the NO2 - → NO3 - step of the process for 20 days the NO2 - concentration did not decrease in the presence of the S2- ion, and in the presence of ethyl, methyl alcohol and S2- only 15-35% of the NO2 - ions were oxidized, in comparison with the witness test.

Aquatic nitrogen pollution is one of the most urgent environmental issues requiring prevention and mitigation. Large quantities of high-ammonium wastewaters are generated by several industrial sectors, such as fertilizer and anaerobic-digestion plants. Nitrification of these wastewaters is commonly carried out, either to remove nitrogen or produce liquid fertilizers. Standard control methodologies for the efficient nitrification of high-ammonium wastewaters to produce liquid fertilizers have not yet been established and are still within their early stages of development. In this paper, novel pH-based control algorithms are presented that maintain operation at the microbial maximum reaction rate (umax) in batch and continuous reactors. Complete conversion of ammonium to nitrate was achieved in a batch setup, and a conversion of 93% (±1%) was achieved in a continuously-stirred-tank-reactor. The unparalleled performance and affordability of the control schemes proposed offer a steppingstone to the future of sustainable fertilizer production. [ABSTRACT FROM AUTHOR]

In order to better understand the biogeochemical cycle of nitrogen in meromictic lakes, which can serve as a model for past aquatic environments, we measured dissolved concentrations of nitrate, nitrite, ammonium, and organic nitrogen in the deep (39 m maximal depth) subarctic Lake Svetloe (NW Russia). The lake is a rare type of freshwater meromictic water body with high concentrations of methane, ferrous iron, and manganese and low concentrations of sulfates and sulfides in the monimolimnion. In the oligotrophic mixolimnion, the concentration of mineral forms of nitrogen decreased in summer compared to winter, likely due to a phytoplankton bloom. The decomposition of the bulk of the organic matter occurs under microaerophilic/anaerobic conditions of the chemocline and is accompanied by the accumulation of nitrogen in the form of N-NH4 in the monimolimnion. We revealed a strong relationship between methane and nitrogen cycles in the chemocline and monimolimnion horizons. The nitrate concentrations in Lake Svetloe varied from 9 to 13 μM throughout the water column. This fact is rare for meromictic lakes, where nitrate concentrations up to 13 µM are found in the monimolimnion zone down to the bottom layers. We hypothesize, in accord with available data for other stratified lakes that under conditions of high concentrations of manganese and ammonium at the boundary of redox conditions and below, anaerobic nitrification with the formation of nitrate occurs. Overall, most of the organic matter in Lake Svetloe undergoes biodegradation essentially under microaerophilic/anaerobic conditions of the chemocline and the monimolimnion. Consequently, the manifestation of the biogeochemical nitrogen cycle is expressed in these horizons in the most vivid and complex relationship with other cycles of elements. [ABSTRACT FROM AUTHOR]

Most of nitrogen emissions can be ascribed to agro-industrial activities. Since digestate produced by fermentation of agro-industrial residues can be difficult to dispose of due to its high ammonium content, advanced technical- and cost-effective technologies must be developed and applied in order to significantly reduce its impact on the environment. In this study, aerobic granules were successfully cultivated in a granular sludge sequencing batch reactor (GSBR) fed with the ammonium-rich (approx. 2500 mg L−1) effluent of a 3-stage anaerobic digester treating agro-industrial residues. The peculiar characteristics of such wastewater required a 2-step operating strategy aimed at the selection of nitrifying biomass (Step 1) and the formation of aerobic granular sludge (Step 2). During Step 1, nitrifying biomass selection was achieved by properly regulating the cycle length: N H 4 + - N removal rates progressively increased from 42 to 109 mgN L−1d−1, and a corresponding increase in N H 4 + - N specific removal rates from 8 to 24 mgN gVSS−1d−1 was also observed. During Step 2, the increase in selective pressures (i.e. minimum settling velocity and volumetric organic loading rate) led to the formation of compact (average diameter, 1.02 ± 0.43 mm) and well-settling granules (SVI5, 28.6 ± 3.8 mL gTSS−1), which were able to remove up to 89 ± 2% of organic matter (as COD), 79 ± 3% of N H 4 + - N and 59 ± 4% of nitrogen (as a sum of N H 4 + - N , N O 2 – - N and N O 3 – - N ). The 2-step operating strategy played a key role in biomass selection and subsequent granule formation and maintenance in the GSBR, and may be successfully adopted for the treatment of different ammonium-rich wastewaters. [ABSTRACT FROM AUTHOR]

ABSTRAK Saat ini kualitas badan air semakin menurun akibat pembuangan limbah domestik dan industri secara langsung pada aliran sungai. Kualitas air sungai dengan beban nutrien dan organik yang tinggi mempersulit pengolahan air minum di salah satu industri DKI Jakarta. Salah satu dampak dari memburuknya beban nutrien air baku adalah tingginya kandungan parameter amonium yang berakibat tidak efisiennya proses klorinasi. Hal ini membuat dibangunnya unit MBBR aerob, dengan tujuan menyisihkan kandungan amonium. Akan tetapi, unit MBBR aerob ini tidak berfungsi secara optimal. Masalah ini akan diatasi dengan mengalihfungsikan unit pra-sedimentasi yang ada menjadi unit MBBR anaerob secara pre-anoxik, sehingga dapat melengkapi proses penyisihan amonium yang terdiri dari nitrifikasi dan denitrifikasi. Tujuan dari modifikasi ini adalah mendapatkan efisiensi penyisihan amonium sebesar 90%. Metode yang digunakan pada perancangan ini dimulai dengan mengumpulkan data sekunder, lalu dilakukan perhitungan perancangan unit MBBR anaerob. Hasil perancangan menunjukkan bahwa dimensi yang dibutuhkan untuk unit MBBR anaerob ini adalah dengan ukuran panjang 18 m, lebar 7 m, dan kedalaman 9.5 m. Dengan efisiensi akhir diharapkan sebesar 90% untuk MBBR anaerob dengan konsentrasi akhir amonium diharapkan sebesar 1.05 mg.L-1. Kata kunci: amonium, denitrifikasi, MBBR, nitrifikasi, pre-anoksik ABSTRACT At present the quality of water bodies is decreasing due to the disposal of domestic and industrial waste directly in the river flow. River water quality with high nutrients and organic load is difficult to drinking water treatment in one of the industries in DKI Jakarta. One of the effects of the worsening raw water nutrient load is the high content of ammonium parameters which results in inefficient chlorination processes. The declining raw water condition makes build an MBBR aerobic unit, with the aim to remove the ammonium content. However, the existing MBBR aerob unit does not function optimally. This problem can be overcome by changing the pre-sedimentation unit into an anaerobic MBBR unit pre-Anoxikally, so as to complete the ammonium removal process consisting of nitrification and denitrification. The purpose of this modification is to obtain an ammonium removal efficiency of 90%. The method used in this design is to collect secondary data. Then, anaerobic MBBR unit design is calculated. The results of the design show that the dimensions needed for this anaerobic MBBR unit are 18 m long, 7 m wide, and 9.5 m height. With a final efficiency expected of 90% for anaerobic MBBR with an ammonium final concentration expected to be 1.05 mg.L-1. Keywords: ammonium, denitrification, MBBR, nitrification, pre-Anoxic