Denitrifying bacteria

An innovative inbuilt moving bed biofilm reactor (MBBR) was created to protect fish from nitrogen in a household aquarium. During the 90 experimental days, the ammonia nitrogen (NH4 + -N) concentration in the aquarium with the inbuilt MBBR was always below 0.5 mg/L, which would not threaten the fish. Concurrently, nitrite and nitrate nitrogen concentrations were always below 0.05 mg/L and 4.5 mg/L, respectively. However, the blank contrast aquarium accumulated 1.985 mg/L NH4 + -N on the 16th day, which caused the fish to die...

Due to the widespread use of sliver nanoparticles (AgNPs), a large amount of AgNPs has inevitably been released into the environment, and there is growing concern about the toxicity of AgNPs to nitrogen-functional bacteria. In addition to traditional anaerobic denitrifying bacteria, heterotrophic nitrification-aerobic denitrification (HNAD) bacteria are also important participants in the nitrogen cycle. However, the mechanisms by which AgNPs influence HNAD bacteria have yet to be explicitly demonstrated. In this study, the inhibitory effects of different concentrations of AgNPs on a HNAD bacteria Zobellella sp...

Microorganisms encode proteins that function in the transformations of useful and harmful nitrogenous compounds in the global nitrogen cycle. The major transformations in the nitrogen cycle are nitrogen fixation, nitrification, denitrification, anaerobic ammonium oxidation, and ammonification. The focus of this report is the complex biogeochemical process of denitrification, which, in the complete form, consists of a series of four enzyme-catalyzed reduction reactions that transforms nitrate to nitrogen gas...

The increasing production and utilization of polycyclic aromatic hydrocarbons (PAHs) and commercial silver nanoparticles (AgNPs) have raised concerns about their potential environmental release, with coastal sediments as a substantial sink. To better understanding the effects of these contaminants on denitrification processes in coastal marine sediments, a short-term exposure simulation experiment was conducted. We investigated the effects of single and combined contamination of phenanthrene (Phe) and AgNPs on denitrification processes in a coastal marine sediment...

Paddy fields are hotspots of microbial denitrification, which is typically linked to the oxidation of electron donors such as methane (CH4 ) under anoxic and hypoxic conditions. While several anaerobic methanotrophs can facilitate denitrification intracellularly, whether and how aerobic CH4 oxidation couples with denitrification in hypoxic paddy fields remains virtually unknown. Here we combine a ~3300 km field study across main rice-producing areas of China and 13 CH4 -DNA-stable isotope probing (SIP) experiments to investigate the role of soil aerobic CH4 oxidation in supporting denitrification...

Achieving partial denitrification (PD) by using fermentation products extracted from waste activated sludge (WAS) rather than commercial organic matters is a promising approach for providing nitrite for anammox, while sludge reduction could also be realized by WAS reutilization. This study proposed an In-situ Sludge Fermentation coupled with Partial Denitrification (ISFPD) system and explored its performance under different conditions, including initial pH, nitrate concentration, and organic matters. Results showed that nitrite production increased with the elevation of initial pH (from 6 to 9), and the highest nitrate-to-nitrite transformation ratio (NTR) reached 77% at initial pH 9...

Under the influence of many factors, such as climate change, anthropogenic eutrophication, and the development of aquaculture, the area and frequency of algal blooms have showed an increasing trend worldwide, which has become a challenging issue at present. However, the coupled relationship between nitrous oxide (N2 O) and algal blooms and the underlying mechanisms remain unclear. To address this issue, 15 N isotope cultures and quantitative polymerase chain reaction (qPCR) experiments were conducted in Zhanjiang Bay during algal and non-algal bloom periods...

Composting is widely used for organic waste management and is also a major source of nitrous oxide (N2 O) emission. New insight into microbial sources and sinks is essential for process regulation to reduce N2 O emission from composting. This study used genome-resolved metagenomics to decipher the genomic structures and physiological behaviors of individual bacteria for N2 O sources and sinks during composting. Results showed that several nosZ -lacking denitrifiers in feedstocks drove N2 O emission at the beginning of the composting...

The active denitrifying communities performing methane oxidation coupled to denitrification (MOD) were investigated using samples from an aerobic reactor (∼ 20% O2 and 2% CH4 ) and a microaerobic reactor (2% O2 , 2% CH4 ) undertaking denitrification. The methane oxidation metabolites excreted in the reactors were acetate, methanol, formate and acetaldehyde. Using anaerobic batch experiments supplemented with exogenously supplied 13 C-labelled metabolites, the active denitrifying bacteria were identified using 16S rRNA amplicon sequencing and RNA-stable isotope probing (RNA-SIP)...

Although complexation between dissolved organic matter (DOM) and ubiquitous Fe is known to have a major influence on electron transferring ability in redoximorphic soil, it was unclear whether and how this complexation affected nitrate reduction and N2 O productivity. The nitrate reduction of paddy soil in the presence of crop residues returning under flooding conditions was explored in this study. The rate of nitrate reduction in control soil was 0.0677 d-1 , while it improved 1.99 times in treatment soil with Chinese milk vetch (CMV) straw returning...

A limited understanding of microbial interactions and community assembly mechanisms in constructed wetlands (CWs), particularly with different substrates, has hampered the establishment of ecological connections between micro-level interactions and macro-level wetland performance. In this study, CWs with distinct substrates (zeolite, CW_A; manganese ore, CW_B) were constructed to investigate the nutrient removal efficiency, microbial interactions, metabolic mechanisms, and ecological assembly for treating rural sewage with a low carbon-to-nitrogen ratio...

Due to limited land availability in municipal wastewater treatment plants, integrated fixed-film activated sludge (IFAS) technology offers significant advantages in improving nitrogen removal performance and treatment capacity. In this study, two systems, IFAS and Anaerobic-Anoxic-Oxic Activated sludge process (AAO), were compared by adjusting parameters such as hydraulic retention time (HRT), nitrifying solution recycle ratio, sludge recycle ratio, and dissolved oxygen (DO). The objective was to investigate pollutant removal capacity and differences in microbial community composition between the two systems...

In this study, a SNAD-SBBR process was implemented to achieve ammonia removal and carbon reduction of mature landfill leachate under extremely low dissolved oxygen conditions (0.051 mg/L) for a continuous operation of 266 days. The process demonstrated excellent removal performance, with ammonia nitrogen removal efficiency reaching 100 %, total nitrogen removal efficiency reaching 87.56 %, and an average removal rate of 0.180 kg/(m3 ·d). The recalcitrant organic compound removal efficiency reached 34...

Aerobic denitrification has emerged as a promising and efficient method for nitrogen removal from wastewater. However, the direct application of aerobic denitrifying bacteria has faced challenges such as low nitrogen removal efficiency, bacterial loss, and poor stability. To address these issues, this study developed a novel microbial particle carrier using NaHCO3 -modified polyvinyl alcohol (PVA)/sodium alginate (SA) gel (NaHCO3 -PVA/SA). This carrier exhibits several advantageous properties, including excellent mass transfer efficiency, favorable biocompatibility, convenient film formation, abundant biomass, and exceptional pollutant treatment capacity...

An in situ integrated system, consisting of ecological floating islands (EFI), ecological riverbeds (ER), and ecological filter dams (EFD), was built in a ditch only receiving the effluent of sewage plant; the effect of in situ technologies on the distribution of aquatic pathogen was investigated. The results showed the aquatic pathogen decreased along the ditch. Specifically, the relative abundance of Legionella, Aeromonas, and Acinetobacter decreased from 0.032, 0.035, and 0.26 to 0.026%, 0.012%, and 0.08%, respectively...

Recent studies show that greenhouse gas (GHG) emissions from urban landscape water are significant and cannot be overlooked, underscoring the need to develop effective strategies for mitigating GHG production from global freshwater systems. Calcium peroxide (CaO2 ) is commonly used as an eco-friendly reagent for controlling eutrophication in water bodies, but whether CaO2 can reduce GHG emissions remains unclear. This study investigated the effects of CaO2 dosage on the production of methane (CH4 ) and nitrous oxide (N2 O) in urban landscape water under anoxic conditions during summer...

Global warming trend is accelerating. This study proposes a green and economical methane (CH4 ) control strategy by plant combination in constructed wetlands (CWs). In this study, a single planting of Acorus calamus L. hybrid constructed wetland (HCW-A) and a mixed planting of Acorus calamus L. and Eichhornia crassipes (Mart.) Solms hybrid constructed wetland (HCW-EA) were constructed. The differences in nitrogen removal performance and CH4 emissions between HCW-A and HCW-EA were compared and analyzed. The findings indicated that HCW-EA demonstrated significant improvements over HCW-A, with NH4 + -N and TN removal rates increasing by 21...

Nitrate attenuation during river bank infiltration is the key process for reducing nitrogen pollution. Temperature is considered to be an important factor affecting nitrate attenuation. However, the magnitude and mechanism of its impact have not been clear for a long time. In this study, the effects of temperature and temperature gradient on the nitrate denitrification rate were investigated via static batch and dynamic soil column simulation experiments. The results showed that temperature had a significant effect on the denitrification rate...

Nitrate leaching from agricultural soils is increasingly found in groundwater, a primary source of drinking water worldwide. This nitrate influx can potentially stimulate the biological oxidation of iron in anoxic groundwater reservoirs. Nitrate-dependent iron-oxidizing (NDFO) bacteria have been extensively studied in laboratory settings, yet their ecophysiology in natural environments remains largely unknown. To this end, we established a pilot-scale filter on nitrate-rich groundwater to elucidate the structure and metabolism of nitrate-reducing iron-oxidizing microbiomes under oligotrophic conditions mimicking natural groundwaters...

Nitrate-nitrogen pertains to the nitrogen component of the overall nitrate present in a given sample in order to reduce nitrate nitrogen pollution in water, nitrate nitrogen removal methods based on iron-carbon micro-electrolysis have become a key research focus. The process and mechanism of nitrate nitrogen removal by microbial coupling was comprehensively explored in a novel iron-carbon micro-electrolysis (ICME) system. In order to establish the transformation pathway of nitrate nitrogen in water, the transformation paths of nitrate nitrogen in water before and after coupling microorganisms in three groups of continuous flow reaction devices, namely sponge iron (s-Fe0 ), sponge iron + biochar (s-Fe0 /BC) and sponge iron + biochar + manganese sand (s-Fe0 /BC/MS), were studied...