Nitrification Denitrification Research Articles

Exploring the potential of biochar for the remediation of microbial communities and element cycling in microplastic-contaminated soil

The detrimental effects of microplastics (MPs) on soil microbial and elemental raise significant environmental concerns. The potential of remediation with biochar to mitigate these negative impacts remains an open question. The remediation effects of biochar derived from corn and cotton straw on MPs concerning soil microorganisms and element cycling were investigated. Specifically, biochar induced substantial remediations in microbial community structure following MP exposure, restoring and fortifying the symbiotic network while exerting dominance over microbial community changes. A combined treatment of biochar and MPs exhibited a noteworthy increase in the abundance of NH4+, NO3−, and available phosphorous by 0.46–2.1 times, reversing the declining trend of dissolved organic carbon, showing a remarkable increase by 0.36 times. This combined treatment also led to a reduction in the abundance of the nitrogen fixation gene nifH by 0.46 times, while significantly increasing the expression of nitrification genes (amoA and amoB) and denitrification genes (nirS and nirK) by 22.5 times and 1.7 times, respectively. Additionally, the carbon cycle cbbLG gene showed a 2.3-fold increase, and the phosphorus cycle gene phoD increased by 0.1-fold. The mixed treatment enriched element-cycling microorganisms by 4.8–9.6 times. In summary, the addition of biochar repaired the negative effects of MPs in terms of microbial community dynamics, element content, gene expression, and functional microbiota. These findings underscore the crucial role of biochar in alleviating the adverse effects of MPs on microbial communities and elemental cycling, providing valuable insights into sustainable environmental remediation strategies.

Ecological processes in separated structures of electroactive wetlands: Determinism versus stochasticity

Combined systems are an important direction in electroactive wetlands (EWs) research, with unique advantages in treating high-nutrient wastewater, but neither series nor parallel mode is conducive to system stabilization and performance enhancement. To evaluate the relationships between different series and parallel combined designs and the performance of systems, two combined designs based on two-stage EWs were proposed: pre-multiple parallel (MP) (A) and post-MP (B). The two-stage series design (C) was used as the control. Design A exhibited superior nitrogen (72.81 % ± 0.30 %) and phosphorus (92.78 % ± 0.01 %) removal efficiency as well as power production. There was coupling of shortcut nitrification denitrification (SCND) and anaerobic ammonium oxidation (ANAMMOX) in A, which increased the maximum series current density (27.03 mA/m2) and reduced the internal resistance (39.97 Ω). The pre-MP design increased the stochasticity of microbial community assembly (R2 = 0.8781) in accordance with neutral community model, which led to the enhancement of diversity and the functional potential of the microbial community. Proteobacteria was the dominant phylum of the cathodic microbial community and was mainly present in A, accounting for 38.86 %–65.06 %, and played a dominant role in nitrogen removal. Metabolites mediated information exchange between plants and microorganisms; this signaling rate was more rapid in A, which increased the sensitivity of the organisms to environmental changes. This study offers a new approach for practical treatment of rural domestic sewage and engineering applications of EWs.

Intermittent hydroxylamine dosing to strengthen stability of partial nitrification and nitrogen removal efficiency through continuous-flow anaerobic–aerobic-anoxic reactor treating municipal wastewater

Intermittent hydroxylamine (NH2OH) dosing strategy was applied to enhance the stability of partial nitrification and total nitrogen (N) removal efficiency (TNRE) in a continuous-flow process. The results showed 2 mg/L of NH2OH dosing (once every 6 h) could maintain stably partial nitrification with nitrite accumulation rate (NAR) of 91.6 % and TNRE of 92.6 %. The typical cycle suggested NH2OH dosing could promote simultaneous nitrification–denitrification (SND) and endogenous denitrification (END) while inhibit exogenous denitrification (EXD). Nitrification characteristics indicated the NH2OH dosing enhanced stability of partial nitrification by suppressing specific nitrite oxidation rate (SNOR), Nitrospira and nitrite oxidoreductase enzyme (Nxr). The microbial community suggested the aerobic denitrfiers, denitrifying glycogen accumulating organisms (DGAOs) and traditional denitrfiers were the potential contributor for advanced N removal. Moreover, NH2OH dosage was positively associated with NAR, SND and END. Overall, this study offers a feasible strategy to maintain sustainably partial nitrification that has great application potential.

Effects of Cd(II) on nitrogen removal by a heterotrophic nitrification aerobic denitrification bacterium Pseudomonas sp. XF-4

Simultaneous heterotrophic nitrification and aerobic denitrification (SND) is gaining tremendous attention due to its high efficiency and low cost in water treatment. However, SND on an industrial scale is still immature since effects of coexisting pollutants, for example, heavy metals, on nitrogen removal remains largely unresolved. In this study, a HNAD bacterium (Pseudomonas sp. XF-4) was isolated. It could almost completely remove ammonium and nitrate at pH 5–9 and temperature 20 ℃-35 ℃ within 10 h, and also showed excellently simultaneous nitrification and denitrification efficiency under the coexistence of any two of inorganic nitrogen sources with no intermediate accumulation. XF-4 could rapidly grow again after ammonium vanish when nitrite or nitrate existed. There was no significant effects on nitrification and denitrification when Cd(II) was lower than 10 mg/L, and 95 % of Cd(II) was removed by XF-4. However, electron carrier and electron transport system activity was inhibited, especially at high concentration of Cd(II). Overall, this study reported a novel strain capable of simultaneous nitrification and denitrification coupled with Cd(II) removal efficiently. The results provided new insights into treatment of groundwater or wastewater contaminated by heavy metals and nitrogen.

Partial nitrification and simultaneous denitrification in sequential anaerobic and aerobic reactors: performance and microbial community dynamics

ABSTRACT The removal of organic matter and nitrogen from domestic sewage was evaluated using a system composed of two sequential reactors: an anaerobic reactor (ANR) with suspended sludge and an aerobic (AER) reactor with suspended and adhered sludge to polyurethane foams. Nitrogen removal consisted of AER operating at low dissolved oxygen (DO) concentrations; this favoured the simultaneous nitrification and denitrification (SND) process. The concentration of COD and N were 440 mgO2.L−1 and 37 mgTN.L−1, respectively. The operation was divided into three phases (P), lasting 51, 53, and 46 days, respectively. The initial DO concentrations applied in the AER were: 3.0 (PI) and 1.5 mg.L−1 (PII and PIII). In PIII, the AER effluent was recirculated to the ANR at a ratio of 0.25. Kinetic assays were performed to determine the nitrification and denitrification rates of the biomasses (ANR and AER in PIII). Changes in the microbial community were evaluated throughout phases PI to PIII by massive sequencing. In PIII, the best results obtained for chemical oxygen demand (COD) and total nitrogen (TN-N) removal efficiencies, were close to 94% and 65%, respectively. Under these conditions, system effluent concentrations below 30 mg COD.L−1 and 15 mg TN-N.L−1 were verified. The nitritation and nitration rates were 10.5 and 6.5 mg N.g VSS−1.h−1, while the denitrification via nitrite and nitrate were 6.8 and 5.8 mg N.g VSS−1.h−1, respectively. A mixotrophic community was prevalent, with Rhodococcus, Nitrosomonas, Pseudomnas, and Porphyromonas being dominant or co-dominant in most of the samples, confirming the SND process in the AER sludge.

A comparative study of algal-bacterial granular sludges and aerobic granular sludge at different C/N ratio: Granule characteristics, SND progress and Microbial community

The algal-bacterial synergistic effect in algal-bacterial granular sludge (ABGS) made its nitrogen metabolism mechanism different from that of aerobic granular sludge (AGS). In this study, the effects of algae on granules characteristics, SND process and community structure in ABGS were studied by treating wastewater with different C/N (13:1–20:1) ratios. The results showed that ABGS and AGS had excellent nitrogen removal capacity of 86 % and 91 %, respectively, and SND efficiency was above 90 %. ABGS granules were looser due to the phototaxis of algae, and the oxygen penetration depth was higher than that of AGS. The NH4+-N removal efficiency of AGS was higher than that of ABGS, but the SND efficiency of ABGS was better than that of AGS. In ABGS, photosynthesis provided organic carbon for denitrification in anaerobic period, and organic carbon might be more important than strict anaerobic environment. In aerobic period, The SND process in ABGS was mainly heterotrophic nitrification aerobic denitrification (HAND), while in AGS was conventional simultaneous nitrification denitrification (CSND). The results of this study would provide a theoretical foundation for further understanding the difference between ABGS and AGS nitrogen removal mechanisms and help to further expand the application of ABGS in practical engineering.

Nanoparticles of Zinc Oxides Mitigated N2O Emissions in Tea Plantation Soil

The excessive application of nitrogen in tea plantations leads to severe soil acidification and N2O emission boosting. To promote sustainable agriculture, nanoparticles (NPs) have emerged as alternative fertilizers, but their effects on soil nitrification and greenhouse gas emissions in tea plantations remain unclear. In this study, the effects of NP type (ZnO-NPs and Fe2O3-NPs) and dose (0, 1, 10, and 100 mg·kg−1) on soil N2O emissions were investigated via a lab incubation trial. Soil pH, ammonium, and nitrate changes were also monitored during the incubation period. The abundance of functional genes related to nitrification and denitrification processes was analyzed as well. The results showed that ZnO-NPs led to a decrease in N2O emissions. The reduction effect was stronger with increasing dose and resulted in a 33% reduction at an addition rate of 100 mg·kg−1. The cumulative N2O emissions had significantly positive correlations with NH4+-N and NO3−-N. ZnO-NP addition showed a significantly negative effect on Ammonia-Oxidizing Archaea (AOA) but a positive effect on Ammonia-Oxidizing Bacteria (AOB) gene abundance. In contrast, Fe2O3-NPs showed an insignificant impact on N2O emissions and soil N content, as well as nitrification–denitrification gene abundance, regardless of different doses. These results imply that the application of ZnO-NPs may inhibit nitrification through the retarding of AOA activity. This study provided us with a potential practice to reduce N2O emissions in tea plantations by applying ZnO-NPs, but the efficiency of this reduction needs further examination under ambient conditions before field application.

Nitrification–Autotrophic Denitrification Using Elemental Sulfur as an Electron Donor in a Sequencing Batch Reactor (SBR): Performance and Kinetic Analysis

Simultaneous nitrification and autotrophic denitrification (SNAD) has received attention as an efficient biological nitrogen removal alternative. However, SNAD using elemental sulfur (S0) has scarcely been studied. Thus, the main objective of this research was to study the behavior of a simultaneous nitrification–autotrophic denitrification operation in a sequential batch reactor (SNAD-SBR) at a lab scale using S0 as an electron donor, including its kinetics. Two-scale reactors were operated at lab scales in cycles for 155 days with an increasing nitrogen loading rate (NLR: 0.0296 to 0.0511 kg N-NH4+/m3/d) at 31 °C. As a result, simultaneous nitrification–autotrophic denitrification using S0 as an electron donor was performed successfully, with nitrification efficiency of 98.63% and denitrification efficiency of 44.9%, with autotrophic denitrification as the limiting phase. The kinetic model adjusted for ammonium-oxidizing bacteria (AOB) was the Monod-type kinetic model (µmax = 0.791 d−1), while, for nitrite-oxidizing bacteria (NOB), the Haldane-type model was employed (µmax = 0.822 d−1). For denitrifying microorganisms, the kinetic model was adjusted by a half order (k1/2v = 0.2054 mg1/2/L1/2/h). Thus, we concluded that SNAD could be feasible using S0 as an electron donor, with kinetic behavior similar to that of other processes.

Genetic variation in Zea mays influences microbial nitrification and denitrification in conventional agroecosystems

Abstract Background and Aims Nitrogenous fertilizers provide a short-lived benefit to crops in agroecosystems, but stimulate nitrification and denitrification, processes that result in nitrate pollution, N2O production, and reduced soil fertility. Recent advances in plant microbiome science suggest that genetic variation in plants can modulate the composition and activity of rhizosphere N-cycling microorganisms. Here we attempted to determine whether genetic variation exists in Zea mays for the ability to influence the rhizosphere nitrifier and denitrifier microbiome under “real-world” conventional agricultural conditions. Methods To capture an extensive amount of genetic diversity within maize we grew and sampled the rhizosphere microbiome of a diversity panel of germplasm that included ex-PVP inbreds (Z. mays ssp. mays), ex-PVP hybrids (Z. mays ssp. mays), and teosinte (Z. mays ssp. mexicana and Z. mays ssp. parviglumis). From these samples, we characterized the microbiome, a suite of microbial genes involved in nitrification and denitrification and carried out N-cycling potential assays. Results Here we are showing that populations/genotypes of a single species can vary in their ecological interaction with denitrifers and nitrifers. Some hybrid and teosinte genotypes supported microbial communities with lower potential nitrification and potential denitrification activity in the rhizosphere, while inbred genotypes stimulated/did not inhibit these N-cycling activities. These potential differences translated to functional differences in N2O fluxes, with teosinte plots producing less GHG than maize plots. Conclusion Taken together, these results suggest that Zea genetic variation can lead to changes in N-cycling processes that result in N leaching and N2O production, and thereby are selectable targets for crop improvement. Understanding the underlying genetic variation contributing to belowground microbiome N-cycling into our conventional agricultural system could be useful for sustainability.

Forming densified activated sludge in a modified simultaneous nitrification–denitrification and phosphorus removal (SNDPR) system by introducing shift work mode

Forming granular-like sludge in the Simultaneous Nitrification-Denitrification and Phosphorus Removal (SNDPR) process would promote nutrient removal and improve the sludge settleability. This study introduced the “shift work mode” into an SNDPR system, which featured that 50 % of sludge was temporarily transferred into and “rested” in a side-stream reactor a cyclic time rather than let it keep “working” in the mainstream SNDPR reactor. Results showed that 77.6 % of inorganic nitrogen and 80.6 % of orthophosphate were removed well even after the combination, which attributed to the co-work of Candidatus_Competibacter (10.1 %–29.0 %), nitrifiers, and phosphate accumulating organisms. The 30-min settled sludge volume and sludge volume index were 8 % and 45.8 mL/g, respectively, the sludge density was 1.045 g/mL, and cumulative 90 % of the particle diameter was less than 80 µm; these indicated the densified activated sludge was formed. After analyses, the increase in the food-to-microorganisms ratio and temporary enrichment of filamentous bacteria Thiothrix might be the causes. Such shift work mode promisingly serves as a simple and practical way to improve settleability and promote granulation.

Treatment of Pickle Wastewater under Varying Salinity Conditions within the Sequencing Batch Biofilm Reactor System

Pickle wastewater is a highly saline organic effluent that poses a significant ecological risk. In this study, a sequencing batch biofilm reactor (SBBR) was used to treat such wastewater, and a denitrification system capable of simultaneously removing high levels of nitrogen and organic matter was successfully established. Through salinity incremental increase, the system operated stably, and the removal rates of COD, TN, and NH4+-N could be maintained at about 96%, 93%, and 99% under the salinity of 3.0%. The effect of salinity on the structure and function of microbial communities in the reactor was investigated by high-throughput sequencing. The results showed that increasing salinity could reduce the diversity, change the structure, and reduce the functionality of the microbial community. Under high-salt conditions (salt content of 3.0%), salt-tolerant microorganisms such as Actinobacteriota became dominant populations. As salinity increased, NOB (nitrite oxidizing bacteria) was strongly inhibited, and its abundance decreased rapidly until it disappeared. Partial nitrification–denitrification (PND) gradually became the main denitrification pathway. In conclusion, this experiment not only shows that SBBR treatment of pickle wastewater has strong feasibility, but also provides a theoretical research basis for the engineering treatment of pickle wastewater.

Conversion behavior of heterotrophic nitrification - aerobic denitrification bacterium Paracoccus denitrificans HY-1 in nitrogen and phosphorus removal

The heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria harbored remarkable removal capacity in eliminating single nitrogen pollutant, but their comprehensive performance in dealing with mixed nitrogen sources remained unknown. In this study, the denitrification capacity of HN-AD bacteria Paracoccus denitrificans HY-1 was explored through whole-genome sequencing and nitrogen metabolic pathway analysis, and the complex nitrogen sources with gradient concentration were used to validate its nitrogen removal efficiency under both aerobic and anaerobic conditions. The results demonstrated that strain HY-1 harbored an efficient degradation capacity on three nitrogen sources, and the removal rates of NH4+-N, NO2−-N and NO3−-N were 10.67 mg·L−1·h−1, 27.81 mg·L−1·h−1, and 22.05 mg·L−1·h−1, respectively. The denitrification rate of 15.33 mg·L−1·h−1 was obtained under anaerobic condition with mixed nitrogen sources. Also, the simultaneous nitrification denitrification phosphorus removal (SNDPR) trial revealed that strain HY-1 could eliminate PO43−-P with a rate of 0.38 mg·L−1·h−1 under coexistence condition of the three nitrogen sources. Combined with the nitrogen balance analysis, the results indicated that strain HY-1 possesses a great potential for application in complex nitrogen and phosphorus contaminated environments.

Harnessing the Potential of Extracellular Polymeric Substances in Enhancing ANAMMOX Processes: Mechanisms, Strategies, and Perspectives

Anaerobic ammonium oxidation (ANAMMOX) has emerged as a promising sustainable nitrogen removal technology that offers significant advantages over conventional nitrification–denitrification processes, such as reduced energy consumption, a 60% reduction in oxygen demand, and a 90% reduction in sludge production. However, the practical application of ANAMMOX is hindered by several challenges, including the slow growth of ANAMMOX bacteria, long start-up periods, and high sensitivity to environmental disturbances. Recent studies have highlighted the crucial role of extracellular polymeric substances (EPSs) in the formation, activity, and stability of ANAMMOX biofilms and granules. An EPS is a complex mixture of high-molecular-weight polymers secreted by microorganisms, mainly composed of polysaccharides, proteins, nucleic acids, and lipids. The diverse physicochemical properties and functional groups of EPSs enable them to serve as a structural scaffold, protective barrier, sorption site, electron shuttle, and nutrient source for ANAMMOX bacteria. This review aims to provide an overview of the latest research progress on harnessing the potential of EPSs to enhance the ANAMMOX process. The characteristics, compositions, and extraction methods of ANAMMOX-derived EPSs are summarized. The mechanisms of how EPSs facilitate the enrichment, immobilization, aggregation, and adaptation of ANAMMOX bacteria are elucidated. The strategies and effects of EPS supplementation on improving the performance and robustness of ANAMMOX reactors under various stresses are critically reviewed. The challenges and future perspectives of the EPS-mediated optimization of the ANAMMOX process are also discussed. This review sheds new light on exploiting EPSs as a renewable bioresource to develop more efficient and stable ANAMMOX applications for sustainable wastewater treatment.

Simultaneous removal of ammonia nitrogen, calcium and cadmium in a biofilm reactor based on microbial-induced calcium precipitation: Optimization of conditions, mechanism and community biological response

With the enhancement of environmental governance regulations, the discharge requirements for reverse osmosis wastewater have become increasingly stringent. This study proposes an innovative approach utilizing heterotrophic nitrification and aerobic denitrification (HNAD)-based biomineralization technology, combined with coconut palm silk loaded biochar, to offer a novel solution for resource-efficient and eco-friendly treatment of reverse osmosis wastewater. Zobellella denitrificans sp. LX16 were loaded onto modified coir silk and showed removal efficiencies of up to 97.38, 94.58, 86.24, and 100% for NH4+-N (65 mg L−1), COD (900 mg L−1), Ca2+ (180 mg L−1), and Cd2+ (25 mg L−1). Analysis of the metabolites of microorganisms reveals that coconut palm silk loaded with deciduous biochar (BCPS) not only exerts a protective effect on microorganisms, but also enhances their growth, metabolism, and electron transfer capabilities. Characterization of precipitation phenomena elucidated the mechanism of Cd2+ removal via ion exchange, precipitation, and adsorption. Employing high-throughput and KEGG functional analyses has confirmed the biota environmental response strategies and the identification of key genes like HNAD.

Nitrogen removal and carbon reduction of mature landfill leachate under extremely low dissolved oxygen conditions by simultaneous partial nitrification anammox and denitrification

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 34.96 %. Nitrogen mass balance analysis revealed that the Anammox process contributed to approximately 98.1 % of the nitrogen removal. Candidatus Kuenenia achieved a relative abundance of 1.49 % in the inner layer of the carrier. In the SNAD-SBBR system, the extremely low DO environment created by the highly efficient partial nitrification stage enabled the coexistence of AnAOB, denitrifying bacteria, and Nitrosomonas, synergistically achieving ammonia removal and carbon reduction. Overall, the SNAD-SBBR process exhibits low-cost and high-efficiency characteristics, holding tremendous potential for landfill leachate treatment.

Nitrate denitrification rate response to temperature gradient change during river bank infiltration.

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. Temperature effects were first observed in denitrifying bacteria. At low temperatures, the microorganism diversity was low, resulting in a lower denitrification rate constant. The static experimental results showed that the denitrification rate at 19°C was approximately 2.4 times that at 10°C. The dynamic soil column experiment established an exponential positive correlation between the nitrate denitrification decay kinetic constant and temperature. The affinity of denitrifying enzymes for nitrate in the reaction substrate was ordered as follows: decreasing temperature gradient (30°C → 10°C) > zero temperature gradient (10°C) > increasing temperature gradient condition (0°C → 10°C). This study provides a theoretical basis for the biogeochemical processes underlying river bank infiltration, which will help aid in the development and utilization of groundwater resources.

Research Progress,Problems and Future Prospects of A New Combined Anaerobic Ammonia Oxidation and Nitrogen Removal Process

Anaerobic ammonium oxidation (Anammox) is a cost-effective and efficient process for nitrogen removal, which has attracted widespread attention in the field of wastewater treatment due to its significant advantages. However, the slow rate of growth of anaerobic ammonium oxidizing bacteria (AnAOB) and its sensitivity to operational and environmental conditions hinder its wide application. Although various control strategies have been explored and developed, the application of Anammox process still faces many challenges, including unstable nitrogen removal performance and the necessity for additional treatment of effluent nitrate nitrogen. Due to the importance and necessity of Anammox in wastewater denitrification, this paper first introduces the present biological denitrification system based on Anammo. In view of the insufficient source of nitrite nitrogen in nitrogen-containing wastewater, nitrite nitrogen can be provided by partial nitrification (PN) or partial denitrification (PD) , however, the stability of system operation and efficiency of denitrification are still the difficulties in Anammox engineering applications. It is especially crucial to study the combined new processes based on Anammox to achieve stable deep biological nitrogen removal from wastewater. Therefore, this paper focuses on latest research progress in Anammox coupled simultaneous partial nitrification, denitrification and anammox (SPNDA) , constructed wetland (CW) , phosphorus removal/ recovery process, sulfur denitrification removal (SDA) and denitrifying anaerobic methane oxidation (ADAMO) . The nitrogen removal performance, influencing factors, operation advantages, research progress, application prospects and challenges are reviewed. Compared with the single Anammox process, the combined process offers several advantages, including overcoming the issue of nitrate in the effluent (SPNDA, A-DAMO, SDA) , alleviate the inhibition of organic matter on AnAOB (SPNDA, SDA) , recover non-renewable resources (HAP) , and achieve a clean environment with significant economic benefits (A-CW) , providing flexibility for the promotion and application of Anammox process. The study outlines future directionsfor researching, developing, and applying the Anammox combined nitrogen removal process, and at the same time provides as a reference for lowering energy consumption, achieving efficient and stable nitrogen removal processes, and broadensing the scope of engineering application.

Start-up of pilot-scale ANAMMOX reactor for low-carbon nitrogen removal from anaerobic digestion effluent of kitchen waste

The pilot-scale simultaneous denitrification and methanation (SDM)-partial nitrification (PN)-anaerobic ammonia oxidation (Anammox) system was designed to treat anaerobic digestion effluent of kitchen waste (ADE-KW). The SDM-PN was first started to avoid the inhibition of high-concentration pollutants. Subsequently, Anammox was coupled to realize autotrophic nitrogen removal. Shortcut nitrification–denitrification achieved by the SDM-PN. The NO2–-N accumulation (92 %) and NH4+-N conversion (60 %) were achieved by PN, and the removal of TN and COD from the SDM-PN was 70 % and 73 %, respectively. After coupling Anammox, the TN (95 %) was removed with a TN removal rate of 0.51 kg·m−3·d-1. Microbiological analyses showed a shift from dominance by Methanothermobacter to co-dominance by Methanothermobacter, Thermomonas, and Flavobacterium in SDM during the SDM-PN. While after coupling Anammox, Candidatus kuenenia was enriched in the Anammox zone, the SDM zone shifted back to being dominated by Methanothermobacter. Overall, this study provides new ideas for the treatment of ADE-KW.

Enhancing swine manure treatment: A full-scale techno-economic assessment of nitrogen recovery, pure oxygen aeration and effluent polishing

In regions with intensive livestock production, managing the environmental impact of manure is a critical challenge. This study, set in Flanders (Belgium), evaluates the effectiveness of integrating process intensification measures into the treatment of piggery manure to mitigate nitrogen (N) surplus issues. The research investigates the techno-economic benefits of implementing three key interventions: pure oxygen (PO) aeration, ammonia (NH3) stripping-scrubbing (SS) pretreatment, and tertiary treatment using constructed wetlands (CW), within the conventional nitrification-denitrification (NDN) process.Conducted at a full-scale pig manure treatment facility, our analysis employs steady-state mass balances for N and phosphorus (P) to assess the impact of these process intensification strategies. Findings indicate that the incorporation of advanced treatment steps significantly enhances the efficiency and cost-effectiveness of the manure management system. Specifically, the application of PO aeration is shown to reduce overall treatment costs by nearly 4%, while the addition of an NH3 SS unit further decreases expenses by 1–2%, depending on the counter acid utilized. Moreover, the implementation of a CW contributes an additional 4% in cost savings.Collectively, these measures offer substantial improvements in processing capacity, reduction of by-product disposal costs, and generation of additional revenue from high-quality fertilising products. The study highlights the potential of advanced treatment technologies to provide economically viable and environmentally sustainable solutions for manure management in livestock-dense regions, emphasizing the cumulative economic benefit of a holistic approach to process intensification (10%).

Promoting denitrification via high electron conversion ratio in the iron valence Cycle: Prospects for Pseudomonas sp. JM-7 application in environmental engineering

The interdependence between iron and nitrogen in the environment is of utmost importance, and this study has explored the intricate relationship between denitrification and iron valence cycling using Pseudomonas sp. strain JM-7 (P. JM-7) as a model bacteria. Our research demonstrated that P. JM-7 had the ability to effectuate electron transfer from the periplasmic space to electron acceptors, such as nitrate, via Cytochrome c-proteins (c-Cyts). We found that iron valence state transformations with Fe(II)/Fe(III) promoted P. JM-7′s denitrification of nitrate coupled to yeast extract powder (YEP) oxidation. Denitrification rates depended on temperature (>21 °C) and pH (6–9). During logarithmic growth, 5 g/L YEP enabled 350 mg/L nitrate removal, increasing to 1650 mg/L in stable growth. Addition of 4 mM Fe(II)/Fe(III) increased denitrification to 500 mg/L during logarithmic growth. The dynamic test results displayed that compared to the SiO2 filler control group, iron-containing fillers could facilitate P. JM-7 to reduce 100 mg/L nitrate with 50 mg/L YEP electrons, corresponding to 6 times the maximum electron transfer efficiency in the static test. Overall, iron redox cycling significantly enhanced P. JM-7 denitrification, imparting insights into iron–nitrogen interactions. In summary, our research imparts valuable insights into the nexus between iron and nitrogen in the environment, highlighting the potential application of P. JM-7 in environmental engineering. Our findings indicate that P. JM-7 exhibits a significant denitrification capability, and further research is recommended to investigate its ability to remove phosphorus and promote sustainable environmental remediation practices.