Low NH3 Research Articles

Layered Ti3C2Tx MXene heterostructured with V2O5 nanoparticles for enhanced room temperature ammonia sensing

To enhance ammonia sensing at room temperature (25°C), Two-dimensional transition metal carbonyl nitride (Ti3C2Tx MXene) modified by vanadium pentoxide nanoparticle (V2O5) is synthesized by hydrothermal method. The effects of weight ratio on the microstructure and ammonia sensing performance at room temperature are studied. The results indicate that when the weight percentage of V2O5 is 25 %, V2O5 nanoparticles with an average size of 90.33 nm are produced on the surface and between the layers of the two-dimensional MXene. The prepared MXene/V2O5 composites sensor has a good response (12.12) to 10 ppm NH3. The enhanced sensing performance can be attributed to the modification of V2O5 nanoparticles as well as the catalytic effect and the formation of heterojunction. The doped V2O5 nanoparticles open up the unstratified portion of MXene and catalyze the chemisorption of oxygen and oxidation of NH3. The difference in Fermi level between two-dimensional MXene and V2O5 drives the charge transfer at the heterojunction interface, enriching the electrons on the surface of V2O5, thus improving the sensitivity. Density functional theory suggests that the composite adsorption system is more stable and has lower NH3 adsorption energy. This work provides a feasible route to develop high-performance gas sensors with MXene-based composites.

Effects of cutting schedule and inoculation on chemical composition, ensiling characteristics and digestive utilisation of alfalfa silages

ABSTRACT The objective of this study was to evaluate the effects of ensiling alfalfa cut in the morning or the afternoon with or without inoculant on chemical composition, ensiling characteristics, and digestive utilisation of alfalfa silages. Fresh forage was obtained from 3 plots of alfalfa, each one subdivided into 12 subplots. The experimental design was a 2 × 2 factorial (cut AM or PM and with or without inoculant), with three replications (alfalfa plots) and three subsamples (subplots). Forage from each subplot was employed to fill one experimental silo. Variables of chemical composition, fermentation characteristics, and in vitro digestive utilisation were determined. Data obtained were analysed by a mixed procedure and least square means were compared. Correlations between variables of chemical composition of original forage and composition and fermentation of silages, as well as between variables of chemical composition and digestive utilisation of silages were analysed. PM cutting led to silages with higher content of remaining soluble sugars (P = 0.01), lower pH (P < 0.01), lower NH3–N concentration (P = 0.02), and higher IVTDMD (P = 0.03) than silages made in the morning. Providing enough WSC through cutting forage in the afternoon led to improvements in conservation quality and in vitro digestive utilisation and was more effective than inoculating alfalfa.

Non-adiabatic effect on NOx emissions for premixed H2-blended NH3/air combustion under rich-lean-staged conditions

The non-adiabatic effect on NOx emission for the swirl premixed NH3/H2/air combustion under fuel-rich/quick-mix/fuel-lean (RQL) conditions was experimentally studied. The wall temperature of the quartz combustor was controlled by surrounding heating. Results showed that both H2-blending and thermal insulation were in favor of enlarging the low-NOx range and lowering the valley NOx, due to the less NO and unburnt NH3, and smaller flow rate from the primary stage. In the post-flame zone of the primary stage, increasing combustion temperature significantly enhanced NO reduction, Thus, for low NOx emission, it is essential to keep enough thermal insulation there. Experimental measurements also found remarkable N2O could be formed in the secondary stage when combustion temperature was low and much unburnt NH3 was excessive. Kinetic analyses showed this phenomenon was due to the high combination rate of NH and NO, and low reduction rate of H radical.

Electrochemical Synthesis of Metasequoia-Like Reduced Graphene Oxide Coated Cobalt-Silver Catalyst for Stable and Efficient Electrocatalytic Nitrate Reduction to Ammonia.

Electrocatalytic nitrate (NO3 -) reduction to ammonia (NH3) is a green and efficient NH3synthesis technology. Metallic silver (Ag) is one of the well-known electrocatalysts for NO3 - reduction. However, under alkaline conditions, its poor water-splitting ability fails to provide sufficient protonic hydrogen required for NH3 synthesis, resulting in low NH3 selectivity. Additionally, metal catalysts are prone to leaching and oxidation during electrocatalysis, resulting in poor stability. Herein, cobalt (Co) into Ag (CoAg) catalyst is doped, which not only increases the NH3 selectivity by 34.4%, but also reduces the reduction potential by 0.1V. Meanwhile, reduced graphene oxide (rGO) as a protective "armor" is used to encapsulate the CoAg catalyst (rGO2.92@CoAg). The rGO2.92@CoAg catalyst shows excellent stability for over 300 hours (h) of continuous reaction. The Co and Ag contents in the rGO2.92@CoAg catalyst after continuous tests decreases by only 4.3% and 3.1%, respectively, which are much lower than those of the CoAg catalyst without the rGO (90.8%, 52.6%). Moreover, the rGO2.92@CoAg catalyst shows high Faradaic efficiency (99.3%) and NH3 yield rate (1.47mmol h-1 cm-2). Therefore, a high performance and strong stability rGO2.92@CoAg catalyst is obtained by Co doping and rGO coating, which provides theoretical basis for practical industrial application.

Fat Distribution and Urolithiasis Risk Parameters in Uric Acid Stone Formers and Patients with Type 2 Diabetes Mellitus.

Key Points Under a controlled diet, uric acid stone formers (UASFs) and diabetic patients have higher endogenous net acid production.Under a controlled diet, UASFs have lower ammonium-to-net acid excretion ratio.Body fat inversely correlates with urine buffer capacity in normal individuals, but this relationship is lost in diabetic patients and UASFs. Background Uric acid (UA) nephrolithiasis affects approximately 10% of kidney stones, with a greater preponderance among patients with obesity and diabetes mellitus (DM). UA lithogenicity is driven by abnormally acidic urine pH. Distinguishing the contribution of intrinsic (e.g., body adiposity) versus external (e.g., dietary) factors to UA stone propensity is challenging because of uncontrolled diets in outpatients in previously published studies. Methods This compilation of metabolic studies with body composition examined by dual-energy x-ray absorptiometry scan and blood and urine biochemistry collected under a controlled metabolic diet was conducted across three distinct populations: 74 UA stone formers (UASF group), 13 patients with type 2 DM without kidney stones (DM group), and 51 healthy volunteers (HV group). Results Compared with HVs, both UASFs and patients with DM exhibited higher levels of net acid excretion (NAE) and significantly lower urine pH and lower proportion of NAE excreted as ammonium (NH4 +/NAE), all under controlled diets. UASFs exhibited significantly lower NH4 +/NAE compared with patients with DM. UASFs also showed higher total body and truncal fat compared with HVs. Among the HVs, lower NH4 +/NAE ratio correlated with higher truncal and total fat. However, this association was abolished in the UASF and DM groups who exhibit a fixed low NH4 +/NAE ratio across a range of body and truncal fat. Conclusions The findings suggest a dual defect of diet-independent increase in acid production and impaired kidney NH4 + excretion as major contributors to the risk of UA stone formation. There is an inverse physiologic association between body fat content and NH4 +/NAE in HVs, whereas NH4 +/NAE is persistently low in UASFs and patients with DM, regardless of body fat, representing pathophysiology.

Pt-modified hollow tube-like polyaniline-based NH3 sensor

Polyaniline (PANI) has significant applications in room-temperature NH3 detection due to its unique and reversible doping-dedoping chemical state, stable electrical conductivity and easy and convenient synthesis process. However, pristine PANI still suffers from poor performance in terms of sensitivity, response speed and detection limit. To address issues of low sensitivity and high detection limit, a platinum (Pt)-modified hollow PANI (Pt-PANI) sensor was designed. The Pt-PANI was fabricated by an in-situ sacrificial template method, and Pt-MnO2 nanowires obtained from hydrothermal combined impregnation methods, utilizing the potential generated during the sacrificial reaction with acid to induce the polymerization of aniline on the nanowires' surfaces. This hollow tube-like structure with the unique inlay of Pt particles provides numerous gas diffusion pathways, facilitating the penetration of the target gas into the internal space, enhancing the utilization of the inner surface and accelerating the electron transfer. Meanwhile, the presence of Pt particles not only forms Schottky junctions that cause large changes in the resistance of the composites, but also catalysis and accelerates the gas sensing reaction between the target gas and the sensitive materials. Gas sensitivity tests revealed that the prepared Pt-PANI-3 gas sensor exhibits a low NH3 detection limit of 20.3 ppb, along with reproducibility and long-term stability. Compared to pure PANI-sensor, the sensitivity to 20 ppm NH3 increased by 17 times. This work offers real-time sensing and monitoring of environmental changes, making it highly promising for future applications.

Optimization control strategy for diesel urea-selective catalytic reduction (SCR) urea injection based on the interior point method (IP) + higher order SCR model

In order to ensure that the NOx and NH3 emissions of diesel engines comply with the Euro VII emission standards, this paper optimizes the urea injection using a SCR model combined with the interior point method. First, the equations of the higher-order SCR model were simplified by the variable substitution method and the line method and solved by the backward difference formula to improve computational accuracy. The Levenberg-Marquardt algorithm was used to calibrate the chemical reaction rate parameters to optimize model performance. Second, an optimization cost function was designed to optimize the upstream NH3 concentration in combination with the interior point method and the higher-order SCR model to meet the requirements of Euro VII emission standards. Third, the model effect was verified by performing WHTC hot-start testing on an engine complying with the National VI emission standard. The results show that the average error between the measured NOx concentration and the calculated is 1.49 ppm, which verifies the high accuracy of the model. Finally, the effects of the interior point method, NSGA-II, and MOPSO algorithms in optimizing the upstream NH3 concentration were compared. The results showed that the interior point method outperformed the other algorithms in terms of optimization time and effect, with an optimization time of 149 s, a NOx conversion rate of 97.36 %, and an average downstream NH3 concentration of 4.65 ppm. This achieved a high NOx conversion rate and low NH3 slip in accordance with the requirements of the Euro VII regulation.

Effect of bedding application and air change rates on environmental ammonia concentrations for intensively housed beef cattle

Context Manure deposition during livestock export voyages contributes to air ammonia levels, potentially affecting human and animal health if not managed. Mitigation strategies may include increased air change rates and application of bedding. Aim This study examined the effect of bedding application rate (BAR) and air change rate (ACH) on air ammonia (NH3) concentrations and pad properties, including pad surface condition, pH, moisture, and pad ammonium (NH4+) concentrations, for intensively housed beef cattle. Methods Six 7-day runs were conducted with 72 Bos indicus cross steers (mean liveweight ± s.d. = 338 ± 32 kg) housed in respiration chambers by using a 3 × 3 factorial design. The BARs were set to 0%, 50%, and 100% of the Australian Standards for the Export of Livestock (ASEL), and ACH were varied at 20, 35, and 52. Air NH3 was measured twice daily at three heights. Pad surface condition was collected with the first air NH3 measurement. Video footage captured standing and lying behaviours for each steer. Pad samples were collected on the final day for pad chemical analysis. Key results The ACH of 20 changes per hour resulted in higher air NH3 concentration than ACH of 35 and 52. Higher BAR led to lower pad pH and moisture, with slightly lower pad NH4+ concentration in 100% and 50% BAR than 0% BAR. Although air NH3 concentration on Day 7 was positively correlated with pad NH4+ concentration, BAR had no marked effect on air NH3 concentration (within the temperature range of this experiment). Drier and firmer pad surfaces were associated with each high BAR and high ACH. Moreover, high BAR increased the frequency of lying behaviour in steers. Conclusions These findings indicated that NH3 can be mitigated by optimising air changes to minimise air NH3 concentration and utilising bedding to minimise pad NH4+. This offers practical solutions for intensively housed beef cattle, such as livestock export voyages to improve human and animal welfare onboard. Implications The study results emphasised the importance of optimising ACH to maintain low air NH3 concentrations in livestock export conditions. Although there was no evidence that BAR affects air NH3 directly, it reduced pad NH4+ and improved pad conditions for overall animal comfort and environmental quality in confined housing with sufficient air changes.

Fe(OH)3/Ti3C2Tx nanocomposites for enhanced ammonia gas sensor at room temperature

Two-dimensional material (2D material) MXene has great application potential in gas sensors because of its excellent controllable performance and vast specific surface area. In this study, we used a straightforward in-situ electrostatic self-assembly technique to create Fe(OH)3/Ti3C2Tx nanocomposites, which were then used to fabricate gas sensors for ammonia detection at room temperature (25 ℃). Several characterization methods were performed aimed at determining the surface appearance and construction of the nanocomposites, and the sensing characteristics and mechanism were also systematically examined. The findings demonstrate the effective incorporation of amorphous Fe(OH)3 nanoparticles on the surface of Ti3C2Tx. Additionally the nanocomposites of Fe(OH)3/Ti3C2Tx have considerably higher specific surface area than pure Ti3C2Tx, hence offering more active NH3 adsorption sites. The response of the sensor to 100 ppm NH3 was 48.6% at room temperature, which was 9.3 times more higher than that of pure Ti3C2Tx. The sensors also have the advantages of long-term stability (33 days), low NH3 detection limit (500 ppb), and rapid recovery time (85 s) and response times (78 s). It is anticipated that this work will be helpful for developing the new generation of wearable ammonia sensors at room temperature.

Low Strength Wastewater Treatment Using a Combined Biological Aerated Filter/Anammox Process

To achieve the in situ capacity expansion of the post-denitrification biological aerated filter (BAF-DN), the integration of BAF with the anammox process (BAF/AX) was proposed. With the objective of maximizing retaining ammonia nitrogen, the operational optimization of BAF was achieved by two distinct strategies. The treatment performance of BAF demonstrated that the removal efficiencies of chemical oxygen demand (COD) and ammonia nitrogen (NH4+-N) was 66.3~67.3% and 4~12%, respectively, under conditions of low aeration intensity (0.4 m3·m−2·h−1) or a shortened empty bed residence time (EBRT) of 30 min. Residual NH4+-N in the BAF effluent served as the ammonia substrate for the subsequent anammox process, which was successfully launched by using ceramic particles and sponges as carriers. Notably, the sponge carrier facilitated a shorter start-up period of 41 to 44 days. Furthermore, the sponge-based anammox reactor exhibited a superior NH4+-N removal capacity (≥85.7%), under operations of a shorter EBRT of 40 min, low influent NH4+-N concentrations (≤30 mg/L), and COD levels of ≤67 mg/L. In addition, a comprehensive evaluation of the BAF/AX process was conducted, which considered performance, cost-effectiveness, and engineering feasibility. The performance results illustrated that the effluent quality met the standard well (with a COD level of ≤ 50 mg/L, and a TN of ≤3.1~10.5 mg/L). Following a comparison against the low aeration intensity operation, it was recommended to operate BAF at a low EBRT within the BAF/AX process. Consequently, the treated volume was double the volume of the standalone BAF-DN, synchronously achieving low costs (0.413 yuan/m3).

Bimetallic Cu11Ag3 Nanotips for Ultrahigh Yield Rate of Nitrate-to-Ammonium.

Electrochemical reduction of nitrate to ammonia (NRA) offers a sustainable approach for NH3 production and NO3 - removal but suffers from low NH3 yield rate (<1.20 mmol h-1 cm-2). We present bimetallic Cu11Ag3 nanotips with tailored local environment, which achieve an ultrahigh NH3 yield rate of 2.36 mmol h-1 cm-2 at a low applied potential of -0.33 V vs. RHE, a high Faradaic efficiency (FE) of 98.8 %, and long-term operation stability at 1800 mg-N L-1 NO3 -, outperforming most of the recently reported catalysts. At a NO3 - concentration as low as 15 mg-N L-1, it still delivers a high FE of 86.9 % and an NH3 selectivity of 93.8 %. Finite-element method and density functional theory calculations reveal that the Cu11Ag3 exhibits reduced adsorption energy barrier of *N intermediates, favorable water dissociation for *H generation and high energy barrier for H2 formation, while its tip-enhanced enrichment promoting NO3 - accumulation.

Bimetallic Cu11Ag3 Nanotips for Ultrahigh Yield Rate of Nitrate‐to‐Ammonium

Electrochemical reduction of nitrate to ammonia (NRA) offers a sustainable approach for NH3 production and NO3‐ removal but suffers from low NH3 yield rate (&lt;1.20 mmol h‐1 cm‐2). We present bimetallic Cu11Ag3 nanotips with tailored local environment and tip‐enhanced effects, which achieve an ultrahigh NH3 yield rate of 2.36 mmol h‐1 cm‐2 at a low applied potential of ‐0.33 V vs. RHE, a high Faradic efficiency (FE) of 98.8%, and long‐term operation stability at 1800 mg‐N L‐1 NO3‐, outperforming most of the recently reported catalysts. At a NO3‐ concentration as low as 15 mg‐N L‐1, it still delivers a high FE of 86.9% and an NH3 selectivity of 93.8%. Operando ATR‐FTIR spectra, finite‐element method, and DFT calculations reveal that the Cu11Ag3 exhibits reduced adsorption energy barrier of *N intermediates, favorable water dissociation for *H generation and high energy barrier for H2 formation, while its tip‐enhanced enrichment promoting NO3‐ accumulation.

Bio-refinery of organic pollutants for wastewater reclamation

With rapid development of global climate change and resource scarcity, the demand for sustainable wastewater reclamation technologies is growing rapidly. Alginate like exopolymers (ALE) are value-added biopolymers that can be recovered from excess biomass. In this study, a novel biopolymer value-driven moving bed biofilm reactor (bMBBR) was constructed to achieve high-efficiency conversion of organics to Alginate like exopolymers (ALE). The results revealed that excellent COD and low NH4+-N reduction could be achieved, with the reduction efficiencies of 87.7 ± 0.6 % and 12.6 ± 0.8 %, respectively. It is indicated that high-rate organics conversion and blockage of nitrification activity for energy saving could be simultaneous achieved in this process. Additionally, the superior settleability (SVI30 < 80 mL/g) and functional genera related to extracellular polymeric substances (EPS) secretion were observed, making it promising for ALE recovery from residual biomass. The yields of ALE extraction from biofilm and suspended biomass ranged of 232.9–381.5 mg/g VSS. The property analyses demonstrated that the biopolymer had a similarity functional group between two samples and commercial alginate. Meanwhile, the profit evaluation results suggested that the net profit could be reached of 0.54 CNY/kg SS in the present study, which was higher than that of conventional waste activated sludge (−1.92 CNY/kg SS). Moreover, the economic value of ALE (0.38 CNY/m3 wastewater treated) was also 2.93 times of that obtained from CH4 (0.13 CNY/m3 wastewater treated). In general, the present study provides a prove of concept that bio-refinery of organics into value-added biopolymers could offer a promising direction towards next generation of sustainable wastewater treatment plants.

Tempo-spatial Variations in Nitrogen and Phosphorus Loads in Jianli-Hankou Reach of the Middle Yangtze River During the Past 20 Years

Ammonia nitrogen （NH4+-N） and total phosphorus （TP） were the major control pollutants in the Yangtze River Basin. Based on measured data from 2003 to 2020, the temporal and spatial variations in concentrations and fluxes of NH4+-N and TP in the Jianli to Hankou （JL-HK） reach of the Middle Yangtze River were studied, and the impacts of flow-sediment factors, tributary inflows, and others on variations in NH4+-N and TP fluxes were discussed. The results showed that： ① In recent years, NH4+-N and TP concentrations in the mainstream have declined significantly, with annual NH4+-N and TP concentrations at each monitoring station in 2020 averagely decreasing by 41% and 34% compared to those in 2003, respectively. Spatially, NH4+-N and TP concentrations decreased and then increased along the mainstream. NH4+-N and TP concentrations of tributary inflows, which include the Dongting Lake and Han River, were generally lower than that of the mainstream. The multi-year average values of NH4+-N and TP concentrations were both averaged at 0.12 mg·L-1 in the mainstream and were averaged at 0.11 mg·L-1 and 0.09 mg·L-1 in the tributary inflows. ② The flux differences between the upper and lower sections net of tributary confluences showed that NH4+-N and TP fluxes were lost in the Jianli to Luoshan （JL-LS） sub-reach and increased in the Luoshan to Hankou （LS-HK） sub-reach in most years. NH4+-N and TP fluxes decreased in the JL-LS sub-reach, which was related to the lower NH4+-N and TP concentrations in lateral inflows, such as Dongting Lake, and thus lowered the NH4+-N and TP concentrations in the mainstream. The LS-HK sub-reach showed the opposite trends, and the water and sediment loads increased in this sub-reach. Across the whole JL-HK reach, TP flux as well as water and sediment loads were recharged along the reach, whereas NH4+-N flux was reduced greatly, which could be attributed to the pollution abatement conducted in the Yangtze River Basin, which mainly focused on NH4+-N. ③ The correlation analysis results showed that NH4+-N fluxes had the strongest correlation with NH4+-N concentrations but not significantly correlated with discharges and sediment transport rates, indicating that NH4+-N was mainly controlled by point source pollution in the study reach. TP fluxes had higher correlations with discharges and sediment transport rates in high flow level periods, and the correlations between TP fluxes and TP concentrations were better in low flow level periods, reflecting that point source pollution contributed more to TP in dry seasons compared to flood seasons.

Tracking control of dynamic ammonia coverage ratio references based on DC-SMC under a novel SCR-DeNOX structure

In response to the growing challenges of nitrogen oxides (NOX) emission control, NH3-based selective catalytic reduction (SCR) technology has been widely adopted to reduce NOX emission from marine diesel engine exhaust. In this study, the SCR mechanism model is based on a refined eight-state model. A novel structure of SCR-DeNOX system is established, which incorporates a by-pass valve and pipe. Unlike existing parallel and series SCR-DeNOX platforms, the novel structure shows a certain advantage in reducing NH3 and maintains a relatively high NOX conversion efficiency. Adaptive sliding mode observers (ASMO) are designed to generate dynamic ammonia coverage ratio references, replacing traditional fixed references. In addition, they also address the variations in the SCR-DeNOX model. The sliding mode control (SMC) is used to track the ammonia coverage ratio reference in upper cell by controlling ammonia injection. The decoupling with SMC (DC-SMC) is proposed to track the ammonia coverage ratio reference in the lower cell by controlling split ratio. The simulation results show the system with DC-SMC shows a 15.46% improvement in NOX conversion efficiency compared to that with SMC. Additionally, it shows a lower NH3 cost.

Combustion characteristics on ammonia injection velocity and positions for ammonia co-firing with coal in a pilot-scale circulating fluidized bed combustor

Ammonia (NH3) co-firing with coal in thermal power plant offers a viable solution for reducing CO2 emissions. Optimizing the NH3 injection method is crucial to achieving comparable performance and pollutant emissions in NH3–coal co-firing compared to coal only combustion in a circulating fluidized bed combustion system. The impact of NH3 co-firing with coal on the injection velocity and location in related to the NH3 supply method was evaluated. Injection velocity was controlled by varying the number of ammonia supply ports and their heights (0.2 m and 1.8 m from the distributor). Injecting NH3 through one port at a high velocity of 2.4 m/s increases CO emissions while decreasing NO emissions due to the formation of a reducing environment. Conversely, utilizing two ports with low NH3 injection velocity of 1.2 m/s exhibited the opposite trend in CO and NO emissions, achieving the highest combustion efficiency without the formation of N-containing components. This injection velocity promotes better mixing of gases (air and NH3) and solids (bed materials and coal) without hindering coal combustion. Regarding greenhouse gases emissions, the part of CO2 emissions decreased by considering CO2 concentration and flue gas flow rate, while the part of N2O emissions significantly increased due to N-chemistry by > 5 times.

Effect of electrooxidation pretreatment on treatment efficiency, membrane fouling and microbial community of a membrane bioreactor treating sludge dewatering wastewater

This study investigated electrooxidation (EO) pretreatment for sludge dewatering wastewater and condensate generated during the process, aiming to enhance its treatment via a membrane bioreactor (MBR) and prevent membrane fouling. EO treatment could achieve a complete suspended solids (SS) removal along with 97.4 % EPS and 90.1 % colour removal under the optimum conditions. However, the NH4+-N and total organic carbon (TOC) concentration in wastewater increased (16 % and 72.8 %, respectively) due to break down of the complex organic substances present in the wastewater. MBR treating EO pretreated wastewater showed significant improvement against membrane fouling, as shown by reduction in transmembrane pressure (TMP) from 15 kPa in control to 0 kPa in the experimental reactor. The MBR operated with EO-treated wastewater and a 16-day HRT resulted in a low effluent NH4+-N concentrations of 469.3 mg/L (74.9 % removal) along with a very low TOC concentration of 24.3 mg/L (98.7 % removal). The microbial community analysis revealed that enrichment of selected organic carbon degraders (Defluviitoga, Pedobacter, and Flavobacteriaceae) and nitrogen cycle bacteria (Dechloromonas, Comamonas, Arenibacter, Brevundimonas, Thauera, and Aequorivita), including some aerobic denitrifiers (Aquamicrobium and Chryseobacterium) in the experimental reactor treating EO-pretreated wastewater is responsible for enhancing microbial degradation and its overall performance.

Parasitism by Cuscuta gronovii mediated soil legacy effects and the competitive ability of invasive and native plant species by changing soil abiotic and biotic properties

Parasitic plants can mediate soil conditioning by invasive and native host plant species, but how this may affect the competitive ability of these plants when they later grow in the conditioned soil has never been tested. This study tested whether soil conditioned by three invasive and three native plant species, either parasitized by a holoparasitic plant Cuscuta gronovii or non-parasitized, would differentially affect the competitive ability of those species. In the first phase, field soil was conditioned using individuals of the six host plant species, either parasitized or non-parasitized. The second phase tested the competitive ability of individuals of those invasive and native plants by growing them alone or in competition with Trifolium repens in either live or sterilized conditioned soil. In the soil conditioning phase, parasitism significantly increased soil NH4+-N concentration by 17 %, decreased soil organic carbon by 18 %, and marginally decreased microbial biomass carbon concentration by 21 %. In the soil feedback phase, native plant species generally had higher competitive ability in soil that was conditioned by parasitized plants than in soil that was conditioned by non-parasitized plants. In contrast, soil conditioned by parasitized plants had only a marginal effect on the competitve ability of invasive plants, compared to growth in soil conditioned by non-parasitized plants. Native plants had greater competitive ability in soil with lower soil organic carbon, while invasive plants had greater competitive ability in soil with higher microbial biomass carbon and lower NH4+-N. These findings demonstrate that parasitism by C. gronovii mediated different soil legacy effects of invasive and native plant species through changes in soil organic carbon, soil NH4+-N, and microbial biomass carbon levels. Broadly, these results suggest that parasitic plants may limit invasions by alien plant species and promote the co-existence of the invaders with native plant species through soil-mediated legacy effects.

Self-regenerable oxygen system using microalgae-bacterial consortium for ammonium removal from wastewater

This study investigated self-regenerable oxygen system using microalagae-bacterial consortium for ammonium removal from wastewater and its kinetic modeling based on a combined mechanistic and empirical approach. By mechanistic modeling using a simple microalgal-bacterial Monod model, based on algal growth due to NH4+, NO3− and NO2−, the nitrogen and DO profiles were accurately predicted under different nitrogen conditions (low, medium, and high NH4+ concentrations). The mathematical modeling results showed that sufficient oxygen was available for nitrification at low initial NH4+ ammonium concentration levels, even when dual nitrogen substrate (NH4+–NO2−, NH4+–NO3− or NO2−–NO3−) or all three in combination (NH4+–NO2−–NO3−) were used, compared with high initial ammonium concentration levels. The DO profile was successfully used to monitor N transformation and N uptake in the PSBR based on net O2 uptake rate, O2 production rate, and O2 saturation profile. By empirical modeling of the data obtained, the actual O2 produced by microalgae with the different N species was calculated based on N mass balance and empirical equations. The empirical model further revealed that low NH4+ concentration levels (up to 82.5 mg N/L) favored successful nitrification due to the sufficient production of O2 in the system. However, NH4+ concentration in the range 82.5–132.5 mg N/L affected the nitrification efficiency due to insufficient O2 produced in the system, whereas high ammonium concentration results in nitritation/partial nitrification due to the high demand of O2 by AOB and inhibition in the growth of NOB.

Analyzing performance and microbial mechanisms in an incineration leachate treatment after waste separation: Integrated metagenomic and metaproteomic analyses

The absence of food waste after separation poses a significant challenge to incineration leachate treatment, as it decreases the C/N ratio and COD of leachate, greatly impacting the biological treatment process. A one-year in-situ study was systematically conducted in an incineration leachate treatment plant that experienced waste separation, focusing on the variations in carbon and nitrogen removal performance as well as the involved microbial mechanism of the “anaerobic digestion (AD) + two-stage A/O” process. Results indicated that the biodegradability of leachate significantly decreased over time, with COD concentration decreasing by 10 times and the average C/N ratio decreasing from 12.3 to 1.4. The AD process was maintained stable, achieving a COD removal efficiency exceeding 92 %. The nitrification process also remained stable; while the denitrification process was significantly affected, and a nine-fold increase in external glucose addition was required to achieve a nitrogen removal efficiency of 85 %. Metagenomic analysis indicated that comammox Nitrospira (contributing 90 % to ammonia monooxygenase) occupied the dominant position over Nitrosomonas for nitrification due to the low NH4+-N concentration in A/O tanks (<35 mg/L), and Methanothrix was substituted by Methanosarcina for methanogenesis in AD unit. Metaproteomic results further elucidated that the expression of enzymes responsible for denitrification process, i.e., Nir, Nor, Nos (convert NO2− to N2), was decreased significantly, although the expression of enzymes related to glycolysis and TCA cycle were stimulated by glucose addition. The expression of Nar (convert NO3−-N to NO2−-N) remained stable, while the imbalance expression within denitrifying enzymes might have facilitated occurrence of partial denitrification, attributed to the low C/N ratio. The results prove that the function robustness and metabolic versatility were achieved in leachate treatment plant after waste separation but at the cost of the high external carbon resource addition, highlighting the urgent requirement for low-carbon nitrogen removal technologies.