Ammonium Removal Performance Research Articles

Synergistic chemical traction and pre-intercalation strategies enable high-quality MnO2 composites for efficient ammonium capture

The δ-MnO2 exhibits an ideal capacitive deionization (CDI) electrode for the efficient removal of ammonium ions (NH4+), owing to its unique layered structure that facilitates effective insertion and extraction of ions. However, MnO2 is constrained by self-aggregation, inadequate electrical conductivity, and sluggish reaction kinetics in practical applications, leading to subpar ammonium removal performance. Here, the polyaniline (PANI) intercalated MnO2 and carbon nanotubes (CNTs) composites (P/M-C-X) were synthesized by a straightforward and swift one-step inorganic/organic interface reaction using the chemical traction effect of aniline. The synergistic effect of the increased layer spacing and the introduced oxygen vacancy after PANI intercalated and the 1D/2D conductive interconnect structure constructed by CNTs can effectively improve the electrical conductivity, promote ions/electrons diffusion, and enhance the charge reaction kinetics. As results, P/M-C-50 exhibits excellent NH4+ removal performance, including the maximum salt adsorption capacity (SAC) (160.0 mg g−1), ultra-high salt adsorption rate (SAR) (1.07 mg g−1 s−1), and good cyclic stability. Furthermore, the comprehension of NH4+ storage mechanism has been enhanced through structural characterization, electrochemical analysis, and theoretical calculation. This study shows that P/M-C-50 has broad potential as a CDI ammonium removal electrode, and lays a solid foundation for the effective recovery and reuse of ammonium resources.

Formation of iron-rich encrustation layer on anammox granules for high load stress resistance: Performance, advantages, and mechanisms

Anaerobic ammonia oxidation (anammox) is a cost-effective technology but its performance can be seriously inhibited by high load stress. This study has created an innovative iron-rich encrustation layer (IEL) on the surface of anammox granules (AnGS) through the addition of a certain amount of nano zero-valent iron. The IEL was formed through the aggregation of a gel network and the binding of iron species with extracellular polymeric substances (EPS), resulting in a significant increase in settling ability, EPS secretion, and heme content. Metagenomic analysis indicated a notable rise in the functional genes associated with nitrogen andiron metabolism in IEL AnGS. Under high load stress, the ammonia removal performance of AnGS without IEL severely declined. In contrast, IEL AnGS exhibited excellent ammonia removal efficiency of over 90%. The IEL served as a protective barrier for AnGS, effectively mitigating the strong shear forces, thereby enhancing their resistance to high load stress.

Effect of Nitrogen, Carbon Dioxide, and Air Activation on the Low-Temperature Ammonia Removal Performance of Activated Carbon during Nitric Oxide Removal

Effect of Nitrogen, Carbon Dioxide, and Air Activation on the Low-Temperature Ammonia Removal Performance of Activated Carbon during Nitric Oxide Removal

Biofiltration matrix optimization for efficient nitrogen removal from domestic onsite wastewater

Bench-scale columns were packed with marble chip, zeolite and gravel to treat septic tank effluent at elevated hydraulic loadings (0.48–0.64 m3 m−2 d−1) to challenge their hydraulic performance and ammonium (NH4+-N) removal performance. The results showed that higher NH4+-N removal efficiency was achieved in zeolite (75.8–94.1 %) and marble chip (54.9–83.9 %) columns than in sand (32.9–76.6 %) column without clogging during the experimental period (4 months). Biochar amendment (30 % v/v) resulted in a 23–29 % decrease of effluent NH4+-N in marble chip columns, while no impact was observed in the zeolite columns. Nitrification rather than adsorption contributed to the major NH4+-N removal (82–95 %) in zeolite, biochar amended zeolite and biochar amended marble chip columns. In addition, higher abundance of nitrifying microorganisms observed in the top layer of zeolite column (1.2 × 107 - 3.1 × 107amoA copies g−1, 3–10 times higher than marble chip) suggested NH4+-N was concentrated on zeolite surface by adsorption which then facilitated nitrification and promoted nitrifying biomass growth. Collectively, this study suggested that zeolite and biochar amended marble chip could serve as the filter materials for efficient NH4+-N removal from onsite wastewater at elevated wastewater loadings without clogging concerns.

Nitrogen removal performance of improved subsurface wastewater infiltration system under various influent carbon-nitrogen ratios.

Subsurface wastewater infiltration system (SWIS) has been recognized as a simple operation and environmentally friendly technology for wastewater purification. However, effectively removing nitrogen (N) remains a challenge, hindering the widespread application of SWIS. In this study, zero-valent iron (ZVI) and porous mineral material (PMM) were applied in SWIS to improve the soil matrix. Our results suggested that the addition of ZVI and PMM could simultaneously enhance N removal efficiency and reduce nitrous oxide emissions. This could be attributed to the abundant electrons generated by ZVI alleviating the electronic limitation of denitrification and the porous structure of PMM providing solid phase support for microbial growth. In addition, the abundance of microbial functional genes increased in modified SWIS, which could further explain the higher pollutant removal efficiency. Overall, this study provides new insights into the mitigation of wastewater pollution and greenhouse gas emissions in SWIS. PRACTITIONER POINTS: ZVI and PMM can adapt to different C loads and enhance pollutant removal efficiency in SWIS. Increasing C-N ratios positively affected the nitrate removal performance and negatively affected ammonium removal performance in SWIS. The amending soil matrix promoted the reduction of the N2 O to N2 and greenhouse gas emissions were well controlled. The abundance of microbial functional genes increased with the improvement of the soil matrix.

Multidrug-resistant plasmid RP4 inhibits the nitrogen removal capacity of ammonia-oxidizing archaea, ammonia-oxidizing bacteria, and comammox in activated sludge

In wastewater treatment plants (WWTPs), ammonia oxidation is primarily carried out by three types of ammonia oxidation microorganisms (AOMs): ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and comammox (CMX). Antibiotic resistance genes (ARGs), which pose an important public health concern, have been identified at every stage of wastewater treatment. However, few studies have focused on the impact of ARGs on ammonia removal performance. Therefore, our study sought to investigate the effect of the representative multidrug-resistant plasmid RP4 on the functional microorganisms involved in ammonia oxidation. Using an inhibitor-based method, we first evaluated the contributions of AOA, AOB, and CMX to ammonia oxidation in activated sludge, which were determined to be 13.7%, 41.1%, and 39.1%, respectively. The inhibitory effects of C2H2, C8H14, and 3,4-dimethylpyrazole phosphate (DMPP) were then validated by qPCR. After adding donor strains to the sludge, fluorescence in situ hybridization (FISH) imaging analysis demonstrated the co-localization of RP4 plasmids and all three AOMs, thus confirming the horizontal gene transfer (HGT) of the RP4 plasmid among these microorganisms. Significant inhibitory effects of the RP4 plasmid on the ammonia nitrogen consumption of AOA, AOB, and CMX were also observed, with inhibition rates of 39.7%, 36.2%, and 49.7%, respectively. Moreover, amoA expression in AOB and CMX was variably inhibited by the RP4 plasmid, whereas AOA amoA expression was not inhibited. These results demonstrate the adverse environmental effects of the RP4 plasmid and provide indirect evidence supporting plasmid-mediated conjugation transfer from bacteria to archaea.

Rapid start-up of the biofilter for simultaneous manganese and ammonia removal at low temperature: Effects of phosphate and copper

In low-temperature environments, low nutrients such as inorganic salts limiting microbial proliferation further extended the start-up period of biofilters for drinking water treatment. This study explored the ammonia and manganese (Mn) removal performance and the relevant mechanisms under single and combined PO43− at 30 μg/L and Cu2+ at 10 μg/L. The start-up periods of R0 (control), R1 (Cu2+ single), R2 (PO43− single) and R3 (combined Cu2+ and PO43−) were 98, 82, 32 and 24 days, respectively. PO43− increased the concentration of extracellular polymeric substances (EPS) by stimulating cellular metabolism, which promoted the formation of biofilm. Additionally, the combined Cu2+ and PO43− significantly promoted the ammonia monooxygenase (AMO) and nitrite oxidoreductase (NXR) activities, which further facilitated the removal of ammonia. The combined Cu2+ and PO43− accelerated the conversion of NH4+-N to NO2−-N and NO2−-N to NO3−-N processes thereby reducing the inhibition of Mn removal by NH4+-N and NO2−-N, and the kinetics of biological manganese oxidation showed that the combined Cu2+ and PO43− increased the rate of Mn removal, which both promoted the Mn removal in the biofilters. Furthermore, the combined Cu2+ and PO43− supported the proliferation of functional microorganisms. In summary, the synergistic effect of Cu2+ and PO43− enhanced the Mn and ammonia removal performance and achieved rapid start-up of the biofilter at low temperatures.

Intelligent optimization strategy for electrochemical removal of ammonia nitrogen by neural network embedded in a non-dominated sorting genetic algorithm

Electrochemical is a promising approach for the removal of ammonia nitrogen, but the challenge is to achieve better performance under lower energy consumption. In this study, a new electrochemical system hybrid with intelligent optimization algorithms was developed for the efficient removal of ammonia nitrogen and energy saving. Ammonia removal performance and energy consumption were recorded when the traditional electrochemical system operated at various parameters. As the premise of model training, the data were processed through Scatter diagram matrix, Box plot, Principal Component Analysis, Spearman correlation and Shapley Additive Explanations to evaluate the redundancy and independence of parameters. Backpropagation neural network based on deep learning was used as surrogate model of non-dominated sorted genetic algorithm-II, meanwhile, the range of electrochemical parameters was used as the constraint for multi-objective optimization. The optimized result is the Pareto front and the optimal solution was obtained by combining the Technique for Order Preference by Similarity to an Ideal Solution. This new hybrid system achieved an increase of 11.75 % ~ 13.61 % in ammonia removal and a reduction of 21.31 % ~ 36.84 % in energy consumption. The optimal solution represents a better ammonia removal performance at low energy consumption, which is meaningful for the concept of a real-time controlled electrochemical system.

Use of soluble iron salt as an electron acceptor to provide Fe(III) for Feammox process: Ammonium removal performance and mechanism

Fe(III) reduction coupled with anaerobic ammonium oxidation (Feammox) is a newly discovered biological ammonium removal technology. Compared to anaerobic ammonium oxidation (anammox) process, Feammox does not require NO2−-N as a reaction substrate and is more tolerant to heavy metals. In this study, soluble iron salts FeCl3 was added to anaerobic sequencing batch reactor (ASBR) to start Feammox process. The effects of Fe/N, pH and temperature on the Feammox performance were investigated. Optimal working conditions were determined by combining the variation law of nitrogen and iron elements. The results showed that the best NH4+-N removal efficiency when Fe/N, pH and temperature were 0.15, 6.5 and 30 °C, respectively. The modified Boltzmann model fitted better in Feammox kinetic analysis (R2 = 0.9789), which could clearly explain that the degradation of substrate and the generation of product. Microbial analysis showed that in addition to the typical iron-reducing bacteria, the dominant genus Candidatus_Brocadia of anammox was also enriched in the system with relative abundance of 3.16 %, implying that both Feammox and anammox contributed to the transformation of NH4+-N. Overall, optimizing the operating conditions of Feammox is important significance to maintain the stability of NH4+-N removal performance and provide theoretical basis for constructing a novel wastewater treatment process.

Long-term performance and biofilms of the novel nano manganese dioxide coupling carbon source pre-loaded biological activated carbon filters for drinking water

In order to accelerate the start-up of biological activated carbon (BAC) filters and enhance ammonium (NH4+-N) removal performance, three substrates (sucrose and/or nano manganese dioxide (nMnO2)) pre-loaded BAC filters were set up to investigate the pollutants removals and microbiological characteristics for a long-term operation of 197 days. The average NH4+-N removal performance treated by the sucrose coupled with nMnO2 loaded BAC filter was the highest (71.18 %), which was 3.83 times of that by the control filter (18.58 %). 29 % of NH4+-N treated by the sucrose coupled with nMnO2 loaded BAC removed through the traditional nitrification and denitrification, or simultaneous nitrification and denitrification (SND) pathways according to the calculation of the alkalinity consumption (6.12 mmol/L). There was no leakage of carbon source and Mn, and no accumulation of nitrite from the substrates loaded BAC. The dominant bacteria in the sucrose coupled with nMnO2 loaded BAC were Dechloromona (accounting for 8.02% of the total bacterial) and Acidaminobacter (accounting for 15.16% of total bacterial) on the Day 180, which had the capacity of nitrification or denitrification. NH4+-N and micropollutants removals treated by the combined process of peracetic acid (PAA) pre-oxidation and substrates loaded BAC were significant due to the generation of assimilable organic carbon (AOC) (5.98 ± 1.93 μg-C/mL) by PAA (100 μM)/Fe2+ pre-oxidation and the higher biomass ((4.57 ± 3.07) × 107 cells/g DW BAC) in the sucrose coupled with nMnO2 loaded BAC filter. Therefore, nMnO2 coupling carbon source pre-loading strategy could not only enhance initial colonization, but also promote pollutants removals for long-term operation.

Effects of zero-valent iron (ZVI) on nitrogen conversion, transformation of sulfamethoxazole (SMX) and abundance of antibiotic resistance genes (ARGs) in aerobic granular sludge process

Even after pre-treatment, livestock and poultry wastewater still contain high concentrations of ammonia and residual antibiotics. These could be removed economically using the aerobic granular sludge (AGS) process with zero-valent iron (ZVI). The interaction of antibiotics and nitrogen in this process needs to be clarified and controlled, however, to achieve good removal performance. Otherwise, antibiotics might generate transformation products (TPs) with higher toxicity and lead to the emergence of antibiotic-resistant bacteria carrying antibiotic resistance genes (ARGs), which could cause persistent toxicity and the risk of disease transmission to the ecological environment. This study investigated the impact of ZVI on AGS for nitrogen and sulfamethoxazole (SMX) removal. The results show that AGS could maintain good ammonia removal performance and that the existence of SMX had a negative impact on ammonia oxidation activities. ZVI contributed to an increase in the abundance of nitrite oxidation bacteria, denitrifying bacteria and the functional genes of nitrogen removal. This led to better total nitrogen removal and a decrease in N2O emission. Accompanied by biological nitrogen transformation, SMX could be transformed into 14 TPs through five pathways. ZVI has the potential to enhance transformation pathways with TPs of lower ecotoxicity, thereby reducing the acute and chronic toxicity of the effluent. Unfortunately, ZVI might enhance the abundance of sul1, sul2, and sul3 in AGS, which increases the risk of sulfonamide antibiotic resistance. In AGS, Opitutaceae, Xanthomonas, Spartobacteria and Mesorhizobium were potential hosts for ARGs. This study provides theoretical references for the interaction of typical antibiotics and nitrogen in the biological treatment process of wastewater and bioremediation of natural water bodies.

MOF incorporated adsorptive nanofibrous membranes for enhanced ammonia removal by membrane distillation

This study presents the design and fabrication of a new adsorptive nanofibrous membrane incorporating metal-organic framework (MOF) by electrospinning technique for removing ammonia-nitrogen from wastewater via direct contact membrane distillation (DCMD) process. Three types of MOF particles (HKUST-1, AlFu, and UiO-66-NH2) were used as functional nanoadditives and incorporated into the nanofibrous membrane matrix. The ammonia removal performance of these nanocomposite membranes was comprehensively investigated and compared with an activated carbon (AC) incorporated nanofibrous membrane. Various parameters such as ammonia removal efficiency, ammonia separation factor, overall ammonia mass transfer coefficient, ammonia flux, and membrane stability were evaluated. Among the tested MOFs, UiO-66-NH2 demonstrated excellent performance and was selected for further optimization. The 5.0 wt.% UiO-66-NH2 incorporated membrane exhibited the best performance for ammonia removal. Additionally, the mechanism of MOF incorporated nanofibrous membranes for ammonia removal from aqueous solution by DCMD was schematically analyzed. In overall, this study confirmed the feasibility of fabricating MOF incorporated electrospun adsorptive nanofibrous membranes with outstanding ammonia removal performance, demonstrating the potential of membrane distillation to remove ammonia-nitrogen from the aquatic environment.

Insights on biological phosphorus removal with partial nitrification in single sludge system via sidestream free ammonia and free nitrous acid dosing

The sidestream sludge treatment by free ammonium (FA)/free nitrous acid (FNA) dosing was frequently demonstrated to maintain the nitrite pathway for the partial nitrification (PN) process. Nevertheless, the inhibitory effect of FA and FNA would severely influence polyphosphate accumulating organisms (PAOs), destroying the microbe-based phosphorus (P) removal. Therefore, a strategic evaluation was proposed to successfully achieve biological P removal with a partial nitrification process in a single sludge system by sidestream FA and FNA dosing. Through the long-term operation of 500 days, excellent phosphorus, ammonium and total nitrogen removal performance were achieved at 97.5 ± 2.6 %, 99.1 ± 1.0 % and 75.5 ± 0.4 %, respectively. Stable partial nitrification with a nitrite accumulation ratio (NAR) of 94.1 ± 3.4 was attained. The batch tests also reported the robust aerobic phosphorus uptake based on FA and FNA adapted sludge after exposure of FA and FNA, respectively, suggesting the FA and FNA treatment strategy could potentially offer the opportunity for the selection of PAOs, which synchronously have the tolerance to FA and FNA. Microbial community analysis suggested that Accumulibacter, Tetrasphaera, and Comamonadaceae collectively contributed to the phosphorus removal in this system. Summarily, the proposed work presents a novel and feasible strategy to integrate enhanced biological phosphorus removal (EBPR) and short-cut nitrogen cycling and bring the combined mainstream phosphorus removal and partial nitrification process closer to practical application.

Characterization and metabolic pathway of Pseudomonas fluorescens 2P24 for highly efficient ammonium and nitrate removal

The ammonium and nitrate removal performance and metabolic pathways of a biocontrol strain, Pseudomonas fluorescens 2P24, were investigated. Strain 2P24 could completely remove 100 mg/L ammonium and nitrate, with removal rates of 8.27 mg/L/h and 4.29 mg/L/h, respectively. During these processes, most of the ammonium and nitrate were converted to biological nitrogen via assimilation, and only small amounts of nitrous oxide escaped. The inhibitor allylthiourea had no impact on ammonium transformation, and diethyl dithiocarbamate and sodium tungstate did not inhibit nitrate removal. Intracellular nitrate and ammonium were detectable during the nitrate and ammonium transformation process, respectively. Moreover, the nitrogen metabolism functional genes (glnK, nasA, narG, nirBD, nxrAB, nirS, nirK, and norB) were identified in the strain. All results highlighted that P. fluorescens 2P24 is capable of assimilatory and dissimilatory nitrate reduction, ammonium assimilation and oxidation, and denitrification.

Quinone electron shuttle enhanced ammonium removal performance in anaerobic ammonium oxidation coupled with Fe(III) reduction

Anaerobic ammonium oxidation coupled with Fe(III) reduction (Feammox) is a newly discovered ammonium removal process, but the low ammonium removal efficiency restricts its application in practical wastewater treatment. In this study, iron compounds Fe2O3, Fe(OH)3 and Fe3O4 were added to anaerobic sequencing batch reactors (ASBR) to explore the effect of different iron sources for the Feammox reaction on ammonium removal performance. The removal efficiencies of ammonium in Fe2O3, Fe(OH)3 and Fe3O4 groups were 34.02%, 22.8% and 7.58%, respectively. Additionally, to investigate electron shuttle effect of the quinone compound anthraquinone-2,6-disulfonate (AQDS) between Fe2O3, Fe(OH)3, Fe3O4 and ammonium and whether AQDS can improve the efficiency of Feammox, batch experiments were carried out in 250 mL serum bottles. The ammonium removal efficiency of the AQDS-Fe2O3 group was 48.53%, while those of the AQDS-Fe(OH)3 and AQDS-Fe3O4 groups were 35.63% and 15.46%, respectively. This implied that AQDS enhanced the ammonium removal performance of Feammox, especially accelerating the electron shuttle rate between Fe2O3 and ammonium. X-ray diffraction showed new iron minerals appear in the system. Moreover, modified Boltzmann model was more suitable to describe the removal of NH4+-N and showed a good correlation(R2 >0.99). This study demonstrates the significant influence of AQDS on Feammox process, which provides a theoretical basis for the application of Feammox in practical sewage treatment.

Nitrogen removal by algal-bacterial consortium during mainstream wastewater treatment: Transformation mechanisms and potential N2O mitigation

This work investigated nitrogen transformation pathways of the algal-bacterial consortium as well as its potential in reducing nitrous oxide (N2O) emission in enclosed, open and aerated reactors. The results confirmed the superior ammonium removal performance of the algal-bacterial consortium relative to the single algae (Chlorella vulgaris) or the activated sludge, achieving the highest efficiency at 100% and the highest rate of 7.34 mg N g MLSS−1 h−1 in the open reactor with glucose. Enhanced total nitrogen (TN) removal (to 74.6%) by the algal-bacterial consortium was achieved via mixotrophic algal assimilation and bacterial denitrification under oxygen-limited and glucose-sufficient conditions. Nitrogen distribution indicated that ammonia oxidation (∼41.8%) and algal assimilation (∼43.5%) were the main pathways to remove ammonium by the algal-bacterial consortium. TN removal by the algal-bacterial consortium was primarily achieved by algal assimilation (28.1–40.8%), followed by bacterial denitrification (2.9–26.5%). Furthermore, the algal-bacterial consortium contributed to N2O mitigation compared with the activated sludge, reducing N2O production by 35.5–55.0% via autotrophic pathways and by 81.0–93.6% via mixotrophic pathways. Nitrogen assimilation by algae was boosted with the addition of glucose and thus largely restrained N2O production from nitrification and denitrification. The synergism between algae and bacteria was also conducive to an enhanced N2O reduction by denitrification and reduced direct/indirect carbon emissions.

Active chlorine mediated ammonia oxidation in an electrified SnO2–Sb filter: Reactivity, mechanisms and response to matrix effects

Ammonia pollution control has gained increasing attention as a result of the existential threat to the environment. The electrochemical advanced oxidation process has demonstrated to be an attractive and environmentally benign platform for aqueous ammonia removal because it only requires electricity and water as a clean “reagent”. Herein, we developed a porous SnO2–Sb filter toward high-efficient ammonia conversion. Despite the introduction of enhanced convection, chlorine-mediated ammonia oxidation dominated the reaction mechanism of the electrified SnO2–Sb filter at circumneutral pH. At an extremely short hydraulic contact time (1.0–5.1 min), ammonia was primarily oxidized to N2 with no chloramines detected. Matrix effect assays showed that the chloride–to–ammonia ratio was vital to determine the removal rate and product selectivity. A pH buffer, HCO3−, might prompt ammonia removal whilst inhibiting chlorate formation. In contrast, the ammonia removal performance of the SnO2–Sb filter deteriorated in the presence of dissolved organic matter (e.g., humic acid). The matrix effects significantly influenced the process efficiency to treat municipal sewage and lake water. The results of this study can advance our understanding of electrochemical ammonia oxidation and provide insight into the effective implementation and optimization of the flow-through process.

Effect of steel slag on ammonia removal and ammonia-oxidizing microorganisms in zeolite-based tidal flow constructed wetlands

The ammonia removal performance of tidal flow constructed wetlands (TFCWs) requires to be improved under high hydraulic loading rates (HLRs). The pH decrease caused by nitrification may adversely affect the NH4+–N removal and ammonia-oxidizing microorganisms (AOMs) of TFCWs. Herein, TFCWs with zeolite (TFCW_Z) and a mixture of zeolite and steel slag (TFCW_S) were built to investigate the influence of steel slag on NH4+-N removal and AOMs. Both TFCWs were operated under short flooding/drying (F/D) cycles and high HLRs (3.13 and 4.69 m3/(m2 d)). The results revealed that a neutral effluent pH (6.98–7.82) was achieved in TFCW_S owing to the CaO dissolution of steel slag. The NH4+-N removal efficiencies in TFCW_S (91.2 ± 5.1%) were much higher than those in TFCW_Z (73.2 ± 7.1%). Total nitrogen (TN) removal was poor in both TFCWs mainly due to the low influent COD/TN. Phosphorus removal in TFCW_S was unsatisfactory because of the short hydraulic retention time. The addition of steel slag stimulated the flourishing AOMs, including Nitrosomonas (ammonia-oxidizing bacteria, AOB), Candidatus_Nitrocosmicus (ammonia-oxidizing archaea, AOA), and comammox Nitrospira, which may be responsible for the better ammonia removal performance in TFCW_S. PICRUSt2 showed that steel slag also enriched the relative abundance of functional genes involved in nitrification (amoCAB, hao, and nxrAB) but inhibited genes related to denitrification (nirK, norB, and nosZ). Quantitative polymerase chain reaction (qPCR) revealed that complete AOB (CAOB) and AOB contributed more to the amoA genes in TFCW_S and TFCW_Z, respectively. Therefore, this study revealed that the dominant AOMs could be significantly changed in zeolite-based TFCW by adding steel slag to regulate the pH in situ, resulting in a more efficient NH4+–N removal performance.

The Feasibility of Maintaining Biological Phosphorus Removal in A-Stage via the Short Sludge Retention Time Approach: System Performance, Functional Genus Abundance, and Methanogenic Potential.

The increasing concerns on resource and energy recovery call for the modification of the current wastewater treatment strategy. This study synthetically evaluates the feasibility of the short sludge retention time approach to improve the energy recovery potential, but keeping steady biological phosphorus removal and system stability simultaneously. SBRS-SRT and SBRcontrol that simulated the short sludge retention time and conventional biological phosphorus removal processes, respectively, were set up to treat real domestic sewage for 120 d. SBRS-SRT achieved an efficient COD (91.5 ± 3.5%), -P (95.4 ± 3.8%), and TP (93.5 ± 3.7%) removal and maintained the settling volume index around 50 mL/gSS when the sludge retention time was 3 d, indicating steady operational stability. The poor ammonia removal performance (15.7 ± 7.7%) and a few sequences detected in samples collected in SBRS-SRT indicated the washout of nitrifiers. The dominant phosphorus accumulating organisms Tetrasphaera and Hydrogenophaga, which were enriched with the shortened sludge retention time, was in line with the excellent phosphorus performance of SBRS-SRT. The calculated methanogenic efficiency of SBRS-SRT increased significantly, which was in line with the higher sludge yield. This study proved that the short sludge retention time is a promising and practical approach to integrate biological phosphorus removal in A-stage when re-engineering a biological nutrient removal process.

High-efficiency capture of ammonia using hierarchically porous Zr-MOF nanoarchitectures under ambient conditions: Thermodynamics, kinetics, and mechanisms

Zirconium-based metal–organic frameworks (Zr-MOFs) have emerged as a promising candidate for efficiently eliminating toxic chemicals under ambient conditions. Herein, we demonstrate the remarkable ammonia capture capabilities of the hierarchically porous MOF-808 xerogel (G808) macrostructure and its amino-functionalized analogue (G808-NH2), which were constructed through a sol–gel-based strategy combined with convenient ambient pressure drying. Static isotherm measurements and dynamic breakthrough tests using engineered Zr-MOF xerogel granules were conducted to illuminate the thermodynamic and kinetic characteristics for ammonia sorption. The G808 and G808-NH2 xerogels manifest substantially higher ammonia uptake, intensified interfacial interactions, and enhanced irreversible retention toward ammonia compared with the state-of-the-art activated carbon-based materials, particularly at the low-concentration region. Moreover, these hierarchical Zr-MOF nanoarchitectures exhibit extraordinary ammonia removal performance as well as excellent environmental robustness under simulated respirator canister/protection filter circumstances, with the breakthrough capacities of G808-NH2 being individually more than two and one orders of magnitude greater than those for the pristine and metal-amine impregnated carbons. The kinetic ammonia adsorption behaviors can be well delineated by the pseudo-first-order Wheeler-Jonas model. An in-depth discussion on the ammonia sorption regime, detailing five binding patterns besides reversible physisorption with a special focus on the impacts of polar amino groups and humidity, was proposed based on multiple characterizations and Grand Canonical Monte Carlo simulation.