Drawing inspiration from the self-regulating carbon–nitrogen cycling of saline ecosystems, this study investigates how substrate flux and biomass density co-regulate the structure and function of marine sediment-derived halophilic heterotrophic ammonia assimilation (HAA) microbiome cultivated in saline ammonia-containing wastewater with a COD/N radio of 20 under volumetric exchange ratios (VER) of 75 %, 50 %, and 25 % and mixed liquor suspended solids (MLSS) increasing from 5 to 15 g/L. The combined variation in VER and MLSS generated a gradient in food-to-microorganism radio (F/M). With increasing in biomass, COD removal efficiencies peaked at 94.4–99.3 % at 15 g MLSS/L, whereas ammonia removal efficiencies reached at 90.3–96.8 % at 12.5 g MLSS/L before declining. A VER of 25 % reduced sludge activity, while a VER of 75 % impaired floc settleability. The directed HAA community shifted in substrate flux and biomass density, centering on dominant genera such as Halomonas and Marinobacter, ultimately forming a stable microbiome.

The synthesis of sulfur-doped activated coke (SAC) using SO₂ as an activator enables simultaneous desulfurizer production and sulfur resource utilization. This study systematically investigated the evolution of carbon properties through sulfur doping and the enhanced desulfurization mechanism through experiments and density functional theory (DFT) calculations. The results demonstrated that SO₂ was primarily converted to elemental sulfur (maximum yield: 92.17 %) via redox reactions with carbon, while doped sulfur mainly existed as thiophene and oxidized sulfur groups (maximum doping: 18.92 wt%). Surface sulfur doping modified carbon's physicochemical properties and produced unique saddle-shaped SO₂ adsorption curves. Transient experiments and DFT calculations revealed enhanced hydrophilicity through strengthened H₂O interactions with sulfur-containing groups (the maximum adsorption energy of H₂O reached −58.70 kJ/mol, 2.64 times that of pristine sulfur-free carbon), which promoted H₂SO₄ migration in micropores via concentration-gradient diffusion to enhance desulfurization. This work provided both a waste-to-resource strategy for desulfurizer preparation and atomic-level insights into the desulfurization enhancement mechanism of SAC, offering design principles for advanced carbon materials in flue gas purification.

Ceramic nanofiltration (NF) membranes are emerging as a reliable solution for advanced wastewater treatment, owing to their robustness, high chemical and thermal resistance, and high fouling resistance compared to the polymeric alternatives. These membranes, typically composed of metal oxides such as titania (TiO₂) and alumina (Al₂O₃), therefore offer advantages in rejecting organic compounds, oil, and colloidal particles.....

Microbially induced carbonate precipitation (MICP) presents a promising strategy for the softening and purification of produced water. However, produced water from heavy oil reservoirs exhibits high salinity, refractory organics, particularly with hardness ions such as Ca²⁺ and Mg²⁺, all of which substantially inhibit microbial mineralization activity. Industrially viable continuous-flow operational strategies remain underdeveloped, and the underlying biomineralization mechanisms are not yet fully elucidated. Here, we report the successful construction of an engineering microbiome through substrate gradient acclimation, achieving continuous and stable precipitation of Ca²⁺ (87.28 %) and Mg²⁺ (84.16 %). The process also revealed the sequential transformation of organic functional groups under high salinity perturbation. Hydroxyl groups (−OH) in extracellular polymeric substances preferentially bound divalent cations under neutral conditions, whereas carboxyl groups (−COO⁻) served as nucleation sites for carbonate formation under alkaline conditions. Extracellular carbonate precipitation predominated, while a minor fraction of amorphous magnesium carbonate was accumulated intracellularly. The engineering microbiome, dominated by urease-positive and hydrocarbon-degrading taxa, tolerated extreme salinity and hardness through metabolic complementarity and coordinated gene regulation. These findings demonstrate a robust, continuous-flow MICP process for HPW treatment, offering a foundation for industrial-scale integration with improved stability, efficiency, and microbiome resilience in complex environments.

Food waste leachate is a high–strength wastewater characterized by refractory organics, high–salinity and elevated ammonium concentrations, posing challenges for effective treatment and nitrogen resource recovery. In this study, a novel strategy integrating UV/PMS advanced oxidation pretreatment with aerobic heterotrophic ammonium assimilation (HAA) was employed to enhance microbial nitrogen assimilation and carbon removal. Long–term monitoring revealed that the UV/PMS–HAA system achieved superior NH₄⁺–N and COD removal efficiencies of 84.04 % and 90.74 % compared to the control. EPS analysis indicated higher protein content and tighter sludge structure, supporting improved microbial aggregation. Microbial diversity was significantly enhanced in the UV/PMS–HAA system, with enrichment of functional genera such as Halomonas, Pseudomonas and Thauera. Network and robustness analysis revealed intensified microbial cooperation and reduced disturbance sensitivity. Substantial upregulation of ammonium assimilation genes (gdhA, glnA, gltB), while nitrification–related genes (amoA, hao) were nearly absent, confirming a heterotrophic assimilation–dominated pathway. Enzyme activity analysis further supported this trend, with elevated GS, GOGAT activity and higher intracellular Glu, Gln, and TAA levels in the UV/PMS–HAA. UV/PMS pretreatment effectively reshaped microbial structure and function, promoting nitrogen recovery through assimilation rather than loss via nitrification, and provides a promising solution for treating complex nitrogen–rich wastewaters.

Heterotrophic nitrification and aerobic denitrification (HN-AD) represents an innovative biological nitrogen removal strategy for saline wastewater treatment. However, how HN-AD microbes could be applied to environmental microbiomes and conduct nitrogen metabolic performance remains ambiguous. Here we established synthetic heterotrophic microbiomes using halophilic HN-AD strains - biofilm-forming Pseudomonas kunmingens 8-C and Acinetobacter johnsonii 2–1-H, and characterized nitrogen metabolism in pure-cultured strains and microbiomes. The pure-cultured HN-AD strains removed ammonium primarily via ammonium assimilation (> 46 % contribution) and heterotrophic nitrification, comprehensively validated by nitrogen balance, ¹⁵N stable isotopic labeling tests, enzyme activity assays and functional gene identification. Four synthetic halophilic microbiomes constructed by biofilm-forming and HN-AD strains achieved ammonium and total nitrogen removal efficiencies of 76-92 % and 72–86 %. Biofilm-forming strains facilitated heterotrophic microbiome assembly by shaping microbial communities through the deterministic assembly process. Notably, initial functional strains selectively recruited environmental microbes with efficient ammonium-assimilating capacity, manifested as a stable and relatively high abundance of glnA gene in microbiomes. But the invasion of microbes consequently led to the overwhelming dominance of ammonium assimilation over nitrification in microbiomes. Our results provided a framework for constructing environmental microbiomes using functional microbes and highlighted the distinct nitrogen metabolism shifting from HN-AD pure-cultured bacteria to microbial consortia.

Gas quenching granulation is one of the most important modern methods utilized in molten steel slag (MSS) treatment, more positive and accurate simulated methods play a crucial role in guiding the whole gas quenching which dominate the stability, cementitious activity, magnetic separation of Magnetite and sensible heat recovery of MSS products, etc. However, the frequently used Volume of Fluid (VOF) methods can only predict the fragmentation process, but there appeared much deviation in identifying and calculating subsequent particle fragmentation and particle size distribution changes. To address these noticeable deviations, the VOF to DPM model is innovatively introduced to clarify the morphological spatial and temporal evolution for MSS by designing a transition from the continuous phase to the discrete phase for the divergent liquids. The DPM model is expert in tracking MSS particles in DPM form, and the motion, size changes, particle concentration and size distribution of divergent liquids were real-time counted and measured. Compared to the on-site particle size obtained using the air-quenching at Zhengfeng Steel Plant in China, the relative error between the two was less than 10%. The morphological spatial and temporal evolutions of MSS in the main body region, non-mutual adhesion region and particle field region were systematically studied from qualitative and quantitative aspects under different working conditions. Finally, scientific data was provided to optimize process parameters and improve granulation efficiency. These research findings provide valuable universal applicability in all the fields of gas quenching and fragmentation process and lay a theoretical foundation for subsequent strictly controlled granulated particles.

Oxygen is essential for heterotrophic ammonia assimilation (HAA), driving the microbial degradation of organic compounds and ammonia assimilation in aerobic wastewater treatment. However, the mechanisms underlying carbon-nitrogen transformation and microbial community assembly by heterotrophs under aerobic conditions remained elusive. This study investigated the impact of aeration rates (0.1, 0.5, 1, and 3 L/min·L) on the pollutant removal and microbial dynamics of HAA bioreactors over a 120-day operation period to improve the performance of the system by regulating the microbial oxygen affinity. The NH₄⁺ -N and COD removal efficiencies of the highest aeration rate (3 L/min·L) were as high as 94.8 % and 96.8 %. Batch tests on nitrogen balance verified that nitrogen removal was attributed to assimilation rather than nitrification. The kinetic and mass balances analysis highlighted enhanced microbial activity and substrate utilization at increased aeration rates. Halomonas, emerged as dominant taxa, correlating with improved ammonia assimilation under higher aeration rates. Increased aeration enhanced the microbial robustness and reduced the modularity of microbial interactions, and stochastic processes emerged as the primary drivers of community assembly. The aeration rates of 1-3 L/min·L were considered as the parameter range of optimal pollutant removal, and the aeration rate parameter close to 1 L/min·L was considered as the optimal efficiency combined with the cost. This study provides valuable insights for optimizing biotechnological applications and engineering microbial systems for enhanced environmental performance.

Ceramic nanofiltration is a potential one-step treatment for industrial waste streams. It can remove colloidal particles, oil droplets and some organic molecules. The drawback of the technology is that backwash cannot be applied to remove the accumulated cake layer from the membrane surface. At the moment only chemical cleaning with aggressive oxidizing agents like chlorine are effective to restore the permeability of the membranes after fouling. However, calcium carbonate (CaCO3) precoating has shown potential benefits in preliminary research, but have only been executed at laboratory scale, under a constant pressure and with a limited number of experimental cycles. In the presented work, the CaCO3 precoat/acid cleaning method was comprehensively studied under varying operational conditions. Dead-end filtration of a CaCO3-dispersion was used to precoat the membrane surface. Three different acids were tested to partly dissolve the precoat and remove the cake layer from the membrane surface. It was found that citric acid performed the best to recover the permeability of the membrane, probably due to the chelating properties, capturing the calcium ions, with a good removal of the cake layer during forward flush as a result. The size of precoat particles influenced the efficacy of permeability recovery. The smaller the deposited precoating particles on the membrane surface were, the better the cleaning effect was. It is expected that, when filtering real sewage water, these membranes can operate with one precoat during about 25 days with five consecutive citric acid cleaning cycles before a chlorine-based chemical treatment should thoroughly clean the membrane module.

Marine microorganisms have an inherent advantage in the treatment of saline wastewater due to their halophilic properties. Ammonium assimilation is the most important and common nitrogen conversion pathway in the ocean, which means that it may be a suitable nitrogen removal strategy under high salinity conditions. However, the targeted construction of engineering microbiomes with ammonium assimilation function for nitrogen recovery has not been realized. Here, we constructed four halophilic ammonium assimilation microbiomes from marine microbial community under varying chemical oxygen demand (COD) to nitrogen (COD/N) ratios. The regulation of COD/N ratio on microbial self-assembly was explored at the phenotypic, genetic, and microbial levels. The results of nitrogen balance tests, functional genes abundance and microbial community structure confirmed that the microbiomes regulated by different COD/N ratios all performed obligate ammonium assimilation functions. >93% of ammonium, 90% of TN, 98% of COD, and 82% of phosphorus were simultaneously removed by microbial assimilation under the COD/N ratio of 20. COD/N ratios significantly affected the self-assembly of microbiomes by selectively enriching heterotrophic microorganisms with different preference for organic carbon load. Additionally, the increase of COD/N ratio intensified the competition among species within the microbiome (the proportion of negative connections of microbial network increased from 5.0% to 24.4%), which may enhance the stability of community structure. Taken together, these findings can provide theoretical guidance for the construction and optimization of engineering microbiomes for synergistic nitrogen removal and recovery.

This study aims at applying and verifying the MFI-UF method to predict particulate fouling in RO plants. Two full-scale RO plants treating surface water, with average capacity of 800–2000 m³/h, were studied. Firstly, the MFI-UF of RO feed and concentrate was measured using 5–100 kDa membranes at same flux applied in the RO plants (20–26 L/m².h). Subsequently, the particle disposition factor (Ω) was calculated to simulate particle deposition in RO cross-flow filtration. Finally, particulate fouling rates were predicted based on MFI-UF and Ω, and compared with the actual fouling rates in the plants. For plant A, the results showed that the fouling rates predicted using MFI-UF measured with 100 kDa membrane have the best agreement with the actual fouling (with 3–11 % deviation). For plant B, the fouling rates predicted based on both 10 and 100 kDa membranes agree well with the actual fouling (with 2 % and 15 % deviation, respectively). However, the fouling predicted based on 5 kDa membrane is considerably overestimated for both plants, which is attributed to the effect of the low surface porosity of 5 kDa membrane. More widespread applications of MFI-UF in full-scale RO plants are required to demonstrate the most suitable MFI-UF membranes for fouling prediction.

The contradiction between theoretical metabolism of ammonium assimilation and experiential understanding of conventional biosystems makes the rational optimization of the ammonium-assimilating microbiome through carbon to nitrogen (C/N) ratios perplexing. The effect of different C/N ratios on ammonium-assimilating biosystems was investigated in saline wastewater treatment. C/N ratios significantly hindered the nutrient removal efficiency, but ammonium-assimilating biosystems maintained functional stability in nitrogen conversions and microbial communities. With sufficient biomass, higher than 86% ammonium and 73% phosphorus were removed when C/N ratios were higher than 25. Ammonium assimilation dominated the nitrogen metabolism in all biosystems even under relatively low C/N ratios, evidenced by the extremely low abundances of nitrification functional genes. Different C/N ratios did not significantly change the bacterial community structure of ammonium-assimilating biosystems. It is anticipated that the ammonium-assimilating biosystem with advantages of clear metabolic pathway and easy optimization can be applied to nutrient removal and recovery in saline environments.

Wastewater with high salinity is one of the major challenges for conventional wastewater treatment. Although nitrogen management is vital for wastewater treatment, efficient strategies for nitrogen recovery and removal from saline wastewater remain challenging. Here we propose microbial ammonium assimilation to achieve efficient nitrogen removal and recovery into biomass from saline wastewater without gaseous nitrogen release opposite to the conventional wastewater treatment,. We find one marine bacterium Psychrobacter aquimaris A4N01 with the ability to form sedimentary granular biofilms that can be engineered to construct an efficient ammonium-assimilating microbiome followed the bottom-up design. We demonstrate that the microbiome removes ammonium through assimilation without reactive nitrogen intermediates and gaseous nitrogen emission, according to the functional gene abundance and nitrogen balance. More than 80% of ammonium, total nitrogen and total phosphorus are removed and recovered into biomass, with more than 98% of COD removed from saline wastewater. As one prototypic microbe to form ammonium-assimilating biofilms, Psychrobacter aquimaris A4N01 plays key role in nutrient metabolism and microbiome construction. We stress that ammonium assimilation with a clear and short pathway is a promising method in future saline wastewater treatment and sustainable nitrogen management.