The sulfur autotrophic denitrification packed-bed (SPB) process is widely used in wastewater treatment due to its simplicity, cost-effectiveness, and sustainability. However, in practical SPB applications, the selection of wastewater flow direction was arbitrary, and its differences were completely overlooked, which may lead to insufficient filter bed efficiency and unnecessary economic losses. This study systematically evaluated the differences between upflow SPB (USPB) and downflow SPB (DSPB) in terms of clogging rate and denitrification performance, and explored the mechanisms underlying these differences. The results showed that the head loss growth in DSPB followed an exponential increase with an exponent of 4.5, while that in USPB was much lower, with an exponent of 0.6. Meanwhile, USPB also exhibited 1.28 times higher denitrification efficiency than DSPB, demonstrating significantly better performance. The performance difference between the two modes arose from the different accumulation of N2 bubbles. In DSPB, the greater accumulation of N2 bubbles led to the occupation of the voids between sulfur particles (which are used for water flow), resulting in an increase in head loss. The occupation of voids also led to a decrease in the actual hydraulic retention time (AHRT), which in turn resulted in lower denitrification efficiency in DSPB. Moreover, the mixed flow pattern in DSPB was another factor that resulted in worse clogging (higher flow collision) and lower denitrification efficiency (greater short-circuiting) compared to USPB (piston flow). Overall, this study provides fundamental insights for the selection and operation of the SPB process in practical wastewater treatment applications.

Lab-scale wastewater treatment studies, including urine recovery, often rely on oversimplified synthetic wastewater, thereby compromising the reliability of results and data. Here, we systematically evaluate how using full-component versus simplified synthetic urine formulations affects the performance and engineering-economic assessment of bipolar membrane electrodialysis. Our findings reveal that simplification fundamentally alters fouling mechanisms. While urea alone causes significant damage to anion exchange membranes through hydrogen bonding aggregation, natural organic co-components in real urine mitigate fouling via inhibitory interactions-a mechanism confirmed by molecular dynamics simulations and experimental characterization. After seven batches, the full-component formulations showed 29.3% less performance decay and 10-14% higher urea recovery than the simplified formulation. Moreover, the complete removal of organic components disrupts ion-organic co-aggregation pathways on cation exchange membranes, shifting fouling toward mineral crystallization on bipolar membranes. Simplification also distorts the engineering-economic assessment, overestimating cleaning costs by 15.9% and underestimating membrane lifespan by 12.5%. These findings necessitate identifying key wastewater constituents and ensuring experimental integrity to bridge lab-industry gaps, advocating designs comprehensively addressing multi-component interactions.

Urea is widely adopted in the synthesis of NiCu catalysts, yet its intrinsic regulatory mechanism during electrodeposition remains ambiguous. In this study, experiments combined with molecular dynamics (MD) simulations were used to uncover the modulation effect of urea on Ni/Cu electrodeposition for electrocatalytic NH3 cracking toward H2 production. Among the three tested urea concentrations (0, 5, and 10 mmol L-1), 5 mmol L-1 was identified as the optimal dosage. This optimal condition yielded the maximum current density (47.47 mA cm-2) and the largest electrochemically active surface area (243.33 cm2). The as-fabricated NiCu catalyst achieved an outstanding NH3-N degradation efficiency of 91.44%, a nitrogen selectivity of 73.21%, a Faradaic efficiency of 53.57%, and a minimized energy consumption of 16.08 kW & centerdot;h kg-1 . Combined electrode characterization and MD simulations revealed an explicit structure-performance relationship: urea retarded the migration of Ni2+ and Cu2+ and regulated their deposition kinetics, thereby enabling a uniform Ni-Cu elemental distribution. This study demonstrates that a moderate urea concentration is a feasible strategy to tailor NiCu deposition behavior, providing a rational guideline for the targeted design of high-efficiency alloy electrocatalysts.

Electrochemical ammonia oxidation reaction (AOR) offers a promising route for simultaneous wastewater treatment and energy-saving hydrogen production. However, the development of efficient and non-precious electrocatalysts remains a significant challenge. This study presents the synthesis of NiCu-modified molybdate (NCMO) with a 3D nanoflower architecture for high-performance AOR. The catalyst requires only 463 mV (vs. SCE) to achieve 20 mA/cm2 with a low Tafel slope of 32 mV/dec in 1 M KOH with 0.1 M NH3. Under optimized condition, the response current of NCMO is 3.4 times higher than that of NiCu(OH)2, demonstrating its good activity. Comparative experiments confirm the critical synergistic effect between Ni and Cu and the essential role of Mo in enhancing active sites and charge transfer efficiency. Furthermore, the NCMO shows outstanding stability and a high ammonia removal rate of 92.58% within 6 h in a two-chamber reactor. This work provides a novel design strategy for high-performance AOR electrocatalysts and advances the integration of environmental remediation with renewable energy conversion.

Treating pharmaceutical wastewater containing moxifloxacin or other refractory antibiotics is challenging due to the frequent coexistence of high concentrations of ethanol and chloride ions (Cl-), which inhibit oxidative degradation and downstream biological processes. Here, we comparatively evaluated the Fenton, UV/Na2SO3, and UV/H2O2 processes for moxifloxacin removal under certain concentration Cl- and ethanol conditions. The results revealed that the removal of moxifloxacin stagnated for Fenton (16.21%) and UV/Na2SO3 (37.72%), while the UV/H2O2 maintained a removal rate of >90%. Mechanistic analysis indicated that although Fenton could remove moxifloxacin in the presence of Cl-, its dominant radical was Cl-2(-) rather than OH, resulting in a lower defluorination rate. Cl- and ethanol consumed Fe2+ through reactive species like Cl, Cl-2(-), and HO2, which reduced Fe2+ concentration and blocked the Fenton reaction. In contrast, UV/H2O2 not only sustained direct photolysis but also overcame the reaction inhibition caused by insufficient Fe2+ concentration and maintains continuous OH production. And moxifloxacin adsorbed H2O2 than ethanol, Cl-, generating OH around the moxifloxacin, leading to more effective removal and defluorination (47.30%). Importantly, UV/H2O2 pretreatment restored the nitrification activity of downstream bioprocesses, demonstrating its robustness and practical potential for detoxifying antibiotic-laden wastewater under complex conditions.

High ammonia concentrations can be toxic to microorganisms, leading to the accumulation of hydrogen (H2) and acids in anaerobic digestion (AD) system. In this study, a side gas recycling strategy (SGR), coupled with a primary reactor and a small side-stream reactor, which recirculates biogas between primary reactor and side reactor was employed to mitigate ammonia inhibition. This approach enabled the mesophilic side-stream gas recirculation system (SMGR) and the thermophilic side-stream gas recirculation system (STGR) to ultimately withstand ammonia stress levels of 2.5 g/L and 3.5 g/L, respectively, while maintaining lower hydrogen partial pressures. In contrast, the control group experienced system failure at an ammonia concentration of 2 g/L. Enzyme activity, microbial community, and metaproteomic analysis indicated that the side reactor enriched microorganisms with strong hydrogen-utilizing capacity, while the primary reactor was enriched with Methanosaeta. Furthermore, key pathways related to propionate metabolism, ABC transporters, and methane production were enhanced in the primary reactor, along with increased ATPase activity. The activity of key enzymes involved in AD was also significantly enhanced. This study enhances the understanding of the impact of gas atmosphere control on the microbial ecology and metabolic characteristics of AD system, providing valuable insights and practical guidance for the development of Engineering applications in this field.

Polyaluminum chloride (PAC) is commonly used as a flocculant in wastewater treatment plants to aid in the removal of phosphorus (P) from wastewater. As a result, the P element present in PAC -treated sludge is predominantly in the form of Al -P. This study proposes the use of alkaline anion exchange resin (AAER) as a pretreatment method for PAC -treated sludge to enhance P extraction and achieve cleaner P recovery from this type of sludge. The findings of the study indicate that the optimal concentration of AAER is 12 g/g TS, resulting in a P extraction efficiency of 67.2 %. This represents a 26.5 % increase compared to alkali treatment at the same pH (pH = 12.23). Stepwise extraction analysis and molecular dynamics simulations suggest that during AAER treatment, Al(OH) 3 is converted into dissolved [Al(OH) 4 ] - . These species then agglomerate with PO 4 3- and subsequently get adsorbed by the - N(CH 3 ) + groups on the AAER. Furthermore, even after undergoing five regeneration cycles, the AAER still exhibits a significant adsorption capacity for P. Ultimately, high -purity Ca 10 (PO 4 ) 6 (OH) 2 is obtained as the final product with a recovery rate of 90.5 %. Meanwhile, the Al extracted by AAER can be reused as a feedstock for polymerized aluminum chloride. This demonstrates that AAER extraction is a promising and efficient waste management strategy for the clean recovery of P and Al from PAC sludge.

Herein, a copper-doped nickel phosphide (CuxNi2-xP) electrode with a tailored metal d-band center was designed to boost ammonia (NH3) selectivity during electrocatalytic nitrate (NO3-) reduction (NO3RR) by modulating atomic hydrogen (H*) behavior. The Cu doping accelerated both the Volmer step of water splitting to form H* and the H*-mediated hydrogenation steps for NH3 production, addressing the mismatch between H* supply and utilization. Consequently, the CuxNi2-xP electrode achieved 100 % NO3- conversion efficiency and 99.2 % NH3 selectivity at a low NO3- concentration of 50 mg L- 1, outperforming Ni2P and Cu counterparts. The crucial role of H* in the performance enhancement was elucidated via in-situ characterizations and density functional theory (DFT) calculations. Furthermore, an integrated device combining NO3RR, organic pollutant degradation and NH3 recovery was constructed, demonstrating its scalability for practical wastewater treatment. This study paves the way for collaboratively addressing environmental and energy challenges through improving NH3 recovery from nitrate-laden wastewater.

The development of electrocatalytic systems with tandem hydroxyl radical (center dot OH)- and singlet oxygen (1O2)-mediated pollutant degradation routes broadens the application scenarios for electrochemical water treatment technology. Nonetheless, the precise tuning of the electrocatalytic O2 reduction reaction (ORR) to achieve synchronous synthesis of center dot OH and 1O2 is still challenging in electro-Fenton (EF)-like systems. Herein, an FeTiO3-based flow-through electrochemical cell is proposed for highly efficient and selective ORR to yield both center dot OH and 1O2, which is achieved by regulating the adsorption/desorption of key intermediates (*OOH, *O2 center dot- and *H2O2). The accumulated concentrations of center dot OH and 1O2 in the FeTiO3-based system reach 83 and 31 mu mol L-1 after 120 min, respectively, outperforming the TiO2 counterpart. Such an advanced system demonstrates outstanding performance for the degradation of electron-rich contaminants, even in complex wastewater matrices. The mechanistic insights reveal an enhanced *O2 adsorption, leading to highly selective *O2-to-*O2 center dot-- to-1O2 and *O2-to-*H2O2-to-center dot OH pathways at Fe-O-Ti sites. Therefore, this work provides a new flow-through system for simultaneous center dot OH and 1O2 production, significantly expanding the potential applicability of electrocatalytic processes.

The manuscript discusses Feammox reaction from aspects of Feammox inoculum from five soil sources (paddy soil, forest soil, pond sediment, planting red soil, and planting black soil), optimization by 0-50 mmol ferrihydrite and application to ammonia removal by continuous upflow anaerobic sludge blanket (UASB). The results demonstrated that Feammox enrichment from pond sediment had the highest NH4+-N removal rate of 45.92 %, which was used as the seed sludge of ferrihydrite optimization. Under the optimal concentration of ferrihydrite (10 mmol L- 1), Feammox enrichment removed 79.09 % NH4+-N and comparably removed 80 % phosphorus. In UASB reactor, the predominant bacteria of Anaerolineaceae, Candidatus Brocadia, Denitratisoma, Terrimonas, and Nitrosomonas involved conversion of Fe3+/Fe2+ and ammonia removal (66.05 % NH4+-N removal rate) within 154 days at pH 6, comparably facilitating over 40 % of TP removal. In the interacting process of NH4+, NO2 - and NO3- , the theoretical calculation results signify that ferrihydrite exhibits a significant affinity for NH4+ adsorption over NO2 - and NO3-. These findings enhance our understanding of the Feammox process under various environmental conditions and provide insights into the Fe/N transformation process.

Iron (Fe) derived substances are widely used in the removal of phosphorus (P) in the wastewater treatment process. In the waste activated sludge, through the sequential P and Fe extraction, inorganic P accounted for 90.3% of the total P, which was extracted mainly in Fe(III)-P, Fe(II)-P and Al-P pools, and they account for 82.5% of the total P. The Fe (III) and Fe (II) combined with P mainly formed amorphous FerPO4(OH)3r-3 and vivianite, accounting for 39.0% and 43.5% of total Fe, respectively. By adding different reducing agents (ascorbic acid, cysteine, oxalate) and complexing agents (ethylene diamine tetra acetic, nitrous triacetic acid, citric acid) and adjusting the pH to 3.0, this study found that citric acid presented the best performance on P release, releasing 46.2% of the total P. Ascorbic acid presented the best performance for Fe release, with a releasing efficiency of the 68.1% of the total Fe. The addition of different proportions of ascorbic acid and citric acid to the sludge, along with pH adjustment. It was found that the maximum P release (70.8% of total P) was obtained with the VC/Cit ratio of 0.2/0.8. The high P release can be attributed to the co-effect of the reduction of Fe(III) by VC and the complexation of Fe and Al by Cit. The released P and Fe could be recovered by thermally induced precipitation to high purity FePO4 with a P recovery of 53.4%, which is a main precursor for LiFePO4. This study provides a new direction for the recovery and utilization of P from sludge.

Enhancing the conversion efficiency of methane production from food waste (FW) is always a hot issue. Biological carriers and micro-aeration had demonstrated notable advantages in enhancing anaerobic digestion (AD) efficiency, but their synergistic potential remained largely untapped. This study introduced polyurethane carriers into micro-aeration assisted AD, trying to explore their synergism in enhancing the digestive efficiency of FW. Results revealed that an optimal blend of carriers and micro-aeration pose significant improvement to the digestive performance. Their combination enhanced microbial metabolic activity, accelerated the consumption or conversion of dissolved organic matter (DOM) molecules, promoted the aggregation of microorganisms, which improved their tolerance capacity under the oxygen stress brought by the micro-aeration, ensuring the system stability. It also enriched methane-producing microorganisms, and balanced methane-producing pathways. Additionally, the combination of micro-aeration and carriers promoted key enzyme expression in metabolic pathways, providing ample support for methane production. These findings held significance for optimizing FW treatment, improving methane production efficiency, and reducing the burden of organic waste treatment.

N,N-bis(carboxymethyl)-l-glutamate (GLDA) is an eco-friendly chelating agent that effectively extracts multivalent metal ions from waste activated sludge (WAS) flocs, which could potentially alter their structure. However, the effect of GLDA on the production of volatile fatty acids (VFAs) from WAS is not well known. Here, we demonstrate that pretreatment with GLDA at a concentration of 200 mmol per kg VSS results in a significant increase of 142% in extractable extracellular polymeric substances and enhances the total VFAs yield by 64% compared to untreated samples. We reveal GLDA's capability to mobilize organic-binding multivalent metal ions within sludge flocs. Specifically, post-pretreatment analyses showed the release of 69.1 mg L−1 of Ca and 109.8 mg L−1 of Fe ions from the flocs, leading to a more relaxed floc structure and a reduced apparent activation energy (10.6 versus 20 kJ mol−1) for WAS solubilization. Molecular dynamic simulations further demonstrate GLDA's preferential binding to Fe3+ and Ca2+ over Mg2+. Our study suggests that GLDA pretreatment causes minimal disruption to reactor stability, thereby indicating the stability of microbial community composition. GLDA has emerged as a viable pretreatment agent for enhancing volatile fatty acids production from waste activated sludge.

Wastewater treatment plants (WWTPs) contribute significantly to the control of pollution in water. However, they are significant energy consumers. Identifying the factors influencing energy consumption is crucial for enhancing the energy efficiency of WWTPs. To address this, the unit energy consumption (UEC) of WWTPs was predicted using machine learning models. In order to accurately evaluate WWTPs' energy utilization efficiency, a comprehensive energy evaluation indicator, UEC (kWh/kg TODremoved) was utilized in this study. Among the prediction models, the eXtreme Gradient Boosting (XGBoost) achieves the highest prediction accuracy. SHapley Additive exPlanations (SHAP) was adopted as the model explanation system, and the results revealed that UEC was negatively affected by TN concentration, which was the most influential factor. The stoichiometry-based model calculation result indicates that the nitrification consumes average 77 % of the overall oxygen demand. SHAP analysis illustrated that the UEC of main technologies decreases with increasing influential factors. Partial dependence plot (PDP) compared average UEC of these technologies and SBR consumed the least amount of energy. The research also indicated that low influent TN concentration is the main problem in China. Consequently, it is imperative to exert efforts in ensuring the influent TN concentration while simultaneously making appropriate adjustments to the treatment process. This study provides valuable implications and methods for retrofitting and upgrading WWTPs.

Improving the efficiency of digestion is a major focus of waste activated sludge (WAS) anaerobic digestion (AD) research. This study investigates the viability and mechanism of sodium disilicate (SD) in enhancing the digestive efficacy of WAS. Batch AD experiments for the sludges pretreated by varied amounts of SD were carried out, and the results revealed that a dosage of 90 mmol/L resulted in the highest methane yield (247.9 mL/g & sdot;VS), marking a 90.0 % increase compared to the raw sludge. Mechanistic investigations highlighted that SD pretreatment facilitated EPS degradation, cell lysis, and modulation of interfacial interaction energy, ultimately enhancing sludge disintegration and methane generation. Microbial community analysis unveiled an enrichment of crucial functional microorganisms associated with hydrolysis, acidification, and methanation. The heightened presence of acetotrophic and hydrogenotrophic methanogens significantly boosted methane production. Furthermore, metagenomic analysis corroborated that the SD pretreatment stimulated amino acid metabolism, energy metabolism (specifically ABC transporter proteins), and carbohydrate metabolism, thereby enhancing methanogenic activity through increased microbial metabolic activities and upregulated key enzyme expression. This research underscores the potential of SD-assisted pretreatment strategies in augmenting WAS digestion, introducing supplementary pretreatment avenues for optimizing anaerobic biotechnology.

High ammonia concentration inhibits archaea's activity, causing the accumulation of H2 and acetate, which suppresses methane production in anaerobic digestion (AD). The study aimed to enhance microbial hydrogen metabolism through a side-stream hydrogen domestication (SHD) strategy, which involves applying hydrogen stimulation to a portion of the sludge separately. SHD maintained a stable methane yield of 407.5 mL/g VS at a high total ammonia nitrogen (TAN) concentration of 3.1 g/L. In contrast, the control group gradually decreased and stopped methane production at a TAN concentration of 2.3 g/L. Further analysis using enzyme activity assays, flow cytometry, and metagenomics explored the mechanisms underlying ammonia tolerance of SHD-treated group. SHD reshaped the microbial community, enriching homoacetogens and Methanosaeta-dominated methanogenic archaea. Key metabolic pathways including homoacetogenesis, butyrate degradation, propionate degradation, and methane production were enhanced. The activity of related enzymes also increased. Gene abundance in energy-generating pathways, such as glycolysis, was enhanced, ensuring adequate ATP production. Additionally, the high gene abundance of ion transport systems contributed to regulating proton imbalance and supplementing intracellular K+. This study provides important insights and practical guidance for developing novel techniques in the field of anaerobic digestion.

ABSTRACT Adding trace calcium peroxide and magnetite into a semi-continuous digester is a new method to effectively improve the anaerobic digestion of food waste. However, the microbial mechanism in this system has not been fully explored. Metaproteomics further revealed that the most active and significantly regulated genus u_p_Chloroflexi had formed a good cooperative relationship with Methanomicrobiales and Methanothrix in the system. u_p_Chloroflexi decomposed more organic compounds into CO 2 , acetate, amino acids, and other substances by alternating between short aerobic-anaerobic respiration. It perceived and adapted to the surrounding environment by producing biofilm, extracellular enzymes, and accelerating substrate transport, formed a respiratory barrier, and enhanced iron transport capacity by using highly expressed cytochrome C. The methanogens formed reactive oxygen species scavengers and reduced iron transport to prevent oxidative damage. This study provides new insight for improving the efficiency of anaerobic digestion of food waste and identifying key microorganisms and their regulated functional proteins in the calcium peroxide-magnetite digestion system. IMPORTANCE Previous study has found that the combination of calcium peroxide and magnetite has a good promoting effect on the anaerobic digestion process of food waste. Through multiple omics approaches, information such as microbial population structure and changes in metabolites can be further analyzed. This study can help researchers gain a deeper understanding of the digestion pathway of food waste under the combined action of calcium peroxide and magnetite, further elucidate the impact mechanisms of calcium peroxide and magnetite at the microbial level, and provide theoretical guidance to improve the efficiency and stability of anaerobic digestion of food waste, as well as reduce operational costs. This research contributes to improving energy recovery efficiency, promoting sustainable management and development of food waste, and is of great significance to environmental protection.

For hydrogen (H2) storage and carbon dioxide (CO2) emission reduction, biomethanation under thermophilic condition (55 degrees C) was considered. To enhance the efficiency of biomethanation, current studies have focused on the contribution of iron-containing metal nanoparticles, neglecting the contribution of other key trace elements. In order to fill this gap, this study evaluates the role of Fe2NiO4 NPs in biomethanation, as Ni is a key trace element essential for microbial growth. Results indicate that the addition of Fe2NiO4 NPs improved the utilization and conversion rates of H2 and CO2, boosting methane (CH4) yield by 37.12 %. Its participation induced microbial secretion of abundant extracellular polymeric substances (EPS) rich in fulvic acids (FAs) as electron mediators, which increased the electron transfer rate by 21.60 %. Microbial community analysis reveals that the addition of Fe2NiO4 NPs reduced competition among autotrophic microbes for carbon sources, reinforcing carbon conversion to CH4. Lastly, the addition of Fe2NiO4 NPs increased the level of microbial metabolism and also elevated the abundance/enzymatic activity of enzymes associated with the hydrogenotrophic methane production pathways, thus facilitating the efficiency of biomethanation.