Search Results (140)

This study examined a strategy for effective reject water treatment involving hydrodynamic cavitation (HC) combined with subsequent adsorption using natural zeolites. Two experiments were conducted: The first involved the selection of optimal pre-treatment conditions of HC for biodegradability and to reduce the ammonium nitrogen and phosphate content. Three inlet pressures of 3, 5, and 7 bar and two types of cavitation inducers, i.e., multiple- and single-hole orifice plates, were evaluated. Adsorption experiments were conducted in batch mode using natural zeolite, and three doses of zeolite (50, 100, and 200 g/L) and six contact times (4–24 h) were examined. In the HC experiments, the application of 3 bar pressure, a single-hole cavitation inducer, and a cavitation time of 30 min resulted in the removal of ammonia nitrogen and phosphates amounting to 26.5 and 23%, respectively. In this case, 3.6-fold enhancement in the biodegradability index was also found. In the second experiment, the use of zeolite led to a decrease in the remaining content of both ammonia nitrogen and phosphates, improving the chemical oxygen demand-to-total nitrogen ratio. The highest removal efficacy was found for the highest zeolite dose of 200 g/L and the longest cavitation time of 24 h. Under these conditions, the ammonia nitrogen and phosphate removal rates were 70 and 94%, respectively. Full article

The development of efficient and sustainable water recycling systems is essential for long-term human missions and the establishment of space habitats on the Moon, Mars, and beyond. Humidity condensate (HC) is a low-strength wastewater that is currently recycled on the International Space Station (ISS). The main contaminants in HC are primarily low-molecular-weight organics and ammonia. This has caused operational issues due to microbial growth in the Water Process Assembly (WPA) storage tank as well as failure of downstream systems. In addition, treatment of this wastewater primarily uses adsorptive and exchange media, which must be continually resupplied and represent a significant life-cycle cost. This study demonstrates the integration of a membrane-aerated biological reactor (MABR) for pretreatment and storage of HC, followed by brackish water reverse osmosis (BWRO). Two system configurations were tested: (1) periodic MABR fluid was sent to batch RO operating at 90% water recovery with the RO concentrate sent to a separate waste tank; and (2) periodic MABR fluid was sent to batch RO operating at 90% recovery with the RO concentrate returned to the MABR (accumulating salinity in the MABR). With an external recycle tank (configuration 2), the system produced 2160 L (i.e., 1080 crew-days) of near potable water (dissolved organic carbon (DOC) < 10 mg/L, total nitrogen (TN) < 12 mg/L, total dissolved solids (TDS) < 30 mg/L) with a single membrane (weight of 260 g). When the MABR was used as the RO recycle tank (configuration 1), 1100 L of permeate could be produced on a single membrane; RO permeate quality was slightly better but generally similar to the first configuration even though no brine was wasted during the run. The results suggest that this hybrid system has the potential to significantly enhance the self-sufficiency of space habitats, supporting sustainable extraterrestrial human habitation, as well as reducing current operational problems on the ISS. These systems may also apply to extreme locations such as remote/isolated terrestrial locations, especially in arid and semi-arid regions. Full article

Anaerobic fermentation has been recognized as an effective approach to harness livestock manure resources. In the present study, cow dung and pig manure were employed as fermentation substrates. These were subjected to co-fermentation experiments with sodium hydroxide-pretreated corn straw. Additionally, biochar derived from artificial wetland substrate was introduced as a conditioner to investigate the impact of varying addition quantities on the pretreated anaerobic co-fermentation process. Our findings indicate that for the anaerobic co-fermentation of cow dung, an optimal addition of 4% biochar reduced the gas production cycle by 35–45%, although the total methane yield remained relatively unchanged. Conversely, in the anaerobic co-fermentation of pig manure, a 6% biochar addition proved most effective. This adjustment, while not significantly altering the gas production cycle, led to a marked increase in the total methane content, ranging from 18.53% to 150.18%. The PCA analysis results of the cow manure experimental group showed a significant positive correlation between the addition of biochar and ammonia nitrogen. For the pig manure fermentation system, the addition of biochar can increase the final methane production potential, from 47.43 mL/g VS to 122.24 mL/g VS in the P2C experimental group. Biochar mainly regulates the activity of anaerobic bacteria through changes in pH and conductivity, thereby affecting methane production. Full article

The utilization of nettle (Urtica cannabina) as feed is restricted by its material properties (antibacterial activity and high buffering capacity). This study hypothesized that the use of lactic acid bacteria (LAB) attached to nettles can improve these problems. Lactococcus garvieae (LG), Pediococcus pentosaceus (PP), and LG + PP (LP) isolated from nettles were inoculated into nettle silage to explore nutrient retention and the microbial community structure. The results showed that inoculation significantly delayed dry matter and crude protein loss, inhibited neutral detergent fiber and acid detergent fiber degradation, and reduced ammonia nitrogen (NH₃-N) accumulation. There was a significant increase in Firmicutes abundance after inoculation, and the dominant genus, Aerococcus, was negatively correlated with NH₃-N accumulation. In the later stages of the PP treatment, Atopistipes synergistically inhibited Clostridia with acetic acid. However, the high buffering capacity and antibacterial components of raw nettle led to increased pH values during the later fermentation stages, limiting sustained acid production by LAB. These results confirm that nettle-derived LAB can effectively improve the quality of silage by regulating the microbial community and the acidification process; however, they must be combined with pretreatment strategies or optimized composite microbial agents to overcome raw material limitations. This study provides a theoretical basis and technical support for the utilization of nettle as feed. Full article

Membrane contactors have proved to be effective for recovering ammonia from wastewater by absorbing it into a trapping solution. This study compares the performance of sulfuric acid and citric acid as trapping solutions in a pilot-scale plant for recovering ammonia from sludge digestion liquors using membrane contactors in a liquid–liquid configuration operating at pH 10 and a temperature of 37 °C and using ultrafiltration (UF) technology as pretreatment. The performance of the process using sulfuric acid at a lower pH (9.5) and temperature (30 °C) was also studied, as well as the advantage of including a CO₂-stripping module in the process. The ammonia elimination efficiency was 88% and 86% when using sulfuric acid and citric acid, respectively. The nitrogen concentration of the produced ammonium sulfate and ammonium citrate reached 23.2 and 14.7 g NH₃-N·L⁻¹, respectively. The ammonia elimination efficiency when using sulfuric acid decreased to 49% when decreasing the pH to 9.5 and to 85% when decreasing the temperature to 31 °C. UF technology was able to reduce the concentration of suspended solids by 90% and the chemical oxygen demand by 37%. However, the UF membranes for the pretreatment and the membrane contactors for ammonia recovery had to be constantly cleaned with acid due to scaling, which significantly increased maintenance efforts. The CO₂-stripping module reduced the consumption of the caustic soda solution by 23% for increasing the pH level of the treated water. Finally, the specific energy consumption of the plant was 8 kWh·m⁻³. Full article

Citric acid (CAC) is a ubiquitous, odorless, and non-toxic food additive. Soft rot, caused by the pathogen Rhizopus stolonifer, is a major postharvest disease affecting sweet potato (Ipomoea batatas (L.) Lam). The main theme of this study is to determine the CAC inhibitory mechanism against Rhizopus stolonifer, the causative agent of sweet potato soft rot. To ascertain the practical applicability of CAC, both in vitro and in vivo methodologies were employed. The aim of the in vitro experiments in this study was to delineate the effects of a 0.5% (w/v) CAC solution on the growth inhibition of Rhizopus stolonifer, encompassing mycelial morphology and colony expansion. In vivo experiments were carried out using “Xinxiang” sweet potato varieties and the application of a 0.5% (w/v) CAC solution as a pretreatment. Specifically, the tissue treated with 0.5% CAC maintained better appearance quality and texture characteristics; peroxidase, β-1,3-glucanase, chitinase, and phenylalanine ammonia-lyase activities were enhanced. Conversely, the same treatment resulted in a downregulation of polyphenol oxidase, catalase, ascorbate peroxidase, cellulase, and polygalactosidase activities. Moreover, CAC treatment was found to maintain elevated levels of total phenolics and flavonoids within the sweet potato tissues. In summary, the study demonstrates that 0.5% CAC fortifies the resistance of sweet potato to soft rot by activating defense-related enzymes, suppressing the activity of cell wall-degrading enzymes, and promoting the accumulation of antimicrobial compounds. These results advocate for the utilization of CAC as a postharvest treatment to mitigate the incidence of sweet potato soft rot. Full article

Lignification often occurs during low-temperature storage in loquat fruit, leading to increased firmness and lignin content, water loss, and changes in flavor. As induced stress factors, short-time high-oxygen pre-treatment (SHOP) can initiate resistant metabolism and regulate the physicochemical qualities during fresh fruit storage. However, the effect of SHOP on the lignification and quality of loquat has been reported less. In the present study, loquat fruit was immersed in oxygen concentrations of 70%, 80%, and 90% for 30 min before being stored at 4 ± 1 °C. The results showed that the 80% SHOP samples had lower lignin accumulation and firmness, showing reductions of 23.1% and 21.1% compared to the control at 50 days. These effects were associated with the inhibition of the activities of lignin synthesis-related enzymes, including phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD). Meanwhile, 80% SHOP improved the antioxidant enzyme system and maintained the structural integrity of the cells. Furthermore, SHOP retained the color and suppressed decay and weight loss and the decline in the soluble solids content (SSC) and titratable acidity (TA). As a convenient and cheap physical approach, SHOP is a promising technology for delaying lignification by regulating lignin synthesis in loquat storage. Full article

Vanadium precipitation is the key step in producing vanadium products from vanadium solution. The sustainable development of the vanadium industry requires new environmentally friendly processes for vanadium precipitation. In this study, NaVO₃ solution was pretreated with manganese salt to preliminarily separate the vanadium and sodium components. The product of vanadium extraction by manganese salt was dissolved by acid to produce manganese vanadate solution. After vanadium precipitation by hydrolysis, manganese removal, and calcination, the target product V₂O₅ was obtained. Scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma emission spectrometry (ICP-OES), and atomic absorption spectrometry (AAS) were used to perform the characterization and analyses. The results showed that vanadium and manganese have a strong binding ability. The rate of vanadium extraction by manganese salt reached 99.75%, and the product of vanadium extraction by manganese salt was Mn₂V₂O₇, with a sodium content of only 0.089%, confirming the effective separation of vanadium and sodium. The acid dissolution rate of the vanadium extraction product reached 99.95%, and the rate of vanadium precipitation by hydrolysis reached 97.87%. After manganese removal and calcination, the purity of the V₂O₅ product reached 98.92%. In addition, the recyclability of manganese sulfate and ammonium sulfate was analyzed. The process reduced the production of ammonia–nitrogen wastewater, laying a foundation for researching new technologies for extracting vanadium from vanadium slag. Full article

The anaerobic digestion (AD) of livestock blood represents a sustainable solution for the management of waste generated by the meat processing industry while simultaneously generating renewable energy. The improper treatment of livestock blood, which is rich in organic matter and nutrients, can result in environmental risks such as water pollution, soil degradation, and greenhouse gas emissions. This review examines a range of AD strategies, with a particular focus on technological advances in reactor design, pretreatment, and co-digestion, with the aim of optimizing process efficiency. While the high protein content of blood has the potential to enhance biogas production, challenges such as ammonia inhibition and process instability must be addressed. Innovations such as bio-carriers, thermal pretreatment, and co-digestion with carbon-rich substrates have demonstrated efficacy in addressing these challenges, resulting in stable operation and enhanced methane yields. The advancement of AD technologies is intended to mitigate the environmental impact of livestock blood waste and facilitate the development of a circular bioeconomy. Furthermore, the possibility of utilizing slaughterhouse blood for the recovery of valuable products, including proteins, heme iron, and bioactive peptides, was evaluated with a view to their potential applications in the pharmaceutical and food industries. Furthermore, the potential of utilizing protein-rich blood as a substrate for mixed culture fermentation in volatile fatty acid (VFA) biorefineries was explored, illustrating its viability in biotechnological applications. Full article

Ammonia synthesis is one of the most important chemical reactions. Due to thermodynamic restrictions and the reaction requirements of the current commercial iron catalysts, it is also one of the worst reactions for carbon dioxide emissions and energy usage. Ruthenium-based catalysts can substantially improve the environmental impact as they operate at lower pressures and temperatures. In this work, we provide a screening of more than 40 metals as possible promoter options based on a Ru/Pr₂O₃ catalyst. Cesium was the best alkali promoter and was held constant for the series of double-promoted catalysts. Ten formulations outperformed the Ru-Cs/PrO_x benchmark, with barium being the best second promoter studied and the most cost-effective option. Designs of experiments were utilized to optimize both the pretreatment conditions and the promoter weight loadings of the doubly promoted catalyst. As a result, optimization led to a more than five-fold increase in activity compared to the unpromoted catalyst, therefore creating the possibility for low-ruthenium ammonia synthesis catalysts to be used at scale. Further, we have explored the roles of promoters using kinetic analysis, X-ray Photoelectron Spectroscopy (XPS), and in situ infrared spectroscopy. Here, we have shown that the role of barium is to act as a hydrogen scavenger and donor, which may permit new active sites for the catalyst, and have demonstrated that the associative reaction mechanism is likely used for the unpromoted Ru/PrO_x catalyst with hydrogenation of the triple bond of the dinitrogen occurring before any dinitrogen bond breakage. Full article

Assessing bacterial communities across water resources is crucial for understanding ecological dynamics and improving water quality management. This study examines the functional profiles of bacterial communities in drinking water resources in Mega Manila, Philippines, including Laguna Lake tributaries, pre-treatment plant sites, groundwater sources, and post-treatment plant sites. Using eDNA sequencing, flux balance analysis, and taxonomy-to-phenotype mapping, we identified metabolic pathways involved in nutrient metabolism, pollutant degradation, antibio- tic synthesis, and nutrient cycling. Despite site variations, there are shared metabolic pathways, suggesting the influence of common ecological factors. Site-specific differences in pathways like ascorbate, aldarate, and phenylalanine metabolism indicate localized environmental adaptations. Antibiotic synthesis pathways, such as streptomycin and polyketide sugar unit biosynthesis, were detected across sites. Bacterial communities in raw and pre-treatment water showed potential for pollutant degradation such as for endocrine-disrupting chemicals. High levels of ammonia-oxidizing and sulfate-reducing bacteria in pre- and post-treatment water suggest active nitrogen removal and pH neutralization, indicating a need to reassess existing water treatment approaches. This study underscores the adaptability of bacterial communities to environmental factors, as well as the importance of considering their functional profiles in assessing drinking water quality resources in urban areas. Full article

The expanding global population has increased the demand for sustainable protein sources, and microbial protein (MP) has emerged as a promising alternative. However, conventional carbon (glucose) and nitrogen (ammonia, urea) sources needed for MP production pose environmental and economic issues. This study aims to produce protein using lignocellulosic biomass (LCB) as a carbon source and the nitrogen fixation ability of Klebsiella oxytoca M5A1 as a nitrogen source. The study investigates the pretreatment of LCB (switchgrass), enzymatic hydrolysis, protein quantification, nitrogen fixation, glucose utilization and organic acids production. K. oxytoca M5A1 harnessed free nitrogen from the atmosphere and used abundant, cheap glucose from LCB to produce MP and organic acids as by-products. Protein production occurred in two phases: first within the initial 8 h and secondly, within the last 16 h. The highest protein concentration was at 40 h, with approximately 683.46 µg/mL protein content. High-performance liquid chromatography system (HPLC) analysis revealed a dynamic profile of glucose utilization and organic acids (Lactic acid, Propionic acid, Acetic acid, and Succinic acid) production. K. oxytoca M5A1 exhibited an early high rate of glucose consumption, and conversion to organic acids, that were later used for second-phase protein production. The acids profile revealed intra-conversion from one acid to another via metabolic pathways (glycolysis and tricarboxylic acid cycle). Overall, leveraging LCB and the nitrogen-fixing ability of K. oxytoca M5A1 for MP production offers an eco-friendly and cost-effective alternative to traditional protein sources, contributing to a sustainable circular economy. Full article

The excessive discharge of nitrogen leads to water eutrophication. The partial nitritation and anammox (PN/A) process is a promising technology for biological nitrogen removal in wastewater treatment. However, applying it to mature landfill leachate (MLL) faces challenges, as the toxic substances (e.g., heavy metal) within MLL inhibit the activity of anammox bacteria. Therefore, most previous studies focused on diluted, pretreated, or chemically adjusted MLL. This study demonstrated at full scale that the two-stage PN/A process can treat raw MLL. Initially, the operational issue of sludge floatation resulted in rapid biomass loss with overflow discharging, which selectively suppresses nitrite-oxidizing bacteria (NOB), promoting the achievement of nitrite accumulation. After that, the NOB suppression was self-sustained by the high in situ free ammonia concentration, i.e., 26.2 ± 15.9 mg N/L. In the subsequent anammox tank, nitrogen removal primarily occurred via the anammox process, complemented by denitrification, achieving total nitrogen removal efficiency exceeding 72%. In addition, the nitrogen removal capacity of this system was significantly influenced by temperature with the nitrogen-loading rate above 0.4 kg N/m³/d at 38 °C and approximately 0.1 kg N/m³/d at 21 °C. The optimization of system operation, such as gradually increasing MLL content, remains necessary to enhance nitrogen removal capacity further. Full article

Electrochemical oxidation of ammonia is an attractive process for wastewater treatment, hydrogen production, and ammonia fuel cells. However, the sluggish kinetics of the anode reaction has limited its applications, leading to a high demand for novel electrocatalysts. Herein, the electrode with the in situ growth of NiCu(OH)₂ was partially transformed into the NiCuOOH phase by a pre-treatment using highly oxidative solutions. As revealed by SEM, XPS, and electrochemical analysis, such a strategy maintained the 3D structure, while inducing more active sites before the in situ generation of oxyhydroxide sites during the electrochemical reaction. The optimized NiCuOOH-1 sample exhibited the current density of 6.06 mA cm⁻² at 0.5 V, which is 1.67 times higher than that of NiCu(OH)₂ (3.63 mA cm⁻²). Moreover, the sample with a higher crystalline degree of the NiCuOOH phase exhibited lower performance, demonstrating the importance of a moderate treatment condition. In addition, the NiCuOOH-1 sample presented low selectivity (<20%) towards NO₂⁻ and stable activity during the long-term operation. The findings of this study would provide valuable insights into the development of transition metal electrocatalysts for ammonia oxidation. Full article

Particle size reduction is a commonly used pretreatment technique to promote methane production from anaerobic digestion (AD) of food waste (FW). However, limited research has focused on the effect of micron-sized particles on AD of FW. This research presented an ultrafine wet milling (UFWM) pretreatment method to reduce the particle size of FW particles. After four hours of milling, D90 was reduced to 73 μm and cumulative methane production boosted from 307.98 mL/g vs. to 406.75 mL/g vs. without ammonia inhibition. We evaluated the performance of the AD systems and explored their facilitation mechanisms. Kinetic analysis showed that the modified Gompertz model predicted experimental values most accurately. UFWM pretreatment increased the maximum methane production rate by 44.4% and reduced the lag time by 0.65 days. The mechanical stress and collisions of milling resulted in a scaly surface of the particles, which greatly increased the voids and surface area. A rise in the XPS peak area of the C–N and C=O bonds proved the promotion of the liberation of carbohydrates and fats. Further microbial community analysis revealed that the relative abundance of Bacteroidota and Methanosarcina were enriched by UFWM. Meanwhile, methane metabolism pathway analysis confirmed that module M00567, module M00357, and related enzymes were stimulated. This study provided a theoretical basis for UFWM pretreatment applications and improvements in AD of FW. Full article