Environmental Technology最新文献

Electrochemical reduction is an efficient method for treating high-concentration nitrate wastewater, providing benefits such as enhanced controllability and the elimination of secondary pollution. In this study, the CuNi/NF electrode was fabricated by direct current electrodeposition of copper and nickel onto nickel foam, which served as the cathode for the electrochemical reduction of nitrate. The electrode demonstrated superior nitrate removal performance, achieving an NO₃^--N removal rate of 83% after 5 h of reaction at an initial concentration of 500 mg/L, significantly outperforming the Cu/NF electrode (76%) and Ni/NF electrode (57%). The influence of key operating parameters on nitrate reduction was systematically investigated. The results indicated that the electrode prepared with a deposition time of 20 min exhibited the highest removal efficiency. Under optimal conditions (current density of 25 mA/cm², Cl^- concentration of 2 g/L, and initial pH of 7), the NO₃^--N removal rate reached 85%, with N₂ selectivity as high as 93.7%. The CuNi/NF electrode also exhibited good stability over five consecutive cycles. Finally, a plausible mechanism for nitrate reduction was proposed. This study provides fundamental data and theoretical support for the practical application of electrochemical methods in treating high-concentration nitrate wastewater.

The following study uses Life Cycle Assessment as a tool to determine the impacts generated by the treatment of sludge from municipal wastewater treatment plants (EWC 190805). In this paper, four scenarios of technologies used for sludge disposal are presented: scenario A considers dewatered and undigested sludge sent to landfill; in scenario B the sludge undergoes a stabilization process for use on land; scenario C considers incineration of the dried sludge; and in scenario D the sludge undergoes the same treatment as in scenario B but for final use as compost. The system boundaries include transport to the various disposal centers, using functional units equal to one ton of dried sludge. House made software was used to calculate the impacts, using input data from an existing plant located in central Italy. The environmental categories analyzed were global warming potential, acidification potential and eutrophication potential. The results per functional unit indicate that land application has the lowest GWP impact, while incineration without recovery produces the highest. The analysis was then extended to the national level with data from the ISPRA database. Research using LCA can be useful for decision-makers and stakeholders on strategies to improve environmental performance on the topic.

Potassium ferrate (K₂FeO₄) has been widely applied as a pretreatment agent for residual sludge digestion, but the complete synthesis of its solid form is costly. In this study, the use of ferrate anode solution (FAS) was examined as a more economical alternative. FAS is generated as an intermediate byproduct during the electrolytic production of solid K₂FeO₄. The performance of FAS was compared with that of conventional solid K₂FeO₄ to assess their respective effects on anaerobic acid production and sludge dewatering. The results indicate that sludge soluble chemical oxygen demand (SCOD) was increased to 3807 mg/L at the low dosage of 10 mL/L, and the production of short-chain fatty acids (SCFAs) reached 2142 mg COD/L. At this dosage, higher efficiencies in protein and polysaccharide release were achieved compared with high-dose K₂FeO₄ (0.5 g/g TSS). Sludge settling and dewatering properties were also improved, and reductions of 9.1% in sedimentation ratio and 9.7% in cake moisture content were achieved during pretreatment. These findings suggest that FAS, as an intermediate byproduct, can replace solid K₂FeO₄ for sludge pretreatment because of its high efficiency at low dosages and its distinct enhancement of dewatering performance. FAS may therefore serve as a more economical and effective option.

Mineral recovery from aqueous streams induced by bacteria has emerged as a sustainable and eco-friendly approach to improving water quality while retrieving valuable minerals. In this study, 11 out of 15 marine bacterial isolates collected from Hurghada and Ras Sedr cities were chosen based on the halotolerant-growth profile on 50 g/L NaCl. The isolate HR-106 was chosen based on the highest mineral bioprecipitation of 282 ± 0.6 mg/100 mL. This isolate produced 53.27 ± 0 µg/mL ammonia and 126.83 ± 0 mg/L non-proteinic nitrogen; in addition to that, it showed positive urease activity. This marine isolate was identified as Micrococcus luteus. It was exposed to increasing doses of gamma radiation and NaCl concentration (275 g/L). A confirmation of the bioprecipitated mineral profile was performed for non-irradiated and irradiated Micrococcus luteus using Energy Dispersive X-Ray (EDX) and X-ray Diffraction (XRD). Scanning Electron Microscope (SEM) images showed different morphologies. The Fourier Transform Infrared (FTIR) spectrum for both non-irradiated and irradiated bioprecipitate showed similar patterns that indicated that exopolysaccharides are present in both samples, acting as nucleation sites for both samples. The results demonstrated that both non-irradiated and irradiated Micrococcus luteus produced Ca-Mg-P bioprecepitate that showed the same chemical formula Ca_8.02Mg_9.98O₄₈P₁₂, which represents stanfieldite-like. Gamma irradiation (2kGy) stimulated mineral recovery by 40% under the tested conditions. The findings highlight the potential use of irradiated bacteria in other biotechnological applications, such as water treatment.

The effectiveness of enzyme preparations was investigated under real-life conditions in a commercially operated full-scale biogas plant, aiming to bridge the gap between promising laboratory results and the challenges of practical application. The selected biogas plant represents a typical agricultural setup, processing a feedstock mixture with high proportions of cattle slurry and manure (each up to 29% of the fresh mass input), combined with feed rye and grass silage. These components are considered difficult to degrade, which suggested a high potential for enzymatic treatment. The enzyme products used are characterized by a combination of different enzymatic activities, enabling the breakdown of both dung and straw contained in manure, as well as viscous components from grass and whole crop silages. Due to the substrate-specific nature of enzymatic activity, the selected enzyme products and the applied feedstock mixture appeared to be an excellent match. A comparison between a 14-week reference phase and a 12-week phase with enzyme application revealed a clear impact on plant performance. The specific methane yield increased by 18% during the application period, reaching an average of 346 m³ CH₄/t oDM. This resulted in an average surplus of 210 kWh of electrical energy per ton of oDM. Power self-consumption remained stable at an average of 6.7%. The observed effects confirm the suitability of the applied enzyme products and are based on an exceptionally large dataset, including daily monitoring of plant performance and weekly feedstock characterization.

Phenolic compounds are hazardous industrial pollutants due to their acute environmental toxicity. This study investigates the degradation of 4-chlorophenol (4-CP) using an Ozone Plasma Nanobubble Reactor (OPNR) under varying gas flow rates (1-5 L/min), voltages (10 and 17 kV), and initial 4-CP concentrations (50 and 250 mg/L). The results showed that at an initial 4-CP of 50 mg L^-1 and oxygen flow rate of 4L min^-1, the process at voltages of 5, 10, and 17 kV for 30 minutes resulted in 4-CP degradation of 33.96, 100, and 99.98% respectively. The process using oxygen generated higher 4-CP degradation percentage values (up to 100%) than that using free air input (up to 89.01%). The process at a voltage of 17 kV and various oxygen gas flow rates of 1, 2, 3, 4, and 5 L min^-1 for 60 minutes resulted in 4-CP degradation of 99.80, 99.90, 99.93, 100, and 99.66% at an initial 4-CP of 50 mg L^-1 and then 89.01, 99.60, 99.84, 98.91, and 99.55% at an initial 4-CP of 250 mg L^-1. Therefore, the highest 4-CP degradation using oxygen input by using a voltage of 17 kV for 60 minutes with initial concentrations of 50 mg L^-1 and 250 mg L^-1 was 100% (using oxygen flow rate of 4L min^-1) and 99.60% (using oxygen flow rate of 2L min^-1), respectively. It shows that the OPNR reactor can work optimally.

Selenium(IV) (Se(IV)) supplementation was evaluated as a biostimulant to enhance m-dichlorobenzene (m-DCB) biodegradation in laboratory-scale biotrickling filters (BTFs) inoculated with Brevibacillus agri DH-1. An optimal Se(IV) concentration of 4.0 mg/L increased steady-state m-DCB removal efficiency from 74.38% to 81.74% at an empty bed residence time (EBRT) of 90 s. When the EBRT was reduced to 30 s, BTF2 maintained a 41.74% removal efficiency, compared with only 17.64% for BTF1. Se(IV) promoted extracellular polymeric substance production, strengthened biofilm adhesion, enhanced catechol-1,2- and catechol-2,3-dioxygenase activities, and moderated surface charge to favour microbial aggregation. Fourier-transform infrared spectroscopy confirmed Se(IV)-facilitated dechlorination and aromatic-ring cleavage, while 16S rRNA sequencing revealed enrichment of key degraders including Brevibacillus, Pseudomonas, Bacillus, Rhodanobacter, and Sphingobium. These findings demonstrate a novel micronutrient-based strategy to improve BTF performance for treating chlorinated aromatic exhaust gases.

The substances in ecosystems flow along the food chain. Therefore, we should establish a monitoring system for antibiotic resistance genes (ARGs) in fertilizer products as soon as possible to regulate the use of fertilizers. In this study, three groups of cattle manure organic fertilizers were set up according to the ratio of straw addition, namely CK: cattle manure: straw = 6:4; M1: cattle manure = 100%; M2: cattle manure: straw = 8:2. All groups were supplemented with microbial agents. Their effects on ARGs, class 1 integron integrase genes (intI1) and bacterial communities were investigated. At the end of composting, the relative abundance of sul1, sul2, tetG, and intI1 in M1 and M2 were significantly lower than that in the CK group, and most of the ARGs in each group were removed. The changes in the relative abundance of ARGs are related to changes in microbial community structure. The establishment of temperature conditions is a key factor affecting the structure of microbial communities. Bacillus may play an important role in controlling the relative abundance of ARGs. We found that the most suitable ratio of cattle manure to straw was 8:2 among the three groups, which not only ensured the balanced nutritional composition of organic fertilizers, but also effectively reduced the abundance of ARGs.

Nowadays, the presence of triazine-based azo dyes like Reactive Red 120 (RR 120) in textile wastewater poses a significant hazardous environmental impact, deteriorating the aquatic biota and requiring an effective treatment method. Compared to conventional energy-intensive and secondary waste-generating physicochemical methods, biological methods, especially microbial biodegradation, offer a sustainable, eco-friendly, and cost-effective alternative for the treatment of effluents containing dye-laden wastewater. This study evaluated the efficacy of Bacillus tequilensis MCC2908 for biodegradation and detoxification of RR 120 using a continuously Packed Bed Bioreactor (PBBR). The experimental findings revealed an optimum range of ILR within 75-85 mg/L.day, achieving 94.2 ± 2.71% RE and 24.1 ± 1.205 mg/L.day EC, avoiding limitations imposed by mass transfer and bioreaction, and maintaining a robust and efficient bioreactor system. Crystal Violet staining test confirmed the quantitative assessment of biofilm growth, while SEM images made it observable on the polyurethane bio-carrier. The FTIR spectra confirmed the biodegradation of RR 120, showing significant changes in the functional groups. The detoxification was demonstrated using bacterial and phytotoxicity, validating the toxicity reduction, further duly supported by photosynthetic pigment analysis. The Monod model and the Andrew-Haldane kinetics significantly described microbial growth under non-inhibitory and inhibitory conditions, respectively. Nevertheless, the present findings not only highlighted the potential of biofilm-based PBBR but also delivered an eco-friendly, sustainable solution for the remediation of textile wastewater. Future studies may explore the scaling up of this biotechnological solution for the mitigation of industrial challenges and establish hybrid approaches to further enhance biodegradation efficiency.HighlightsPBBR significantly achieved efficient biodegradation and detoxification of RR 120.An optimum ILR of 75-85 mg/L.day exhibited the best operating conditions for PBBR.Microbial biomass and biofilm formation were quantified using the Crystal Violet Staining method.Phytotoxicity, photosynthetic pigment analysis, and bacterial toxicity unveiled the RR 120 detoxification.Moderate K_i and low K_s values depicted the resilience and high microbial activity for RR 120.

As the wetland ecosystem is a potential sink of plastics pieces, the photodegradation of microplastics could be boosted by iron(hydr) oxides, which considered as the Fenton or Fenton-like reactions induced. However, the pathways and internal mechanisms by which iron(hydr) oxides enhanced the ultraviolet degradation of plastics in the wetlands remain unclear. Therefore, the degradation of polystyrene (PS) and polyvinyl chloride (PVC) under ultraviolet light (365 nm) was studied in the UV Fenton and simulated micro wetlands. Results showed that UV irradiation caused notable changes in the surface morphology of plastics. Fenton reaction led to more significant, and generated oxygen-containing functional groups such as C = O. The weight loss rate of PS reached 28.3 ± 6.64%, while PVC reached 35.6 ± 1.52%, significantly surpassing the individual conditions of UV light at 20.3 ± 1.66% and 20.98 ± 8.48%, respectively. The mechanism of •OH in the process of plastic degradation was elucidated, while analysis of the degradation products was conducted. The potential risks for the UV degradation of PS and PVC were explored in constructed wetlands by detecting the changes of microbes. After preliminary aging, microbial activity associated with the degradation of polycyclic aromatic hydrocarbon compounds produced during plastic degradation is enhanced. Therefore, there may exist microbial communities in wetland ecosystems that are capable of degrading plastic. This study supported a hypothesis that the goethite/haematite Microcosm Constructed Wetlands (MCWs) would be efficiency for the degradation of plastic. It would be proved further and the organic carbon releasing during the plastic degradation should also be focused on.