Environmental Technology最新文献

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.

The present study attempted to investigate the impact of the micro-aerobic condition in a conventional Up-Flow Anaerobic Sludge Blanket Reactor (UASB) using different media for the treatment of municipal wastewater. The Hydraulic Retention Time (HRT), Dissolved Oxygen (DO), intermittent and continuous aeration were the important operating conditions of this study carried out for more than 1015 days. Fourier transform infra red (FTIR) spectra and SEM analysis indicate the significant growth of the microbiota responsible for the removal of nutrients. Significant increase in the removal of the chemical oxygen demand (COD)∼ 91%, biochemical oxygen demand (BOD)∼ 90%, suspended solids (SS)∼ 92%, and ammonical nitrogen (NH₄⁺-N)∼ 90%, were observed at lower DO levels. Sulphate was dominant due to sulphide oxidation during micro-aerobic conditions in almost all study phases, which resulted in an increase of up to 90% of the influent sulphates. The micro-aerobic UASB process could be a feasible option for achieving the latest treated effluent disposal norms and significantly reducing the energy demand for wastewater treatment.

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.

Microbe-assisted phytoremediation is emerging as one of the most effective methods for degrading organic contaminants in soils through the interaction of plants and their associated rhizosphere microbes. However, the mechanisms behind plant-microbe interactions remain ambiguous. In this study, a 35-day pot experiment was conducted to remediate benzo[a]pyrene using rye (Secale cereale L.) and a white rot fungi (Trametes versicolor) solid-state fermentation agent. The benzo[a]pyrene removal efficiency, soil microbial community structure response, and the effect of Trametes versicolor (T. versicolor) on plant growth were investigated. Results indicated that white rot fungi-assisted phytoremediation was more effective in removing benzo[a]pyrene than plant or fungal treatments alone. The addition of T. versicolor and rye significantly increased dehydrogenase activity in the soil. Although T. versicolor reduced the richness and diversity of the microbial community, they promoted the growth of Chaetomium, Mortierella, Fusicolla. In contrast, the T. versicolor inhibited the growth of rye, and the root reactive oxygen species content in the combined plant-fungi remediation group was significantly higher than in the plant-only group. While this growth inhibition poses challenges for plant vigor, the combined plant - fungi system demonstrated excellent benzo[a]pyrene degradation efficiency and enhanced soil enzymatic activity. Therefore, this strategy may be particularly suitable for situations where pollutant removal is prioritized over biomass accumulation.

Polyhydroxyalkanoates (PHAs) are eco-friendly, biodegradable thermoplastics that have the potential to replace conventional plastics with sustainable biopolymers for several applications. This study aimed to isolate and identify halotolerant strains and to optimise the parameters influencing PHA production using response surface methodology. Furthermore, enhancing PHA production and evaluating the effects of low-dose gamma irradiation on Halomonas mongoliensis AL-ARS. Fifteen bacterial isolates were screened using Sudan Black B for PHA production. The most efficient isolate was Halomonas mongoliensis AL-ARS, identified through morphological, biochemical, and molecular techniques. Response surface methodology using Plackett-Burman and central composite design models is used to optimise factors influencing PHA synthesising. Additionally, the effect of low-dose gamma irradiation was examined. The purified PHA polymer was structurally characterised using FTIR, XRD, and ¹H-NMR. Glucose was the optimal carbon source, while minimal salt media was the most suitable media for PHA production. The best production conditions (10 g/L glucose, 40.5°C, 6.5 days, 2.5% inoculum) yielded 0.0960 g/L of PHA. Remarkably, gamma irradiation at 0.5 kGy significantly increased PHA production by 76%, confirming its role as a stress-inducing factor and highlighting irradiation's potential to overcome production bottlenecks. Structural analyses confirmed the purified polymer as a standard PHA. This work is the first study highlighting the integration of gamma irradiation with a statistical optimisation to boost PHA biosynthesis using Halomonas mongoliensis AL-ARS, a halophilic strain with no previous study on PHA improvement, presenting a scalable strategy for sustainable, eco-friendly, cost-effective bioplastic production, and bridging the gap between lab-scale and industrial application.

This study addressed the issue of elevated ammonia nitrogen pollution in wastewater from ionic rare earth mining operations. Given the high costs and limited efficiency of conventional biological denitrification methods, the sulphur-based autotrophic denitrification (SAD) process was explored as a cost-effective alternative to improve nitrogen removal performance. A sequencing batch reactor was operated over 70 days to cultivate and maintain granular sludge, successfully enriching sulphur-oxidising bacteria (SOB). During this cultivation phase, the average sludge particle size increased from 228.69 μm to 709.95 μm, the granulation rate reached 84.56%, and the relative abundance of the SOB genus Thiobacillus rose to 13.57%. An orthogonal experimental design was employed to optimise the operational parameters of the SAD granular sludge. Single-factor experiments were first conducted to assess the effects of sodium bicarbonate concentration (0-2000 mg/L), sludge concentration (3500-6000 mg/L), reaction duration (2-12 h), and sodium sulfide concentration (0-300 mg/L) on the removal efficiencies of total inorganic nitrogen (TIN). The results indicated that sodium bicarbonate concentration was the most influential factor. Subsequently, an L₉(3⁴) orthogonal experiment was designed to determine the optimal operational conditions: 1600 mg/L sodium bicarbonate, 5000 mg/L sludge concentration, 8 h of reaction time, and 37.5 mg/L sodium sulphide. Under these optimised conditions, the TIN removal efficiency reached 67.64%. Economic analysis demonstrated that the unit denitrification cost of the SAD process was 31.83% lower than that of the heterotrophic denitrification process, highlighting its potential as a low-carbon and efficient solution for treating rare earth mining wastewater.

The biomass in agricultural and forestry waste has a high value for resource utilization. In this study, biochar materials were prepared for treating wastewater containing polycyclic aromatic hydrocarbons (PAHs). To eliminate pyrene rather than transfer it onto the adsorbent, this study employed a chemical oxidation method to degrade pyrene using persulfate as the oxidant and biochar as the activator. When the pH of the solution was 3 and the dosage of biochar was 0.9 g/L, the biochar (BC₁, BC₂ and BC₃) prepared from sawdust, coconut shells and agricultural straw reduced the C/C₀ value to 0.12, 0.09 and 0.05 respectively, indicating that the biochar had a good adsorption effect on pyrene. BC₃ was chosen to activate persulfate to degrade pyrene, and under the conditions of solution pH of 3, persulfate concentration of 10 mM, and BC₃ dosage of 1.5 g/L, the C/C₀ value decreased to 0.04 and the removal efficiency of pyrene was 96%. In the BC₃/persulfate oxidation system, oxidative degradation played a dominant role in the removal of pyrene. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FITR) analyses demonstrated that the catalysis of persistent free radicals (PFRs) on the biochar surface was the main mechanism for the activation of persulfate to produce SO₄^•- for the degradation of pyrene.

Volatile organic compounds (VOCs) endanger the environment and human health. Among various control methods, activated carbon (AC) adsorption has become an industrial mainstream due to its high removal efficiency. The traditional iodine value (IV) assessment method is time-consuming and difficult to apply in real time. It is important to note that AC, after adsorbing VOCs, is classified as hazardous waste. This study explores indirectly characterizing the adsorption performance of AC through electrical resistance (ER) measurements. Experiments conducted at 26°C and 50% RH using an optimized device (with dimensions of 78 × 157 × 72 mm, equipped with graphite electrodes and applying a pressure of 750 Pa) revealed a significant negative correlation between ER and IV: ER increases monotonically as IV decreases, and both stabilize when the adsorption reaches saturation. The ER of the initial AC is significantly affected by the environment: for every 15% increase in relative humidity, ER decreases by 27.2%; for every 10°C increase in temperature, ER increases by 1.5 Ω. Based on this, a temperature-humidity compensation model was established to correct environmental interferences, with an IV prediction coefficient of determination (R²) of 0.85. This ER-IV correlation, combined with the compensation model, provides a new method for the rapid assessment of the adsorption performance of AC; further optimization is required to improve its universality and accuracy under different conditions.

Municipal solid waste incineration (MSWI) fly ash is a hazardous waste, and traditional landfill disposal lacks sustainability. Resource utilization offers a viable pathway for its future management. Heavy metals are key hazardous components in fly ash, and their stabilization is essential for resource utilization. However, traditional high-temperature treatments are energy-intensive and costly, limiting large-scale application. This study proposed an energy-efficient, medium-temperature treatment method for fly ash and evaluated its environmental risks. Molecular dynamics simulations were conducted to elucidate the underlying mechanisms of heavy metal stabilization. The study revealed that co-sintering fly ash with clay at 750°C and 950°C led to a significant reduction in heavy metal leachability, with Pb and Zn concentrations decreasing by 97.4% and 61.7%, respectively. The sintered products developed new fibrous mineral phases, predominantly wollastonite and rankinite, within which heavy metal ions were incorporated through isomorphic substitution for Ca²⁺ in the crystal lattice, leading to stable immobilization. Sequential extraction analysis showed that the chemical forms of heavy metals shifted from acid-soluble to more stable reducible and oxidizable fractions after treatment. Consequently, the environmental risk levels of Zn and Pb decreased from moderate to negligible, while that of Cd was reduced from high to negligible. Long-term leaching tests under simulated acid rain conditions confirmed that the sintered products maintain high stability during prolonged environmental exposure.