Environmental Technology最新文献

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.

Elevated contamination levels of domestic wastewater pose challenges to its treatment and reuse in Controlled Ecological Life Support System (CELSS). To address this, biologically treated domestic wastewater was employed as a primary nutrient source for leafy vegetables. A comparative analysis of growth parameters and nutrient assimilation was performed on two vegetables with distinct salt tolerance capacities, ice plant (Mesembryanthemum crystallinum) and lettuce (Lactuca sativa), under two cultivation systems: recycled wastewater and Hoagland solution. Key findings indicated that: Both had comparable edible biomass in recycled wastewater (ice plant: 127.28 g·plant⁻¹; lettuce yield marginally lower) vs Hoagland controls (ice plant: 124.87 g·plant⁻¹), with no significant difference. Lettuce exhibited enhanced root development in wastewater, with significantly greater underground biomass (p < 0.05) than Hoagland-grown counterparts, suggesting adaptation to saline stress (wastewater EC: 6.39 mS·cm^-1). Nutrient-wise, recycled wastewater had gently changed elemental ratios and pH maintained weakly acidic during cultivation. Vegetables in recycled wastewater took up more K⁺, Na⁺, and trace elements vs. Hoagland (e.g. lettuce Na content: 3.2× Hoagland controls). ∼13.12 m² of ice plant could intake sodium from one person's daily urine under the experiment. These results demonstrate that recycled wastewater serves as a viable primary nutrient source for CELSS agriculture. Ice plant exhibited higher sodium assimilation efficiency and systemic adaptation to recycled wastewater, whereas lettuce developed compensatory root morphological modifications to mitigate high salinity.

New strategies for effluent treatment aimed at reducing environmental pollutants have significantly advanced, particularly biological methods involving enzymatic processes. In this context, this study evaluated the efficacy of a laccase-enriched enzymatic extract (specific laccase activity = 0.45 U/mg), obtained from the fungus Xylaria sp. for treating pharmaceutical effluents containing paracetamol, diclofenac, mefenamic acid, ibuprofen, and sulfamethoxazole, each at concentrations of 50 ppm. The enzymatic treatment resulted in notably higher degradation efficiencies for paracetamol and mefenamic acid under initial screening (∼70%). These drugs were selected for optimization due to their higher susceptibility to enzymatic degradation and because they are widely consumed pharmaceuticals frequently detected in aquatic environments. Afterward, optimization studies focused on these two pharmaceuticals, employing a statistical experimental design to determine optimal conditions, identified as pH 6.7, temperature of 40°C, and exposure time of 4.5 h. Under these optimized conditions, experimental results indicated a 95.55% reduction in paracetamol and a 55% reduction in mefenamic acid concentrations.Furthermore, enzyme immobilization on chitosan significantly enhanced stability and performance, maintaining approximately 90% reduction of both pharmaceuticals after multiple treatment cycles. These findings highlight the effectiveness of immobilized laccase systems and optimized reaction parameters, supporting their potential application for sustainable and efficient treatment of pharmaceutical effluent. Importantly, this work represents the first demonstration of using Xylaria sp. as a laccase source for pharmaceutical degradation, underlining its novelty and potential.

Chromium (Cr) contamination represents a risk to the biodiversity of ecosystems, requiring the application of remediation processes for its recovery. One form of bioremediation can be done by bacteria resistant to hexavalent chromium (Cr(VI)). In the present study, the rhizobacterium Exiguobacterium indicum was isolated from the aquatic macrophyte Hymenachne grumosa, collected in the Santa Bárbara channel, located in southern Brazil. The Cr(VI) removal capacity and the response of oxidative stress biomarkers were analysed, in addition to the optimal pH and temperature conditions for maximum removal. The minimum inhibitory concentration of growth (MIC) of the isolate was 400 mg L^-1 of Cr(VI) and the results showed that E. indicum HG8 was able to grow and remove Cr in a wide range of incubation temperatures (20-45°C) and pH (5.0-9.0), evidencing its ability to adapt to different factors. The ideal conditions for cultivation and removal of Cr(VI) were verified at pH 6.0 and at 30°C. E. indicum HG8 was able to efficiently remove 99.6% of Cr(VI) and 89.4% of total Cr in 24 h of incubation. The increase in malondialdehyde levels in the extracellular extract demonstrates that there was lipid damage, in parallel with the increase in the adaptive response of antioxidant enzymes, indicating that oxidative stress was established. The data suggest that E. indicum HG8 possibly altered the permeability of the cell membrane, forming a kind of barrier.

Microalgae are widely recognized for their eco-friendly and cost-effective contributions to water pollution mitigation. However, practical applications face efficiency and toxicity tolerance limitations. This study overcomes these hurdles by engineering a titanium dioxide-microalgae composite, T. obliquus/TiO₂, specifically to enhance the degradation of phenolic compounds like o-cresol in wastewater treatment. The results demonstrate a significant improvement, with the o-cresol degradation rate using the composite being 1.79 times higher than that of T. obliquus alone. This enhancement is primarily attributed to the synergistic interplay between TiO₂ nanoparticles (NPs) and microalgal metabolism, particularly photosynthesis. The TiO₂ NPs interact with chloroplasts to reduce bandgap, decrease photoelectron-hole recombination, and improve light energy utilization. Electrochemical analyses, including cyclic voltammetry (CV) and Tafel tests, reveal enhanced extracellular electron transfer, while indicators of respiratory activity and cell energy levels, such as electron transport system activity (ETSA) and adenosine triphosphate (ATP), point to increased intracellular electron transfer. Additionally, the composite shows improved biomass and metabolic activity, as indicated by total chlorophyll content and nicotinamide adenine dinucleotide (NADH) levels, alongside reduced oxidative stress markers like malondialdehyde (MDA) and superoxide dismutase (SOD). These findings offer valuable insights into sustainable strategies for organic wastewater treatment and remediation.

The mixotrophic alga Ochromonas danica efficiently synthesizes lipids through phagotrophy and osmotrophy. This study explored its growth using alkali-pretreated waste activated sludge (WAS). Pretreatment at pH 12 for 24 h released 56.4% of WAS organics as microbial cells and dissolved substrates. During 96-hour cultivation, O. danica consumed 91.5% of liberated cells and 63.0% of dissolved organics, converting 28.6% of WAS organics into algal biomass containing 42.4% lipids (dry weight). This algal assimilation step proved pivotal in an integrated 30-day process (1-day alkali treatment, 4-day algal growth, 25-day anaerobic digestion), which achieved 61% total organic reduction - a 2.7-fold acceleration over anaerobic digestion with untreated sludge (23% in 30 days) and a 1.3-fold acceleration over anaerobic digestion with alkali treatment alone (48% in 30 days). The synergy between alkaline solubilization and algal phagotrophy thus simultaneously enhance WAS organics reduction while producing lipid-rich biomass, presenting a time-efficient strategy for sludge management.

Agricultural waste management is critical for reducing environmental pollution and enhancing soil health, particularly the treatment of organic waste containing heavy metals. This study investigates the distinct effects of mesophilic and thermophilic microbial inoculation on composting. Using rice straw and swine manure as feedstocks, composting piles were inoculated with mesophilic (Bacillus subtilis and Trichoderma reesei) or thermophilic (Geobacillus stearothermophilus and Aspergillus fumigatus) microorganisms, alongside a control group with no inoculation. The results revealed that thermophilic inoculation significantly enhanced organic degradation and humification, leading to more efficient stabilization of heavy metals such as Pb, Zn, and Cr, especially during the thermophilic and mature phases. Microbial community analysis showed that thermophilic inoculation created a more connected microbial network and boosted the microbial functionality. Spearman correlation analysis indicated that the enhanced key metabolic pathways of IT, particularly those involved in organic matter degradation and heavy metal detoxification, were associated with reduced metal bioavailability during thermophilic phase. These findings highlighting the potential of thermophilic inoculants for sustainable waste management and environmental protection.