Environmental Technology最新文献

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.

This study evaluated the extent to which laboratory-scale biochemical methane potential (BMP) assays predict actual methane production in a full-scale tubular anaerobic digester operating under psychrotrophic conditions. The 8 m³ farm-scale digester, situated in a cold, high-altitude climate, was retrofitted with passive solar heating, resulting in an average sludge temperature of 21.5 ± 1.2°C. In contrast, the mean ambient temperature was kept at 10.6 ± 1.4°C. BMP tests were conducted using the digester influent and effluent as substrate and inoculum, respectively, at mesophilic (35 ± 2°C) and psychrotrophic (23 ± 2°C) temperatures. The methane yield in the full-scale system (0.36 Nm³ CH₄ kg^-¹ VS), operated at an average temperature of 21.5°C, significantly exceeded the values obtained in the batch BMP tests (0.19 Nm³ CH₄ kg^-¹ VS at 35°C and 0.18 Nm³ CH₄ kg^-¹ VS at 23°C). No statistically significant correlation was found between laboratory and field data. These findings show the limited predictive power of BMP testing for farm-scale digester performance in decentralized, low-temperature environments.

PES/PVP membranes are widely used at industrial scale for skim milk ultrafiltration aiming at protein content standardization. Membranes are systematically fouled by proteins which are removed twice a day using formulated detergents among which enzymatic detergents often appear to be an eco-friendly solution. In this study, proteases called subtilisins, are selected and incorporated into a detergent formulation whose only variable was the source of subtilisin. Since liquid enzymes are commercially available in stabilized form, this allows to focus on the role of stabilizing agents on cleaning performance, even at very low concentrations. The selected UF membrane (HFK-131, Koch) has been fouled by skim milk at 50°C. Then, the cleaning efficiency of the prototype detergents was evaluated at 50°C from the residual protein quantified on membrane by ATR-FTIR. With equivalent enzymatic activity, detergents based on each one of the three selected enzyme sources, removed at least 95% of the proteins present at start evidencing the high cleaning efficiency. Simultaneously, the water flux recovery post-cleaning ranged from 1.9 to 3.8 requiring detailed and complex analysis to interpret this value greater than 1. Aiming at such understanding, a de-formulation approach was undertaken, combined with complementary ATR-FTIR characterization of membranes at every step. The discussion provides an explanation of the WFR behaviour likely associated with the variation in membrane hydrophilicity resulting to detergent ingredient adsorption. Besides the role of one given surfactant of the formulation, the impact of enzyme stabilizers was also demonstrated with possible synergetic effects with other ingredients.

Heavy metal contaminated soils have attracted worldwide attention, and there is a growing interest in the use of detergents to remediate heavy metal contaminated soils. In this study, the response surface methodology was used to determine the optimal drenching parameters by combining the interaction between the factors and the pollution safety index. The elution of heavy metals by the two-step elution method and the mixed elution method was investigated under optimal conditions (77.66 mmol.L^-1 MGDA, 145.01 mmol.L^-1 HH, pH 3.29, 90 min, S/L = 1:10, 25 °C). The results showed that the mixed solution was more effective in the elution of heavy metals, and the removal of lead, copper and nickel was 8.11%, 16.27% and 1.36%, respectively. The different forms of heavy metals were extracted by the modified Tessier method after water washing, and the results showed that the iron-manganese oxide-bound and carbonate-bound fractions of Pb, Cu and Ni were significantly reduced after water washing. Among them, the carbonate-bound state of Pb, Cu and Ni decreased by 90.30, 256.85 and 4.00 mg.kg^-1, respectively; the ferromanganese-oxidised state of Pb, Cu and Ni decreased by 531.00, 1493.33 and 48.74 mg.kg^-1, respectively; before and after drenching MCSI decreased by 10.85% compared with that before drenching. FTIR analysis of heavy metals after water washing showed that the mixture had no significant effect on soil properties after water washing. The above results indicated that the mixture of HH and MGDA can be used as a washing solution for heavy metal contaminated soil.

Coal chemical wastewater, characterized by high toxicity, salinity, and refractory organics (e.g. phenols), poses significant environmental challenges. An innovative system integrating micro-nano bubbles (MNBs) and acclimated bacterial consortia (DP-1) was developed in this study. It was designed to achieve efficient phenol degradation and chemical oxygen demand (COD) removal. DP-1 was domesticated under MNBs aeration, high phenol (up to 400 mg/L), and high-salt (1-15 g/L) conditions, exhibiting remarkable adaptability. The MNBs@DP-1 system achieved 100% phenol degradation and 88.9% COD removal within 24 h at 600 mg/L phenol, demonstrating robust performance across a wide pH range (6-9) and salinity (1-15 g/L). Notably, in a sequencing batch biofilm reactor (MNB-AR), long-term treatment of actual coal chemical wastewater (COD: 1300-1600 mg/L) yielded a stable average COD removal of 76.2% with <1.6% fluctuation. Microbial community analysis revealed Proteobacteria (99.1%) dominance post-acclimation, with Acinetobacter (65.7%) and Comamonas (29.7%) as key functional genera driving phenol mineralization. Comparative studies confirmed the superior efficacy of MNBs@DP-1 over conventional aeration systems, attributing enhanced degradation to MNBs-induced bacterial activity and biofilm stability. This work provides a scalable strategy for achieving 'zero discharge' in coal chemical wastewater treatment by synergizing bubble technology and microbial acclimation.