Environmental Technology最新文献

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.

In the era of rapid urbanization and environmental concerns, efficient waste resource utilization is vital for sustainable development. This study innovatively constructs a hydrogen production system model for municipal solid waste and sludge chemical looping gasification (MSCLG). The research finds that the optimal operating condition is when the mass mixing ratio of sludge to MSW is 4:6. Under the conditions of 680°C and 1 atm, the H₂ concentration at the outlet of the gasification reactor exceeds 70%. In the simulation, with a flow rate of 4000 kg/h for CS-MgO-ZrO₂ and 6000 kg/h for steam, when the carbon conversion rate is 0.8 and the syngas injection ratio is 0.15, the system achieves self-heating and generates 14.57 kW of heat. When combined with a CCS module, near-zero carbon emissions can be basically achieved, offering an efficient way for urban waste energy use and green hydrogen production.

In-situ bacterial remediation has shown substantial potential for decommissioned uranium mining areas. Our previous research indicated that the similar redox potentials of Fe(III)/Fe(II) and U(VI)/U(IV), along with iron's significance in bacterial growth and metabolism, provide a basis for synergistic uranium remediation. This study investigated the impacts of diverse electrode voltages on U(VI) immobilisation by Leifsonia sp. in an iron-sulfur co-existing system. Bacteria immobilise U(VI) by adsorption. SEM-EDS and XPS analyses confirmed that electro-stimulated bacteria (under applied voltage) reduced U(VI) to U(IV), forming Fe-U complexes. For comparison, under open-cell conditions (i.e. the electrochemical cell was in an open-circuit state without applying any external constant voltage), U(VI) removal was negligible. The optimal voltage (3.0 V) enhanced U(VI) removal via bacterial adsorption and incorporation into Fe-S compounds. However, too high a voltage hindered U(VI) removal.HighlightsElectro-biological reduction boosts U(VI) removal in iron-sulfur environment to 98.05%.Different voltages ensure economy and prevent over-consumption of electricity.Micro-electric field activates indigenous bacteria to convert U(VI) to U(IV).

Greenhouse gas emissions are abundantly produced every year by human activities. They are the main cause of global warming and the changes observed in the climate. In this study, we used the microwave plasma torch system (MPT) to drive the conversion of CO₂ through the Boudouard reaction pathway. The necessary microwave power applied has efficiently activated the coal used as a reductant agent to initiate the chemical decomposition of CO2. The specific energy consumption reached 94 kJ/mol to ensure the continuous decomposition process of carbon dioxide under microwave plasma torch technology at atmospheric pressure. Experimentally, the conversion rate of 20 lpm of CO₂ under the MPT developed in this research reached 64% at a moderate temperature of 680°C with a specific recipe composed of the operating conditions coupled to the geometry of the designed reactor. In addition, the numerical model built in Aspen Plus V12 supported the experimental results by producing similar patterns in the conversion of CO₂ as a function of microwave power. Thus, the entire process tends to be energy-saving and an efficient solution for greenhouse gas mitigation for a clean and sustainable environment.

This study deciphers sludge biodrying through a microbial-structural coevolution framework: Thermophilic consortia (Geobacillus/Bacillus; 63.27% abundance) drive bio-heat generation (>65°C), triggering particle fragmentation (decreased particle size by 63%), pore-network expansion (SEM-validated), and matrix loosening (decreased fractal dimension by 32%). This structural evolution enables phase-specific moisture redistribution - surface water (decreased from 68.52% to 19.82%) transforms into interstitial water (increased from 28.71% to 69.08%) and ultimately vapour flux, a process accelerated by capillary migration and enhanced airflow diffusion. The synergy of microbial succession (with dominance shifting from Firmicutes to Actinobacteria), structural reconfiguration, and moisture thermodynamics achieves deep dewatering (reducing moisture content from 80.62% to 41.62%), while mechanistic insights enable precision aeration phasing for energy reduction and cycle shortening via moisture-state-guided control.

This study proposes an inverse support vector machine (ISVM) framework to optimise aeration control in a sequencing batch reactor(SBR), addressing the balancing of energy efficiency and regulatory compliance in wastewater treatment. By integrating data-driven modelling with constrained optimisation, the method dynamically adjusts aeration rate to maintain effluent NH₃-N concentrations below 5 mg/L while minimising energy consumption. A support vector machine (SVM) establishes input-output correlations between process parameters (influent NH₃-N, ORP, conductivity, aeration rate) and effluent NH₃-N concentration, enabling the ISVM to resolve constraint-driven aeration rate optimisation. Experimental validation across 20 operational cycles demonstrated a 20.3% reduction in energy usage compared to conventional fixed-rate aeration, achieving 95% compliance with discharge standards. The framework's penalty-based optimisation and gradient clipping mechanisms ensure stability in applications, overcoming limitations of traditional PID controllers and mechanistic models. This work advances intelligent control strategies for sustainable wastewater management, providing a constraint-aware optimisation template for environmental engineering systems.

We propose a novel sludge treatment process involving aerobic digestion without aeration. A sponge carrier is used to trap sludge, followed by biological degradation of the sludge by predation and endogenous respiration. In the experiment, sludge was fed into the sponge carrier and sludge degradation was measured over 21 days at ambient temperature (average of 20°C). The suspended solids, volatile suspended solids (VSS), and total chemical oxygen demand of the initial sludge on day 0 were 403, 286, and 378 mg, respectively. Oxygen was naturally supplied from atmosphere or through recirculation of water with high dissolved oxygen. Sludge degradation occurred rapidly within the first 7 days, and after 21 days, VSS was reduced by approximately 40%. Molecular analysis showed changes in the microbial community structure and the presence of aerobic organisms during the 21-day experiment. The nitrogen stable isotope ratio (δ¹⁵N) increased by more than 3‰ from 0 to 7 days and became stable between 7 and 21 days. The increase in δ¹⁵N could be attributed to an increase in the average trophic level of the microbial community, which implies that predation within the microbial community effectively causes sludge degradation during the first 7 days. In summary, sludge degradation was effectively performed by predation within the first 7 days, followed by other functions such as endogenous respiration after 7 days under aerobic conditions. This proposed aerobic digestion process may be effective for sludge degradation without aeration.