Environmental Technology最新文献

Healthcare wastewater (HCWW) is often rich in nutrients and pollutants that cause colour, posing serious environmental and public health risks if untreated. This study evaluated the effectiveness of horizontal subsurface flow constructed wetlands (HSSFCWs) for removing nutrients and colour from HCWW, using locally available substrate materials, with and without Cyperus alternifolius. Four pilot-scale wetland systems were installed in parallel at the Jimma Institute of Technology to treat wastewater discharged from the Jimma Institute of Health, with hydraulic retention times (HRT) of 4, 8, 12, and 24 days. Systems with an ignimbrite substrate planted with Cyperus alternifolius showed the highest removal rates: 96.33% for nitrate, 94.19% for phosphate, and 98.82% for colour at a 24-day HRT. The statistical analysis indicated that both substrate type and HRT significantly affect waste removal performance of the CW units (p < 0.0001). FTIR and XRD analysis of substrates before and after treatment revealed changes in functional groups and adsorption properties, supporting the treatment results. The findings indicate that Horizontal subsurface flow constructed wetlands, which utilize ignimbrite beds and Cyperus alternifolius, offer a sustainable and eco-friendly approach for mitigating the risks associated with healthcare wastewater, aligning with the Sustainable Development Goals (SDGs) and directly targeting SDG 6, specifically 6.3 and 6.6. This approach is particularly beneficial in resource-limited areas.

This study demonstrates the long-term stability and low-energy operation of a continuous-flow granular sludge system for simultaneous nitrification, denitrification and phosphorus removal (SNDPR) from real domestic wastewater. The impacts of distinct hydraulic retention time (HRT) and sludge retention time (SRT) combinations (9 h and 33 days, 6 h and 22 days, 4.5 h and 17 days) on system performance, granular sludge characteristics and microbial community dynamics (specifically archaeal and bacterial populations) were systematically evaluated. The results showed that the performance decreased with shortening of HRT. At an HRT of 4.5 h, the settling performance and stability of SNDPR granules deteriorated, while loosely bound proteins (LB-PN) and the protein-to-polysaccharide ratio (PN/PS) significantly increased. This suggests that exogenous proteins in real domestic wastewater, which were difficult to fully hydrolyse under short HRT, likely accumulated on the outer layer of the granules. High-throughput sequencing analysis of bacterial and archaeal communities revealed that under real domestic wastewater conditions, the abundance of denitrifying and phosphorus-removing functional microorganisms significantly decreased, while the rapid proliferation of filamentous microorganisms was identified as the primary factor contributing to the deterioration of granular sludge structure. Finally, the phylogenetic classification of functional genera indicates that archaeal and bacterial communities played significant roles in denitrification, phosphorus removal and maintaining the stability of SNDPR granules.

Petroleum hydrocarbons are highly toxic and carcinogenic substances that adversely affect ecosystems and human health. This study aimed to evaluate the impact of biochar and sodium humate treatments on phytotoxic indicators of soils contaminated with oil. The results show that Haplic Chernozem is more sensitive to remediation than Haplic Cambisol, as evidenced by a significantly greater reduction in the integral phytotoxicity index (IPT). Oil pollution in both Haplic Chernozem and Haplic Cambisol led to a decrease in radish root growth compared to the control group. Application of biochar at all tested dosages promoted increased root growth in both soil types. The study identified the most effective doses of ameliorants for oil-polluted soils: biochar (10 and 20%); sodium humate (1% water solution). Notably, the integral phytotoxicity index of Haplic Cambisol proved more resistant to oil pollution following the application of ameliorants. Among the assessed parameters, the length of radish roots emerged as the most informative and sensitive phytotoxic indicator for monitoring the remediation of oil-contaminated soils. These findings confirm the effectiveness and reliability of the proposed approach for biodiagnosis of oil-contaminated soils, providing a solid foundation for monitoring soil health and quality. Future research should focus on: (1) Expanding the use of phytotoxicity assessment as a quick, simple, and cost-effective method for evaluating the condition of oil-contaminated soils after remediation; (2) studying the biochemical parameters of plants used in phytotesting of remediated oil-contaminated soils; (3) investigating the phytotoxicity and efficacy of microbiological preparations in the remediation of oil-contaminated soils.

The quality and stability of sewage sludge generated in municipal wastewater treatment plants are strongly influenced by treatment technology and post-treatment processes. Extended aeration activated sludge (EAAS) systems operate at long solids retention times, which may promote partial aerobic stabilization of the biomass; however, additional treatment is often required to ensure adequate biological stability and hygienization. This study evaluated, at pilot scale, the influence of three sludge dehydration strategies, namely, conventional drying beds (ConDry), solar drying (SolDry), and solar drying combined with ultraviolet radiation (SolDry + UV), on moisture reduction, biological stability, and fecal coliform removal. Sludge samples were obtained from two EAAS systems operating under contrasting climatic and operational conditions. The SolDry + UV strategy exhibited the highest drying efficiency, achieving moisture contents below 60% within 19 days for EAAS₁ and 26 days for EAAS₂. Solar-based strategies significantly enhanced volatile solids reduction, reduced specific oxygen uptake rates, and promoted greater pathogen removal compared to conventional drying. Overall, the results demonstrate that solar drying, particularly when combined with UV irradiation, substantially improves sludge stabilization and hygienization, enabling the attainment of Class A biosolid quality and supporting its safe agricultural reuse.

The coexistence of phenolics is ubiquitous in real environments. However, competitive and complementary adsorptions between phenolics, including tannins and bisphenol A (BPA), remain unclear because of the different adsorption preferences of the adsorbent surface. In this study, novel H₃PO₄/NaOH modified porous carbons derived from corn were synthesized. The objective was to investigate the effect of the adsorption site availability on phenolics adsorption determined by pore size. Results showed that BPA and GA (gallic acid) exhibited high adsorption on H₃PO₄-modified porous carbon (220.74, 144.52 mg·g^-1, respectively). TA (tannic acid) demonstrated high adsorption on NaOH-modified porous carbon (201.38 mg·g^-1). The adsorption of BPA, GA and TA involved multiple interactions, including hydrogen bond, π-π interactions, hydrophobic interactions and pore filling. Analysis of approximate energy distribution indicated that H₃PO₄/NaOH activation increased the number of adsorption sites of porous carbons. The energy distributions of BPA were overlapped with that of GA, which further verified that BPA competed for adsorption to GA more than to TA. Although BPA occupied adsorption sites on porous carbon over GA and TA, it modified the heterogeneity and hydrophilicity of porous carbons, and promoted the adsorption of GA (126%-200%) and TA (121%-320%). This suggests a complex co-adsorption mechanism where competition is counterbalanced by surface modification effects.

ABSTRACTOrganic matter in waste activated sludge (WAS) is trapped within intact cell structures and stable extracellular polymeric substances (EPS), and its slow hydrolysis severely restricts short-chain fatty acids (SCFAs) production in anaerobic fermentation. Therefore, this study evaluated the synergistic effect of combined free nitrous acid (FNA) and peroxydisulfate (PDS) pretreatments to enhance SCFAs yield. Under optimal conditions (250 mg/L nitrite and 0.07 g/g TS PDS), the SCFAs yield peaked on day 8 at 426.5 ± 25.9 mg COD/g VS, which was 18.3 times higher than that of the control (22.1 ± 1.3 mg COD/g VS). This mechanism was systematically investigated. The results demonstrated that the combined pretreatment significantly enhanced WAS disintegration. This was evidenced by a remarkable increase in soluble chemical oxygen demand (SCOD) in the supernatant, along with significant increases in the protein and polysaccharide contents of EPS. The substantial release of nitrogen and phosphorus further indicated effective cell rupture and hydrolysis. Furthermore, pretreatment upregulated key hydrolytic enzymes (protease and α-glucosidase), while suppressing methanogenesis via coenzyme F420 inhibition, thereby facilitating SCFAs accumulation. Fluorescence spectroscopy confirmed the enhanced degradation of released organic matter. Microbial analysis also showed that pretreatment altered the microbial community and enriched acidogenic bacteria such as Macellibacteroides and Fonticella. This study demonstrated that combined FNA and PDS pretreatment is a highly effective strategy for boosting SCFAs production from WAS, offering a promising avenue for sustainable sludge resource recovery.

This study employed a single-stage aerobic sequencing batch reactor (SBR) to establish a simultaneous short-cut nitrification-denitrification (SSND) system, addressing the denitrification challenges in wastewater with low carbon-to-nitrogen (C/N) ratios. By controlling low dissolved oxygen (DO, 0.3-0.5 mg/L) and employing a strategy of gradually increasing influent nitrogen loading, short-cut nitrification was rapidly initiated within 18 days, achieving a nitrite accumulation rate exceeding 95%. Under conditions of an influent C/N ratio of 2, chemical oxygen demand (COD) of 1000 mg/L, and total nitrogen (TN) of 500 mg/L, the single-stage aerobic (O) mode demonstrated superior denitrification efficiency compared to the A/O mode, achieving COD and TN removal rates of 84.2% and 68.9%, respectively. Microbial community analysis revealed successful directed succession of functional bacterial communities: ammonium-oxidizing bacteria (Nitrosomonas) were effectively enriched (abundance increased to 11.10%), while nitrite-oxidizing bacteria (Nitrospira) were effectively suppressed (abundance <0.1%); Functional denitrifying bacteria (Thauera genus) emerged as the dominant genus (30.58% abundance). These bacteria undergo a 'saturation-starvation' cycle, utilising intracellular poly-β-hydroxybutyrate (PHB) accumulated during the anaerobic phase as an endogenous electron donor to drive simultaneous denitrification during the aerobic phase. Additionally, the study revealed that under carbon-limited conditions (C/N = 1), environmentally induced autolysis and extracellular polymer secretion occur, explaining fluctuations in effluent COD. This research provides theoretical support for applying the SSND process to treat low C/N wastewater.

The escalating generation of multilayer packaging waste presents significant environmental challenges due to their complex laminated structure comprising paperboard, polyethylene, and aluminum foil. This study presents a novel integrated hydrolysis-calcination pathway for complete valorization of Aluminun multilayer pakaging waste, achieving simultaneous production of green hydrogen and β-alumina solid electrolyte. Following hot water separation of the paperboard fraction, the LDPE/aluminum laminate undergoes alkaline hydrolysis, generating hydrogen gas with a yield of 97.5% (215 mL from 5.9 g waste) while preserving intact LDPE film for direct mechanical recycling. Kinetic analysis reveals that increasing NaOH concentration reduces activation energy from 26.2 kJ/mol (1M) to 12.7 kJ/mol (4M). The resulting sodium aluminate solution is transformed into pure β-alumina (NaAl₁₁O₁₇) phase via controlled precipitation at pH 9 and calcination at 1000°C. Comprehensive characterization (XRD, SEM-EDS, FTIR, TGA, photoluminescence) confirms good material quality suitable for advanced energy storage applications. This zero-waste process exemplifies circular economy principles, converting challenging multilayer packaging into four high-value products: renewable hydrogen fuel, advanced battery electrolyte material, recycled polymers, and cellulosic feedstock.

The Fenton-like application potential of MoS₂ has recently attracted widespread interest in advanced oxidation processes. This study utilized natural molybdenite ore as the source of MoS₂, and the Fenton-like reactivity of molybdenite was further enhanced by dropping Fe(III) ions on the basal planes of MoS₂. EDS elemental analysis and XPS results suggest that Fe species were successfully anchored on the molybdenite surface, which exhibited exceptional efficiency in peracetic acid (PAA) activation. The Fe-molybdenite/PAA system achieved 83.2% degradation of sulfamethazine (SMT) within 30 min, and the reaction efficiency by Fe-molybdenite was 3.3 times higher than that of the unmodified molybdenite. HO^• and Fe(V) were identified as the reactive species (RSs) during PAA activation, and SMT was degraded by these RSs. Increasing Fe-molybdenite and PAA dosages enhanced SMT degradation, with optimal performance observed at pH 4. Hydroxylation, nitrification, Smiles rearrangement and radical recombination reactions were involved during SMT degradation. Tetracyclines, dyes and other sulphonamide antibiotics could also be well degraded by Fe-molybdenite/PAA. This study elucidates fundamental design principles for engineering Fenton-like catalysts from natural mineral precursors.

This study explores the valorisation of alkali-treated RS as support for lipase immobilisation through physical adsorption, aiming to develop an efficient biocatalyst for treating lipid-rich wastewater. The immobilised lipase was characterised using SEM, TGA, BET, XRD, and FTIR techniques, revealing changes after immobilisation. BET results show an increase in surface area from 1.19 m²/g to 10.95 m²/g following alkali treatment, with a subsequent decrease to 0.35 m²/g after immobilisation. XRD analysis revealed an increase in crystallinity from 69.40% to 83.12% after NaOH treatment, followed by a decrease to 64.83% after lipase immobilisation, indicating effective support modification and enzyme attachment. FTIR analysis revealed a distinct N-H bending vibration corresponding to the amide II band in the immobilised matrix, confirming successful immobilisation of lipase. Kinetic studies revealed an improved performance of the immobilised lipase, with a reduction in Km from 0.438 to 0.330 mM, indicating enhanced substrate affinity, and a 2.18-fold increase in Vmax compared to the free enzyme, reflecting higher catalytic efficiency. The immobilised lipase exhibited superior thermal and pH stability, with storage stability tests showing 59% activity retention after 30 days at 4°C, compared to 19% for the free enzyme. Lipid-rich wastewater treatment using PPL immobilised NaOH-treated RS (lipase loading: 15 mg. g⁻¹ support) achieved 75.60 ± 2.43% lipid degradation, after 48 h at 37°C and 150 rpm, while the free enzyme achieved 16.64 ± 3.33%. These results demonstrate that RS provides a sustainable support for lipase immobilisation, offering an effective strategy for treating lipid-rich wastewater.