Environmental Technology最新文献

This study presents a comprehensive characterisation of sludge generated from chicken processing industry wastewater (CPW) treated by two advanced methods: electrochemical treatment using iron (Fe) electrodes and chemical coagulation employing alum and polymeric flocculants (Rishfloc 8163, Telfloc 5630). Using a suite of analytical techniques - FTIR, SEM-EDX, TEM, Raman, NMR, XRD, TGA, ICP-OES and nutrient profiling - the chemical, structural, and reuse properties of the resulting sludges were elucidated. Electrochemical treatment produced a compact, iron-rich sludge with low ionic contamination, dominated by amorphous iron hydroxides formed via in situ electrode dissolution. In contrast, chemical coagulation resulted in a lighter, porous sludge containing alum residues and polymeric materials, reflected in higher salinity and conductivity. EDX confirmed dominant iron and oxygen in electrochemical sludge, while chemical sludge showed aluminum and silicon signatures. FTIR and Raman analyses indicated more advanced organic degradation in electrochemical sludge, with distinct iron oxide bands and reduced organic complexity. TEM revealed nanostructured iron particles in electrochemical sludge versus larger amorphous aggregates in chemical sludge. Nutrient analysis demonstrated agronomic potential in both, although chemical sludge contained higher nitrogen and phosphorus. Heavy metal content was within safe limits for reuse. This study underscores the advantages of electrochemical treatment in producing stable, nanostructured sludge suitable for sustainable agro-industrial applications, while recommending further risk assessment for long-term soil health impact.

This study investigates the use of constructed wetlands (CWs) with ceramsite derived from surplus sludge pyrolysis ash for acid mine drainage (AMD) remediation. The system, incorporating ceramsite, limestone, and gravel, used soybean wastewater as a microbial carbon source. Results showed that the ceramsite-based system effectively raised pH from 3.5 to 8.0, achieving removal rates of 99.96% for Fe, 96.53% for Mn, 94.84% for Cu, 99.26% for Zn, and 96.02% for total phosphorus. Metal ion removal was primarily through ceramsite adsorption, with minor plant-mediated adsorption. Microbial analysis revealed that pH and metal concentrations influenced bacterial composition, with dominant genera including Trichococcus, Clostridium_Sensu_Stricto_1, and Citrobacter. Sulfate-reducing bacteria such as Desulfovibrio and Desulfobulbus played crucial roles in sulfate reduction. This study demonstrates a sustainable AMD treatment method that not only improves metal ion removal but also addresses sludge disposal challenges, highlighting the environmental benefits of using waste-derived materials for pollution control and resource recovery.

The acceleration of the composting process and improvement of the humification degree are critical objectives in kitchen waste (KW) composting. In this research, the synergistic effects of sodium persulfate, manganese dioxide, ferrous sulfate, and microbial agents on KW composting were systematically investigated with a focus on humus processes, bacterial community structure, and functional metabolism. The results demonstrated that the combined treatment achieved a remarkable cellulose degradation rate of 30.15%. Humus (HS) and humic acid (HA) contents increased significantly, reaching 178.75 and 58.92 mg·g^-1, respectively. The combined treatment significantly increased the aromaticity of HA. Microbial community analyses revealed that the combined treatment enriched functional microorganisms, including Acetobacter and Pseudomonas while suppressing the population of Ascomycetes. Metabolic pathway analysis indicated enhanced humification-related activities in the combined treatment. Redundancy analysis (RDA) identified Pseudomonadota as the key phylum positively associated with HA biosynthesis. In summary, the combined treatment optimized composting efficiency by stimulating OM-degrading bacteria and enhancing the humification degree.

Total and volatile mixed liquor suspended solids concentrations (MLSS and MLVSS) are key parameters in activated sludge (AS) process design, monitoring, and modelling. Yet for the emerging AS version of aerobic granular sludge (AGS), representative sampling and pipetting of the granular mixed liquors are challenging, leading to uncertainties when measuring the suspended solids by standard methods. In this study, new MLSS methods based on correct sampling principles were developed and evaluated to determine the suspended solids (SS) of AGS reactors. Method-1 used as a reference consisted of sacrificing the whole mixed liquor (ML) of each reactor as an exhaustive sample that was all ground to determine the total solids (TS) of the slurry; this allowed for accurate estimates of the MLSS and its volatile fractions (ivt_bio), which, in turn, led to the MLVSS. In parallel, Methods-2 and -4 were tested, both based on small homogeneous subsamples of ML, which were ground or drained before measuring the total solids of the slurry or of the drained granule paste. Compared to the reference, these latter methods allowed the MLSS and ivt_bio of AGS with large granules to be determined with much greater accuracy than the current standard Method-3 (direct SS measurement). The study's good sampling practices are readily applicable to laboratory reactors and would henceforth improve solids measurement in AGS research. At large plants, the developed procedures of subsampling, granule grinding or draining, and MLSS calculation formulas would reduce sampling errors and enhance process monitoring.

The growing demand for water, driven by rapid urbanization and industrialization, necessitates sustainable wastewater management solutions. Greywater, comprising 50-80% of domestic wastewater, presents a valuable opportunity for reuse due to its relatively low pollutant load. This study evaluates the operational performance and applicability of a greywater filtration system employing water treatment sludge (WTS) as a filter medium. The effects of three parameters, namely hydraulic loading rate (HLR), WTS media depth, and WTS particle size were evaluated through long-term column experiments treating real settled greywater. Response Surface Methodology (RSM) based on the Box-Behnken Design was employed to analyse and optimize the system performance. The filters achieved significant pollutant removal, with effluent turbidity, COD, BOD, NH₄⁺-N, and PO₄³^--P reduced to 2.2 NTU, 74, 56, 3.88, and 0.08 mg/L, respectively, and a cumulative filtered volume of 460 L under optimum conditions - HLR 6 m³/m²/day, WTS depth 18 cm, and WTS size 0.98 mm. Better performance was observed at lower HLRs, finer media sizes, and moderate to greater media depths. This study demonstrates that WTS-based filters offer a cost-effective, resource-efficient, and sustainable solution for decentralized greywater treatment, supporting circular economy principles and improving access to water reuse technologies in resource-limited settings.

Incineration fly ash, a hazardous waste from municipal solid and hazardous waste incineration, contains heavy metals, soluble chlorides, and dioxins. A full-scale 'water washing + low-temperature thermal decomposition (LTD)' process for the treatment of incineration fly ash was evaluated in this study, which was conducted in a 20,000-ton/year project in Yancheng, China. Bench-scale tests were used to optimize washing parameters (30 min, 1:3 solid-to-liquid ratio, pH 6, 50-70°C) and LTD conditions (400°C, 45 min), achieving 99.5% dioxin removal - from 440.26 ng TEQ/kg in raw ash to 2.02 ng TEQ/kg. A significant reduction in heavy metal leaching was confirmed during full-scale operation. The treated fly ash was utilized in hollow brick production by mixing with cement, aggregates, and water in a mass ratio of 5:1:4:1, followed by moulding and curing. Additionally, crystalline salt was generated that met industrial standards, while hollow bricks were manufactured in compliance with GB/T 15229-2011 (compressive strength MU 10.0). This integrated technology facilitates the harmless treatment (via detoxification) of hazardous fly ash and the resource recovery of byproducts, thereby addressing the shortcomings of conventional landfilling and high-energy consumption processes. The approach establishes a scalable technical framework for the management of incineration fly ash, thereby contributing to the advancement of circular economy and environmental sustainability objectives.

As the wetland ecosystem is a potential sink of plastics pieces, the photodegradation of microplastics could be boosted by iron(hydr) oxides, which considered as the Fenton or Fenton-like reactions induced. However, the pathways and internal mechanisms by which iron(hydr) oxides enhanced the ultraviolet degradation of plastics in the wetlands remain unclear. Therefore, the degradation of polystyrene (PS) and polyvinyl chloride (PVC) under ultraviolet light (365 nm) was studied in the UV Fenton and simulated micro wetlands. Results showed that UV irradiation caused notable changes in the surface morphology of plastics. Fenton reaction led to more significant, and generated oxygen-containing functional groups such as C = O. The weight loss rate of PS reached 28.3 ± 6.64%, while PVC reached 35.6 ± 1.52%, significantly surpassing the individual conditions of UV light at 20.3 ± 1.66% and 20.98 ± 8.48%, respectively. The mechanism of •OH in the process of plastic degradation was elucidated, while analysis of the degradation products was conducted. The potential risks for the UV degradation of PS and PVC were explored in constructed wetlands by detecting the changes of microbes. After preliminary aging, microbial activity associated with the degradation of polycyclic aromatic hydrocarbon compounds produced during plastic degradation is enhanced. Therefore, there may exist microbial communities in wetland ecosystems that are capable of degrading plastic. This study supported a hypothesis that the goethite/haematite Microcosm Constructed Wetlands (MCWs) would be efficiency for the degradation of plastic. It would be proved further and the organic carbon releasing during the plastic degradation should also be focused on.

The effectiveness of enzyme preparations was investigated under real-life conditions in a commercially operated full-scale biogas plant, aiming to bridge the gap between promising laboratory results and the challenges of practical application. The selected biogas plant represents a typical agricultural setup, processing a feedstock mixture with high proportions of cattle slurry and manure (each up to 29% of the fresh mass input), combined with feed rye and grass silage. These components are considered difficult to degrade, which suggested a high potential for enzymatic treatment. The enzyme products used are characterized by a combination of different enzymatic activities, enabling the breakdown of both dung and straw contained in manure, as well as viscous components from grass and whole crop silages. Due to the substrate-specific nature of enzymatic activity, the selected enzyme products and the applied feedstock mixture appeared to be an excellent match. A comparison between a 14-week reference phase and a 12-week phase with enzyme application revealed a clear impact on plant performance. The specific methane yield increased by 18% during the application period, reaching an average of 346 m³ CH₄/t oDM. This resulted in an average surplus of 210 kWh of electrical energy per ton of oDM. Power self-consumption remained stable at an average of 6.7%. The observed effects confirm the suitability of the applied enzyme products and are based on an exceptionally large dataset, including daily monitoring of plant performance and weekly feedstock characterization.

Polyurethane grouting is a type of chemical grouting with the potential to immobilize contaminants in the deep vadose zone (DVZ), which lies above the groundwater table and typically below the depth at which open excavation is practical or cost-effective. One concern with grouting is the risk of mobilizing contaminants and dispersing them over a wider area, potentially worsening the situation. This study presents laboratory grouting tests to investigate the contaminant displacement during polyurethane grouting in the DVZ at the Hanford Site. Additionally, the study evaluates the effectiveness of soil desiccation and soil freezing in reducing contaminant displacement by reducing the amount of movable containing contaminant water. The test results indicate that polyurethane grouting immobilizes 9.1 ± 3.5% of contaminants. Soil desiccation effectively reduces contaminant displacement to 2.3%. In contrast, soil freezing does not significantly reduce contaminant displacement, primarily due to two factors: polyurethane flushing and gas production during curing. Gas generated during polyurethane curing can mobilize soil water, leading to contaminant displacement. Test results with different rates of gas production also indicate higher rates of gas production lead to a larger iodide displacement ratios. The resin with the highest measured gas production rate of 1.56 × 10^-4 mol/(mL·h) resulted in a displacement ratio of 0.351, whereas the resin with the lowest measured gas production rate 7.00 × 10^-5 mol/(mL·h) resulted in a much lower displacement ratio of 0.101 when both tests used soil water content of 5%. These findings offer valuable insights for using polyurethane grouting to immobilize contaminants in DVZs.

Electrochemical reduction is an efficient method for treating high-concentration nitrate wastewater, providing benefits such as enhanced controllability and the elimination of secondary pollution. In this study, the CuNi/NF electrode was fabricated by direct current electrodeposition of copper and nickel onto nickel foam, which served as the cathode for the electrochemical reduction of nitrate. The electrode demonstrated superior nitrate removal performance, achieving an NO₃^--N removal rate of 83% after 5 h of reaction at an initial concentration of 500 mg/L, significantly outperforming the Cu/NF electrode (76%) and Ni/NF electrode (57%). The influence of key operating parameters on nitrate reduction was systematically investigated. The results indicated that the electrode prepared with a deposition time of 20 min exhibited the highest removal efficiency. Under optimal conditions (current density of 25 mA/cm², Cl^- concentration of 2 g/L, and initial pH of 7), the NO₃^--N removal rate reached 85%, with N₂ selectivity as high as 93.7%. The CuNi/NF electrode also exhibited good stability over five consecutive cycles. Finally, a plausible mechanism for nitrate reduction was proposed. This study provides fundamental data and theoretical support for the practical application of electrochemical methods in treating high-concentration nitrate wastewater.