Environmental Technology最新文献

Biological desulfurization provides a sustainable and cost-effective alternative to conventional physicochemical methods for removing hydrogen sulfide (H₂S) from industrial gas streams, particularly in medium-scale applications. This study investigates the enrichment and application of an enriched sulfur-oxidizing bacterial (SOB) consortium, isolated from sulfur-rich natural environments in Iran, for the selective biological conversion of sulfide to elemental sulfur in a fed-batch airlift bioreactor. A Central Composite Design-Response Surface Methodology (CCD-RSM) was employed to statistically evaluate and optimize the effect of dissolved oxygen (DO), pH, and sulfide loading rate, aiming to maximize sulfur selectivity while minimizing by-product formation. Optimization results revealed that both DO concentration and sulfide loading rate significantly influenced sulfur selectivity. Notably, low DO levels enhanced the selective production of elemental sulfur, while higher pH and sulfide loading rates promoted thiosulfate formation. The optimal conditions determined were pH 8.5, DO concentration of 0.2 mg L^-1, and a sulfide loading rate of 97.2 mg L^-1 h^-1. Under these optimized fed-batch conditions, 71% of the inlet sulfide was selectively converted to elemental sulfur, with complete (100%) sulfide removal achieved across all experimental runs. These findings demonstrate the potential of using enriched SOB together with well-controlled process conditions can make biodesulfurization more efficient, selective, and environmentally friendly for industrial applications. Compared with conventional physicochemical methods, the optimized biological process operates under mild conditions, is more cost-effective and environmentally sustainable, while maintaining high sulfide removal and sulfur recovery.

A highly pure biomethane stream (≈97% CH₄) was produced continuously under halo-alkaline conditions (pH > 9, 0.6 M Na⁺) from complex alkaline organic waste residue originating from biopolymer extraction from sewage sludge. During the proof-of-concept operation, the substrate was degraded with similar efficiency (40% of the volatile solids, VS) compared to neutral conditions (36% of the VS). Operational data was utilised in a technical evaluation to identify bottlenecks for full-scale implementation at an early stage of process development and for comparison to conventional biogas upgrading using pressure swing and membranes. Initially identified bottlenecks for alkaline fermentation were related to overcautious assumptions, while others could be technically solved. Alkaline fermentation offers an attractive method for supplying increasingly needed high-purity biomethane using various recalcitrant substrates that have undergone alkaline pre-treatment. This is more feasible than the conventional ex-situ biogas upgrading. Next, upscaling steps for alkaline fermentation should be pursued. Strategies for integrated CO₂ sequestration and nutrient recovery are outlined, which will offer additional benefits in the future.

ABSTRACTThe volumetric oxygen mass transfer coefficient () is a critical parameter in the design, scale-up, and operation of bioreactors. In this study, a fully automated dynamic method was developed for determining $k_{L}a$, eliminating manual intervention and ensuring reproducible and reliable estimates. The approach includes a probe response-time correction and was validated under different operational conditions in an aerated stirred system. The influence of two representative pollutants was evaluated: phenol and benzalkonium chloride (BAC). While phenol produced a small enhancement (≈18%) of the overall $k_{L}a$, BAC caused a reduction in $k_{L}a$, mainly due to its pronounced effect on the surface mass transfer coefficient ($k_L{a}_S$). To the best of our knowledge, this work provides the first experimental evidence of BAC effects on oxygen transfer in bioreactors. These results expand the current understanding of how pollutants can simultaneously act as metabolic inhibitors and as modifiers of gas-liquid mass transfer, with significant implications for optimising aeration strategies in biological wastewater treatment.

Wet and dry atmospheric deposition plays a crucial role in the removal of airborne pollutants, being influenced by both meteorology and chemical composition. While these processes occur on intra-event (hourly) time scales, most existing monitoring approaches rely on daily or event-based sampling, which limits our understanding of short-term variations in gas scavenging and pollutant deposition. Here, we present the development and application of R-WASH (RainWater Automatic Sampler Hardware), a low-cost, open-source, and semi-automatic device for high-resolution (hourly) rainwater sampling. The system consists of modules for collection, distribution, and storage (up to 24 bottles). We tested the system in nine rainfall events, in which 91 hourly samples were collected and analyzed for ammonium, nitrite, nitrate (via spectrophotometry), and particulate-bound metals (Cd, Cu, Cr, Ni, Zn) using acid digestion and atomic absorption spectroscopy. Recovery tests confirmed high sampling efficiency and chemical integrity. The data revealed distinct temporal behaviours: particulate metals showed peak concentrations during the initial hours of rain events, while nitrogen compounds displayed quasi constant concentration throughout. Correlation analysis showed that metals were positively associated with PM and negatively with temperature and time step, suggesting strong links to particulate-mediated deposition and early-stage scavenging. In contrast, nitrogen species showed weaker and more variable correlations, likely due to their higher solubility and continuous atmospheric input. The performance of regression models improved with increasing bin width, particularly for metals Cu and Zn (R² > 0.85 under 5-hour binning). These findings highlight the value of high-resolution sampling in understanding the deposition processes.

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.

Extracellular polymeric substances (EPS) play a vital role in forming microbial aggregates such as biofilms, flocs, and granules. However, standardised methods for extracting EPS from the activated sludge across different wastewater treatment processes remain elusive. The anaerobic-anoxic-oxic (A²O) process, widely used in wastewater treatment, was selected to investigate EPS extraction from its activated sludge. This study compared twenty-five physicochemical methods for EPS extraction from the activated sludge collected from the secondary sedimentation basin of an A²O reactor, evaluating EPS yield, composition, and cell lysis. The results show that combined chemical-physical extraction methods, particularly NaOH/heat treatment, achieved higher extraction rates while preserving EPS characteristics. This method yielded higher concentrations of proteins (PN) and polysaccharides (PS) with reduced cell lysis compared to other techniques. In most methods, protein content exceeded polysaccharides content, with PN/PS ratios ranging from 0.005 to 4.17 g/g. Higher PN/PS ratios were associated with smoother, more uniform EPS morphology. Particle size distribution of the treated sludge showed minimal variation between methods. Fourier transform infrared (FTIR) and excitation emission matrix (EEM) fluorescence spectroscopy confirmed the presence of proteins, polysaccharides, and DNA in EPS, with NaOH/heat treatment more effectively preserving functional groups. Optimisation tests identified 45 min as the ideal heating duration for maximum EPS extraction. Overall, this study provides a systematic evaluation of EPS extraction methods from the activated sludge in A²O systems, offering methodological insights for future wastewater treatment research.

Aqueous contamination by arsenic and antimony has become a significant concern due to its prevalence in smelting activities. Nowadays, adsorption stands out as an effective method for the removal of these heavy metal ions from water, particularly when the goal is to achieve high levels of purification and ensure safety. However, the complex nature of smelting wastewater often leads to a decrease in the selectivity and salt resistance of adsorbents under industrial conditions. In this study, we introduce a novel designated composite-resin material (KYE003), which is tailored for the deep purification of arsenic and antimony. By precisely adjusting the synthesis ratios, we have controlled the intrinsic kinetics of material synthesis, enabling the in-situ loading of ferric oxide onto the resin surface, coupled with organic functional groups (-COOH and -SH). The resin's inherent porous structure not only promotes the nucleation and growth of amorphous iron oxide but also establishes a quantitative basis for nano-scale binding sites. Further surface characterisation analysis indicates that interfacial functional groups, including (-COOH, -SH, and -OH), are instrumental in the complexation of arsenic and antimony. The synergistic interactions, such as -O-As/Sb, -COO-As/Sb, and -S-As/Sb, demonstrate that the hybridisation of these groups restructures the interfacial electronic state, thereby enhancing the adsorption performance. The KYE003 material exhibits exceptional adsorptive selectivity and chemical stability under complex conditions, capable of maintaining arsenic concentrations in the effluent below 20 µg·L^-1 until the bed volumes ratio surpasses 6240. This research presents a new perspective for the deep purification of heavy metal ions.

Iron oxides and natural organic matter are widely recognised for their roles in mitigating heavy metal contamination due to their surface reactivity. Magnetite, featuring Fe(II), is of particular interest for its reductive properties. However, limited studies have explored its synergistic interaction with organic matter in removing anionic contaminants like Cr(VI). In this study, magnetite-fulvic acid (Mt-FA) complexes with varying C/Fe molar ratios were synthesised and tested for Cr(VI) removal through batch experiments and spectroscopic analyses. Fulvic acid decreased the specific surface area of magnetite and partially blocked adsorption sites, leading to reduced adsorption capacity with increasing FA content. Under acidic conditions (pH 3), Mt-FA with a C/Fe ratio of 0.5 exhibited the highest Cr(VI) adsorption capacity (6.38 mg/g). FT-IR and XPS analyses confirmed that both FA and magnetite were involved in Cr(VI) adsorption and reduction, with Fe(II) contributing to redox reactions. Additional tests with FA alone revealed its inherent reductive capacity (1.12-1.59 mg/g), while magnetite alone contributed ∼1.34 mg/g. The combined Mt-FA complexes exhibited higher reduction capacity (1.57-2.11 mg/g), indicating a synergistic effect. FA not only provides redox-active groups but also facilitates electron transfer from magnetite to Cr(VI), enhancing Cr(VI) reduction. This dual-function material offers a promising approach for remediation of Cr(VI)-contaminated environments and highlights the importance of interfacial interactions between iron oxides and natural organic matter.

Mycoremediation, the application of fungi for pollutant degradation, offers a sustainable solution for bioremediating contaminated environments. In mixed microbial settings, microbial competition can influence the efficiency of fungi by modulating pollutant degradation and nutrient availability. We investigated the bioremediation potential of boreal white-rot fungi (WRF) in fiberbank sediments, targeting organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements (PTEs). Previously isolated and identified thirteen WRF species were screened in sterilized and unsterilized substrates to evaluate the effects of microbial interactions on pollutant degradation and metal uptake. Key findings revealed that unsterilized fiberbank material supported superior PAH degradation, with Trametes hirsuta achieving up to 94% removal, suggesting synergistic interactions between WRF and native microbial communities. Conversely, sterilized substrates enhanced PTE uptake, with Phlebia tremellosa demonstrating significant accumulation of cadmium, bioconcentration factor (BCF) of 5.56 in sterile conditions and 0.85 in unsterile conditions, and lead, BCF of 1.65 under sterile conditions, and 0.38 for unsterile conditions, this enhanced accumulation might be due to reduced microbial competition. Statistical analyses confirmed significant differences (p < 0.001) in pollutant removal and metal uptake between the two substrate conditions. These results underline the importance of tailoring bioremediation strategies to substrate conditions. A dual approach, employing unsterilized substrates for organic pollutant degradation and sterilized substrates for metal accumulation, emerges as a promising framework. Future applications could focus on large-scale implementation of these strategies to rehabilitate industrially contaminated sites like fiberbanks, balancing ecological sustainability with remediation efficacy.