Frontiers of Environmental Science & Engineering最新文献

Substantial NO_x emission mitigation is crucial for the synergistic reduction of particulate matter and ozone (O₃) pollution in China. The traditional air quality model does not consider heterogeneous HONO chemistry, leading to uncertainties in estimating the benefits of NO_x control. Previous studies have shown that the parameterization of heterogeneous HONO formation increases both the simulated value of sulfate–nitrate–ammonium (SNA) and that of O₃, thus adding the heterogeneous reactions of HONO into air quality models inevitably leads to changes in the estimated benefits of NO_x abatement. Here we investigated the changes in SNA and O₃ concentrations from NO_x emission reduction before and after adding heterogeneous HONO reactions in the Community Multi-Scale Air Quality (CMAQ) model. Including heterogeneous HONO reactions in the simulation improved the benefits of NO_x reduction in terms of SNA control in winter. With 80% NO_x reduction, the reduction in SNA increased from 36.9% without considering heterogeneous HONO reactions to 42.8% with heterogeneous HONO chemistry. The reduction in the maximum daily 8h average (MDA8) O₃ in summer caused by NO_x reduction increased slightly from 4.7% to 5.2% after adding heterogeneous HONO reactions. The results in this study highlight the enhanced effectiveness of NO_x controls for the reduction of SNA and O₃ after considering heterogeneous HONO formation in a complex chemical ambient, demonstrating the importance of NO_x controls in reducing PM_2.5 and O₃ pollution in China.

Viable but non-culturable (VBNC) bacteria have been detected in source water and effluent of drinking water treatment processes, leading to significant underestimation of viable cell counts. Limited information exists on VBNC bacteria in tap water, particularly in public places. To address this gap, a comprehensive nine-month study was conducted in a major city in south-eastern China, using culture-based and quantitative PCR with propidium monoazide (PMA) dye methods. Forty-five samples were collected from five representative public places (railway station, campus, hospital, shopping mall, and institution). The findings revealed that culturable bacteria represented only 0–17.51% of the viable 16S rRNA genes, suggesting that the majority of viable bacteria existed in an uncultured or VBNC state. Notably, opportunistic pathogens such as Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, Salmonella sp., and Shigella sp. were primarily detected as VBNC cells, with concentrations ranging from 1.03 × 10⁰ to 3.01 × 10³, 1.20 × 10⁰ to 1.42 × 10², 1.32 × 10⁰ to 8.82 × 10⁰, 1.00 × 10⁰ to 6.71 × 10¹, and 2.07 × 10⁰ to 1.93 × 10² cell equivalent/100 mL, respectively. Culturable P. aeruginosa was observed in tap water after prolonged stagnation, indicating potential risks associated with bacterial regrowth. Spatial and temporal factors accounted for 17.1% and 26.0%, respectively, of the variation in tap water community structure during the sampling period, as revealed by 16S rRNA amplicon sequencing. This study provides quantitative insights into the occurrence of VBNC bacteria in tap water and highlights the need for more sensitive monitoring methods and microbial control techniques to enhance tap water safety in public locations.

The migration and transformation of phosphorus components in wastewater treatment plants (WWTPs) play a crucial role in the convergence and circulation of phosphorus. However, the composition and variation of dissolved organic phosphorus (DOP) in WWTPs were unclear because of its complex nature, hindering its efficient detection. In this study, the DOP species and their transformation during the treatment process in WWTP were comprehensively analyzed. First, two enrichment methods were assessed for their effectiveness at facilitating wastewater analysis: lyophilization and aluminum salt precipitation. Aluminum salt precipitation was found to be better because its application allowed ³¹P nuclear magnetic resonance (³¹P NMR) spectroscopy to identify more species in the secondary effluent: orthophosphate (Ortho-P) (81.1%–89.3% of the dissolved total phosphorus), pyrophosphates (Pyro-P) (0%–2.3%), orthophosphate monoesters (Mono-P) (7.0%–10.77%), orthophosphate diesters (Di-P) (1.0%–2.96%), and phosphonate (Phos-P) (1.7%–5.16%). Furthermore, the variation and transformation mechanism of phosphorus, particularly those of DOP, during the entire sewage-treatment process were elucidated. Among the treatment steps, biological treatment combined tertiary treatment achieved better DOP removal efficiencies. Therein, biological treatment mainly removed Mono-P and Di-P with removal efficiencies of 33.3% and 41.7% compared with the effluent of the grit chamber. Di-P has higher bioavailability and is more easily converted and utilized by microorganisms than Mono-P. However, Phos-P, with low bioavailability, was hardly utilized by microorganisms, which showed only 18.4% removal efficiency in biological treatment. In tertiary treatment, coagulation process exhibited higher removal ability of Ortho-P (69.1%) and partial removal efficiencies of DOP, resulting in an increase in the DOP proportion in TP. In addition, Phos-P could not be effectively removed through the biological treatment and was only partially reduced via the adsorption process by large particles, zoogloea or multinuclear hydroxyl complexes. The results of this study can provide a theoretical basis for efficient phosphorus removal in WWTPs.

Antimicrobial resistance (AMR) has emerged as a significant challenge in human health. Wastewater treatment plants (WWTPs), acting as a link between human activities and the environment, create ideal conditions for the selection and spread of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB). Unfortunately, current treatment processes are ineffective in removing ARGs, resulting in the release of large quantities of ARB and ARGs into the aquatic environment through WWTP effluents. This, in turn, leads to their dispersion and potential transmission to human through water and the food chain. To safeguard human and environmental health, it is crucial to comprehend the mechanisms by which WWTP effluent discharge influences the distribution and diffusion of ARGs in downstream waterbodies. In this study, we examine the latest researches on the antibiotic resistome in various waterbodies that have been exposed to WWTP effluent, highlighting the key influencing mechanisms. Furthermore, recommendations for future research and management strategies to control the dissemination of ARGs from WWTPs to the environment are provided, with the aim to achieve the “One Health” objective.

Efficiently predicting effluent quality through data-driven analysis presents a significant advancement for consistent wastewater treatment operations. In this study, we aimed to develop an integrated method for predicting effluent COD and NH₃ levels. We employed a 200 L pilot-scale sequencing batch reactor (SBR) to gather multimodal data from urban sewage over 40 d. Then we collected data on critical parameters like COD, DO, pH, NH₃, EC, ORP, SS, and water temperature, alongside wastewater surface images, resulting in a data set of approximately 40246 points. Then we proposed a brain-inspired image and temporal fusion model integrated with a CNN-LSTM network (BITF-CL) using this data. This innovative model synergized sewage imagery with water quality data, enhancing prediction accuracy. As a result, the BITF-CL model reduced prediction error by over 23% compared to traditional methods and still performed comparably to conventional techniques even without using DO and SS sensor data. Consequently, this research presents a cost-effective and precise prediction system for sewage treatment, demonstrating the potential of brain-inspired models.

Digested wastewater contains pathogenic microorganisms and high ammonia concentrations, which can pose a potential risk to public health. Effective removal of pathogens and nitrogen is crucial for the post-treatment of digested wastewater. Partial nitrification-anammox is an energy-saving nitrogen removal process. Free nitrous acid (FNA), an intermediate product of partial nitrification, has the potential to inactivate microorganisms. However, the efficiency and mechanisms of FNA-related inactivation in pathogens during partial nitrification remains unclear. In this study, Enterococcus and Escherichia coli (E. coli) were selected to investigate the efficiency and mechanisms of FNA-related inactivation in partial nitrification process. The results revealed that 83% ± 13% and 59% ± 27% of E. coli and Enterococcus were removed, respectively, in partial nitrification process at FNA concentrations of 0.023–0.028 mg/L. When the concentration of FNA increased from 0 to 0.5 mg/L, the inactivation efficiencies of E. coli and Enterococcus increased from 0 to 99.9% and 89.9%, respectively. Enterococcus exhibited a higher resistance to FNA attack compared to E. coli. 3D-laser scanning microscopy (3D-LSM) and scanning electron microscopy (SEM) revealed that FNA exposure caused the surface collapse of E. coli and Enterococcus, as well as visible pore formation on the surface of E. coli cells. 4′,6-Diamidino-2-phenylindole dihydrochloride n-hydrate (DAPI)/propidium iodide (PI) and biomolecule leakage confirmed that inactivation of E. coli and Enterococcus occurred due to breakdown of cell walls and cell membranes. These findings indicate that partial nitrification process can be used for the removal of residual pathogenic microorganisms.

Effective waste management is a major challenge for Small Island Developing States (SIDS) like Maldives due to limited land availability. Maldives exemplifies these issues as one of the most geographically dispersed countries, with a population unevenly distributed across numerous islands varying greatly in size and population density. This study provides an in-depth analysis of the unique waste management practices across different regions of Maldives in relation to its natural and socioeconomic context. Data shows Maldives has one of the highest population density and per capita waste generation among SIDS, despite its small land area and medium GDP per capita. Large disparities exist between the densely populated capital Male’ with only 5.8 km² area generating 63% of waste and the ∼194 scattered outer islands with ad hoc waste management practices. Given Male’s dense population and high calorific waste, incineration could generate up to ∼30 GW/a energy and even increase Maldives’ renewable energy supply by 200%. In contrast, decentralized anaerobic digestion presents an optimal solution for outer islands to reduce waste volume while providing over 40%–100% energy supply for daily cooking in local families. This timely study delivers valuable insights into designing context-specific waste-to-energy systems and integrated waste policies tailored to Maldives’ distinct regions. The framework presented can also guide other SIDS facing similar challenges as Maldives in establishing sustainable, ecologically sound waste management strategies.

Groundwater quality assessment and prediction (GQAP) is vital for protecting groundwater resources. Traditional GQAP methods can not adequately capture the complex relationships among attributes and have the disadvantage of being computationally demanding. Recently, the application of machine learning (ML) in GAQP (GQAPxML) has been widely studied due to ML’s reliability and efficiency. While many GQAPxML publications exist, a thorough review is missing. This review provides a comprehensive summary of the development of ML applications in the field of GQAP. First, the workflow of ML modeling is briefly introduced, as are data preparation, model development, model evaluation, and model application. Second, 299 publications related to the topic are filtered, mainly through ML modeling. Subsequently, many aspects of GQAPxML, such as publication trends, the spatial distribution of study areas, the size of data sets, and ML algorithms, are discussed from a bibliometric perspective. In addition, we review in detail the well-established applications and recent findings for several subtopics, including groundwater quality assessment, groundwater quality modeling using groundwater quality parameters, groundwater quality spatial mapping, probability estimation of exceeding the groundwater quality threshold, groundwater quality temporal prediction, and the hybrid use of ML and physics-based models. Finally, the development of GQAPxML is explored from three perspectives: data collection and preprocessing, model building and evaluation, and the broadening of model applications. This review provides a reference for environmental scientists to better understand GQAPxML and promotes the development of innovative methods and improvements in modeling quality.

Substantial environmental and economic benefits can be achieved by recycling used lithium-ion batteries. Hydrometallurgy is often employed to recover waste LiNi_xCo_yMn_zO₂ cathode materials. As Ni, Co and Mn are transition metals, they exhibit similar properties; therefore, separating them is difficult. Thus, most researchers have focused on leaching processes, while minimal attention has been devoted to the separation of valuable metals from waste LiNi_xCo_yMn_zO₂ cathode materials. Herein, we propose an environment-friendly, gentle process involving the usage of pyrometallurgy and hydrometallurgy to gradually leach valuable metals and effectively separate them. Interestingly, Li is recovered through a reduction roasting and water leaching process using natural graphite powder, Ni and Co are recovered through ammonia leaching and extraction processes and Mn is recovered through acid leaching and evaporation-crystallization processes. Results show that ∼87% Li, 97.01% Co, 97.08% Ni and 99% Mn can be leached using water, ammonia and acid leaching processes. The result obtained using the response surface methodology shows that the concentration of (NH₄)₂SO₃ is a notable factor affecting the leaching of transition metals. Under optimal conditions, ∼97.01% Co, 97.08% Ni and 0.64% Mn can be leached out. The decomposition of LiNi_xCo_yMn_zO₂ is a two-step process. This study provides valuable insights to develop an environment-friendly, gentle leaching process for efficiently recycling valuable metals, which is vital for the lithium-ion battery recycling industry.