Due to water scarcity challenges around the world, it is essential to think about non-conventional water resources to address the increased demand in clean freshwater. Environmental and public health problems may result from insufficient provision of sanitation and wastewater disposal facilities. Because of this, wastewater treatment and recycling methods will be vital to provide sufficient freshwater in the coming decades, since water resources are limited and more than 70% of water are consumed for irrigation purposes. Therefore, the application of treated wastewater for agricultural irrigation has much potential, especially when incorporating the reuse of nutrients like nitrogen and phosphorous, which are essential for plant production. Among the current treatment technologies applied in urban wastewater reuse for irrigation, wetlands were concluded to be the one of the most suitable ones in terms of pollutant removal and have advantages due to both low maintenance costs and required energy. Wetland behavior and efficiency concerning wastewater treatment is mainly linked to macrophyte composition, substrate, hydrology, surface loading rate, influent feeding mode, microorganism availability, and temperature. Constructed wetlands are very effective in removing organics and suspended solids, whereas the removal of nitrogen is relatively low, but could be improved by using a combination of various types of constructed wetlands meeting the irrigation reuse standards. The removal of phosphorus is usually low, unless special media with high sorption capacity are used. Pathogen removal from wetland effluent to meet irrigation reuse standards is a challenge unless supplementary lagoons or hybrid wetland systems are used.

\n Traditionally constructed wetlands face significant limitations in treating tailwater from wastewater treatment plants, especially those associated with sugar mills. However, the advent of novel modified surface flow constructed wetlands offer a promising solution. This study aimed to assess the microbial community composition and compare the efficiencies of contaminant removal across different treatment wetlands: CW1 (Brick rubble, lignite, and\n Lemna minor\n L.), CW2 (Brick rubble and lignite), and CW3 (\n Lemna minor\n L.). The study also examined the impact of substrate and vegetation on the wetland systems. For a hydraulic retention time of 7 days, CW1 successfully removed more pollutants than CW2 and CW3. CW1 demonstrated removal rates of 72.19% for biochemical oxygen demand (BOD), 74.82% for chemical oxygen demand (COD), 79.62% for NH\n 4\n +\n -N, 77.84% for NO\n 3\n −\n -N, 87.73% for ortho phosphorous (OP), 78% for total dissolved solids (TDS), 74.1% for total nitrogen (TN), 81.07% for total phosphorous (TP), and 72.90% for total suspended solids (TSS). Furthermore, high-throughput sequencing analysis of the 16S rRNA gene revealed that CW1 exhibited elevated Chao1, Shannon, and Simpson indices, with values of 1324.46, 8.8172, and 0.9941, respectively. The most common bacterial species in the wetland system were Proteobacteria, Spirochaetota, Bacteroidota, Desulfobacterota, and Chloroflexi. The denitrifying bacterial class Rhodobacteriaceae also had the highest content ratio within the wetland system. These results confirm that CW1 significantly improves the performance of water filtration. Therefore, this research provides valuable insights for wastewater treatment facilities aiming to incorporate surface flow-constructed wetland tailwater enhancement initiatives.\n

Constructed wetlands play a critical role in mitigating aquaculture wastewater pollution. However, the comprehensive treatment performance of aquatic plants and microorganisms under various water treatment processes remains insufficiently understood. Here, a multi-stage surface flow constructed wetland (SFCW) comprising four different aquatic plant species, along with aeration and biofiltration membrane technologies, was investigated to explore the combined effects of aquatic plants and epiphytic biofilms on wastewater removal efficiency across different vegetation periods and treatment processes. The results demonstrated that the total removal efficiency consistently exceeded 60% in both vegetation periods, effectively intercepting a range of pollutants present in aquaculture wastewater. Changes in the vegetation period influenced the performance of the SFCW, with the system’s ability to treat total nitrogen becoming more stable over time. The removal efficiency of the treatment pond planted with submerged plants was highest in July, while the pond planted with emergent plants showed an increased removal rate in November. The aeration pond played a significant role in enhancing dissolved oxygen levels, thereby improving phosphorus removal in July and nitrogen removal in November. Additionally, the α-diversity of epiphytic bacteria in the aeration and biofiltration ponds was significantly higher compared to other ponds. In terms of bacterial composition, the abundance of Firmicutes was notably higher in July, whereas Nitrospirota and Acidobacteriota exhibited a significant increase in November. Furthermore, the functional genes associated with sulfur metabolism, nitrogen fixation, and oxidative phosphorylation displayed significant temporal variations in the aeration pond, highlighting that both growth period changes and treatment processes influence the expression of functional genes within biofilms. Our findings suggest that the integration of water treatment processes in SFCWs enhances the synergistic effects between aquatic plants and microorganisms, helping to mitigate the adverse impacts of vegetation period changes and ensuring stable and efficient wastewater treatment performance.

The discharge of micro-polluted water from sources such as agricultural runoff, urban stormwater, and treated effluents presents significant challenges to aquatic ecosystems. Constructed wetlands (CWs) have gained recognition as an eco-friendly solution for removing pollutants from various wastewater sources and are increasingly applied for micro-polluted water treatment. By reviewing 78 full-scale CW studies from Web of Science, it is summarized that the ranges of ammonium nitrogen (NH-N) concentrations in runoff, wastewater treatment plant effluent and polluted river were 0.1-6.6, 0.3-12.3, and 0.2-41.1 mg/L, respectively. The ranges of nitrate nitrogen concentrations were 0.2-14.2, 0-5.7, and 0-2.6 mg/L, respectively. Removal efficiencies of CWs for micro-polluted water varied by CW types. The total nitrogen removal efficiencies for subsurface-flow CWs, free-water surface-flow CWs, and hybrid CWs ranged from 27.4 % to 66.5 %, 16.8 % to 89.8 %, and 19.4 % to 88.2 %, respectively. The NH-N removal efficiencies ranged from 34.2 % to 73.6 %, 38.4 % to 89.4 % and 13.5 % to 94.2 %, respectively. Additionally, other factors influencing contaminant removal efficiency such as hydraulic retention time, vegetation types, redox micro-environment and influent water quality were evaluated. Based on these findings, two strategies for improving the purification performance of CWs were proposed: the selection of incorporating electron donor substrates and the optimization of operation parameters. This paper serves as a synthesis of information to guide future research and full-scale CW applications in micro-polluted water treatment.Copyright © 2025. Published by Elsevier B.V.

Nitrogen removal is an important process for wastewater ponds prior to effluent release. Bacteria and archaea can drive nitrogen removal if they possess the genes required to metabolize nitrogen. In the tropical savanna of northern Australia, we identified the previously unresolved microbial communities responsible for nitrogen cycling in a multi-pond wastewater stabilization system by measuring genomic DNA and cDNA for the following: nifH (nitrogen fixation); nosZ (denitrification); hzsA (anammox); archaeal AamoA and bacterial BamoA (ammonia oxidation); nxrB (nitrite oxidation); and nrfA (dissimilatory NO reduction to NH). By collecting 160 DNA and 40 cDNA wastewater samples and measuring nitrogen (N)-cycling genes using a functional gene array, we found that genes from all steps of the N cycle were present and, except for nxrB, were also expressed. As expected, N-cycling communities showed daily, seasonal, and yearly shifts. However, contrary to our prediction, probes from most functional groups, excluding nosZ and AamoA, were different between ponds. Further, different genes that perform the same N-cycling role sometimes had different trends over space and time, resulting in only weak correlations between the different functional communities. Although N-cycling communities were correlated with wastewater nitrogen levels and physico-chemistry, the relationship was not strong enough to reliably predict the presence or diversity of N-cycling microbes. The complex and dynamic response of these genes to other functional groups and the changing physico-chemical environment provides insight into why altering wastewater pond conditions can result an abundance of some gene variants while others are lost.

Due to its unique structure and excellent purification efficiency (e.g., 98% for organic matter and between 94 and 100% for nutrients), multi-soil-layering (MSL) has emerged as an efficient eco-friendly solution for wastewater treatment and environmental protection. Through infiltration-percolation, this soil-based technology allows pollutants to move from the MSL upper layers to the outlet while maintaining direct contact with its media, which helps in their removal via a variety of physical and biochemical mechanisms. This paper attempts to comprehensively evaluate the application of MSL technology and investigate its progress and efficacy since its emergence. Thus, it will attempt via a bibliometric analysis using the Web of Science database (from 1993 to 1 June 2022) related to MSL technology, to give a clear picture of the number of publications (70 studies), the most active academics, and countries (China with 27 studies), as well as collaborations and related topics. Furthermore, through hybrid combinations, pollutant removal processes, MSL effective media, and the key efficiency parameters, this paper review will seek to provide an overview of research that has developed and examined MSL since its inception. On the other hand, the current review will evaluate the modeling approaches used to explore MSL behavior in terms of pollutant removal and simulation of its performance (R2 > 90%). However, despite the increase in MSL publications in the past years (e.g., 13 studies in 2021), many studies are still needed to fill the knowledge gaps and urging challenges regarding this emerging technology. Thus, recommendations on improving the stability and sustainability of MSLs are highlighted.

The use of decentralized wastewater treatment technologies is a reasonable solution for rural areas. As a decentralized treatment technology, the multi-soil-layering (MSL) system has recently drawn an increasing amount of attention owing to its merits, such as a high hydraulic load rate, small land area occupation, low probability of clogging, low investment, and low operation cost. This review summarizes the progress in MSL systems in the past decade, focusing on the directions of efforts for system optimization, the latest applications of MSL systems to various wastewater treatments, and the integration of MSL with other technologies. The great application potential of MSL systems is illustrated, and future research directions regarding better application of MSL systems are provided.

The massive loss of nitrogen (N) and phosphorus (P) from farmland ditches contributes to non-point source pollution, posing a significant global environmental challenge. Effectively removing these nutrients remains difficult in intensive agricultural systems. To address this, a novel composite ecological ditch system (CEDS) was developed by modifying traditional drainage ditches to integrate a grit chamber, zeolite, and ecological floating beds. Dynamic monitoring of N and P levels in water, plants, and zeolite was conducted to evaluate the system’s nutrient interception performance and mechanisms. The results showed the following: (1) Water quality improved markedly after passing through the CEDS, with nutrient concentrations decreasing progressively along the flow path. The system intercepted 41.0% of N and 31.9% of P, with inorganic N and particulate P as the primary forms of nutrient loss. (2) Zeolite removes N primarily through ion exchange, and P likely through chemical reactions, with maximum capacities of 3.47 g/kg for N and 1.83 g/kg for P. (3) Ecological floating beds with hydroponic cultivation enhanced nutrient uptake by the roots of Canna indica and Iris pseudacorus, with N uptake surpassing P. (4) Nutrient interception efficiency was positively correlated with temperature, ditch inlet concentrations, and rice runoff concentrations, but negatively with precipitation. This study demonstrates the CEDS’s potential for improving farmland water quality and suggests further enhancements in design and management to increase its economic and aesthetic value.

为对农村分散生活污水进行资源化处理,以空心菜为湿地植物,在温度（32±2）℃、水力负荷2.40 m³/（m²·d）条件下进行湿地污水处理实验,评价了蔬菜型人工湿地对污水的处理性能及其资源化回收潜能。结果表明,当COD、TP、NH₄⁺-N平均进水浓度分别为198.52、2.92、20.69 mg/L时,平均去除率分别为63.8%、64.0%、27.6%,将COD、TP、NH₄⁺-N平均进水浓度降低为148.12、1.81、15.14 mg/L时,湿地去除效果明显提升,平均去除率分别为76.5%、73.0%、41.3%,平均出水浓度分别为34.83、0.49、8.89 mg/L,出水COD、TP、TN达到《城镇污水处理厂污染物排放标准》（GB 8918–2002）一级A标准,NH₄⁺-N达到二级标准,实验期间空心菜生长状态良好,每株平均增重45.88 g,增长47 cm,具有较大的资源回收潜力。

An integrated hybrid system was developed, incorporating sedimentation, anaerobic digestion, biological filtration, and a two-stage hybrid subsurface flow constructed wetland, horizontal subsurface flow constructed wetland (HSSFCW) and vertical subsurface flow constructed wetland (VSSFCW), to treat rural sewage in southern Jiangsu. To optimize nitrogen and phosphorus removal, the potential of six readily accessible industrial and agricultural waste byproducts—including plastic fiber (PF), hollow brick crumbs (BC), blast furnace steel slag (BFS), a zeolite–blast furnace steel slag composite (ZBFS), zeolite (Zeo), and soil—was systematically evaluated individually as substrates in vertical subsurface flow constructed wetlands (VSSFCWs) under varying hydraulic retention times (HRTs, 0–120 h). The synergy among substrates, plants, and microbes, coupled with the effects of hydraulic retention time (HRT) on pollutant degradation performance, was clarified. Results showed BFS achieved optimal comprehensive pollutant removal efficiencies (97.1% NH4+-N, 76.6% TN, 89.7% TP, 71.0% COD) at HRT = 12 h, while zeolite excelled in NH4+-N/TP removal (99.5%/94.5%) and zeolite–BFS specializing in COD reduction (80.6%). System-wide microbial analysis revealed organic load (sludges from the sedimentation tank [ST] and anaerobic tanks [ATs]), substrate type, and rhizosphere effects critically shaped community structure, driving specialized pathways like sulfur autotrophic denitrification (Nitrospira) and iron-mediated phosphorus removal. Annual engineering validation demonstrated that the optimized strategy of “pretreatment unit for phosphorus control—vertical wetland for enhanced nitrogen removal” achieved stable effluent quality compliance with Grade 1-A standard for rural domestic sewage discharge after treatment facilities, without the addition of external carbon sources or exogenous microbial inoculants. This low-carbon operation and long-term stability position it as an alternative to energy-intensive activated sludge or membrane-based systems in resource-limited settings.

农村生活污水治理是农村人居环境整治的主要任务、实施乡村振兴战略的重要举措，也是新时期深入开展农业农村污染治理的关键所在。本文梳理了我国农村生活污水治理在法规条例与标准完善、治理规模、技术提升、环保教育等方面的成效，分析了农村生活污水治理在能力、技术、标准、运行维护方面存在的问题；针对性提出了因地制宜、资源利用、经济简便、科学规划等治理方针，治理模式、技术工艺、资源利用、运行机制等工作要点，污染治理全系统、作用主体全联动的实施路径。研究建议，落实农村生活污水中氮和磷灌溉回用理念，科学制定排放标准；按照经济可行原则，推进农村污水生态与简便处理；完善市场机制，推动农村污水处理专业化托管运行。在国家层面的政策引导下，扎实推进农村生活污水综合治理工作，支持实现“美丽乡村”建设目标。

农村生活污水处理关系到人民生活质量、环境保护与可持续发展。由于农村生活污水具有的特点和农村区域条件,农村生活污水处理遇到诸多挑战。为解决其面临的问题,研发了提高农村生活污水处理效率的新工艺、新技术,改良了传统处理工艺的组成、结构和操作条件,实现了污染物的高效去除。通过使用新功能型材料、采取多种水处理技术杂化,显著降低了农村生活污水处理后尾水中氮磷、新兴污染物对生态环境的威胁。农村生活污水处理的低碳化、智慧化降低了人力成本、运行成本和管理成本,保证了出水水质。虽然目前农村生活污水处理取得了较好进展,但仍存在不足和继续研究的方向。

传统人工湿地（CWs）面临着氧传递效率低而引起的电子受体不足问题,导致还原性的有机物及氨氮的去除受到严重限制。以陶粒与细砂为滤层、芦苇为附着植物,并利用光伏发电系统驱动功能电极,构建生物电化学-人工湿地系统（BES-CWs）。研究BESs强化CWs系统对农村分散式生活污水的去除效果。结果表明,BES-CWs稳定运行后,相对于传统人工湿地,对生活污水中的COD、NH₄⁺-N、TN和TP去除率分别提高了2.64%、27.71%、31.01%和5.48%,污染物去除效果得到明显提升,处理后水质可以达到甘肃省农村污水排放标准（DB62/T 4014–2019）一级标准。BES-CWs中功能电极有效地提高了系统内的电子迁移速率,从而为贫电子受体环境下的污染物去除效率提升提供了新途径。

In order to grasp the latest changes in the quality and quantity of domestic sewage in the Taihu Lake Basin and Chaohu Lake Basin, and to scientifically guide the construction of rural sewage treatment demonstration projects, two typical villages were selected from Taihu Lake Basin and Chaohu Lake Basin respectively for fieldwork continuous monitoring of sewage water quality and quantity. The results show that the typical rural per capita daily drainage in the plain area of the Taihu Lake Basin in summer is 89.4 L·cap−1·d−1, which is significantly higher than that in the typical rural area of the Chaohu Lake Basin (56.5 L·cap−1·d−1). The amount of sewage hourly discharge fluctuated distinctly, and the coefficient of variation of sewage discharge in the two villages ranged from 2.4 to 6.1, showing obvious characteristics of “morning and evening peaks” or “morning, noon and evening peaks”. In addition, the rural sewage water quality in the two places shows the same pattern, and the pollutant concentration of sewage from different sources is significantly different. It was found that the toilet-flush sewage in Wangjiatang village provided 84.42% of TN and 92.94% of NH4\n +-N in the total domestic sewage, while toilet-flush sewage in Qianying village provided 74.31% of TN and 84.56% of NH4\n +-N in the total domestic. Therefore, when constructing a sewage treatment demonstration project, the ideological principles of sewage classification and treatment from the source should be considered.

Nitrous oxide (N2O) is a potent and long-lived greenhouse gas that contributes to global warming with a global warming potential (GWP) 298 times that of carbon dioxide (CO2). In this paper, we analyzed the trend of N2O concentration in vertical layers of the stratosphere from 2005 to 2020 using the N2O observed from the Microwave Limb Sounder (MLS) that is on board the Aura satellite. We found that the local N2O concentration showed a downward trend in the lower stratosphere but rose or fluctuated in the upper stratosphere. The reduction reached −5 ppb/yr at pressure levels of 31.62 hPa and 68.13 hPa, with a confidence level of over 90%. The growth was around 1–2 ppb/yr in the upper stratosphere. In addition, a concentration anomaly was observed in the tropical stratosphere in 2013. After the appearance of this anomaly, the N2O concentration in the middle and lower layers of the tropical stratosphere was lower than before 2013. We speculated that the enhancement of the Brewer–Dobson circulation (BDC) upwelling before and after stratospheric sudden warming (SSW) is the main reason for the abnormal concentration distribution in 2013. Stratospheric N2O has changed significantly in the past 16 years with the mutual coupling effect of BDC and SSW and such changes can have further impact on the chemical equilibrium and radiation balance in the stratosphere, as well as on the persistent climate-warming trend.