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This paper addresses the regulation of water quality influencers such as Organic Nitrogen, Ammonia Nitrogen, Nitrate Nitrogen, Dissolved Organic Carbon and Dissolved Oxygen for a sub-surface flow horizontal wetland in a controlled environment. The plant uncertainty is quantified by using measurement data. The robust control of the process is achieved using a decentralized quantitative feedback theory based control strategy. The control structure also employs a feed-forward mechanism to minimize loop interactions and feedback control to ensure stability, tracking and disturbance rejection. The numerical simulations and hardware-in-loop implementation show that the performance specifications are robustly met. • The control of water quality deciding variables by using a constructed wetland • The parametric uncertainty is quantified using measurement data collected • A decentralized quantitative feedback theory based robust controller is adopted • Each loop is equipped with feed-forward controllers to minimize coupling effects • Performance is verified by numerical simulation and hardware-in-Loop validation [ABSTRACT FROM AUTHOR]

Constructed Wetlands (CWs) were widely used as nature-based solution to effectively remove contaminants from wastewater, while offering benefits for ecological value and landscape services. However, one limited factor for practical applications of CW technology is the conventional construction style, which is a laborious and complex civil engineering. As such, an idea of modular CW (MCW) was proposed and embodiment was made for different scales of treatment wetland projects. This paper introduces the MCW concept and the efforts made to realize it. MCW is a revolutionary approach in wastewater treatment that combines efficiency, adaptability, and environmental sustainability. MCW represents a paradigm shift from traditional CWs, offering a pre-fabricated, modular solution that simplifies the complexities of civil engineering in wastewater management. These prefabricated modular structures, assembled off-site and installed on-site, provide a streamlined, flexible, and user-friendly alternative to conventional CWs. The innovative design of MCWs incorporates advanced substrates and technologies, integrating enhanced processes such as intermittent aeration, tidal flow, and circulating reflux. This novel approach significantly improves pollutant removal efficiency, reduces land usage, and addresses clogging issues through rapid module replacement. The paper comprehensively delved into the structural, substrate, plant, and operational aspects of MCWs. It highlights the environmental and economic benefits of MCWs, emphasizing their role as a cost-effective, environmentally-friendly solution for wastewater treatment. The study concludes by underscoring the potential of MCWs in spearheading new research and development in sustainable wastewater management, marking a new generation in CW systems. [Display omitted] • The novel concept of MCWs was firstly and comprehensively introduced. • Plastic modules were designed & made to allow quickly and flexibly assembling MCW. • Systematical strategies were applied to enhance the MCW treatment effectiveness. • Design factors were given for future design and management of MCWs. [ABSTRACT FROM AUTHOR]

Environment-friendly and cost-effective disposal and reutilization of sludge wastes are essential during the wastewater treatment process. Converting sludge wastes into ceramsite by sintering treatment is a promising strategy for sludge treatment. This paper summarizes existing processes and technologies for regenerating ceramsite from sludge wastes. The synthesis process including raw material pretreatment, sludge characteristics analysis, batching, mixing and molding, drying and preheating, sintering and cooling is discussed. Then, the effects of additives, sintering temperature and time, and sludge content on the preparation and properties of sludge-based ceramsite are summarized. Integrating mechanistic insights and different physicochemical properties highlighted the understanding of the different applications (environmental remediation and architecture ingredients) of sludge-based ceramsite. High-temperature sintering sludge-based ceramsite exhibited excellent performance for the removal of contaminants due to the high porosity, large surface area, and good biocompatibility. Besides, the sludge-based ceramsite could also be used as concrete aggregate and asphalt mixtures due to its high strength, thermal insulation, and seismic resistance. Finally, the challenges and proposals for sludge-based ceramsite are proposed. This paper can provide a theoretical basis and guidance for the preparation and application of sludge-based ceramsite. [Display omitted] • Sludge-derived ceramsite can be used as support material for biofilters. • Sludge-derived ceramsite can be applied as medium filler for constructed wetland. • Sludge-derived ceramsite as adsorbents can effectively remove heavy metals. • Sludge-derived ceramsite has three main roles as a bulking agent in composting. • Sludge-derived ceramsite can also be utilized in concrete and asphalt mixtures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Constructed wetlands have great potential in removing microplastics from sewage. • Key factors of microplastic removal by constructed wetlands are discussed. • How to remove fixed microplastics in wetlands is still a question worth considering. • Constructed wetland may be a vital source of microplastics and ARGs in natural water. • Measures related to optimizing the process are proposed. The persistent presence of microplastics in freshwater environments has posed a threat to the ecological environment and human health. How to remove microplastics from aquatic environments is currently a research focus. Constructed wetlands are alternative facilities for wastewater treatment and have been utilized for the removal of microplastics in wastewater. The primary mechanism for removing microplastics in constructed wetlands is through physical interception, which involves the use of plant roots, substrates, and biofilms on the substrates. However, there is still limited research on the migration and transformation of microplastics in constructed wetlands. The coupling of microplastics and pollutants makes constructed wetlands become a fixed emission source of these pollutants in the natural water environment. Due to limited research on microplastic removal in constructed wetlands, further exploration is needed on the removal mechanism and potential environmental risks. How to remove fixed microplastics by constructed wetlands is still a question worth considering, and there is still a huge knowledge gap in this area. This paper reviews the removal of microplastics by constructed wetland systems. A detailed analysis was conducted on the removal performance and key influencing factors of microplastics from multiple aspects such as wetland plants, wetland substrates, wetland microorganisms, and animals. The impact of microplastic accumulation in constructed wetlands on plants, animals, microorganisms, and carbon and nitrogen conversion was thoroughly discussed. In addition, some challenges and prospects have been raised. This paper provides a theoretical basis for microplastic removal and a new perspective to reveal the potential impact of microorganisms and new pollutants on constructed wetlands. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen removal performance in CWs is affected by MPs/NPs. • MPs/NPs affect nitrogen-transforming microorganisms in CWs. • The toxicity of MPs/NPs can impair the ability of wetland plants to remove nitrogen. • Combined pollution caused by MPs/NPs affects nitrogen removal performance. The occurrence of microplastics (MPs) and nanoplastics (NPs) in the ecosystem has received widespread attention, with research showing that their impact differs from that of conventional pollutants due to the complexity of their effect mechanisms. Constructed wetlands (CWs) as an effective wastewater treatment system using plants, substrates and biofilms can remove MPs/NPs from water bodies. MPs/NPs retained within the systems may have an impact on microorganisms, plants and other aspects of the ecological environment, thus affecting the nitrogen removal performance of CWs. Furthermore, the large specific surface area and abundant adsorption sites of MPs/NPs can result in their adsorption of coexisting environmental pollutants, heightening the potential risks posed by MPs/NPs to the ecological CWs environment. Recent studies have investigated the potential impacts of MPs/NPs on microorganisms and plants in the aquatic environments and in the soil. However, the interrelationships between MPs/NPs, microorganisms and plants in CWs and their ultimate impact on nitrogen removal are not fully understood. Therefore, it is necessary to summarize the current research progress. This review evaluates the effects of MPs/NPs and MPs/NPs carrying environmental pollutants on the nitrogen-transforming microorganisms and plant growth in CWs. The effects of changes in nitrogen-transforming microbial communities and plant growth on nitrogen removal in CWs were analyzed. This paper aims to propose practical suggestions and directions for future research on CWs and their relationship with MPs/NPs by reviewing the mechanism of influence of MPs/NPs on microbial and plant nitrogen removal in CWs. [ABSTRACT FROM AUTHOR]

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants (POPs) that pose significant environmental and human health risks. The presence of PFAS in landfill leachate is becoming an increasingly concerning issue. This article presents a comprehensive review of current knowledge and research gaps in monitoring and removing PFAS from landfill leachate. The focus is on evaluating the effectiveness and sustainability of existing removal technologies, and identifying areas where further research is needed. To achieve this goal, the paper examines the existing technologies for monitoring and treating PFAS in landfill leachate. The review emphasizes the importance of sample preparation techniques and quality assurance/quality control measures in ensuring accurate and reliable results. Then, this paper reviewed the existing technologies for removal and remediation of PFAS in landfill leachates, such as adsorption, membrane filtration, photocatalytic oxidation, electrocatalysis, biodegradation, and constructed wetlands. Additionally, the paper summarizes the factors that exhibit the performance of various treatment technologies: reaction time, experimental conditions, and removal rates. Furthermore, the paper evaluates the potential application of different remediation technologies (i.e., adsorption, membrane filtration, photocatalytic oxidation, electrocatalysis, biodegradation, and constructed wetlands, etc.) in treating landfill leachate containing PFAS and its precursors, such as fluorotelomeres like FTOH and FTSs. The review highlights the importance of considering economic, technical, and environmental factors when selecting control measures. Overall, this article aims to provide guidance for promoting environmental protection and sustainable development in the context of PFAS contamination in landfill leachate. [Display omitted] • Critical review of various treatment techniques for PFAS removal in landfill leachates. • In-depth discussion on the mechanism of PFAS removal by different techniques. • View of various in-situ treatments for PFAS degradation. • Nowadays, the number of PFAS treatment is still very limited. • Future scope for the advancement of research in PFAS treatments is discussed. [ABSTRACT FROM AUTHOR]

Small-scale experiments have been conducted to investigate a wide range of factors suspected to influence treatment wetland (TW) functions and efficiency. One crucial advantage microcosms and mesocosms offer over field-scale systems is that they enable reproduction of experimental treatment units that are as similar as possible, only varying the factor(s) of interest. The goal of this paper is to discuss key methodological issues to consider, as well as the overall potential and limitations of using small-scale experiments as applied specifically to TW research. Planning a successful small-scale experiment to address a scientific question in TW science involves several key decisions to reach the project's goal. Due to financial, space or resources constraints, it is fundamental at the planning stage to carefully determine a suitable compromise between unit size, number of units, number of treatments (both in terms of number of variables and number of levels within each variable) and replication. Producing, properly storing and rigorously distributing the same volume or flow rate of wastewater to each unit is often the most challenging and time-consuming aspect of a small-scale TW experiment. Unavoidable sources of bias inherent in small-scale models must be identified, and when possible, minimized. Small-scale experiments for treatment wetlands can only take on full meaning when the insights obtained through them inform full-scale operations. • Small-scale experiments are essential in investigating mechanisms in treatment wetlands. • Compromise is inevitable between unit size, number of units, number of treatments and replication. • Proper wastewater management and distribution is often the greatest experimental challenge. • Possible biases must be considered before the results can be applied to full-scale systems. [ABSTRACT FROM AUTHOR]

In this work, the practical utility of constructed wetlands (CWs) is described as a promising treatment option for micropollutants (MPs) in wastewater with the aid of their eco-friendly, low-energy, economically feasible, and ecologically sustainable nature. This paper offers a comprehensive review on CW technology with respect to the key strategies for MP removal such as phytoremediation, substrate adsorption, and microbial degradation. It explores the important factors controlling the performance of CWs (e.g., in terms of configurations, substrates, plant-microbe interactions, temperature, pH, oxygen levels, hydraulic loading rate, and retention time) along with the discussions on the pivotal role of microbial populations in CWs and plant-microbe cooperative remediation dynamics, particularly in relation to diverse organic MP patterns in CWs. As such, this review aims to provide valuable insights into the key strategies for optimizing MP treatment and for enhancing the efficacy of CW systems. In addition, the process-based models of constructed wetlands along with the numerical simulations based on the artificial neural network (ANN) method are also described in association with the data exploratory techniques. This work is thus expected to help open up new possibilities for the application of plant-microbe cooperative remediation approaches against diverse patterns of organic MPs present in CWs. [Display omitted] • Performance of different CWs is evaluated for micropollutant removal. • Mechanistic insights of the micropollutant removal are offered in relation to plant and microbe CWs. • Factors affecting the removal efficiency of constructed wetlands are discussed. • Strategies are reviewed for optimizing MP treatment and for enhancing the CW efficiency. [ABSTRACT FROM AUTHOR]

Upgrading treated wastewater systems can provide reclaimed water for different uses. In this paper, the potential for wetland creation and maintenance is evaluated. The upgrading treatment consists of intensified vertical flow constructed wetlands (VFCWs), where the physicochemical and microbiological water quality is improved, followed by free-water surface constructed wetlands (FWSCWs), where biodiversity is enhanced. This renaturalization system has been implemented in two wastewater treatment plants (WWTPs): Monasterios, where one VFCW 60 m2 and two FWSCWs (50 m2 each) have been built, and Carricola, where two VFCWs in series (20 m2 each) have been constructed. The VFCWs were filled with drinking water treatment sludge (DWTS), a waste produced in drinking water treatment plants, hence the circularity of the project. Data obtained during the first year of operation is presented. The mean hydraulic loading rates in the VFCWs were 0.79 and 0.62 m/d in Monasterios and Carricola, respectively. In FWSCWs, the HLRs were 0.35 and 0.32 m/d in FWSCW1, which receives the effluent of the VFCW, and FWSCW2, which receives the secondary treatment effluent, respectively. In the VFCWs, an important reduction of total phosphorus was achieved, 77% in Monasterios and 70% in Carricola, and other pollutants were fairly reduced as well. In FWSCWs, some pollutants, such as total nitrogen or phosphorus, were reduced, but other, such as total suspended solids or organic matter, increased due to algae growth and external inputs. The critical point is that biodiversity is increased thanks to these systems, aquatic invertebrate presented better diversity indexes in the FWSCW receiving the upgraded water from the intensified VFCW. Birds, amphibians, and reptiles have also colonised the created habitats. • Treated wastewater can be upgraded by intensified vertical flow constructed wetlands. • Drinking water treatment sludge is an appropriate adsorbent material. • Valorisation of drinking water treatment sludge integrates circularity in urban water cycle. • Upgraded water benefits the receiving water bodies, enhancing biodiversity. • Birds use the created wetlands to feed, rest and nest. [ABSTRACT FROM AUTHOR]

This special issue of Ecological Engineering provides an overview of research within the Everglades Stormwater Treatment Areas (STAs) over the past decade to understand the ecology and the biogeochemical processes that affect phosphorus (P) retention in these constructed wetlands. This research was established within the South Florida Water Management District's Restoration Strategies Science Plan (RSSP). The RSSP was developed in 2012, updated in 2018, and produced a total of 21 studies. The goal of RSSP research is improve understanding of the factors contributing to P retention, to support management of the STAs to attain and sustain a stringent outflow total P concentration goal (i.e., the Water Quality Based Effluent Limit or WQBEL) and to maintain the wetland plant communities used to achieve this goal. Compliance with the WQBEL will reduce P loads to the Everglades to support restore and maintain this special ecosystem. This synthesis paper presents an overview of the STAs and their purpose and then summarizes the findings from the publications included in this special issue as well as previous STA related research. From this synthesis, a list of potential management options to enhance P retention in the STAs is presented. • Stormwater Treatment Areas (STAs) built to reduce P in runoff entering the Everglades. • STA discharge must meet strict low P concentration limits. • P biogeochemistry research conducted to support management of the STAs. • P removed by particle settling, biogeochemical processes and plant uptake. • Fauna excretion, bioturbation, and internal loads substantially affect P retention. [ABSTRACT FROM AUTHOR]

Managed treatment wetlands technology is now used around the world to treat wastewater and stormwater by removing nutrients and other contaminants to obtain a desired water quality. In this paper we present a brief review of a large-scale application of the nature-based technology known as stormwater treatment areas (STAs). These STAs were constructed to treat agricultural and urban runoff to reduce outflow total phosphorus (TP) concentrations to <20 μg P L−1, which is required to protect downstream water quality and preserve the remaining Everglades ecosystem. Five STAs with a total area of approximately 25,000 ha were built at strategic locations to reduce TP loads to the Everglades Protection Area. For the past three decades, these Everglades STAs have done remarkable job by 70 to 85% TP load reduction, with an average outflow TP concentrations of 15-40 μg P L−1. In this Everglades STAs special issue, we present research findings on the influence of both external and internal drivers influencing STA performance and potential adaptive management strategies to enhance treatment efficiency to further reduce outflow TP concentrations. • Introduction of the Everglades STAs – largest constructed treatment wetland network in the world. • Everglades STAs serve as 'kidneys' of the Everglades ecosystem by reducing phosphorus loads to downstream waterbodies. • Phosphorus loading is one of the key drivers regulating treatment efficiency STAs. [ABSTRACT FROM AUTHOR]

Lake Manzala is considered as an ecosystem of extreme importance to man and biodiversity. This article presents an overview on the different changes of Lake Manzala in terms of plant distribution, diversity, area of vegetation cover, in addition to the benefits and uses offered by such plants. Eleven aquatic macrophyte species dominated by Potamogeton pectinatus, Eichhornia crassipes, Pistia stratiotes, Phragmites australis , Typha domingensis and Echinochloa stagnina , were recorded in the Lake. As a result of climatic changes and human impacts, this Lake faced many environmental problems and intensive pressure that resulted in changing its ecological features, including the decrease in both bare lands (from 52.45 to 45.50%) and water bodies (from 28.19 to 19.32%), as well as the increase in the vegetation cover (from 19.36 to 35.18%) throughout the period from 1992 to 2019. After the beginning of the Egyptian government's development process at the northern and center sectors of the Lake, the inflow of saline water increased, the concentration of chlorophyll "a" decreased from 4.372 mg m−3 in 2015 to 3.725 mg m−3 in 2018, and water quality showed remarkable enhancement. However, the other parts of Lake Manzala were still suffering from the dense vegetation cover that affected its water quality. Aquatic macrophytes are considered as a massive source of raw material for the industrial production of paper pulp, biofuel and natural therapeutics, beside their effective role in their natural habitat and in the remediation of wastewater. Nevertheless, the rapid growth of macrophytes may cause many environmental problems. The data in this article give decision-makers options for achieving sustainability in future development projects related to Lake Manzala, as well as insights in the assessment and management of pollution in this coastal shallow lagoon. [ABSTRACT FROM AUTHOR]

Bioelectrochemical systems have emerged as efficient and sustainable wastewater treatments. Constructed wetland microbial fuel cell has gained considerable attention for electrogenic bacteria-driven wastewater treatment and electricity generation. Electrogenic bacteria play a pivotal role in constructed wetland microbial fuel cell by converting organic waste into electrons, thereby providing a critical biocatalyst for wastewater treatment and electricity generation. However, understanding their regulation, enrichment, and interactions remains lacking. This paper presents a comprehensive and systematic review of current research advancements in electroactive bacteria, offering valuable insights for further investigation. Through a bibliometric analysis and systematic review, this article presents a study on the factors influencing the role of electroactive bacteria and provides a comprehensive overview of the system removal performance. Finally, suggestions and future research directions for constructed wetland microbial fuel cell are presented. [Display omitted] • Bibliometric analysis identified key factors and trends in CW-MFC system. • The structure and operational parameters influencing EAB are studied. • EAB is vital in the removal of traditional and emerging pollutants in CW-MFC. • Research of interactions among EAB, electrodes, and pollutant removal is required. [ABSTRACT FROM AUTHOR]

[Display omitted] • A water-type classification procedure integrating shape, landscape patterns, topography, and phenology was proposed. • The distribution and transition of various wetlands in the middle and lower reaches of the Yangtze River Basin were mapped. • Nearly half of the wetlands experienced a significant trend of decrease in water inundation frequency from 1990 to 2020. • Farmland reclamation was the primary anthropogenic factor in natural wetland loss and degradation. Wetlands are crucial to diverse societies and ecosystems but are threatened globally. Natural wetlands in the middle and lower reaches of the Yangtze River Basin (MLRYRB) have long been exploited to meet the increasing food and energy demands, especially in recent decades. However, how their landscapes and hydrological patterns changed over time was poorly qualified, which was crucial to conserving biodiversity and ecosystems. In this study, we proposed a new wetland classification procedure taking advantage of the shape, topography, landscape patterns, and phenology to map the distribution of six wetland types in the MLRYRB in 1990 and 2020 with Landsat images. The transitions among different wetland types and associated driving factors were examined. Artificial wetlands expanded by 3907.6 km2 while natural wetlands decreased by 423.2 km2, resulting in a net area increase of 3484.4 km2. Farmland reclamations, aquacultural activities, urban expansion, and dam constructions induced 70 % of the area's loss of natural wetlands. Meanwhile, spatiotemporal patterns in wetland inundation dynamics were determined with agglomerative hierarchical cluster analysis. Widespread transitions from perennial water to seasonal wetlands were detected. Notably, 47.8 % of the natural wetlands experienced significant drying trends, and as a result, the mean yearly inundated periods for natural wetlands decreased from 303 days in 1990 to 272 days in 2020. Given the substantial structural alterations, wetland destruction was more severe than the area reflected. Our results suggested that category-based changes in wetland areas, inundation patterns, associated driving forces, and underlying ecological consequences should be comprehensively assessed to conduct scientific conservation and prevent "paper offsets." [ABSTRACT FROM AUTHOR]

Constructed wetland systems have been used for treating a variety of household and industrial wastewater; they are a wastewater treatment technology that has high economic efficiency and environmental effectiveness, especially for sewage treatment in rural areas. Medium filler plays an important role in wetland sewage treatment processes. By carrying out a problem analysis of the ineffective operation and treatment of traditional wetlands, this paper designs different constructed wetland fillers to treat rural household sewage. Using the same plants, this paper chooses four different fillers, namely maifanite, steel slag, bamboo charcoal and limestone as substrates to build constructed wetland systems, and studies rural household sewage treatment in order to examine their effects on the degradation of pollutants. The results show the removal efficiencies obtain good effect. The theoretical maximum adsorption capacities of all these media are ordered as: maifanite > steel slag > bamboo charcoal > limestone. The effluent water quality meets the first class A standard of the “Discharge standard of pollutants for municipal wastewater treatment plant” (GB18918-2002). The selection of medium has an important significance for the operating results of constructed wetland sewage treatment systems. [ABSTRACT FROM AUTHOR]

Constructed wetlands have been used for wastewater treatment for more than fifty years. Most applications have been designed to treat municipal or domestic wastewater but at present, constructed wetlands are successfully applied to many types of wastewater. The early constructed wetlands applied to industrial wastewaters included those for wastewaters from petrochemical, abattoir, meat processing, dairy and pulp and paper industries. During the 1990s constructed wetlands were also used to treat effluents from textile and wine industries or water from recirculating fish and shrimp aquacultures. The most recent applications include those for brewery or tannery wastewaters as well as olive mills effluents. The survey revealed that both subsurface and surface flow constructed wetlands have been used for treatment of industrial wastewaters. Within subsurface flow constructed wetlands both horizontal and vertical flow systems have been designed. Also, the use of various hybrid constructed wetlands for industrial effluent treatment has been reported in the literature recently. The survey also revealed that industrial wastewaters are treated in constructed wetlands in all continents and this paper includes the information from 138 constructed wetlands in 33 countries worldwide. [ABSTRACT FROM AUTHOR]

Industrialization and overpopulation have polluted aquatic environments with significant impacts on human health and wildlife. The main pollutants in urban sewage are nitrogen, phosphorus, heavy metals and organic pollutants, which need to be treated with sewage, and the use of aquatic plants to purify wastewater has high efficiency and low cost. However, the effectiveness and efficiency of phytoremediation are also affected by temperature, pH, microorganisms and other factors. The use of biochar can reduce the cost of wastewater purification, and the combination of biochar and nanotechnology can improve the efficiency of wastewater purification. Some aquatic plants can enrich pollutants in wastewater, so it can be considered to plant these aquatic plants in constructed wetlands to achieve the effect of purifying wastewater. Biochar treatment technology can purify wastewater with high efficiency and low cost, and can be further applied to constructed wetlands. In this paper, the latest research progress of various pollutants in wastewater purification by aquatic plants is reviewed, and the efficient treatment technology of wastewater by biochar is discussed. It provides theoretical basis for phytoremediation of urban sewage pollution in the future. [Display omitted] • Phytoremediation is low-cost efficient method for urban wastewater purification. • Adsorption effect of plants on different pollutants is different. • Repair effect of multiple plants combined with planting is better. • Synergistic action of microorganism and plant contributes to pollutant remediation. • Combination of biochar and nanotechnology improves pollutant efficiency. [ABSTRACT FROM AUTHOR]

The efficiency of active aeration (AE) of constructed wetlands expressed as the ratio between implied oxygen consumption and oxygen delivered to the system is comprehensively reviewed in this paper. The aeration efficiency appears to be rather low with a mean value of 1.73% and median value of 0.48% of oxygen used in the systems for situations with only partial aerobic degradation of the pollutants. For full aerobic degradation, the mean value of AE is 3.74% but median value is much lower 1.08%. For both cases, the standard deviation is higher than the mean value (4.95% and 10.87% respectively), so there is a lot of variability in the data. For systems with the Forced Bed Aeration the results are more uniform and are close to the literature values given for this system, which is an implication that the proposed methodology might be potentially used for rough estimate of the aeration efficiency. [ABSTRACT FROM AUTHOR]

The widely usage of silver nanoparticles in a range of consumer products inevitably results in its being released to the wastewater. As a result, the potential negative effects associated with AgNPs on wastewater treatment systems need to be assessed to develop the regulatory guidelines. In this paper, the exposure experiment at environmentally relevant concentration (100 μg L−1) were conducted to demonstrate the effects of AgNPs on the pollutant removals in constructed wetlands (CWs) with different plants and the spatial distribution of silver. Before adding AgNPs, the system with Arundo donax (VF2) had the better nitrogen removal than Cyperus alternifolius (VF1). After exposure for about 94 d, the average removal efficiencies of NH 4 +-N significantly reduced by 32.43% and 23.92%, TN of 15.82% and 17.18% and TP of 22.74% and 20.46% in VF1 and VF2, respectively, while the COD removal had no difference. However, presence of 100 μg L−1 AgNPs for about 450 d showed no inhibition effects on nutrient removals in two experimental CWs. Two wetlands showed high removal efficiencies of about 98% on AgNPs, indicating CWs could play a crucial role to control the AgNPs release to environment. It was found that AgNPs mainly accumulated in the soil layer with the Ag content of 0.45–5.96 μg g−1 dry weight in lower soil and 2.84–11.37 μg g−1 dry weight in upper soil. The roots of Cyperus alternifolius absorbed more AgNPs, with higher bioconcentration factors (1.32–1.44) than that of 0.59 in Arundo donax. The differences of translocation factors on leaves and stems in two test plants showed that AgNPs assimilated by roots in Cyperus alternifolius were more easily transferred to the leaves. The obtained results showed that the macrophyte Cyperus alternifolius could be better choice for immobilization of AgNPs. Image 1091766 [ABSTRACT FROM AUTHOR]

Constructed wetlands are an environmentally friendly and economically efficient sewage treatment technology, with fillers playing an important role in treatment processes. However, traditional wetland fillers (e.g. zeolite) are known to be imperfect because of their low adsorption capacity. In this paper, the adsorbent sodium titanate nano fillers (T3-F) was synthesized as an alternative to traditional filler with sodium titanate nanofibers (T3) as the raw material, epoxy adhesive as the adhesive agent and NH 4 HCO 3 as the pore-making agent. The properties of T3-F were characterized by powder X-ray diffraction (XRD), scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), porosity. The effect of different parameters such as pH, co-existing ions, contact time, initial metal ion concentrations and temperature was investigated for heavy metal adsorption. The results showed that the adsorption of heavy metal by T3-F followed the pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacities for Cu2+, Pb2+, Zn2+, Cd2+ were about 1.5–1.98 mmol/g, which were 4–5 times that of zeolite, the traditional commonly used filler. Moreover, T3-F could entrap toxic ions irreversibly and maintain structural stability in the adsorption process, which solved the issue of secondary pollution. In the presence of competing ions, the adsorption efficiency for Pb2+ was not reduced significantly. Adsorption was strongest at high pH. From the results and characterization, an adsorption mechanism was suggested. This study lays a foundation for the practical application of T3-F as a constructed wetland filler in the future. Image 1 • A new constructed wetland fillers was prepared by sodium titanate nanofibers. • Fillers show excellent adsorption ability towards Cu2+, Pb2+, Zn2+, Cd2+ ions. • Adsorption occurs through ion exchange mechanism. • Fillers could entrap toxic ions irreversibly. The filler can effectively adsorb heavy metal ions and permanently trap toxic cations in the fiber. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this paper is the development of a methodology for assessing the iron removal efficiency of passive mine water treatment settling lagoons and reed beds. Previous work in the design and sizing of coal mine drainage lagoons and wetlands has focussed on the use of standard hydraulic residence times or using the 10gm−2 d−1 metric, these criteria have been applied without regard to the fundamental physical and chemical processes controlling iron removal in the system, namely the pH dependent rates of Fe(II) oxidation and physical settling of the particulate Fe(III). In this study field water quality data have been collected from lagoons and reed beds. These data are examined alongside data from the UK Coal Authority database and combined with simple mathematical formulations to provide a framework through which to understand passive treatment schemes from a process-orientated perspective. It is demonstrated that for the sites studied reed beds are more efficient for iron removal. This paper recommends that judgements of iron removal performance should be based on a derived treatment efficiency index (ɛ) and that the modelling approach espoused in this paper should be used when designing passive mine water treatment schemes. [Copyright &y& Elsevier]

Abstract: This paper aims to collect and analyse existing information on different filter media used for phosphorus (P) removal from wastewater in constructed wetlands. The most commonly used materials are categorized as natural materials (considered in 39 papers), industrial byproducts (25 papers) and man-made products (10 papers). A majority of studies on sorbents have been carried out in lab-scale systems as batch experiments, and only very few studies have highlighted results on full-scale systems. Among the great variety of filter media studied, most of materials had a pH level >7 and high Ca (CaO) content. The highest P-removal capacities were reported for various industrial byproducts (up to 420g P kg−1 for some furnace slags), followed by natural materials (maximum 40g P kg−1 for heated opoka) and man-made filter media (maximum 12g P kg−1 for Filtralite). We found a significant positive Spearman Rank Order Correlation between the P retention and CaO and Ca content of filter materials (R 2 =0.51 and 0.43, respectively), whereas the relation of P retention to pH level was weak (R 2 =0.22) but significant. There is probably an optimal level of hydraulic loading rate at which the P removal is the highest. Additional important factors determining the applicability of filter materials in treatment wetlands such as saturation time, availability at a local level, content of heavy metals, and the recyclability of saturated filter media as fertilizer should be taken into consideration. [Copyright &y& Elsevier]

Abstract This paper reports on the development and evaluation of a pilot horizontal subsurface flow constructed wetland (HSSFCW) for removal of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), total nitrogen (TN) and total phosphorus (TP) from primary piggery wastewater. Two locally available plants, Pennisetum clandestinum and Pennisetum purpureum, were planted in two of three cells while the remaining unplanted cell served as the control. Monitoring of the wetland influent and effluent wastewater was carried out every two weeks for 7 months. The study revealed successful treatment of the wastewater by the wetland in terms of BOD, COD, TDS, TN and TP effluent compliance with Nigerian discharge standards. Average removal efficiencies were 66.53, 64.95, and 60.27% for BOD 5 ; 44.85, 41.61 and 36.37% for COD; 63.61, 58.27 and 52.88% for TDS; 62.49, 58.89 and 50.14% for TN and 48.53, 44.91 and 41.27% for TP for the three wetland cells including the control respectively. Planted cells achieved the highest removal efficiency with no significant difference in pollutant removal between the two planted cells indicating their suitability for use as wetland plants. Effluent concentrations were within FEPA discharge limits except TP. The performance of the constructed wetland suggests that HSSFCW could be a suitable alternative technology for on-farm treatment of piggery wastewater in Nigeria. The study has provided a starting point for the use of HSSFCW and gives insight of the potential application of this technology for on- farm pollution control in Nigeria. [ABSTRACT FROM AUTHOR]

Abstract: This paper carried on a series of experiments with coupled vertical subsurface flow constructed wetlands(VSSFCWs) and horizontal subsurface flow constructed wetlands(HSSFCWs) for the nitrogen removal of the high concentration nitrogenous domestic sewage. According to the transformation results of inorganic nitrogen in VSSFCWs and HSSFCWs, the paper analyzed the key factors to influence inorganic nitrogen, and discussed the nitrogen removal effects under the conditions of external carbon source addition. The results show that: First point, the VSSFCWs has more powerful nitrification ability, and HSSFCWs has more powerful denitrification ability. Under the condition of excessive high concentration nitrogen in inlet water, not enough carbon source become the restriction of denitrification in HSSFCWs. Second point, in VSSFCWs, when DO is greater than 1.5mg/L, hydraulic retention time is about 2 days, and ammonia nitrogen concentration in inlet water is less than 80mg/L, the ammonia nitrogen concentration in inlet water can be transformed sufficiently into nitrate nitrogen. And so on, in HSSFCWs, adding external carbon source can cause a lower DO level system, and that is helpful to denitrificate successfully. When TOC(Total Organic Carbon)/TN(Total Nitrogen) in inlet water of HSSFCWs is greater than 2.5, the carbon source for denitrification is sufficiently, and the excessive TOC/TN is not constantly advantageous to increase nitrogen removal efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Horizontal subsurface constructed wetlands (HFCWs) are examples of the use of appropriate technology for the sanitation of small communities. The most common problem of HFCWs is clogging; but the exact mechanisms and consequences of clogging in HFCWs are still unclear. This paper describes the methodology followed to acquire and analyse the available data and knowledge to amend the clogging phenomena in constructed wetlands. This manuscript also presents an attempt to integrate and reuse the information extracted from the literature and real experiences, to contribute to the prevention and solution of clogging problem. The management of this information allowed the proposal of an operation and maintenance protocol for clogging. The paper concludes with some recommendations to improve the performance of HFCW technology. [Copyright &y& Elsevier]

Abstract: The 2nd International Symposium on Wetland Pollutant Dynamics and Control (WETPOL 2007), organised by the Department of Geography of the University of Tartu (Estonia) in co-operation with partners from the Estonian University of Life Sciences (Tartu, Estonia), Ghent University (Belgium), and the UNESCO-IHE (Delft, The Netherlands), was held 16–20 September 2007, in Tartu, Estonia. At this meeting, 140 oral presentations (including 9 keynote speeches) and 70 posters by representatives from 38 countries were presented. About half of the presentations considered purification processes in both semi-natural and constructed wetlands. The editorial paper highlights trends in studying the cycling of nitrogen, phosphorus, carbon, heavy metals, and organic pollutants in wetlands, but also in the modelling of pollutant removal and the functioning of plants in the wetland environment. It also describes the WETPOL 2007 meeting, which served as the source of the selected papers, and briefly explains the main aspects of these papers. [Copyright &y& Elsevier]

Constructed wetlands (CWs) are a promising sustainable water-management measure where hydrology plays a fundamental role as the basic driver of mass and energy. Various designs of CWs exist, and these have unique hydrological characteristics that are distinct from those of natural wetlands. However, there have been few reviews of the hydrology and responses of CWs, such that not enough is known of the possible responses of hydraulic, water quality and biology to changing hydrological conditions, especially for different CWs systems. Thus, this paper commences with a review of the basic features of common CWs and their different hydrological conditions. This is followed by the responses of CWs to the hydraulic parameters hydraulic retention time (HRT), hydraulic loading rate (HLR) and water depth that control the changing hydrological conditions of CWs. It is shown that water quality responses are highly related to HRT and HLR and thus a simple method is proposed to predict the responses to the changes of HRT and HLR through a statistical analysis of previous studies. While water depth and inflow patterns appear to have a greater influence on biological responses and some suitable water depths for different species are summarized from papers. Future researchers should pay more attention to the regional ecohydrological patterns of CWs. Long-term hydrological and biological management of CW systems will require the development of frameworks based on an index system for monitoring the responses of interventions. • Bibliometric analysis of recently CWs study trends • Summary of the responses to hydrological changes • A simple method to predict removal efficiency under hydraulic changes • Recommendations for future CWs management in terms of hydrology [ABSTRACT FROM AUTHOR]

The review paper sis based on the analysis or nearly 700 research papers published during 2019 and the first half of 2020 and indexed by Web of Science under the password "constructed wetlands for wastewater treatment". Out of this number 132 papers dealing with "new" topics such as new wastewaters treated in constructed wetlands (CW), new filtration materials, role of vegetation, floating treatment wetlands, microbiology of CW, greenhouse gas emissions from CWs, sustainability and secondary benefits of CWs. For the deeper analysis the supporting literature from previous periods has been cited. The analysis indicates increasing popularity and diversification of types and tasks of CWs. This supports the need for further research of processes and design-related properties of CWs. The research in full scale CWs and long-term studies are only rare and in order to upgrade the CWs technology, research must be also carried out in the field under full-scale conditions. [Display omitted] • The paper evaluates 131 papers on constructed wetlands research in 2019 and 2020. • Less than 10% of the experiments is done in the full-scale constructed wetlands. • Vegetation may play more important role than expected. • Microbiology is affected by wastewater, filtration substrate, type of the wetland, vegetation. • Floating wetlands are still lacking the design and operational parameters. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports data and models for nitrogen processing for the demonstration-scale Tres Rios, Arizona, wetlands. Four field-scale wetlands of approximately 1ha each were operated under varying conditions at a site west of the City of Phoenix. The water supply was partially nitrified effluent from a City wastewater treatment plant. Total nitrogen was reduced by about 60%, from an inflow concentration between 6mg/L and 8mg/L. Speciation of the inflow was approximately 25% organic nitrogen, 25% ammonium nitrogen and 50% nitrate nitrogen. Typical outflow concentrations were about 1.2mg/L organic, 0.5mg/L ammonium, and 0.0–2.5mg/L nitrate. Two wetlands were reconfigured with channelization parallel to flow, and the other two lost vegetation. This paper compares the before and after performance for both changes. Rate constants for nitrate and total nitrogen were decreased by the changes. For loss of vegetation, nitrate k 20-values decreased from 76m/yr to 23m/yr, and total nitrogen k 20-values decreased from 54m/yr to 11m/yr. For reconfiguration, nitrate k 20-values decreased from 83m/yr to 47m/yr, and total nitrogen k 20-values decreased from 49m/yr to 32m/yr. Rate constants were found to be temperature sensitive. It is concluded that the reconfiguration and loss of vegetation both markedly lessened the ability of the wetlands to process nitrogen. Further, reconfiguration was ineffective for mosquito control. [Copyright &y& Elsevier]

Abstract: The paper proposes an approach to designing the control structure and algorithms for optimising control of integrated wastewater treatment plant-sewer systems (IWWTS) under a full range of disturbance inputs. The optimised control of IWWTS allows for significant cost savings, fulfilling the effluent discharge limits over a long period and maintaining the system in sustainable operation. Due to the specific features of a wastewater system a hierarchical control structure is applied. The functional decomposition leads to three control layers: supervisory, optimising and follow-up. A temporal decomposition that is applied in order to efficiently accommodate the system''s multiple time scales leads to further decomposition of the optimising control layer into three control sublayers: slow, medium, and fast. An extended Kalman Filter is used to carry out an estimation of needed but not measured plant states in real time. The robustly feasible model predictive controller produces manipulated variable trajectories based on a dedicated grey box (GB) model of the biological processes and drawing its physical reality from the well known ASM2d model. The GB model parameters are dependant on the plant operating point and therefore are continuously estimated. As it is impossible to efficiently control the plant under all influent conditions that may occur by using one universal control strategy, different control strategies are designed. Recently developed mechanisms for soft switching between the MPC control strategies are applied in order to smooth the state and control transient processes during the switching. The methodologies and algorithms proposed in the paper are validated by simulation based on real data records from a wastewater system located in Kartuzy, northern Poland. The control system was implemented at the case-study site to generate in real time the control actions that were assessed by the plant operators and verified by simulation based on a calibrated plant model. [Copyright &y& Elsevier]

Abstract: This paper describes the development and operation of an Environmental Decision Support System (EDSS) to improve the operation and maintenance of horizontal subsurface-flow constructed wetlands (EDSS-maintenance). Constructed wetlands (CWs) allow wastewater treatment in a sustainable manner since they involve low energy consumption, low construction and functioning costs and low environmental impact. However, operation and maintenance activities are essential to guarantee reliability in CWs performance. The definition of operation and maintenance protocols depends on several quantitative and qualitative aspects such as wastewater treatment plant configuration, CW design, influent characteristics, sensitivity of the receiving media, etc. Bearing this in mind and considering the limited technical knowledge about CWs, the need for a new tool to support CW performance is clear. In this sense, EDSSs offer a new approach because they can tackle problems of complex and uncertain systems. The EDSS-maintenance provides operation and maintenance manuals specifically defined for every CW. To achieve it, the required knowledge was implemented within a rule-based system, which forms the backbone of the EDSS. Several features presented in this paper demonstrate how the EDSS-maintenance provides a proper platform to support the necessary collaborative work in the ecological engineering problem of horizontal subsurface flow CWs operation and maintenance. [Copyright &y& Elsevier]

Constructed wetlands (CWs) for wastewater treatment have been used in the Czech Republic since 1991. Nowadays, there are about 200 full-scale constructed wetlands for treatment of municipal sewage. Most CWS have been designed with horizontal subsurface flow, in the late 2010s and early 2020s, combination of vertical and horizontal flow or two-stage vertical flow CWs have been used. The average number of designed PE is 235 and the average surface area of the Czech CWs is 1132 m2. The average treatment efficiencies are 87.5% for BOD 5 , 78.5% for COD, 85.7% for TSS, 41.8% for N-NH 4 and 41% for TP. The respective average outflow concentrations are (in mg l−1): 12.5, 48.5, 11.2, 16.6 and 3.35. The results from the oldest CWS in the Czech Republic revealed very consistent performance over the period of 30+ years with no refurbishment. The paper also provides information about two CWs which were refurbished after about twenty years of operation from horizontal subsurface flow to hybrid systems. In both CWs, the refurbishment was successful and the treatment efficiency increased. • Constructed wetlands have been used for wastewater treatment in the Czech Republic since 1991. • Most CWs were designed with horizontal subsurface flow. • Treatment efficiency can be consistent for >30 years. • During refurbishment CWs are usually converted into hybrid systems. [ABSTRACT FROM AUTHOR]

Abstract Constructed wetlands (CWs) is an effective way to removal nitrogen (N) from swine wastewater, which accompanying with the process of ammonia (NH 3) volatilization. However, the removal pathway of NH 3 volatilization has adverse impacts on the natural biogeochemical cycle of N. Here, this paper presents the first attempt to investigate the potential use of clinoptilolite in reducing NH 3 volatilization in integrated vertical-flow constructed wetlands (IVCWs) treating swine wastewater. The NH 3 volatilization flux was measured via steady-state chambers. Results showed that the removal rate of TAN (total ammonia nitrogen, NH 3 and NH 4 +-N) in clinoptilolite system was 96.1%, where 93.01% of that was removed by substrate adsorption, it was significantly higher (p < 0.05) than that in quartz sand system (29.6%). Moreover, the microporous structure of zeolite is not conducive for the growth of denitrifying microorganisms. The NH 3 volatilization flux covered a range of 0.02–3.00 mg N m−2 h−1, which was lower than the reported date. Furthermore, the proportion of NH 3 volatilization in Clite was 0.99%, which was obviously lower (p < 0.05) than that in control (9.01%), and the ammonia volatilization quantities decreased by 180.7% in this study. Results suggest that clinoptilolite plays an important role in reducing NH 3 volatilization to the atmosphere. [ABSTRACT FROM AUTHOR]

Highlights • This paper includes water quality and hydrologic data collected before, during, and immediately after several storm events in Florida including Hurricane Irma in September 2017. • This is the first time a treatment wetland has been monitored for nutrients before, during, and after a hurricane. • The hurricane measurements showed shortcomings in the design of the wetland in accommodating hurricane-caused urban runoff. Abstract Understanding the hydrology of a created or restored wetland is a critical component in understanding the overall functioning of its design, and in determining if the original goals of the wetland are being met. Freedom Park, a 20-ha park constructed in Naples, Florida in 2009, includes a 4.6-ha subtropical stormwater wetland treatment system for improving the water quality of the downstream impaired Gordon River and estuaries that flow into the Gulf of Mexico. Subtropical wetlands often present significant issues of sustaining viable wetland vegetation communities because of long wet and then long dry patterns in the wetlands’ hydroperiods. The treatment wetland’s watershed includes 1766 ha of an urbanized Naples metro area. The goals of the stormwater wetlands are to improve the water quality, reduce peak flows discharging into Gordon River and further to Naples Bay, and provide an aesthetic water park for the public. A monthly hydrologic budget for the period August 1, 2016 to January 31, 2018 showed the following averages: pumped surface water inflow of 50.1 cm week−1; average surface outflow of 38.8 cm week−1; precipitation of 3.76 cm week−1, potential evapotranspiration (PET) of 5.34 cm week−1; and estimated seepage of 14.8 cm week−1. During the wet season, water pathways are largely influenced by pumped surface inflow and surface outflow, balanced to not produce significant changes in water level from month to month. Groundwater seepage and evapotranspiration are the most important outflows during the dry season. A stormwater pulsing study during Hurricane Irma (September 10, 2017) showed that after an initial inflow flush due primarily to rainfall, total phosphorus and total nitrogen concentrations were higher at the outflow than at the inflow for several days during and immediately after the hurricane. Similarly, the mass of nutrients leaving the system was 130% and 37% higher for TN and TP, respectively, than the mass entering the system during this 6-day period during and immediately after the hurricane. Ironically, the design of the pump-only inflow did not allow for major urban runoff during the hurricane to enter the wetlands. Samples taken at the inflow and outflow of the system for four other storm events throughout the 2017 wet season (July through October) were also analyzed for their effects on water quality. While total phosphorus removal during and after storm events is comparable to normal conditions at the Freedom Park wetlands and other stormwater treatment wetlands in the world, total nitrogen removal decreased during and after storm events. [ABSTRACT FROM AUTHOR]

Introducing of earthworms to constructed wetlands (CWs) has been considered as a new approach to solve the clogging problems in the long-established systems. Despite its potential advantage, the correlational researches are still in the stage of preliminary observation and speculation. This paper presents a comprehensive and in-depth research about the positive effects of earthworms ( Eisenia foetida ) on clog matter (CM) reduction through different pathways, including in vivo metabolism and uptake, conversion, transport, and promotion of microorganism quantities. The results showed that the metabolism and uptake by Eisenia foetida could effectively reduce the CM content at an average removal rate of 0.155 mg g −1  d −1 , which was obviously higher than the rate of CM decomposition by microorganisms alone. Through the metabolism of earthworms, the amounts of proteins and polysaccharides in CM were decreased, while the amounts of humin and nucleic acids were increased. Simultaneously, the viscosity of CM was reduced by 0.0082 mPa s g −1 d −1 , and the quantity of microorganisms was increased by 0.0109 mg g −1  d −1 , which finally made the treated CM can be easily washed away and decomposed. Furthermore, earthworms could reduce the CM content in the clogging layer by transporting the metabolic products out. A regression model was further performed for describing the interaction between earthworm and CM. The simulated value of porosity fitted well with the measured one, suggesting that the earthworms can increase the substrate porosity at a rate of 0.33 mL g −1  d −1 . This study quantitively depicted the mechanisms of earthworms on the decrement of CM content in CWs, which is of great benefit for the engineering management of constructed wetlands in the future. We also proposed that the density of introduced earthworms should exceed a certain threshold for effectively increasing the substrate porosity and solving the clogging problems. [ABSTRACT FROM AUTHOR]

This paper presents two powerful and productive models, called VART-TP model and VART-NH4 model, for simulating the removal processes of total phosphorus (TP) and ammonium (NH 4 + ), respectively, in constructed wetlands with free water surface (FWS). A distinctive feature of the models is the incorporation of a dynamic diffusion-dominated root-zone. The VART-TP model was tested with data collected from four small test cells of constructed wetlands (TCW) planted with submerged aquatic vegetations in south Florida, USA. The test cells were divided into two groups with the north test cells (N1 & N15) receiving an average phosphorus (TP) concentration of 71 μg/l and the south test cells receiving an average TP concentration of 27 μg/l. Testing results showed that root mean square error (RMSE) of the VART-TP model varied in the range of 4.45-17.50 μg TP/l., respectively, for north test cells while the RMSE ranged between 3.58-7.63 μg TP/l for south test cells. The result suggested that (1) the N1 and N15 test cells receiving high TP concentrations are capable of removing TP with high efficiency and (2) the VART-TP model is capable of simulating the removal processes of TP. The VART-NH4 model was tested with data collected from Lake Manzala Engineered Wetland (LMEW), Egypt, which generally received the influent of high ammonia concentration (average = 2.26 mg NH 4 /l). The testing results showed that the NH 4 + concentrations simulated with the VART-NH 4 model were in reasonable agreement with those monitored at the wetland outlet, as indicated with the RMSE of 0.06 mg/l. The results demonstrated that the VART-TP and VART-NH4 models are reliable and efficient modeling tools for designing constructed wetlands. [ABSTRACT FROM AUTHOR]

Constructed wetlands (CW) are a promising treatment technology for decentralized rural sewage. However, the pollutant removal efficiency of CW is low due to the limitation of DO concentration. In this study, a falling water enhanced tidal flow constructed wetlands (F-TFCW) was constructed to solve the problems of insufficient oxygen supply and low pollutant removal efficiency in CW. In this regard, the effects of falling water reoxygenation, tidal operation, and flood rest ratio (F/R) on the pollutant removal performance of F-TFCW were examined. Also, the pollutant removal mechanism of F-TFCW was revealed through microbial analysis and biochar XPS characterization. The results showed that the COD, NH 4 +-N, and TP removal rates of F-TFCW were 99.50 ± 0.21%, 87.16 ± 1.76%, and 88.43 ± 1.35%, respectively, when the F/R was 3:1. The falling water inflow and tidal operation significantly improved the reaeration influence of the constructed wetland. The microbial community analysis represented that the dominant bacteria of the F-TFCW could degrade organic compounds or adapt to tidal flow operation. The tidal operation remarkably changed the core microorganisms of the artificial wetland. In the flood phase of F-TFCW, the COD removal relied mainly on aerobic degradation and the biochar adsorption process. In the experimental step, the microbes degraded the organic matter adsorbed by biochar, which enabled a certain degree of biochar regeneration. This paper provided a new idea to enhance the pollutant treatment efficiency for constructed wetlands. [Display omitted] • The removal rates of COD, NH 4 +-N and TP of F-TFCW were 99.50 ± 0.21%, 87.16 ± 1.76% and 88.43 ± 1.35% respectively. • The fall water intake can effectively reoxygenate the constructed wetlands. • Tidal flows can significantly alter the core species of microbial communities. • RelYing on in-situ regeneration of biochar, F-TFCW can efficiently remove high concentrations of organic matter. [ABSTRACT FROM AUTHOR]

An understanding of the seasonal variation in the standing stock of metals and nutrients in emergent vegetation of constructed wetlands (CWs), as well as the amounts present in aboveground (AG) and belowground (BG) biomass, is crucial to their design and management. Given that biomass harvesting is a labour and time consuming operation, a paucity of information currently exists on accumulation and standing stocks in biomass in CWs, in particular in North Western European countries. To address this knowledge gap, this paper examined the seasonal variations of metals and nutrients in Phragmites australis (Cav.) Trin. ex Steudel in a CW treating municipal wastewater, with a view to identifying an optimal time for biomass harvesting of the AG vegetation. Although the AG biomass was greatest in August (1636 ± 507 g m −2 ), the maximum concentrations and accumulations of metals and nutrients occurred at different times throughout the duration of the study (April to November). Furthermore, with the exception of zinc and nitrogen, metals and nutrients measured in BG biomass ranged from 66% (phosphorus) to greater than 80% (nickel and chromium) of the AG biomass. This indicates that analysis of only the emergent shoots may significantly underestimate the metal and nutrient uptake and capacity of the plant. In order to effectively target the bulk of metals and nutrients, an AG harvest in late August or September is suggested. [ABSTRACT FROM AUTHOR]

In the context of subsurface drainage, the mitigation of agricultural pollutants means intercepting water flows using green infrastructures such as constructed wetlands (CWs). First, based on a scientific review, this paper analyses how efficiently CWs can remove nitrate and pesticides from the runoff in drained agricultural watersheds. Average efficiency ranges from 20 to 90% and from 40 to 90% for pesticides and nitrate respectively. The main processes involved are based on microbiological activities, for which hydraulic residence time is a key factor. In order to successful implementation of such a wetland system, hydrological diagnosis of water flow and pollutant transfer at different watershed scales should be provided. Typically, the transport and transformation of pollutants shows clear seasonality depending on the application of nitrate (throughout the whole year) and pesticides (only after application periods). We suggest two interception strategies based on field experiments. The “on-stream” strategy means the establishment of free water surface (FWS) CWs directly on streams/ditches and the interception of all drainage flows: a solution suitable for nitrate removal. The “off-stream” strategy requires the establishment of CWs outside of streams/ditches, whereas interception targets only the most polluted water flow, for instance during the period after pesticide application, requiring farmer's involvement. Suggestions are also made for FWS CW design (a geotechnical survey, topography constraints, etc.) respecting ecological engineering concepts. A following size range is proposed: 76 m 3 per drained hectare, equivalent to 1% of the upstream area, given a maximum water depth of 0.8 m. Nevertheless, CWs must be considered as a complementary tool dedicated to transfer reduction, and as part of broader actions aimed at reducing pollutant loading at the plot scale. [ABSTRACT FROM AUTHOR]

In a great number of scientific articles on water quality improvement using constructed wetlands (CW) and riparian buffers zones (RBZ) at catchment scale, contradictory results are found. In most cases this is due to underestimating or even ignoring the role of the hydrological factor for water quality improvement. It has often resulted in biased estimates of buffering systems’ efficiency at catchment scale and, consequently, has caused planning and establishment failures, mistakes and inconsistencies in legislative acts and finally, it has influenced stakeholder’s willingness to support these eco-technological measures. In this paper we present a short but critical overview of the potential of CWs and RBZs in water quality improvement at catchment scale and highlight the most important aspects to be considered when planning, establishing and managing these systems. [ABSTRACT FROM AUTHOR]

Resource efficiency in wastewater treatment (WWT) is widely needed, not least in developing areas. Natural, less capital intensive processes in wastewater purification may offer developing economies an alternative to traditional biological processes. In this paper, we compare a constructed wetland (CW) based wastewater treatment plant to an activated sludge process (ASP) in Matamoros, Mexico. Greenhouse gas (GHG) emissions are calculated using life cycle assessment (LCA) and an economic viability assessment is carried out. Based on a literature review, both treatment methods are considered to produce sufficient treatment efficiency. Water hyacinth was chosen as the aquatic plant in the CW due to its fast growth rate and the possibility of using it in anaerobic digestion (AD) to produce energy and fertiliser for agricultural land. In our calculations, the biogas produced from the water hyacinth biomass is the decisive factor when the two methods are compared. Direct GHG emissions from both methods are of the same order and are dominated by the GHG releases from the purification phase. However, if the water hyacinth can be used for energy production, the CW-based WWT not only fares better in economic terms, but also produces significant net climate benefits. Both methods studied have their downsides, increasing the need for risk evaluation. Although water hyacinth’s fast growth rate is a crucial factor in the analysis, careful management is needed when cultivating the plant, as it has led to serious problems due to uncontrollable spreading. Furthermore, environmental and health risks must be identified and managed properly if wastewater-derived digestate is to be used on arable land, as assumed in the analysis. Additionally, N 2 O leakages from the ASP and CH 4 and N 2 O releases from the CW must be studied further to obtain reliable values for future analyses. [ABSTRACT FROM AUTHOR]

Reed bed systems (RBS) represent an innovative and ecologically sound treatment method for the stabilization of sludge from wastewater treatment plants (WWTPs), which is also able to provide several ancillary ecosystem services. In this study, the performance of sludge stabilization achieved during the operation of an RBS for the stabilization of excess sludge extracted from a WWTP located in Central Italy (“La Fontina” WWTP, 15,000 p.e.) was studied. In order to evaluate the process of sludge stabilization, parameters representing the biochemical, chemical and chemico-structural properties of organic sludge matter have been tracked during the entire period of operation (6 years). The main aim of this paper is to monitor the stabilization process of sludge organic matter occurring during the main RBS operational stages (commissioning, operation and resting), in order to derive useful rules and parameters for the formulation of novel guidelines for RBS design and operation. Each singular operational stage was characterized by the predominance of a specific process of organic matter stabilization as follows: 1) During the commissioning phase, the mineralization of fresh organic matter turned out to be the primary process, as highlighted by the values of water soluble carbon (4195 mg C/kg dw) and dehydrogenase activity (25.5 mg INTF/kg dw h) reached at 24 months; 2) During the operating phase, the mineralization of pseudo-stable organic matter proved to prevail over the humification process, as demonstrated by the decrease of toluene (from 27.5% to 22.9%) derived from chemical-structural organic matter characterization performed by the Py-GC technique; 3) During the resting period, humification and sanitation processes became predominant, thus enabling a final safe reuse of stabilized sludge as biosolids for land application, proved by the absence of Escherichia coli and Salmonella , and by the values of polycyclic aromatic hydrocarbons (1.53 mg/kg dw), di-2-ethylhexyl-phthalate (3.63 mg/kg dw), nonyl-phenols (20.9 mg/kg dw), and linear alkyl benzene sulfonates (4.99 mg/kg dw). [ABSTRACT FROM AUTHOR]

In this paper three different residence time distribution modelling methodologies for horizontal subsurface flow constructed wetlands were compared and these were the impulse response, step change derivative and step change integral modelling methodologies. Impulse response and step change tracer studies were conducted on pilot scale horizontal subsurface flow constructed wetlands to generate the concentration-time data to be fed into the impulse response and step change modelling approaches, respectively. For the unplanted reactor, the two step change modelling methodologies suggested the same fluid flow behaviour reflected by almost identical values for the mean residence time ( t ¯ m ) and the same value for the number of stirred tanks in series (N) and Peclet number (Pe). The impulse response modelling approach suggested a 7% higher t ¯ m and a lower degree of dispersion. For the planted system each modelling methodology suggested different fluid flow behaviour. Practical limitations were attempted to be identified for the two types of tracer experiments. The limitations of the experiments could be considered limitations of the modelling methodologies as they depended on the tracer experiments for data generation. We were unable to collect sufficient data on the peak of the impulse response curve for the unplanted reactor and may have affected the impulse response modelling methodology results. Sampling down the length of the reactor revealed that tracer dispersion had an effect of broadening the impulse response curves to the extent that it was almost impossible to identify non-ideal flow behaviour such as short-circuiting. The mathematical techniques employed by each modelling methodology were also critically assessed. We found that varying the size and hence number of subintervals used in Simpson’s 1/3 rule for numerical integration resulted in different values for t ¯ m / τ for each modelling approach. The lower the sensitivity of the modelling methodology the better as choosing a parameter as arbitrary as subinterval size should not have a noticeable effect on reported hydraulic behaviour. For both reactor systems the step change derivative approach was least sensitive to subinterval selection, reporting a 1% and 4% variation in t ¯ m / τ for the planted and unplanted system, respectively whereas t ¯ m / τ determined by the step change integral and impulse response modelling methodologies varied by 10% or more in some cases. We highlighted the differentiation of F(t) to obtain E(t) to be a potential weakness of the step change derivative methodology as it had the capability to amplify background noise which may have affected the calculation of the hydraulic parameters. It was concluded that each modelling methodology had the potential to output a different reactor model for the same reactor and that each approach has its own inherent strengths and weaknesses. The choice of modelling methodology is ultimately dictated by availability of experimental equipment and the designer’s confidence in using each of the respective approaches. [ABSTRACT FROM AUTHOR]

Sludge treatment reed beds (STRBs) are an environmentally friendly technology which provides integrated dewatering and stabilization of sewage sludge. STRBs do not require the use of chemicals to improve the dewatering process. STRB is both, a low-emission and a low-energy-consuming method. After the stabilization process, sludge is characterized by the chemical composition similar to that of humus. The aim of the paper is to present the comprehensive data from Waste Water Treatment Plant (WWTP) in Gniewino (Poland) where the sewage sludge is dewatered and stabilized in a STRB. Research and literature reports indicate that sewage sludge treated in STRB is dewatered, which results in an increase in the dry matter (dm) (from 1.1% to 15.5%) and stabilization due to the decrease in the content of the organic matter (from 71.2% of the dm to 52.4% of the dm). Likewise, thanks to the high concentration of nutrients (TKN concentration − 3.64% of the dm and P concentration − 3.54% of the dm) and the low concentration of heavy metals (below permissible values for the agricultural use) after the time of stabilization, safe and valuable product can be recycled to the environment. Reject water (RW) generated during this process has relatively stable and much better properties in comparison to these which are generated in high technologies for sludge treatment. Thus, recycling the RW from the slugde dewatering in STRB represents a very low internal pollution and should not alert the treatment proceses of wastewater. [ABSTRACT FROM AUTHOR]

Lower space requirement, simple operation and economical aspects as well as landscape integration make decentralized natural sanitation systems necessary in eco-city construction. This paper focuses on water management through natural and alternative solutions in urban and peri-urban areas. Results and efficiency of raw wastewater by decentralized natural systems, intelligent storm water management and reuse of treated water in urban irrigation are discussed. Several full scale examples are presented regarding to their removal efficiency and environmental benefits. Their contribution in climate change mitigation is presented as a necessity in today's eco-city conception. [ABSTRACT FROM AUTHOR]

Environmental management and restoration aim to accelerate the recovery of ecosystems that have been affected by human activities. This paper presents the diagnosis and management proposal for the Valsequillo wetland, Puebla, Mexico. The study site is a natural wetland dominated by water hyacinth (Eichhornia crassipes) which performs a biofiltration process by reducing the pollutant load of the water. To increase the efficiency of the wetland, an annual harvest plan is proposed in this work. However, the ideal amount of biomass to harvest is unknown. In order determine the optimal annual harvest plan, this natural wetland was modeled as if it were a surface flow wetland by using the equations described. A total of 48 surface water samples were collected in three different seasons of the year (dry, rainy, and winter) and 34 water quality physicochemical parameters were measured. Additionally, two water quality indices were determined, namely: Overall Index Pollution (OIP) and Heavy Metal Evaluation Index (HEI) to determine the degree of contamination in different zones of the study area. The model results showed that in order to achieve the desired removal of total phosphorus (TP) or chemical oxygen demand (COD), 274 ha or 306 ha of aquatic plants must be harvested, respectively. The results of the modeling showed that this action will optimize the function of the wetland by improving the removal of total suspended solids (TSS, 6%), total nitrogen (TN, 24%) TP (31%), chemical oxygen demand (COD, 11%) and biochemical oxygen demand (BOD 5 , 101%). • Natural wetlands can be managed as if they were constructed wetlands. • Phosphorus is the criterion parameter to model naturally occurring wetlands. • The Kadlec and Knight (1996) model can describe a naturally occurring wetland. • Naturally occurring wetlands perform water purification. [ABSTRACT FROM AUTHOR]

A Bayesian hierarchical modeling approach is introduced to pool data properly from multiple flow-through wetlands to estimate wetland-specific long-term phosphorus retention capacity. By pooling data from multiple wetlands, we overcome the difficulties in estimating the effectiveness of using constructed and natural wetlands for nutrient reduction. The Bayesian hierarchical modeling approach reduces estimation uncertainty by shrinking wetland-specific estimates towards the overall average of the same quantity from multiple wetlands, facilitating information sharing across sites, thereby reducing the demand on sample sizes from individual wetlands and avoiding several common pitfalls of using large data (i.e., from multiple systems) induced by Simpson's paradox. In this paper, we develop a sequential updating framework to alleviate the computational burden of compiling and modeling data from multiple wetlands. We then demonstrate the sequential updating process to estimate retention capacity of a suite of wetlands in Ohio, USA. A total of four wetlands, representing both natural and constructed wetlands, were used. The estimated total phosphorus retention capacities range less than 0.01 to well over 1 ton per year per system. As wetland restoration initiatives expand around the Laurentian Great Lakes and nationally, this model serves as an important initial step in developing tools to meet nutrient reduction goals and standards. Extending this work, we have developed a publicly accessible on-line open computation platform that can help natural resource specialists better plan for wetland efficacy in the future. [ABSTRACT FROM AUTHOR]

Constructed wetlands have been increasingly used for treatment of secondary wastewater containing various contaminants. This paper presents a Variable Residence Time (VART)-based model, called VART-BOD model, for simulation of BOD removal processes in constructed wetlands with free water surface (FWS). Mathematically, the VART-BOD model describes a free water surface wetland with three vertical layers, including vegetated water column layer, advection-dominated upper root layer, and diffusion-dominated lower root layer. Biogeochemically, the VART-BOD model simulates various BOD removal processses and mechanisms, including monod kinetics of bacterial growth, mass exchange between water column and root layers, advection, dispersion, and diffusion. A unique feature of the VART-BOD model is the incorporation of a dynamic diffusion-dominated root-zone. The VART-BOD model was tested with data collected from two distinct FWS wetlands: Gustine Wetland, USA and Manzala Wetland, Egypt. Testing results showed that the coefficient of determination (r 2 ) and root mean square error (RMSE) values vary in the ranges of 0.73–0.99 and 0.41–8.70 mg/L, respectively, for Gustine Wetland cells while r 2 = 0.98 and RMSE = 0.72 mg/L for Manzala Wetland. The VART-BOD model is a reliable and efficient tool for designing constructed wetlands and for understanding effects of various processes and mechanisms on the treatment efficiency of wastewater in constructed wetlands. [ABSTRACT FROM AUTHOR]

Rainfall runoff contained toxic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and heavy metals. Bioretention systems can effectively remove PAHs and heavy metals from runoff. When PAHs and heavy metals accumulated in the media of bioretention systems, co-contamination occurred. To reveal the response processes of co-contamination in the media micro-ecosystem, bioretention systems were constructed and simulated rainfall tests were carried out to reveal the media micro-ecosystem evolution in the bioretention system under the co-contamination of PAHs and heavy metals. The simulated rainfall tests showed that the bioretention systems with different media had good purification effects with load reduction rates >90% (PAHs) and >40% (heavy metals). The microbial α-diversities in different media decreased by 6.67%–32.27%, and 9.21%–18.69% after the tests. The most dominant species of microorganisms in the media were Proteobacteria (all relative abundances >62%). As a typical PAHs-heavy metal degrading bacteria, the relative abundances of Pseudomonas increased significantly after the tests (both >9%). The co-contamination of PAHs and heavy metals inhibited all enzyme activities. The long-term operation of the bioretention system gradually increased the level of co-contamination in the media, and the stability of the media micro-ecosystem gradually deteriorated. The results of this paper can provide a theoretical basis and technical support for maintaining the operational efficiency of the bioretention system with modified-media and avoiding the risk of potential contamination. [Display omitted] • Bioretention systems showed high efficiency in load reduction of pollutants. • PAHs and heavy metals formed co-contamination in bioretention system media. • The growth of Pseudomonas was promoted in co-contamination conditions. • The co-contamination of PAHs and heavy metals inhibited the enzyme activities. • The "adsorption-adaptation-change-feedback" response processes were revealed. [ABSTRACT FROM AUTHOR]

Ammonia volatilization from wastewaters with a high concentration of ammonium is a serious environmental and health problem. Constructed wetlands (CWs) are widely used for treating wastewater, and plant diversity clearly improves some functions of ecosystem such as nitrogen removal. However, whether plant diversity can affect ammonia volatilization from wastewater is still unknown. In this study, we conducted a microcosm experiment with different plant diversity treatments using four plant species. Results showed that, (1) ammonia volatilization decreased with increasing plant species richness; (2) ammonia volatilization from systems containing Rumex japonicus was lower than other systems; and (3) ammonia volatilization was affected more by species composition than species richness. This paper is the first to report that ammonia volatilization is reduced by plant diversity, and that some plant species combinations are important to reduce ammonia volatilization from CWs when treating wastewater. [ABSTRACT FROM AUTHOR]