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Special Issue "Constructed Wetlands for Water Treatment: New Developments"

A special issue of Water (ISSN 2073-4441).

Deadline for manuscript submissions: closed (31 August 2016)

Special Issue Editors

Guest Editor
Prof. Dr. Hans Brix

Department of Bioscience, Aarhus University, Aarhus, Denmark
Website | E-Mail
Interests: constructed wetlands; reed beds; wetland management; greenhouse gas emission; carbon sequestration; invasive wetland species; phragmites; spartina
Guest Editor
Dr. Carlos A. Arias

Department of Bioscience - Aquatic Biology, Aarhus University, Aarhus, Denmark
E-Mail
Interests: constructed wetlands; ecotechnologies; wastewater treatment; nutrient removal; water reuse; emergent pollutants
Guest Editor
Dr. Pedro N. Carvalho

Department of Bioscience - Aquatic Biology, Aarhus University, Aarhus, Denmark
Website | E-Mail
Interests: emergent pollutants; organic pollutants; ecotechnologies; bioremediation; environmental chemistry

Special Issue Information

Dear Colleagues,

Constructed wetlands (CWs) are one of the most interesting eco-technologies with proven efficiency and applications from rural to urban and even industrial settings. The achievements in terms of efficiency and implementation of traditional systems (free water surface (FWS), horizontal subsurface flow (HSSF), vertical flow (VF)) are known and thoroughly documented. However, in recent years, researchers and practitioners have been working on new developments and challenging applications. Various approaches for reducing the area requirements and increasing the capacity of traditional CWs systems have been tested. Varying the hydraulics by recirculation of treated waters, use of fill-and-drain cycles, use of reactive media, and forced aeration are examples of common approaches used to increase treatment capacity. CWs are also being tested for their capacity to tackle new challenges, such as the removal of special and sometimes recalcitrant pollutants, e.g., biocides, pharmaceuticals, and other micro-pollutants, as well as many types of industrial wastewaters. Additionally, our mechanistic understanding of the processes going on inside the CW “black-box”, i.e., degradation pathways and kinetics, the interactive roles of plants, microbes and media, etc., has advanced significantly in recent years. This Special Issue of Water is thought to compile the latest advances in the constructed wetlands treatment technology, both in terms of design optimisations, applications and removal processes. We foresee that the papers compiled in this Special Issue will contribute to further develop and disseminate the CW treatment technology as a reliable and robust water treatment solution.

Prof. Dr. Hans Brix
Dr. Carlos A. Arias
Dr. Pedro N. Carvalho
Guest Editor

Manuscript Submission Information

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Keywords

  • treatment wetland
  • aerated wetlands
  • tidal flow wetlands
  • run-off
  • microbial electrochemical wetlands
  • recalcitrant compounds
  • emerging contaminants
  • microbial functions in wetlands
  • new applications

Published Papers (15 papers)

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Editorial

Jump to: Research, Review

Open AccessFeature PaperEditorial Constructed Wetlands for Water Treatment: New Developments
Water 2017, 9(6), 397; doi:10.3390/w9060397
Received: 24 April 2017 / Revised: 16 May 2017 / Accepted: 31 May 2017 / Published: 2 June 2017
PDF Full-text (431 KB) | HTML Full-text | XML Full-text
Abstract
Constructed wetlands (CWs) are currently regarded as established eco-technologies to treat water pollution. Although considered near-natural systems, they are totally engineered solutions for which research has been actively developed over the past decades. This paper provides a brief meta-analysis on the latest scientific
[...] Read more.
Constructed wetlands (CWs) are currently regarded as established eco-technologies to treat water pollution. Although considered near-natural systems, they are totally engineered solutions for which research has been actively developed over the past decades. This paper provides a brief meta-analysis on the latest scientific publications in the field and an overview of the special issue focused on the new developments in the use of CWs for water treatment. The selected papers cover a wide range of relevant developments in the field, including the use of different CW system designs, the capacity to treat different types of pollutants, and studies aiming at getting a better understanding of the treatment processes in CWs. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Research

Jump to: Editorial, Review

Open AccessArticle Multilayer Substrate Configuration Enhances Removal Efficiency of Pollutants in Constructed Wetlands
Water 2016, 8(12), 556; doi:10.3390/w8120556
Received: 8 October 2016 / Revised: 22 November 2016 / Accepted: 23 November 2016 / Published: 29 November 2016
Cited by 4 | PDF Full-text (3537 KB) | HTML Full-text | XML Full-text
Abstract
This study aimed at optimizing horizontal subsurface flow constructed wetlands (CWs) to improve hydraulic performance and pollutant removal efficiency. A groundwater modeling package (MODFLOW) was used to optimize three design parameters (length-to-width ratio, inlet/outlet-to-length ratio, and substrate size configuration). Using the optimized parameters,
[...] Read more.
This study aimed at optimizing horizontal subsurface flow constructed wetlands (CWs) to improve hydraulic performance and pollutant removal efficiency. A groundwater modeling package (MODFLOW) was used to optimize three design parameters (length-to-width ratio, inlet/outlet-to-length ratio, and substrate size configuration). Using the optimized parameters, three pilot-scale CWs were built to treat actual wastewater. For model validation, we used a tracer test to evaluate hydraulic performance, and investigated the pollutant spatial distributions and removal efficiencies. We conclude that MODFLOW is suitable for designing CWs, accurately predicting that increasing hydraulic conductivity from surface to bottom layers could improve performance. However, the effect of vegetation, which decreased the hydraulic conductivity of the surface layer, should be considered to improve simulation results. Multilayer substrate configuration, with increasing hydraulic conductivity from the surface to bottom layers, significantly increased pollutant removal compared with monolayer configuration. The spatial variation in pollutant transport and degradation through the filling substrate showed that the multilayer configuration was able to increase use of the available space and moderately reduced short-circuiting and dead zones. Thus, multilayer CWs had higher experimental retention times, effective volume fractions and hydraulic efficiencies, and lower short-circuiting compared with monolayer CWs operating under similar conditions. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Open AccessArticle Design and Hydrologic Performance of a Tile Drainage Treatment Wetland in Minnesota, USA
Water 2016, 8(12), 549; doi:10.3390/w8120549
Received: 16 September 2016 / Revised: 28 October 2016 / Accepted: 14 November 2016 / Published: 25 November 2016
Cited by 4 | PDF Full-text (3421 KB) | HTML Full-text | XML Full-text
Abstract
Treatment wetlands are increasingly needed to remove nitrate from agricultural drainage water to protect downstream waters, such as the Gulf of Mexico. This project sought to develop a new edge-of-field treatment wetland, designed to remove nitrate-nitrogen and enhance phosphorus removal by plant harvest
[...] Read more.
Treatment wetlands are increasingly needed to remove nitrate from agricultural drainage water to protect downstream waters, such as the Gulf of Mexico. This project sought to develop a new edge-of-field treatment wetland, designed to remove nitrate-nitrogen and enhance phosphorus removal by plant harvest and to monitor its effectiveness. A 0.10 ha wetland was designed and installed to treat subsurface drainage flow from farmland in southwestern Minnesota, USA, in 2013, and monitored for three years by recording flow, nitrate-nitrogen, total phosphorus (TP) and soluble orthophosphorus (OP) input to and output from the wetland. Prior to construction, a level-pool routing, mass balance approach with DRAINMOD flow inputs was used to predict nitrate removal efficiency. Nitrate load removal averaged 68% over three years, nearly matching model predictions. However, most denitrification occurred in the sub-soil of the wetland rather than in surface flow as predicted. Phosphorus removal was approximately 76% over three years, and phosphorus removed by plant uptake exceeded inflow mass in the third year. The edge-of-field design has potential as a cost-effective method to treat field outflows because agricultural landowners can adopt this treatment system with minimal loss of productive farmland. The wet-prairie vegetation and shallow depth also provide the opportunity to remove additional phosphorus via vegetative harvest. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Open AccessArticle Seasonal Variation of Nutrient Removal in a Full-Scale Artificial Aerated Hybrid Constructed Wetland
Water 2016, 8(12), 551; doi:10.3390/w8120551
Received: 11 September 2016 / Revised: 1 November 2016 / Accepted: 10 November 2016 / Published: 24 November 2016
Cited by 3 | PDF Full-text (1370 KB) | HTML Full-text | XML Full-text
Abstract
To improve nutrient removal, a full-scale hybrid constructed wetland (CW) consisting of pre-treatment units, vertical-baffled flow wetlands (VBFWs), and horizontal subsurface flow wetlands (HSFWs) was installed in August 2014 to treat sewage wastewater. Artificial aeration (AA) was applied continuously in the VBFW stage
[...] Read more.
To improve nutrient removal, a full-scale hybrid constructed wetland (CW) consisting of pre-treatment units, vertical-baffled flow wetlands (VBFWs), and horizontal subsurface flow wetlands (HSFWs) was installed in August 2014 to treat sewage wastewater. Artificial aeration (AA) was applied continuously in the VBFW stage to improve the aerobic condition in the hybrid CW. Water samples were collected and analyzed twice a month between the period of August 2015 and July 2016. The results suggest that this new hybrid CW can achieve a satisfactory reduction of chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) with average removal rates of 85% ± 10% (35% ± 19 g/m2 per day), 76% ± 18% (7% ± 2 g/m2 per day), 65% ± 13% (8% ± 2 g/m2 per day), and 65% ± 21% (1 g/m2 per day), respectively. AA significantly improved the aerobic condition throughout the experimental period, and the positive influence of AA on nitrogen removal was found to be higher during summer that during winter. A significant positive correlation between water temperature and nutrient removal (p < 0.01) was observed in the system. Overall, this study demonstrates the application of AA in a full-scale hybrid CW with satisfactory nutrient removal rates. The hybrid CW system with artificial aeration can serve as a reference for future applications areas where land availability is limited. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Open AccessArticle Nitrogen Removal in a Horizontal Subsurface Flow Constructed Wetland Estimated Using the First-Order Kinetic Model
Water 2016, 8(11), 514; doi:10.3390/w8110514
Received: 25 August 2016 / Revised: 26 October 2016 / Accepted: 2 November 2016 / Published: 7 November 2016
Cited by 4 | PDF Full-text (5069 KB) | HTML Full-text | XML Full-text
Abstract
We monitored the water quality and hydrological conditions of a horizontal subsurface constructed wetland (HSSF-CW) in Beijing, China, for two years. We simulated the area-based constant and the temperature coefficient with the first-order kinetic model. We examined the relationships between the nitrogen (N)
[...] Read more.
We monitored the water quality and hydrological conditions of a horizontal subsurface constructed wetland (HSSF-CW) in Beijing, China, for two years. We simulated the area-based constant and the temperature coefficient with the first-order kinetic model. We examined the relationships between the nitrogen (N) removal rate, N load, seasonal variations in the N removal rate, and environmental factors—such as the area-based constant, temperature, and dissolved oxygen (DO). The effluent ammonia (NH4+-N) and nitrate (NO3-N) concentrations were significantly lower than the influent concentrations (p < 0.01, n = 38). The NO3-N load was significantly correlated with the removal rate (R2 = 0.96, p < 0.01), but the NH4+-N load was not correlated with the removal rate (R2 = 0.02, p > 0.01). The area-based constants of NO3-N and NH4+-N at 20 °C were 27 ± 26 (mean ± SD) and 14 ± 10 m∙year−1, respectively. The temperature coefficients for NO3-N and NH4+-N were estimated at 1.004 and 0.960, respectively. The area-based constants for NO3-N and NH4+-N were not correlated with temperature (p > 0.01). The NO3-N area-based constant was correlated with the corresponding load (R2 = 0.96, p < 0.01). The NH4+-N area rate was correlated with DO (R2 = 0.69, p < 0.01), suggesting that the factors that influenced the N removal rate in this wetland met Liebig’s law of the minimum. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Open AccessArticle Treatment Wetland Aeration without Electricity? Lessons Learned from the First Experiment Using a Wind-Driven Air Pump
Water 2016, 8(11), 502; doi:10.3390/w8110502
Received: 30 August 2016 / Revised: 20 October 2016 / Accepted: 24 October 2016 / Published: 2 November 2016
Cited by 2 | PDF Full-text (2144 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Aerated treatment wetlands have become an increasingly recognized technology for treating wastewaters from domestic and various industrial origins. To date, treatment wetland aeration is provided by air pumps which require access to the energy grid. The requirement for electricity increases the ecological footprint
[...] Read more.
Aerated treatment wetlands have become an increasingly recognized technology for treating wastewaters from domestic and various industrial origins. To date, treatment wetland aeration is provided by air pumps which require access to the energy grid. The requirement for electricity increases the ecological footprint of an aerated wetland and limits the application of this technology to areas with centralized electrical infrastructure. Wind power offers another possibility as a driver for wetland aeration, but its use for this purpose has not yet been investigated. This paper reports the first experimental trial using a simple wind-driven air pump to replace the conventional electric air blowers of an aerated horizontal subsurface flow wetland. The wind-driven air pump was connected to a two-year old horizontal flow aerated wetland which had been in continuous (24 h) aeration since startup. The wind-driven aeration system functioned, however it was not specifically adapted to wetland aeration. As a result, treatment performance decreased compared to prior continuous aeration. Inconsistent wind speed at the site may have resulted in insufficient pressure within the aeration manifold, resulting in insufficient air supply to the wetland. This paper discusses the lessons learned during the experiment. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Open AccessArticle Potential of Constructed Wetlands for Removal of Antibiotics from Saline Aquaculture Effluents
Water 2016, 8(10), 465; doi:10.3390/w8100465
Received: 16 August 2016 / Revised: 6 October 2016 / Accepted: 11 October 2016 / Published: 18 October 2016
Cited by 2 | PDF Full-text (2429 KB) | HTML Full-text | XML Full-text
Abstract
This work aimed to evaluate the potential of constructed wetlands (CWs) for removal of antibiotics (enrofloxacin and oxytetracycline) and antibiotic resistant bacteria from saline aquaculture wastewaters. Removal of other contaminants (nutrients, organic matter and metals) and toxicity reduction and the influence of antibiotics
[...] Read more.
This work aimed to evaluate the potential of constructed wetlands (CWs) for removal of antibiotics (enrofloxacin and oxytetracycline) and antibiotic resistant bacteria from saline aquaculture wastewaters. Removal of other contaminants (nutrients, organic matter and metals) and toxicity reduction and the influence of antibiotics with these processes were evaluated. Thus, nine CWs microcosms, divided into three treatments, were assembled and used to treat wastewater (doped or not with the selected antibiotics) between October and December of 2015. Each week treated wastewater was removed and new wastewater (doped or not) was introduced in CWs. Results showed >99% of each antibiotic was removed in CWs. After three weeks of adaptation, removal percentages >95% were also obtained for total bacteria and for antibiotic resistant bacteria. Nutrients, organic matter and metal removal percentages in CWs treated wastewater were identical in the absence and in the presence of each antibiotic. Toxicity in treated wastewaters was significantly lower than in initial wastewaters, independently of antibiotics presence. Results showed CWs have a high efficiency for removing enrofloxacin or oxytetracycline as well as antibiotic resistant bacteria from saline aquaculture wastewaters. CWs can also remove other contaminants independently of drug presence, making the aquaculture wastewater possible to be reutilized and/or recirculated. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Open AccessArticle Dynamics of Bacterial Community Abundance and Structure in Horizontal Subsurface Flow Wetland Mesocosms Treating Municipal Wastewater
Water 2016, 8(10), 457; doi:10.3390/w8100457
Received: 27 June 2016 / Revised: 29 September 2016 / Accepted: 8 October 2016 / Published: 17 October 2016
Cited by 3 | PDF Full-text (3708 KB) | HTML Full-text | XML Full-text
Abstract
Dynamics of bacterial community abundance and structure of a newly established horizontal subsurface flow (HSSF) pilot-scale wetland were studied using high-throughput sequencing and quantitative polymerase chain reaction (PCR) methods. Bacterial community abundance increased rapidly within one month and stabilised thereafter in three replicate
[...] Read more.
Dynamics of bacterial community abundance and structure of a newly established horizontal subsurface flow (HSSF) pilot-scale wetland were studied using high-throughput sequencing and quantitative polymerase chain reaction (PCR) methods. Bacterial community abundance increased rapidly within one month and stabilised thereafter in three replicate HSSF constructed wetland (CW) mesocosms. The most dominant phylum was Proteobacteria, followed by Bacteroidetes in wetland media biofilms and Firmicutes in influent wastewater. CW bacterial community diversity increased over time and was positively related to the wastewater treatment efficiency. Increase in the abundance of total bacteria in the community was accompanied with the abundance of denitrifying bacteria that promoted nitrate and nitrite removal from the wastewater. During the 150-day study period, similar patterns of bacterial community successions were observed in replicate HSSF CW mesocosms. The data indicate that successions in the bacterial community in HSSF CW are shaped by biotic interactions, with a significant contribution made by external abiotic factors such as influent chemical parameters. Network analysis of the bacterial community revealed that organic matter and nitrogen removal in HSSF CW could be, in large part, allocated to a small subset of tightly interconnected bacterial species. The diversity of bacterial community and abundance of denitrifiers were good predictors of the removal efficiency of ammonia, nitrate and total organic C in HSSF CW mesocosms, while the removal of the seven-day biochemical oxygen demand (BOD7) was best predicted by the abundance of a small set of bacterial phylotypes. The results suggest that nitrogen removal in HSSF CW consist of two main pathways. The first is heterotrophic nitrification, which is coupled with aerobic denitrification and mediated by mixotrophic nitrite-oxidizers. The second pathway is anaerobic denitrification, which leads to gaseous intermediates and loss of nitrogen as N2. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Open AccessArticle Integrated Mosquito Management in Experimental Constructed Wetlands: Efficacy of Small-Stature Macrophytes and Fluctuating Hydroperiod
Water 2016, 8(10), 421; doi:10.3390/w8100421
Received: 1 September 2016 / Revised: 19 September 2016 / Accepted: 20 September 2016 / Published: 26 September 2016
Cited by 2 | PDF Full-text (906 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The impact of small-stature alkali bulrush (Bolboschoenus maritimus) and two hydroperiod treatments (early season raised water level or ambient water level) on mosquito production and water quality was studied in replicate 0.09 ha free water surface (FWS) treatment wetlands. Following reconfiguration
[...] Read more.
The impact of small-stature alkali bulrush (Bolboschoenus maritimus) and two hydroperiod treatments (early season raised water level or ambient water level) on mosquito production and water quality was studied in replicate 0.09 ha free water surface (FWS) treatment wetlands. Following reconfiguration of a 1-ha constructed wetland into a system with six replicate wetlands, bulrush was planted on 0.5-m centers in three 5-m wide bands in each wetland in summer, 2012. Open water and the low density of emergent vegetation effectively limited mosquito production from the bands of B. maritimus in each wetland during summer and autumn of year one. After the autumnal senescence of the bulrush culms, water levels were raised in half of the wetlands during winter and early spring to enhance sinking of dead bulrush biomass to reduce harborage for mosquitoes. Macrophyte coverage continued to increase in both hydroperiod treatments during year two, but non-bulrush species proliferated and eventually overgrew B. maritimus. Immature mosquito abundance in dipper samples from wetlands in the raised water level treatment was greater than from wetlands in the constant water level treatment. During spring of year two, adult mosquito production was associated with volunteer vegetation in the center of the test cells and averaged 6–18 mosquitoes m−2·day−1, approximately twice that of the other treatment. Hydrological regime did not significantly affect water quality performance (removal of nitrogen, phosphorus and chemical oxygen demand) in the wetlands. Alkali bulrush can persist in shallow water (depth < 0.2 m), but did not persist in deeper zones (mean depth > 0.4 m) of the wetlands and after comparatively large stature grasses and cattails colonized the wetlands. Raised planting beds interspersed with zones of deeper water are recommended to facilitate persistence of alkali bulrush and to limit proliferation of superior competitors. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Open AccessArticle Treatment of Alkaline Stripped Effluent in Aerated Constructed Wetlands: Feasibility Evaluation and Performance Enhancement
Water 2016, 8(9), 386; doi:10.3390/w8090386
Received: 26 July 2016 / Revised: 29 August 2016 / Accepted: 31 August 2016 / Published: 6 September 2016
Cited by 3 | PDF Full-text (6384 KB) | HTML Full-text | XML Full-text
Abstract
Ammonium stripping has gained increasing interest for nitrogen recovery in anaerobically digested effluents. However, the stripped effluents often still do not meet discharge standards, having high pH and residual pollutants. Constructed wetlands (CWs) are an easy to operate ecosystem and have a long
[...] Read more.
Ammonium stripping has gained increasing interest for nitrogen recovery in anaerobically digested effluents. However, the stripped effluents often still do not meet discharge standards, having high pH and residual pollutants. Constructed wetlands (CWs) are an easy to operate ecosystem and have a long history of application in treatment of wastewaters with extreme pH, such as acid mine drainage. However, knowledge of the mechanistic details involved in the use of CWs to treat high alkaline drainage, such as stripped effluent, is insufficient. This study explored the feasibility and effectiveness of using three sub-surface horizontal flow CWs to treat high alkaline stripped effluent (pH > 10). Two intensification strategies—intermittent aeration and effluent recirculation—were evaluated to enhance nitrogen depuration performance. The results show that the treatment of alkaline stripped effluent is feasible due to the high buffering capacity of the wetlands. Effluent recirculation combined with intermittent artificial aeration improves nitrogen removal, with 71% total nitrogen (TN) removal. Ammonia volatilization from the surface of the wetlands in high alkaline conditions only contributed to 3% of the total removed ammonium. The microbial abundance and activity had significant diversity for the various enhancement strategies used in the constructed wetland systems. Anammox is an important process for nitrogen removal in CWs treating alkaline stripped effluent, and possible enhancements of this process should be investigated further. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Open AccessArticle Performance of Four Full-Scale Artificially Aerated Horizontal Flow Constructed Wetlands for Domestic Wastewater Treatment
Water 2016, 8(9), 365; doi:10.3390/w8090365
Received: 2 June 2016 / Revised: 13 August 2016 / Accepted: 15 August 2016 / Published: 24 August 2016
Cited by 3 | PDF Full-text (3029 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A comparison of the performance of four full-scale aerated horizontal flow constructed wetlands was conducted to determine the efficacy of the technology on sites receiving high and variable ammonia loading rates not yet reported in the literature. Performance was assessed in terms of
[...] Read more.
A comparison of the performance of four full-scale aerated horizontal flow constructed wetlands was conducted to determine the efficacy of the technology on sites receiving high and variable ammonia loading rates not yet reported in the literature. Performance was assessed in terms of ammonia and solids removal, hydraulic conductivity and mixing patterns. The capability of systems to produce ammonium effluent concentrations <3 mgNH4+-N/L was observed across all sites in systems receiving variable loadings between 0.1 and 13.0 gNH4+-N/m2/d. Potential resilience issues were observed in relation to response to spike loadings posited to be due to an insufficient nitrifying population within the beds. Hydraulic conductivity and flow mixing patterns observed suggested deterioration of the reactor effective volume over time. Overall, the study demonstrates the efficacy of the technology where ammonium removal is required on small sites receiving high and variable flow rates, with adequate removal of organics and solids, but no significant benefit to the long term hydraulics of the system. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Review

Jump to: Editorial, Research

Open AccessFeature PaperReview Sludge Dewatering and Mineralization in Sludge Treatment Reed Beds
Water 2017, 9(3), 160; doi:10.3390/w9030160
Received: 6 November 2016 / Revised: 18 December 2016 / Accepted: 21 February 2017 / Published: 24 February 2017
Cited by 3 | PDF Full-text (3168 KB) | HTML Full-text | XML Full-text
Abstract
Sludge Treatment Reed Beds (STRBs) are widely used in Northern Europe to dewater and mineralize surplus sludge from activated sludge systems used to treat urban domestic sewage. STRBs are low-technology, energy-efficient, and do not require addition of chemicals. They dewater and stabilize the
[...] Read more.
Sludge Treatment Reed Beds (STRBs) are widely used in Northern Europe to dewater and mineralize surplus sludge from activated sludge systems used to treat urban domestic sewage. STRBs are low-technology, energy-efficient, and do not require addition of chemicals. They dewater and stabilize the sludge and produce a final product that can be safely used as a fertilizer for agricultural crops. Long-term sludge reduction takes place in the reed beds due to dewatering and mineralization of the organic matter in the sludge. Although, in theory, a simple technique relying largely on natural processes, experience has shown that it is very important to understand and respect the basic design and operation requirements of STRBs. This paper describes the basic design and operation requirements of STRBs, with special focus on pivotal requirements to respect in order to secure proper functioning. Also, the paper summarizes performance experience concerning final dry matter content, degree of mineralization, emission of greenhouse gases, and degradation of micro-pollutants in STRBs. There are still a number of outstanding issues that are not fully understood, particularly in relation to the importance of the sludge quality for the dewatering in an STRB. Therefore, extreme care should be taken when attempting to extrapolate the use of STRBs to applications and regions outside of their ‘normal’ and documented area of application. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Open AccessReview Applying Process-Based Models for Subsurface Flow Treatment Wetlands: Recent Developments and Challenges
Water 2017, 9(1), 5; doi:10.3390/w9010005
Received: 15 September 2016 / Revised: 7 December 2016 / Accepted: 20 December 2016 / Published: 24 December 2016
Cited by 4 | PDF Full-text (2294 KB) | HTML Full-text | XML Full-text
Abstract
To date, only few process-based models for subsurface flow treatment wetlands have been developed. For modelling a treatment wetland, these models have to comprise a number of sub-models to describe water flow, pollutant transport, pollutant transformation and degradation, effects of wetland plants, and
[...] Read more.
To date, only few process-based models for subsurface flow treatment wetlands have been developed. For modelling a treatment wetland, these models have to comprise a number of sub-models to describe water flow, pollutant transport, pollutant transformation and degradation, effects of wetland plants, and transport and deposition of suspended particulate matter. The two most advanced models are the HYDRUS Wetland Module and BIO-PORE. These two models are briefly described. This paper shows typical simulation results for vertical flow wetlands and discusses experiences and challenges using process-based wetland models in relation to the sub-models describing the most important wetland processes. It can be demonstrated that existing simulation tools can be applied for simulating processes in treatment wetlands. Most important for achieving a good match between measured and simulated pollutant concentrations is a good calibration of the water flow and transport models. Only after these calibrations have been made and the effect of the influent fractionation on simulation results has been considered, should changing the parameters of the biokinetic models be taken into account. Modelling the effects of wetland plants is possible and has to be considered when important. Up to now, models describing clogging are the least established models among the sub-models required for a complete wetland model and thus further development and research is required. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Open AccessReview Microbial Community Assessment in Wetlands for Water Pollution Control: Past, Present, and Future Outlook
Water 2016, 8(11), 503; doi:10.3390/w8110503
Received: 31 August 2016 / Revised: 24 October 2016 / Accepted: 26 October 2016 / Published: 2 November 2016
Cited by 3 | PDF Full-text (1948 KB) | HTML Full-text | XML Full-text
Abstract
The field of treatment wetlands (TWs) is rapidly expanding and, arguably, is tasked with studying and understanding one of the most complex water treatment systems available. Microbial communities are generally considered to be responsible for the majority of wastewater constituent degradation in TWs.
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The field of treatment wetlands (TWs) is rapidly expanding and, arguably, is tasked with studying and understanding one of the most complex water treatment systems available. Microbial communities are generally considered to be responsible for the majority of wastewater constituent degradation in TWs. However, they are also known to be spatially heterogeneous, temporally dynamic, as well as structurally and functionally diverse. Presented here is a meta-analysis of all peer reviewed TW journal articles which utilized a microbial community assessment methodology over the period of 1988 to July 2016. A total of 1101 papers were reviewed, 512 from 1988 to 2012, 215 of which included a microbial community assessment aspect and were subsequently classified as representing past research, and 589 from 2013 to July 2016, 196 of which were classified as representing current TW microbial community research. In general, TW microbial community research has increased over time, with a marked surge in the past four years. Microbial community structure is currently the most commonly used methodological type followed by activity, enumeration and function, respectively. Areas of research focus included nitrogen transformations (156), organic degradation (33), and emerging contaminants (32), with general characterization studies also accounting for a significant proportion (243). Microbial communities from a range of TW systems have been investigated over the last four years with meso-scale (10–1000 L) being the most commonly studied system size followed by large-scale (>100,000 L), micro-scale (<10 L), and pilot-scale (1000–100,000 L). Free water surface flow (SF), horizontal subsurface flow (HF), and vertical flow (VF) systems are being studied in approximately equal proportions with the majority of studies focused on gaining fixed media/biofilm samples for analysis (rather than from the rhizosphere or interstitial water). Looking at efforts from a regional perspective shows Asia to be publishing the majority of research with a main focus on VF systems and structural community assessment. European and North American studies are generally more evenly distributed among structure, function, activity, and enumeration with the majority of studies completed on HF systems. South America, Africa, and Oceania published fewer studies but focused on structural community assessment with a selection of HF, SF and VF investigations. Great strides are being made in the field of microbial community assessment in TWs with functional assessment methods being developed, better utilized, and being related directly to water treatment. The use of high-powered metagenomics sequencing such as Illumina HiSeq instrumentation is on the rise, as is the development and utilization of functional assays such as DNA microarrays and community level physiological profiling allowing for more complete community assessment. Used in concert with activity, enumeration and newly implemented stable isotope methodologies, the field of TWs is certainly moving away from the black-box understanding of the past. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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Open AccessReview Large Constructed Wetlands for Phosphorus Control: A Review
Water 2016, 8(6), 243; doi:10.3390/w8060243
Received: 4 May 2016 / Revised: 26 May 2016 / Accepted: 30 May 2016 / Published: 7 June 2016
Cited by 8 | PDF Full-text (3727 KB) | HTML Full-text | XML Full-text
Abstract
This paper reviews aspects of the performance of large (>40 ha) constructed treatment wetlands intended for phosphorus control. Thirty-seven such wetlands have been built and have good data records, with a median size of 754 ha. All are successfully removing phosphorus from a
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This paper reviews aspects of the performance of large (>40 ha) constructed treatment wetlands intended for phosphorus control. Thirty-seven such wetlands have been built and have good data records, with a median size of 754 ha. All are successfully removing phosphorus from a variety of waters. Period of record median concentration reductions were 71%, load reductions 0.77 gP·m−2·year−1, and rate coefficients 12.5 m·year−1. Large wetlands have a narrower performance spectrum than the larger group of all sizes. Some systems display startup trends, ranging to several years, likely resulting from antecedent soil and vegetation conditions. There are internal longitudinal gradients in concentration, which vary with lateral position and flow conditions. Accretion in inlet zones may require attention. Concentrations are reduced to plateau values, in the range of about 10–50 mgP·m−3. Vegetation type has an effect upon performance measures, and its presence facilitates performance. Trends in the performance measures over the history of individual systems display only small changes, with both increases and decreases occurring. Such trends remove little of the variance in behavior. Seasonality is typically weak for steady flow systems, and most variability appears to be stochastic. Stormwater systems display differences between wet and dry season behavior, which appear to be flow-driven. Several models of system performance have been developed, both steady and dynamic. Full article
(This article belongs to the Special Issue Constructed Wetlands for Water Treatment: New Developments)
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