Free Water Surface Wetland Research Articles

Hybrid constructed wetlands and filamentous fungi for treatment of mixed sewage and industrial effluents.

Developing countries face multifaceted problems of water pollution and futile measures to combat water pollution. This study was conducted to explore the potential application of sustainable nature-based solutions, hybrid constructed wetlands, and the application of filamentous fungi to treat polluted river water that receives sewage and industrial wastewater. A pilot-scale hybrid constructed wetland design comprising two types of floating plants in distinct tanks along with a floating wetland and a free-water surface wetland connected in series was commissioned and tested. The system successfully removed organic pollution (BOD 94% and COD 90%), nutrients (NH4-N and NO3-N 67% and PO4-P 81%), and heavy metals (Cr 75%, Ni 56%, and Fe 79%) in 40h and showed a high buffering capacity to cope with the varying pollutant loads. Metagenomics analysis of treated and untreated samples of river water revealed a diversified spatial bacterial community with ~ 25% sequences related to sulfur-metabolizing bacteria, genus Sulfuricurvum. The application of an immobilized strain of A. niger as a mycoremediation technique was also tested. It successfully removed pollutants in the combined sewage and industrial wastewater present in river water: COD (96%), TSS (97%), NH4-N (65%), NO3-N (67%), and PO4-P (78%). This study demonstrated that hybrid constructed wetlands and mycoremediation can be used as sustainable wastewater treatment options in the local context and also in developing countries where most of the conventional wastewater treatment plants do not operate.

Study on the applicability of free water surface wetland (fws) scale of wastewater treatment laboratory for green rest stops

The Free Water Surface wetland (FWS) has emerged as a promising technological solution for wastewater treatment in natural environments. The study aimed at investigating the performance of a laboratory-scale Free Water Surface wetland (FWS) unit designed to treat domestic wastewater with a daily capacity of 20 liters. This model can be applied at some rest stops towards creating "Green Rest Stops" on highways. The laboratory experiments on bronze banana plants have shown that the model operates effectively under specific settings and with the characteristics of residential wastewater from public toilets, which has undergone pretreatment through septic tanks. These conditions are conducive to promoting healthy growth in the plants. The FWS model for cultivating canna hybrid plants (Canna generalis) has a total surface area of 0.26 square meters and operates based on the principles of free wastewater flow. The model has a water retention duration of 70 hours, approximately three days. The treatment efficiency for TSS, BOD5, NH4+ - N, and Coliform is 37-53%, 73-77%, 41-46%, and 37-54%, respectively. The treated wastewater complies with the National technical regulations on water quality, QCVN 14:2008/BTNMT (B) standards

Response of Typha domingensis during an accidental discharge of high Cr(VI) concentration in a full-scale treatment wetland

This work assesses the Cr accumulation and tolerance of Typha domingensis after an accidental discharge of wastewater that produced a concentration of Cr(VI) of approximately 120 mg L−1 in a free-water surface wetland. The wetland was constructed for the final wastewater treatment of a metallurgical manufacturing plant. It is 7 m wide, 20 m long, and waterproofed with a geomembrane. A 1.5 m soil layer was placed on top of the geomembrane. Water, plants, and sediment were sampled before and after an accidental discharge. The root anatomical measurements of the plants from the treatment wetland were compared with those of plants from an uncontaminated wetland (control). Roots and dead leaves from the inlet plants showed the highest Cr concentrations after the accidental discharge (12.4 and 11.6 mg g−1, respectively). SEM-EDX mapping determined that Cr was accumulated in root epidermis. Cr accumulation in plant detritus, plant roots, and sediment were the mechanisms for Cr removal. Plants accumulated Cr in belowground tissues demonstrating their potential for phytostabilization. T. domingensis was capable of modifying its morphology to respond to high Cr concentrations. This macrophyte is a suitable species for wetlands constructed for the treatment of a wastewater with high Cr(VI) concentration. The studied system was capable of minimizing the impact and preserving the environment.

Removal of enrofloxacin using Eichhornia crassipes in microcosm wetlands.

The global consumption of antibiotics leads to their possible occurrence in the environment. In this context, nature-based solutions (NBS) can be used to sustainably manage and restore natural and modified ecosystems. In this work, we studied the efficiency of the NBS free-water surface wetlands (FWSWs) using Eichhornia crassipes in microcosm for enrofloxacin removal. We also explored the behavior of enrofloxacin in the system, its accumulation and distribution in plant tissues, the detoxification mechanisms, and the possible effects on plant growth. Enrofloxacin was initially taken up by E. crassipes (first 100h). Notably, it accumulated in the sediment at the end of the experimental time. Removal rates above 94% were obtained in systems with sediment and sediment + E. crassipes. In addition, enrofloxacin was found in leaves, petioles, and roots (8.8-23.6µg, 11-78.3µg, and 10.2-70.7µg, respectively). Furthermore, enrofloxacin, the main degradation product (ciprofloxacin), and other degradation products were quantified in the tissues and chlorosis was observed on days 5 and 9. Finally, the degradation products of enrofloxacin were analyzed, and four possible metabolic pathways of enrofloxacin in E. crassipes were described.

Experimental checking and modeling of the influence of operation conditions on the first order kinetic constants in free water surface wetlands

The most commonly used model in constructed wetlands is the first-order removal model, and first order kinetic constants (k) are the key parameters. The presumption is often made that k are constants. However, it is possible that k are functions of operating conditions, but the influence of operation conditions on k is unclear. In this study, response surface methodology was used to explore the variation patterns of ka (area rate constants) and kV (volume rate constants) for the removal of total nitrogen (TN) and total phosphorus (TP) in free water surface (FWS) wetlands. The experimental variables included hydraulic loading rate (HLR), water depth, and inlet concentration (Cin). The results showed that kV was more variable than ka, and the area-based first-order model is more suitable for simulating TN and TP in FWS wetlands. Inlet concentration (Cin) was significant for ka; Cin and water depth were significant for kV; HLR and the interaction between factors were insignificant. The effects of Cin on ka and kV can be described by an upward convex quadratic curve, while the effect of water depth on kV demonstrates a downward convex quadratic curve. The first-order area rate constant for TN removal was given by k = −47.66 + 22.01 Cin - 1.154 Cin2; the first-order area rate constant for TP removal was given by k = −27.75 + 95.88 Cin – 30.73 Cin2. Based on the variation patterns, the traditional k-C model was modified to the kψ-C model. The kψ-C model produced the best results at simulating the outlet concentration and removal efficiency (RE).

Seasonal variation in release characteristics and mechanisms of sediment phosphorus to the overlying water in a free water surface wetland, southwest China

Geochemical cycling of iron (Fe) mediated by sediment microbes drives the remobilization of phosphorus (P). Understanding the underlying mechanism is essential for the evaluation of P retention by wetlands. The diffusive gradients in thin film (DGT) and 16S rDNA sequencing techniques were combined to explore seasonal variations in the remobilization mechanism of sediment P in a free water surface wetland in southwest China. A significantly positive correlation between labile P and Fe concentrations was found from the sediment profiles, indicating coupled remobilization of Fe and P in the sediment. Fe-reducing bacterial genera, particularly Sphingomonas and Geothermobacter, were responsible for the reductive dissolution of Fe oxides and subsequent P release in sediment. The efflux of sediment P was higher in the rainy season (95 ± 87 ng cm−2 d−1) than in the dry season (39 ± 29 ng cm−2 d−1). Based on the significantly positive relationship between the efflux and total concentration of sediment P, we propose a promising regression equation for quantifying the release risk of sediment P. The Luoshijiang Wetland exhibited a higher release potential as indicated by a greater regression slope (0.558) compared to the other water bodies (0.055), which was mainly attributed to the lower labile Fe:P molar ratio in the sediment. Based on estimations of the diffusive flux of P at the sediment-water interface, sediment contributed more than 172 and 413 g of P per day to the water column in the dry and rainy seasons, respectively, accounting for 14.0% and 1.9% of the P mass in the surface water of the wetland.

BOD5 dynamics in three vertical layers in free-water surface wetlands

This paper introduces a first-order variable residence time (VART) model, the so-called BOD-VART model, to estimate the biochemical oxygen demand (BOD) in built wetlands with a free-water surface. The BOD-VART model mathematically designs a free-water surface wetland into three vertical layers: the vegetated water column layer, the upper root layer dominated by advection, and the lower root layer dominated by diffusion. It also biogeochemically simulates various processes and mechanisms of BOD removal, including mass transfer between the layers through advection, dispersion, and diffusion. The inclusion of a dynamic diffusion-dominated root zone is a unique feature of the BOD-VART model. In this study, the BOD-VART model was tested using data obtained from the Lake Manzala Engineering Wetland, Egypt. The test results showed that the determination coefficient and root mean square error values were 0.74 and 1.97 mg/l, respectively. The BOD-VART model is a reliable and efficient instrument for modeling designed wetlands and determining the effect of different mass transfer processes on the treatment elements in developed wetlands.

Metal Removal by a Free Surface Constructed Wetland and Prediction of Metal Bioavailability and Toxicity with Diffusive Gradients in Thin Films (DGT) and Biotic Ligand Model (BLM).

The H-02 constructed wetland is a free water surface wetland to remove copper (Cu) and zinc (Zn) from the industrial wastewater. In this study, we evaluated the performance of the wetland from 2018 to 2019 and coupled the diffusive gradients in thin films (DGTs) and biotic ligand model (BLM) to explore metal speciation and bioavailability in wetland waters. Surface water samples were collected and piston DGTs were deployed in different sites of the wetland. The H-02 wetland functioned well during the sampling period with high removal efficiencies (Cu: 73.8 ± 1.2% and Zn: 75.2 ± 16.0%). In our study, with the assumption that the combination of BLM predicted inorganic metals species, BLM Cu(II) and BLM Zn(II), were the bioavailable and toxic species, DGT-Cu did not correlate to BLM Cu(II) (P = 0.47), but DGT-Zn positively correlated to BLM Zn(II) (R2 = 0.35, P < 0.001). Compared to the modeling results of BLM, DGT-indicated labile and/or bioavailable Cu included not only free Cu ions and inorganic Cu complexes but also a high percentage of Cu-labile organic matter complexes. DGT-indicated Zn included free Zn ion, inorganic Zn, and only a low percentage of Zn-labile organic matter complexes. Our findings illustrated the appropriate use of passive sampling techniques and geological modeling when biomonitoring could be substituted. The close monitoring of metal concentrations, speciation, and bioavailability helps us understand metal biogeochemistry and metal removal processes and ensure the long-term sustainability of the constructed wetland.

Spatiotemporal characteristics of hydraulic performance and contaminant transport in treatment wetlands

Wetlands have been proven to be efficient and cost-effective ecological treatment systems for municipal and domestic wastewater. It is essential to understand the hydrodynamic characteristics and the related contaminant transport process to optimize the treatment efficiency in free water surface wetlands. Thirty-six tracer experiments were conducted under different water depths and wetland configurations, such as installing static obstacles and dynamic disturbances. The particle image velocimetry and a novel color-concentration transform method were developed to reveal spatiotemporal flow velocity and residence time distribution. The flow fields are categorized into short-circuiting, circulation flow, dead zones, and the corresponding contaminant transport phenomena are flow advection, shear dispersion, and eddy diffusion. The flow circulation dominates the formation of the dead zone and decreases contaminant dissipation. The flow path could have effectively meandered, and the dead zone and short-circuiting could be reduced by increasing the length of the obstacles. The improved flow field is close to the plug flow, indicating enhanced hydraulic performance and treatment efficiency. The dynamic disturbance reflects the movement of fish in wetlands and provides momentum flux to promote the dissipation of pollutants in the circulation field and dead zone, alleviating the deterioration of water quality caused by pollutant accumulation. The findings of this study may provide a critical reference for the optimal design of wetlands.

CONSTRUCTED WETLANDS A COMPREHENSIVE REVIEW

Constructed wetlands are wastewater treatment systems composed of one or more treatment cells in a building designed and constructed to provide wastewater treatment. Constructed wetlands are classified into two types: free water surface (FWS) wetlands (also known as surface flow wetlands) closely resemble natural wetlands in appearance because they contain aquatic plants that are rooted in a soil layer on the bottom of the wetland and water flows through the leaves and stems of plants. Subsurface flow wetlands (SSF) or known as a vegetated submerged bed (VSB) systems do not resemble natural wetlands because they have no standing water. They contain a bed of media (such as crushed rock, small stones, gravel, sand, or soil) that has been planted with aquatic plants. When properly designed and operated, wastewater stays beneath the surface of the media, flows in contact with the roots and rhizomes of the plants, and is not visible or available to wildlife. Constructed wetlands are an appropriate technology for areas where inexpensive land is generally available and skilled labor is less available. In this paper, a comprehensive review covered types, characteristics, design variation and considerations, limitations, and the advantages and disadvantages of constructed wetlands.

Spatial Changes in Microbial Communities along Different Functional Zones of a Free-Water Surface Wetland.

Constructed wetlands (CWs) are complicated ecosystems that include vegetation, sediments, and the associated microbiome mediating numerous processes in wastewater treatment. CWs have various functional zones where contrasting biochemical processes occur. Since these zones are characterized by different particle-size composition, physicochemical conditions, and vegetation, one can expect the presence of distinct microbiomes across different CW zones. Here, we investigated spatial changes in microbiomes along different functional zones of a free-water surface wetland located in Moscow, Russia. The microbiome structure was analyzed using Illumina MiSeq amplicon sequencing. We also determined particle diameter and surface area of sediments, as well as chemical composition of organic pollutants in different CW zones. Specific organic particle aggregates similar to activated sludge flocs were identified in the sediments. The highest accumulation of hydrocarbons was found in the zones with predominant sedimentation of fine fractions. Phytofilters had the highest rate of organic pollutants decomposition and predominance of Smithella, Ignavibacterium, and Methanothrix. The sedimentation tank had lower microbial diversity, and higher relative abundances of Parcubacteria, Proteiniclasticum, and Macellibacteroides, as well as higher predicted abundances of genes related to methanogenesis and methanotrophy. Thus, spatial changes in microbiomes of constructed wetlands can be associated with different types of wastewater treatment processes.

Effects of Water Depth and Phosphorus Availability on Nitrogen Removal in Agricultural Wetlands

Excess nitrogen (N) from agricultural runoff is a cause of pollution in aquatic ecosystems. Created free water surface (FWS) wetlands can be used as buffering systems to lower the impacts of nutrients from agricultural runoff. The purpose of this paper was to evaluate critical factors for N removal in FWS wetlands receiving high nitrate (NO3−) loads from agriculture. The study was performed in 12 experimental FWS wetlands in southern Sweden, receiving drainage water from an agricultural field area. The effects of water depth (mean depth of 0.4 m and 0.6 m, respectively) and phosphorus (P) availability (with or without additional P load) were investigated from July to October. The experiment was performed in a two-way design, with three wetlands of each combination of depth and P availability. The effects of P availability on the removal of NO3− and total N were strongly significant, with higher absolute N removal rates per wetland area (g m−2 day−1) as well as temperature-adjusted first-order area-based removal rate coefficients (Kat) in wetlands with external P addition compared to wetlands with no addition. Further, higher N removal in deep compared to shallow wetlands was indicated by statistically significant differences in Kat. The results show that low P availability may limit N removal in wetlands receiving agricultural drainage water. Furthermore, the results support that not only wetland area but also wetland volume may be important for N removal. The results have implications for the planning, location, and design of created wetlands in agricultural areas.

Variation in contaminant removal efficiency in free-water surface wetlands with heterogeneous vegetation density

The interaction between flow and vegetation in constructed wetlands plays a major role in determining wetland performance. In this study, a two-dimensional depth-averaged model was used to simulate flow, mass transport and contaminant removal in a conceptual free-water surface (FWS) wetland with heterogeneous vegetation patterns. The main objectives of this study were (1) to quantify the effectiveness of FWS wetlands with different vegetation patterns in reducing pollutant load, and (2) to identify optimal vegetation distributions that maximize contaminant removal. Simulations were performed for different random vegetation fields characterized by imposed mean, variance and correlation lengths of stem density. The wetland was assumed to receive water from a stream and to deliver it back to the same stream according to an imposed head drop. The simulations show that the concentration reduction efficiency increases monotonically with average stem density, whereas mass removal has a peak for an intermediate value of average stem density. The ensemble average of the total mass removal decreases for increasing stem density variance and correlation length, because the presence of vegetation patches with significantly different stem density promotes preferential flow paths. Preferential flow paths parallel to the mean flow direction were found to reduce the hydraulic efficiency of wetlands by producing short-circuiting, whereas, for the same mean stem density, alternating stripes of stem density perpendicular to the flow direction provided higher concentration and mass reduction. By providing a quantitative understanding of the impact of spatial vegetation heterogeneity, the results provide useful guidelines for design and maintenance of constructed wetlands for wastewater treatment.

Improving denitrification in an aquaculture wetland using fish waste - a case study

Cost-efficient, end-of-pipe, nitrate removal techniques are called for by the commercial aquaculture industry. This case study examined how simple flow manipulations improved the denitrification performance of a 19,007 m2 (13,305 m3) constructed, free water surface (FWS) wetland treating aquaculture effluent. The wetland consisted of two separate streams with a common outlet: one stream treating nitrate-rich but carbon deficient effluent from the production unit at a hydraulic retention time (HRT) of 1.5 days (wetland stream 1); and a second stream treating carbon-rich, fish sludge-based effluent at a HRT of 41.0 days (wetland stream 2). During the course of the study (May–July 2017), three increasing proportions (40, 49 and 56%) of nitrate-rich effluent were re-directed from wetland stream 1 to the sludge-fed wetland stream 2 aiming at improving heterotrophic denitrification conditions in wetland stream 2 and consequently nitrogen removal in the wetland as a whole. Inlet C/N ratio in wetland stream 2 decreased from 1086 ± 57 to an average of 234 ± 56 (p < .05), and the area-based, total nitrogen (TN) removal rate in this wetland section increased significantly from 0.1 ± 0.01 to 8.4 ± 1.4 g/m2/d at the highest manipulated flow. In comparison, the flow manipulations had no effect on TN removal rates in wetland stream 1 averaging 1.4 ± 0.2 g/m2/d throughout the study. For the wetland as a whole, the TN removal rate increased from 1.4 ± 0.2 to 3.9 ± 0.8 g TN/m2/d. The flow manipulations furthermore improved the removal rates of total phosphorous and dissolved organic matter in the wetland as a whole. The study demonstrates that denitrification in a constructed aquaculture wetland may be improved by combining sludge-based and nitrogen-rich effluents in right proportions and leading it through an anoxic section of the wetland.

Seasonal variation in nutrient retention in a free water surface constructed wetland monitored with flow-proportional sampling and optical sensors

Constructed free water surface wetlands (CWs) are used to reduce nutrient and sediment loads to receiving waters in highly impacted catchments by e.g., agricultural land use. In this paper, we evaluated the retention effectiveness of a Swedish CW in two consecutive hydrological years, 3–4 years after construction respectively. We compared nutrient loads based on concentrations from flow-proportional sampling (Cfp) and turbidity and nitrate concentrations measured with optical sensors (Cs). CW’s retention was estimated based on differences between inlet and outlet concentrations and flow (Q) at both the inlet and outlet (2Q), or only at the inlet (1Q). In the first year (2012/2013), with a cold winter (mean topsoil temperature −0.2 °C), nitrate-nitrogen (NO3N) retention was 32% (Cfp and Cs, 2Q). In the second year, with a mild winter (mean topsoil temp 1.8 °C) and less water runoff, the corresponding values were 37% (Cfp, 2Q) and 39% (Cs, 2Q). Nitrate-nitrogen retention was significantly correlated to water residence time and temperature, and was most effective relative to the load (80%) in summer and least effective (40%) in winter. Quantitatively, however, summer NO3N retention contributed only 7% (2Q) or 8% (1Q) of yearly NO3N mass retention. Particulate phosphorus (PP) concentrations were significantly correlated with suspended solids (SS) concentrations at both inlet and outlet. Seasonal PP retention (Cfp, 2Q) was related to particle residence time estimated from turbidity measurements by sensors, and was less effective in the cold winter (3%) than in the mild winter (32%) (Cfp, 2Q). Yearly retention (2Q) as a mean of the two years was: SS 40%, total P 36%, PP 34%, dissolved reactive P 30%, total N 56%, NO3N 35%, organic N 75%, and organic C 30%. Overall, the wetland satisfactorily removed nutrients from agricultural drainage water. However, longer-term studies over a range of flow and temperature conditions are needed to evaluate climate conditions and hydrological residence time as key factors in nutrient removal efficiency.

Treatment of landfill leachate in a constructed free water surface wetland system over a decade – Identification of disturbance in process behaviour and removal of eutrophying substances and organic material

An 8 ha free water surface wetland system in Örebro, Sweden, which has sediment traps followed by 10 ponds for treatment of landfill leachate in the methanogenic stage, was studied from 2003 to 2012. The wetland was irregularly loaded and the leachate characteristics showed high temporal and spatial variability, so Multivariate Statistical Process Control was chosen as the diagnostic tool for detecting anomalies prior to assessing removal efficiency for eutrophying substances and organics. Disturbances in process behaviour included those due to intermittent flow, dilution due to snowmelt, an episode of high pollutant load, and sampling technique. The wetland total nitrogen mass removal was 89%, resulting in a first order rate coefficient of 1.7 m/year. Total phosphorus mass removal was 98%, while mass reduction was lower for TOC (60%), although this was still below discharge limits. The low amount of labile organic material and phosphate are probably the main reasons for the low denitrification rate.

Efficiency of two constructed wetland systems for wastewater treatment: removal of bacterial indicators and enteric viruses

AbstractBACKGROUNDPathogenic microorganisms at the effluents of treatment plants entail a potential risk to public health. Enteric viruses such as adenoviruses (AdVs) and enteroviruses (EVs) are responsible for many waterborne diseases. Wastewater treatment methods eliminate successfully the load of indicators but other pathogens such as viruses have been detected in high concentrations at the effluents of wastewater plants. In this perspective, two constructed wetlands (CWs) systems (S1 and S2) were employed and fed with primary wastewater. S1 consists of a free water surface (FWS) wetland and a horizontal subsurface flow (HSSF) wetland working in series, while S2 consists only of the HSSF. Also, both systems included a sand filter (SF) after the HSSF.RESULTSResults showed that these low‐cost systems are capable of eliminating effectively the bacterial indictors (total coliforms, Escherichia coli, Enterococci) achieving removal rates of almost 99% for S1 (3.2–4 Log units) and 89–98% for S2 (1.9–2.7 Log units). Regarding viruses, AdVs, EVs and phages were detected at all sampling points and during all seasons, and they were only partly removed in S1 and/or S2. For example, the virus load was decreased by 2.5 Log units for AdVs and 3.4 Log units for EVs in the case of S1, while the respective values were 4.3 and 1.9 Log units for S2.CONCLUSIONSGenerally, CWs eliminated successfully the bacterial load, while the remaining virus load was significant, thus strengthening the argument that viruses could be a reliable indicator for fecal contamination. © 2019 Society of Chemical Industry

Microbial removal and plant uptake of nitrogen in constructed wetlands: mesocosm tests on influencing factors

Macrophytes and bacteria are key drivers of nitrogen removal in constructed wetlands. Through mesocosm experiments with vegetated submerged beds and free water surface wetlands in various operational modes, wetland configurations, and system layouts, this study developed empirical models for non-destructive estimation of plant biomass growth and associated nitrogen assimilation and explored the combined effects of multiple factors that influence microbial nitrogen removal. The above-ground biomass of individual plants was a power function of plant height for both Cyperus alternifolius and Typha angustifolia. Below- to above-ground biomass ratio was 0.38 for C. alternifolius and 2.73 for T. angustifolia. Because of greater tolerance to ammonia stress, C. alternifolius and C. papyrus grew faster than T. angustifolia. There were no significant effects of wetland type, vegetation, and plant species on microbial nitrogen removal. Microbial nitrogen removal was inhibited by free ammonia at 13.3-16.2mgN/L. Denitrification and anammox were suppressed at dissolved oxygen greater than 1.9mg/L. Microbial removal of ammonia in vegetated submerged beds was sensitive mainly to dissolved oxygen, pH, and influent ammonia concentration, while in free water surface wetlands, it was sensitive to influent ammonia concentration, pH, and temperature.

Hybrid constructed wetlands for the treatment of wastewater from a fertilizer manufacturing plant: Microcosms and field scale experiments

Wastewater from a fertilizer manufacturing plant requires improvement prior to its environmental disposal. Ammonium is the critical contaminant to be removed. The aim of this study was to evaluate the feasibility of using free water surface wetlands (FWSWs), horizontal subsurface flow wetlands (HSSFWs), and their combination in hybrid wetlands (HWs) for the final treatment of wastewater with high ammonium concentration from a fertilizer manufacturing plant. Substrates and macrophytes were evaluated in microcosm experiments during three months. There were no significant differences in contaminant removal among HSSFWs with LECA or FWSWs planted with Typha domingensis or Canna indica. In a second stage, two configurations of pilot-scale HWs were constructed at the manufacturing facilities. Configuration A: HSSFW(A1)-FWSW(A2) and Configuration B: FWSW(B1)-HSSFW(B2) were evaluated during 12 months. There were no significant differences in contaminant removal (%) between the two configurations of HWs for COD (A: 74.5 ± 12.2/B: 81.5 ± 9.4), ammonium (A: 59.5 ± 17.5/B: 57.9 ± 21.4), nitrite (A: 79.8 ± 24.2/B: 80.6 ± 16.8) and dissolved inorganic nitrogen (DIN) (A: 59.4 ± 17.3/B: 50.3 ± 24.4). However, nitrate concentration (9.83 ± 3.11 mg N L−1) was significantly lower after Configuration A than after Configuration B (18.8 ± 5.2 mg N L−1). Comparing FWSWs and HSSFWs, they did not present significant differences in ammonium removal, while FWSWs presented the highest DIN removal. T. domingensis and C. indica in HSSFWs and T. domingensis in FWSWs tolerated wastewater conditions. T. domingensis presented the highest productivity. In further research, FWSWs in series planted with T. domingensis should be studied.

Evaluación de humedales artificiales de flujo libre superficial con macrófitas acuáticas flotantes

&lt;p class="EstiloEstiloJustificadoTimesNewRoman1"&gt;El objetivo del presente trabajo fue evaluar el comportamiento de humedales artificiales con macrófitas acuáticas, en la concentración de contaminantes de efluentes urbanos. Se construyó un sistema a escala piloto, con dos coberturas de plantas flotantes y dos tiempos de residencia hidráulico, trabajando con flujo laminar continuo. La menor concentración de la demanda química de oxígeno y la demanda biológica de oxígeno, se obtuvieron con la menor cobertura y el mayor tiempo de residencia hidráulico; registrándose poca influencia de las variables en la concentración de nitrógeno total y sólidos suspendidos totales, siendo la respuesta significativa para fósforo total con la menor cobertura de plantas. Hubo una remoción altamente significativa de coliformes totales, independientemente de la cobertura y a favor del mayor tiempo de residencia hidráulico. El uso de humedales de flujo libre superficial es auspicioso para el control sanitario, demostrando baja incidencia sobre nitrógeno total y fósforo total.&lt;/p&gt;