Stormwater Wetlands Research Articles

Trace Metal Accumulation in Sediments and Benthic Macroinvertebrates before and after Maintenance of a Constructed Wetland

Stormwater best management practices (BMPs) require regular maintenance. The impact on trace metal concentrations in a constructed stormwater wetland BMP on Staten Island, New York, was investigated by analyzing sediment concentrations and tissue residues of the dominant macroinvertebrates (Tubifex tubifex) prior and subsequent to maintenance. Trace metal concentrations were assessed using standard serial extraction (for sediment) and acid digestion (for tissue burdens) techniques, followed by quantitative determination using graphite furnace atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry, respectively. The results suggest that disturbance of sediment during maintenance of the BMP resulted in an increase in the most mobile fraction of trace metals, especially those associated with finer grained sediments (< 63 tm), and as a consequence, measured metal concentrations in macroinvertebrates increased. Regressions of a subset of metal concentrations (copper, lead, and zinc) in sediment and the macroinvertebrate tissue burden samples generally increased as a result of maintenance. A follow-up sampling event 9 months after maintenance demonstrated that the most readily available form of trace metal in the BMP was reduced, which supports (1) long-term sequestration of metals in the BMP and (2) that elevated bioavailability following maintenance was potentially a transient feature of the disturbance. This study suggests that in the long-term, performing sediment removal might help reduce bioavailability of trace metal concentrations in both the BMP and the receiving water to which a BMP discharges. However, alternative practices might need to be implemented to reduce trace metal bioavailability in the short-term.

Factors affecting mosquito populations in created wetlands in urban landscapes

Constructed, created and restored wetlands are gaining popularity in urban areas due to many ecosystem services they provide. However, there is a concern over mosquito breeding in such wetlands. We studied factors affecting mosquito populations in two experimental flow-through created wetlands, a stormwater wetland, a pond and 40 mono-specific and mixed plant mesocosms (1 m2) at the Olentangy River Wetland Research Park (ORWRP) in Columbus, Ohio. The flow-through created wetlands had less mosquito larval density (2 to 4/dip) compared to the pond (36.2 ± 8.4/dip) (p < 0.00001) and stormwater wetland (24.9 ± 10.2/dip) (p = 0.002). Sites with higher larval density in the flow-through wetlands were outflow regions (p = 0.009) and emergent vegetation sites (p = 0.023). Mixed vegetation communities consisting of Sparganium eurycarpum, Juncus effusus, and Schoenoplectus tabernaemontani rather than mono specific Typha communities provided most conducive environment for mosquito breeding (p < 0.0001). Mesocosm plots with steady inflow (10 cm depth) and deep water (20 cm) in summer and shallow water (5 cm) in spring had higher mosquito densities than mesocosm plots with other hydrological conditions. Among water quality parameters, conductivity (p = 0.004) positively and dissolved oxygen (p = 0.052) negatively correlated with mosquito larval density. Six mosquito species identified in all water bodies were Culex pipiens, Culex salinarius, Culex restuans, Uranotaenia sapphirina, Anopheles quadrimaculatus, and Anopheles punctipennis some of which may transmit deadly human pathogens. This information will be useful for targeting mosquito populations in specific sections of urban created wetlands and to develop improved designs for urban wetlands.

Harvestable Nitrogen Accumulation for Five Storm Water Wetland Plant Species: Trigger for Storm Water Control Measure Maintenance?

As the use of constructed storm water wetlands to treat storm water runoff becomes more frequent, strategies for maintaining or increasing their pollutant removal over time must be examined. One potential strategy is plant harvesting at the water surface to remove nutrients that would otherwise be deposited back into the wetland during senescence. This technical note presents a first look at this strategy from a storm water management perspective. Vegetation was harvested from two storm water wetlands located in Smithfield and Pactolus, North Carolina, to evaluate the ability of five wetland plant species to sequester nitrogen. Biomass samples were collected from the following species of emergent vegetation: Pontederia cordata (Pickerelweed), Saururus cernuus (Lizard Tail), Scirpus cyperinus (Wool Grass), Sagittaria latifolia (Arrowhead), and Schoenoplectus tabernaemontani (Softstem Bulrush). Samples were collected immediately prior to senescence in September and October 2007 and analyzed for nitrogen content on a percent of biomass basis. At the Pactolus wetland the Pontederia cordata, Scirpus cyperinus, and Schoenoplectus tabernaemontani biomass retained significantly (p<0.05) more nitrogen than Sagittaria latifolia and Saururus cernuus. At the Smithfield wetland, Pontederia cordata and Sagittaria latifolia biomass retained significantly more nitrogen than Scirpus cyperinus and Saururus cernuus. Wetland maturity appears to have a direct relationship to harvestable nitrogen, which could explain why the relative amount of nitrogen sequestered in Scirpus cyperinus and Sagittaria latifolia varied between the two wetlands. A positive relationship existed between the density of harvested biomass and nitrogen removal for two species. To estimate the relative amount of harvestable nitrogen, a model for estimating total nitrogen loading in Coastal Plain watersheds in North Carolina was used to compare estimated inflow nitrogen mass to that which could theoretically be harvested. The harvestable N mass was greater than 20% of inflow nitrogen on an annual basis. Storm water wetland plant harvesting as a maintenance activity has potential to supplement wetland nitrogen removal.

A characteristic study on the particles in a constructed stormwater wetland during dry days

ABSTRACT A 0.78 ha stormwater wetland was monitored during dry days for the characteristic behavior of particles over a period of 4 mo (June 9–September 5, 2009). The results indicated that the particles in the outflow were finer than those in the inflow due to resuspension of the fine particles and algal growth in the wetland. Based on the particles number density, the particle removal efficiency varied over a wide range (–4000–100%). This variation was largely dependent on resuspension and antecedent dry days. In terms of particles removal, the wetland can be considered as a fiber-bed filter, which is facilitated by the mechanisms of interception, diffusion and sedimentation. Particles with different size ranges showed different removal behaviors due to the different controlling removal mechanisms. The curve for the removal of particles can be divided into three parts, with two turning points within the ranges of 0.51–1 μm and 2–5 μm. Particles less than 4 μm occupied a higher number fraction, with a lo...

Operation of the vertical subsurface flow and partly submersed stormwater wetland with an intermittent recycle

ABSTRACT In this study, a vertical subsurface flow (VSF) stormwater wetland having a partially submersed zone in the bottom was operated for 90 d. This wetland is designed to recycle the effluent on the basis of designated antecedent dry days (ADDs). A total of four groups of bench-scale VSF wetlands filled with different media such as woodchip, pot gravel, synthetic fiber and volcanic stone were made. Each group of wetlands having the same media was operated with different recycle scheme. Operational results show that at the beginning of the wetland operation for about 30 d, there was a maturation or acclimation phase as usually observed in a filter and biofilm process. After the acclimation phase, the wetland displayed stable functions. Regardless of the media and operational mode employed, all groups of wetland were found to be able to reduce 70% of TSS in the stormwater. For nutrients removal, different medium showed different performances. Woodchip was most effective for TN removal (more than 25%), w...

A characteristic study on the particles in a constructed stormwater wetland during dry days

A characteristic study on the particles in a constructed stormwater wetland during dry days

Operation of the vertical subsurface flow and partly submersed stormwater wetland with an intermittent recycle

Operation of the vertical subsurface flow and partly submersed stormwater wetland with an intermittent recycle

Sustainable Engineering Design Evaluation: Town of Didsbury North Industrial Stormwater Wetland

Sustainable Engineering Design Evaluation: Town of Didsbury North Industrial Stormwater Wetland

Ecosystem service provision by stormwater wetlands and ponds – A means for evaluation?

Stormwater control measures (SCMs) such as constructed stormwater ponds and constructed stormwater wetlands (CSWs) are designed to regulate runoff hydrology and quality. However, these created ecosystems also provide a range of other benefits, or ecosystem services, which are often acknowledged but rarely quantified. In this study, additional ecosystem services, including carbon sequestration, biodiversity, and cultural services, were assessed and compared between 20 ponds and 20 CSWs in North Carolina, USA. Carbon sequestration was estimated through the carbon content of pond and wetland sediments across a gradient of system age. Biodiversity was quantified in terms of the richness and Shannon diversity index of vegetative and aquatic macroinvertebrate communities. Cultural services were qualitatively assessed based on the potential for recreational and educational opportunities at each site. Ponds and wetlands were found to support similar levels of macroinvertebrate diversity, though differences community composition arose between the two habitat types. CSWs demonstrated greater potential to provide carbon sequestration, vegetative diversity, and cultural ecosystem services. This assessment provides an initial framework upon which future assessments of ecosystem service provision by SCMs can build.

Removal of dissolved pesticide mixtures by a stormwater wetland receiving runoff from a vineyard catchment: an inter-annual comparison

Wetlands can collect contaminated runoff from agricultural catchments and have intrinsic physical, chemical and biological retention and removal processes useful for mitigating pesticides. However, knowledge about the ability of stormwater wetlands to mitigate pesticide mixtures in runoff is currently very limited. We show here that stormwater wetlands that primarily serve for flood protection can also be effective tools for reducing concentrations and removing loads of runoff-related pesticides and some of their degradation products into downstream aquatic ecosystems. Dissolved concentrations and loads of seven fungicides, six herbicides and four degradation products in runoff from a vineyard catchment were continuously recorded at the inlet and the outlet of the stormwater wetland during two successive periods of pesticide application (April to June). Reduction of pesticide concentrations by the wetland ranged from 50% (simazine) to 100% (azoxystrobin, cymoxanil, cyprodinil, gluphosinate, terbuthylazine and tetraconazole). Removal rates of dissolved load ranged from 26% for aminomethylphosphonic acid (AMPA) to 100% (azoxystrobin, cymoxanil, cyprodinil, diuron, 1-(3,4-dichlorophenyl)-3-methylurea (DCPMU), gluphosinate, kresoxym methyl, terbuthylazine and tetraconazole). More than 77% of the input mass of total suspended solids was retained, underscoring the capability of the wetland to trap pesticide-laden particles via sedimentation. Inter-annual change in the removal of AMPA, isoxaben, kresoxim methyl and simazine was mainly linked to the larger vegetal cover in 2010. Our results demonstrate that stormwater wetlands can remove pesticide mixtures in agricultural runoff, although removal of individual pesticides can vary over time, depending on the characteristics of runoff events and the vegetation cover.

Hydraulic residence time computation for constructed wetland design

Hydraulic residence time (HRT) is one of the key design parameters controlling the removal efficiency of contaminants and nutrients in stormwater and wastewater wetlands. The paper presents a new approach to the estimation of HRT using the variable residence time (VART) model. The VART model is employed to simulate the major processes (including advection, dispersion, and transient storage of contaminants/nutrients in vegetated zones) affecting HRT and thereby to produce a hydraulic residence time distribution (HRTD) for a design wetland. The HRTD in combination with a moment-based method is then utilized to find a mean design HRT for the design wetland. Methods for estimation of parameters governing the HRTD are proposed. The new approach to HRT computation is demonstrated through a case study for the Tres Rios Demonstration (TRD) Wetlands in Arizona, USA. Modeling results show that the design HRTs for the Hayfield wetland (H1) and the Cobble wetlands (C1 and C2) are 4.04, 4.66, and 2.65 days, respectively. The computed HRTs agree well with those reported by previous studies, confirming the efficacy of the new approach to hydraulic design of constructed wetlands.

Constructed Storm-Water Wetland Installation and Maintenance: Are We Getting It Right?

Constructed storm-water wetlands (CSWs) have become one of the more popular storm-water control measures (SCMs). CSWs offer a hybrid between larger detention technologies like storm-water wet ponds and newer green infrastructure technologies. The systems are characterized as being predominately shallow retention practices, with water elevations sufficiently low to support diverse flora and fauna. Figs. 1(a–c) illustrate several successful examples of CSWs. Many researchers have found that CSWs remove sediment, nutrients, and metals from storm-water runoff (Greenway 2004; Hathaway and Hunt 2010; Line et al. 2008; Kohler et al. 2004; Wadzuk et al. 2010). One of the principal drivers for the use of storm-water wetlands is the amount of credit awarded to them by various governmental agencies with respect to nutrient removal and sequestration [North Carolina Department of Environment and Natural Resources (NCDENR) 2009]. The apparent improvement in nutrient capture from storm-water runoff over that of storm-water wet ponds is one of the main reasons designers choose CSWs over the more traditional wet pond. Extensive coverage of vegetation allows for several pollutant removal mechanisms: filtration of particles, stabilization of sediments, nutrient uptake, microbialrhizophere interaction to promote nitrification and denitrification, and the provision of increased surface area for biofilm/periphyton growth (Greenway 2004). In regions where thermal loads threaten cold water fisheries, CSWs have been shown to release cooler water to streams than do wet ponds because of the shading caused by the vegetation—but absent from wet ponds (Jones and Hunt 2010). Some concerns have also presented themselves with respect to CSWs, which have prevented the practice from outright replacing the wet pond. Foremost among them is the threat of mosquito infestation that wetlands invariably face in relation to the public (QDNR 2000). Research has shown that exorbitantly high mosquito populations need not accompany CSWs, provided they are diversely vegetated (Greenway et al. 2003; Hunt et al. 2006). However, if wetlands are allowed to become monocultures of specific mosquito-protective plants, such as Typha spp. (commonly referred to as cattails in the United States), they can become the very mosquito breeding grounds that the public fears (Greenway et al. 2003; Hunt et al. 2005). If storm-water wetlands are to be constructed, they must both (1) meet their intended water quality (and hydrologic) design goals and (2) not be a public nuisance. Anecdotal observation of CSWs constructed worldwide shows how many well-intended CSW designs fail. Two principal reasons were identified: One appears to be that not enough care was taken to ensure the storm-water wetlands’ normal pool elevation was appropriately shallow (that is, often the elevation of water in CSWs is too deep). The cause has been previously identified by Greenway et al. (2007). The second is clogging of the outlet structure that artificially raises the elevation above normal pool for extended periods of time. In both cases, simple preventative actions could be taken to ensure constructed storm-water wetlands maintain their designed integrity. The purpose of this forum is to document how poor design and inadequate management of two CSWs caused each to effectively become wet ponds, which results in (1) a reduced efficiency in the removal of some pollutants; (2) a degradation of biodiversity, which leads to an increased risk of having the wetlands become mosquito breeding grounds; and (3) degraded aesthetics.

Seasonal Changes of Macroinvertebrate Communities in a Stormwater Wetland Collecting Pesticide Runoff From a Vineyard Catchment (Alsace, France)

Agricultural land use may influence macroinvertebrate communities by way of pesticide contamination associated with agricultural runoff. However, information about the relation between runoff-related pesticides and communities of benthic macroinvertebrates in stormwater wetland that receive agricultural runoff does not currently exist. Here we show changes in macroinvertebrates communities of a stormwater wetland that collects pesticide-contaminated runoff from a vineyard catchment. Sixteen runoff-associated pesticides, including the insecticide flufenoxuron, were continuously quantified at the inlet of the stormwater wetland from April to September (period of pesticide application). In parallel, benthic macroinvertebrate communities, pesticide concentrations, and physicochemical parameters in the wetland were assessed twice a month. Twenty-eight contaminated runoffs ranging from 1.1 to 114 m3 entered the wetland during the study period. Flufenoxuron concentrations in runoff-suspended solids ranged from 1.5 to 18.5 μg kg(-1) and reached 6 μg kg(-1) in the wetland sediments. However, flufenoxuron could not be detected in water. The density, diversity, and abundance of macroinvertebrates largely varied over time. Redundancy and formal concept analyses showed that concentrations of flufenoxuron, vegetation cover, and flow conditions significantly determine the community structures of stormwater wetland macroinvertebrates. This study shows that flow conditions, vegetation cover, and runoff-related pesticides jointly affect communities of benthic macroinvertebrates in stormwater wetlands.

Exploring fecal indicator bacteria in a constructed stormwater wetland

Microbial pollution in surface waters is a concern throughout the world, with both public health and economic implications. One contributing source to such pollution is stormwater runoff, often treated using various types of stormwater control measures. However, relatively little is known regarding microbe sequestration in constructed stormwater wetlands (CSWs), one type of commonly installed stormwater control measure. In this study, indicator bacteria concentrations in both the water and sediment of a CSW were evaluated at multiple locations. Results suggested that fecal coliform concentrations in stormwater runoff decrease through the system, with relatively consistent concentrations noted throughout the second half of the wetland. This potentially indicates a baseline concentration of fecal coliform is present due to internal processes such as animal activity and microbial persistence. However, wetland sediments showed little E. coli present during most sampling events, with minimal patterns existing with respect to sediment sampling location. CSW designs should promote optimization of hydraulic retention time and minimization of stormwater velocities to promote sedimentation and degradation of microbes by way of wetland treatment functions.

Removal of pesticide mixtures in a stormwater wetland collecting runoff from a vineyard catchment

Wetlands can collect contaminated runoff from agricultural catchments and retain dissolved and particle-laden pesticides. However, knowledge about the capacity and functioning of wetland systems with respect to the removal of pesticides is very limited. Here we show that stormwater wetlands can efficiently remove pesticides in runoff from vineyard catchments during the period of pesticide application, although flow and hydrochemical conditions of the wetland largely vary over time. During the entire agricultural season, the inflowing load of nine fungicides, six herbicides, one insecticide and four degradation products was 8.039 g whereas the outflowing load was 2.181 g. Removal rates of dissolved loads by the wetland ranged from 39% (simazine) to 100% (cymoxanil, gluphosinate, kresoxim methyl and terbuthylazine). Dimethomorph, diuron, glyphosate, metalaxyl and tetraconazole were more efficiently removed in spring than in summer. More than 88% of the input mass of suspended solids was retained, underscoring the capability of the wetland to trap pesticide-laden particles via sedimentation. Only the insecticide flufenoxuron was frequently detected in the wetland sediments. Our results demonstrate that stormwater wetlands can efficiently remove pesticide mixtures in agricultural runoff during critical periods of pesticide application, although fluctuations in the runoff regime and hydrochemical characteristics can affect the removal rates of individual pesticides.

Organic nitrogen exports from urban stormwater wetlands in North Carolina

Effluent organic nitrogen concentrations from seven constructed stormwater wetlands in North Carolina were examined to compare background organic nitrogen (ON) concentrations and the fraction of organic nitrogen relative to total nitrogen discharged. Seasonal influences on organic nitrogen concentrations were also examined. The median ON concentration from the stormwater wetlands was 0.78 mg l −1, and despite differences in wetland design and influent ON characteristics, outlet ON concentrations from all but one wetland were not significantly different. ON export from all stormwater wetlands was significantly less than untreated runoff entering the wetlands ( p = 0.002). In addition, median organic:total nitrogen (ON:TN) ratios from stormwater wetlands (0.75) were significantly greater than from untreated urban runoff (0.66), comparing more closely to ON:TN ratios collected from a naturally occurring wetland and reported in the literature for natural landscapes. Seasonal differences in organic nitrogen concentrations were identified with significantly lower concentrations during the winter. Though stormwater wetlands will not (and perhaps should not be expected to) completely remove total nitrogen loads from runoff, these results suggest constructed wetlands can play a role in restoring the balance between organic and inorganic nitrogen forms closer to that of an undisturbed landscape. The presence of background organic nitrogen concentrations from stormwater wetlands similar to those from a naturally occurring wetland highlights the importance of choosing appropriate metrics (e.g., effluent concentrations) when assessing treatment performance.

An Evaluation of the Toxicity of Accumulated Sediments in Forebays of Stormwater Wetlands and Wetponds

Forebays, small settling basins placed at the inlet of Stormwater Best Management Practices, encourage sedimentation with the intention of pollutant consolidation and capture. Regularly, accumulated sediments are excavated to restore forebay storage volume and to further prevent contamination of downstream waterbodies during large storm events. Disposal measures vary according to the toxicity of sediments. To test for the potential toxicity of forebay spoils, 30 stormwater wetland and wetpond forebays of varying age, size, and upstream landuse were sampled across North Carolina and analyzed for seven metals: cadmium, chromium, copper, iron, lead, nickel, and zinc. Ten of 30 sites were also sampled near the outlet structures for spatial comparison of settled sediment and pollutant presence. The relative toxicity of all sampled sediment metal concentrations was evaluated using existing aquatic health sediment guidelines and US Environmental Protection Agency standards for the land application of biosolids (40 CFR503). Of 30 sites, 17 exceeded sediment guidelines for aquatic health, emphasizing the need for routine forebay sediment removal. However, all samples were less than 40 CFR 503 limits with factors of safety ranging from 2.3 to 28, indicating that land application of forebay sediment is unlikely to pose an environmental threat. Additionally, forebay sediment tended to have lower metal toxicity than sediment collected at the pond or wetland outlet.

Integration of Education, Scholarship, and Service through Stormwater Management

Abstract:Education, scholarship, and service are the cornerstones of academia. This paper describes how the design, construction, and research of stormwater control measures on the campus of Villanova University has been used to integrate these three facets of academic life. To date, eleven stormwater control measures have been constructed on Villanova's campus. This paper will focus on how the authors have successfully used three of these stormwater control measures, a constructed stormwater wetland, a rain garden, and a porous asphalt/pervious concrete comparison study, to fulfil the university's commitments to education, scholarship, and service.

Apparent Rapid Loss of Endocrine Disruptors from Wetlands Used to Store Either Tertiary Treated Sewage Effluent or Stormwater Runoff

The disruption of endocrine systems due to environmental contaminants potentially impacts on the developmental, behavioural, regulatory and reproductive systems of animals. A major source of exposure of animals (terrestrial and aquatic) to endocrine-disrupting compounds is through contact with contaminated surface waters contaminated with sewage effluent and/or stormwater discharge. We studied the response to endocrine-disrupting compounds of Gambusia holbrooki mosquito fish resident of wetlands that were used for the storage of either treated sewage effluent or stormwater runoff. We found that fish from wetlands that received polluted waters directly from the source (treated sewage effluent or stormwater runoff) demonstrated a morphological response consistent with endocrine disruption. In contrast, fish in the second in the series of wetlands that housed treated sewage effluent did not show evidence of such response. However, those from the second in the series of stormwater receiving wetlands did display a morphological response, although it could be considered milder than was observed in fish from the first in this effluent stream. Fish were also smaller in the wetland that received sewage effluent directly from the sewage treatment plant than elsewhere. Although the differences were not statistically significant, the average size of fish in the first in the series of stormwater wetlands were also small and second only to those in the first sewage effluent wetland.

Quantification of herbicide removal in a constructed wetland using passive samplers and composite water quality monitoring

Constructed wetlands used as treatment for urban stormwater have the potential to improve water quality. This study aimed to estimate the removal of selected herbicides in stormwater by a constructed wetland using composite water quality monitoring and passive samplers. For the four week duration of the study the wetland was effective in reducing the concentrations of diuron, simazine and atrazine. Mean estimated concentrations over a 28 d period were 192, 70 and 5 ng L −1 at the inlet and 94, 30 and 2 ng L −1 at the outlet for diuron, simazine and atrazine, respectively. Concentrations of these herbicides generally halved as a result of passage through the constructed wetland with a design hydraulic retention time of 7 d. Simple ratios of the inlet and outlet herbicide concentrations as well as hydraulic load-based methods of measuring the wetland’s removal efficiency resulted in a range of estimations 33–51% for diuron and 20–60% for simazine. Due to their lower detection limits, the use of passive samplers provides a more efficient technique than conventional sampling for assessment of stormwater wetland treatment.