Los Angeles, CA, United States
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Kadlec R.H.,Chelsea Management | Zmarthie L.A.,Spicer Group
Ecological Engineering | Year: 2010

A wetland system has operated seasonally at Saginaw Township, MI, USA, for ten years. The system consists of extraction, aeration, settling, intermittent vertical sand filtration, a surface flow wetland treatment with recycle, and discharge to the Tittibawassee River. The 0.85 ha cattail wetland treats the full leachate flow, with a total system detention time of 180 days. The high recycle rate creates a lesser wetland detention time of 60 days. Ammonia is the principal contaminant of concern, because it occurs at high concentrations, typically 300-500 mg/L. Ammonia mass reduction averaged 99.5% for the last nine years, with a 95% mass removal in the startup year. Metals were not present in all samples, with modest reductions in those always present (zinc 16%, arsenic 29%, barium 78%, chromium 67%). Volatile organic compounds were removed to below detection, excepting BTEX, which occurred in only 2% of the outflow samples. Base neutral organics, PCBs and pesticides were also removed to below detection, excepting phthalates with an outlet detection frequency of 29%. No pesticides or PCBs were detected in the system outflow. The ammonia removal rate coefficients for the wetland (12 m/yr) was at the 55th percentile of the distribution for other surface flow wetlands. The vertical filter was likely oxygen limited, and functioned with an apparent oxygen utilization of 30 gO/(m2 d). © 2010 Elsevier B.V. All rights reserved.


Kadlec R.H.,Chelsea Management | Martin D.C.,ASTI Environmental | Tsao D.,Torch Inc
Ecological Engineering | Year: 2012

A 1.28ha free water surface wetland was constructed and operated for 11 years for the purpose of reducing chlorinated ethenes in a contaminated groundwater plume in midwestern USA. The gravity fed wetland received an average of 148m3/d of intercepted groundwater at a mean annual temperature of 12.4°C. After startup, plume concentrations were approximately 2000μg/L of trichloroethylene (TCE) and 1000μg/L of cis-1,2-dichloroethylene (DCE), and were reduced to below 25μg/L each on an annual basis. Vinyl chloride (VC) was reduced from 21μg/L in the plume to 2.9μg/L at the wetland outlet annually, below regulatory limits. Rates of removal were the highest in spring, and the lowest in winter. Flows were mildly variable across seasons, but dissolved oxygen (DO) was very high in spring, and very low in late summer. Tracer tests helped to delineate flow patterns. During the project lifetime, modifications were made, including filling deep zones to discourage muskrats, adding interior finger berms to improve hydraulics, and adding an effluent recirculation (recycle) system to degrade VC during times of low DO. The wetland system developed rapidly to a vegetatively diverse and healthy ecosystem, supporting over 60 bird species and numerous other animal species. © 2012 Elsevier B.V..


Tanner C.C.,NIWA - National Institute of Water and Atmospheric Research | Kadlec R.H.,Chelsea Management
Ecological Engineering | Year: 2013

A simple first-order dynamic model that accounts for hydrology, nitrate concentrations, internal hydraulic efficiency and water temperature was used to evaluate the influence of influent hydrological regimes on nitrate-N removal performance in surface-flow wetlands. The model, run using hourly hydrological and climatic data for a wetland treating subsurface tile drainage, was able to closely simulate flow-proportional nitrate-N concentrations recorded at the wetland outlet. Applying the model to 7 different annual flow regimes showed substantial year-to-year differences in predicted percentage and mass nitrate-N removal performance. Predicted areal mass removal rates declined markedly as wetland size was increased from 0.5 to 5% of contributing catchment, illustrating the diminishing returns achievable and the performance limits of wetland treatment receiving highly variable diffuse flows. Doubling the wetland size from 1% to 2% of contributing catchment provided about 75% increase in performance, but doubling from 2% to 4% of catchment area only provided about 43% further improvement. Large wetland areas occupying 5% of contributing catchment were predicted on average to be able to remove a maximum of 55% of the nitrate-N loads delivered, with removal expected to range between 40 and 70% of the nitrate-N load from year-to-year depending primarily on the flow regime. Application of the model to equivalent wetlands receiving normalised stream flows (same nitrate-N concentration, total flow and load) from up- and down-stream sites in two catchments with contrasting flow regimes predicted substantially better overall performance when flows were steady or exhibited low variability. With increasing flow variability predicted wetland nitrate-N removal efficiency was reduced by 5-14 and 13-21 percentage points for wetlands occupying 1 and 4% of catchment area, respectively. We conclude that flow regime is likely to be a key factor influencing the nitrate-N removal performance of surface-flow wetlands receiving diffuse flows from agricultural catchments. Seasonal patterns and variability of flow need to be seriously considered when assessing expected performance, and in optimising the location and design of wetlands for diffuse pollution management. © 2012 Elsevier B.V.


Walker W.W.,Environmental Engineer | Kadlec R.H.,Chelsea Management
Critical Reviews in Environmental Science and Technology | Year: 2011

Longitudinal gradients in phosphorus (P) stored in the water column, vegetation, and soils develop in the wetlands where inflow P concentrations exceed background levels. Before the mid 1990's, the Everglades regional P gradient ranged from 100-200 mg L -1 in marsh inflows to background levels of 4-8 mg L -1. Subsequent implementation of P controls, including agricultural Best Management Practices and Stormwater Treatment Areas (STAs), has reduced the average inflow concentration along the northern edge of the Water Conservations Areas to approximately 30-50 mg L -1. Additional P controls are being implemented and further measures beyond those currently planned will be required to restore the entire marsh. The authors describe the evolution and application of relatively simple mass-balance models to simulate P storage and cycling processes along P gradients in the STAs and marsh. The models are practical tools with historical and future applications to designing P control measures involving source controls, water management, reservoirs, and STAs, as well as forecasting marsh responses to implementation of those control measures. Copyright © 2011 Taylor & Francis Group, LLC.


Kadlec R.H.,Chelsea Management | Pries J.,CH2M HILL | Lee K.,Municipality of Brighton
Ecological Engineering | Year: 2012

The Town of Brighton, Ontario implemented a 6.2ha marsh in 2000, for the purpose of improving water quality before discharge to receiving waters. The wetlands have successfully operated in this moderately cold climate for over ten years. Phosphorus removal of 2.3gP/(m2yr) was achieved, with an annual areal rate coefficient of 9.2m/yr. The removal is strongly seasonal, with the greatest reductions occurring in spring. The total nitrogen loading was dominated by ammonia (208gN/(m2yr)), with smaller amounts of organic and oxidized nitrogen. Ammonia was reduced to 173gN/(m2yr). Implied areal rate constants were high for mineralization of organic nitrogen (29m/yr) and denitrification (101m/yr), but low for nitrification (4m/yr). CBOD5 was reduced from 5.4 to 3.2mg/L, and TSS was reduced from 13.2 to 7.2mg/L, both with slightly higher values during late winter. The wetland was not effective in reducing pathogens, with Escherichia coli at 167cfu/100ml entering, and 132cfu/100ml leaving. Vegetation was sparse, likely due to muskrats and deep water. Macro-invertebrate diversity was lower than for regional wetlands. Bird use was very high, and birding was a popular human activity. The wetland has been designated as provincially significant. © 2012 Elsevier B.V.


Kadlec R.H.,Chelsea Management
Ecological Engineering | Year: 2010

The dynamics nitrate retention and export were studied at the Des Plaines River wetland demonstration site. Seven wetlands received pulses of river water in discrete pumping events. Twenty-eight wetland events were monitored over 4 years for all hydrologic variables, pumping, rain, storage change, and outflow. Nitrate was measured at high frequency for the ouflows, and at lower frequency for inflows and interior stations. Most events were isolated in time, with sufficient inter-event spacing to allow complete equilibration before the subsequent event. Pumping was selected to provide up to 45 displacements of the wetland water volume. River water averaged 2.3 mg/L of nitrate nitrogen, and wetland effluent averaged 0.9 mg/L. The average mass removal of nitrate was 67% over all events, with a range from 17% to 100%. A calibrated dynamic water mass balance was developed as the framework for interpreting results. Internal hydraulics were characterized by tanks-in-series (TIS) models calibrated to tracer studies. Residence time distributions were describable by three TIS (three wetlands) and five TIS (four wetlands). Dynamic nitrate mass balances were used, in conjunction with a first order areal uptake model, to model the time sequence of NO3N concentrations and flows. Parameter estimation, based on NO3N mass flow fitting, produced rate constants that best described the series of events the wetlands. Rate constants were much higher for the events than for previous steady state performance for the wetlands (k20 = 107 vs. 37 m/yr). Rate coefficients increased at higher water temperatures, with a modified Arrhenius temperature factor of 1.090. Performance for N removal was found to be partially due to displacement of antecedent treated water, and partially due to treatment occurring during the event, and partially due to treatment after the event. Carbon availability was estimated not to limit denitrification, except possibly at the highest nitrate loadings. © 2009 Elsevier B.V. All rights reserved.


Kadlec R.H.,Chelsea Management
Water (Switzerland) | Year: 2016

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. © 2016 by the authors.


Kadlec R.H.,Chelsea Management
Critical Reviews in Environmental Science and Technology | Year: 2012

Large numbers of free water surface treatment wetlands are in use for nitrate reduction. Target applications are field runoff, river and stream improvement, and enhancement of wastewater treatment plants. In total, an extensive database now exists, in many publications and operating reports.Microcosms and mesocosms are not included here because of the lack of transferability to design. A first-order areal model is appropriate, to be implemented with appropriate temperature, hydraulic efficiency, and flow pattern. Annual average rate constants at 20°C have a median of 25 m/year. Performance is better at higher water temperatures, with a modified Arrhenius temperature factor of 1.106. Measured values of the tanks-in-series (TIS) parameter average N = 4.4 TIS. Higher rate coefficients are associated with emergent soft tissue vegetation, and lower efficiencies with submergent vegetation, unvegetated open water, and forested wetlands. Carbon availability can limit denitrification at high nitrate loadings; however, wetlands produce carbon in sufficient quantities to support typical municipal and agricultural loads. Design may be for load reduction or concentration reduction, with the latter requiring larger wetlands. Significant ancillary benefits of ecological diversity and wildlife habitat are certain to accompany the project. A small negative greenhouse gas penalty, which accrues to all new wetlands, is not an important factor. Economic issues may include land cost and pumping cost. Constructed marshes are an ecologically and economically attractive method for reducing nitrate levels in surface waters. Copyright © Taylor & Francis Group, LLC.


Mifsud D.A.,Chelsea Management
Journal of Great Lakes Research | Year: 2014

Amphibians and reptiles are key bioindicators of environmental health and habitat quality and can be used to provide baseline information to help assess habitat conditions and evaluate restoration success. In 2011 and 2012 we conducted comprehensive herpetological surveys throughout the Saginaw Bay area and assessed community composition, species richness, and spatial distribution. We also compared current distributions to historic observations and habitat conditions. A total of 25 taxa (13 species of reptiles and 12 species of amphibians) were observed within the Saginaw Bay area during this study. Herpetofauna were conspicuously unobserved in areas where Phragmites australis dominates the vegetation community and were concentrated in remaining areas of suitable habitat adjacent to Phragmites. Herpetofauna observations were clustered in areas where Phragmites and other invasive plant species were rare or absent. We were able to relate categorization of Phragmites invasion (i.e., 1. = 0-10% colonization detected, 2 = 10-50%, 3 > 50%) to both a biologically and statistically significant decrease in amphibian and reptile species richness. Our results indicate that Saginaw Bay can support a diverse herpetofauna community and there is potential to restore and improve this region for rare and common amphibian and reptile species. Removal of invasive plant species would greatly improve herpetofaunal communities within Saginaw Bay. Our results will help this region's resource professionals assess the quality of habitat and set goals for restoration of amphibian and reptile habitats. © 2013 Elsevier B.V.


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