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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.
Robert H. Kadlec. Large Constructed Wetlands for Phosphorus Control: A Review. Water 2016, 8, 243 .
AMA StyleRobert H. Kadlec. Large Constructed Wetlands for Phosphorus Control: A Review. Water. 2016; 8 (6):243.
Chicago/Turabian StyleRobert H. Kadlec. 2016. "Large Constructed Wetlands for Phosphorus Control: A Review." Water 8, no. 6: 243.
The Town of Brighton, Ontario implemented a 6.2 ha 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 2.3 gP/(m2 yr) was achieved, with an annual areal rate coefficient of 9.2 m/yr. The removal is strongly seasonal, with the greatest reductions occurring in spring. The total nitrogen loading was dominated by ammonia (208 gN/(m2 yr)), with smaller amounts of organic and oxidized nitrogen. Ammonia was reduced to 173 gN/(m2 yr). Implied areal rate constants were high for mineralization of organic nitrogen (29 m/yr) and denitrification (101 m/yr), but low for nitrification (4 m/yr). CBOD5 was reduced from 5.4 to 3.2 mg/L, and TSS was reduced from 13.2 to 7.2 mg/L, both with slightly higher values during late winter. The wetland was not effective in reducing pathogens, with Escherichia coli at 167 cfu/100 ml entering, and 132 cfu/100 ml 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.
Robert H. Kadlec; John Pries; Keith Lee. The Brighton treatment wetlands. Ecological Engineering 2012, 47, 56 -70.
AMA StyleRobert H. Kadlec, John Pries, Keith Lee. The Brighton treatment wetlands. Ecological Engineering. 2012; 47 ():56-70.
Chicago/Turabian StyleRobert H. Kadlec; John Pries; Keith Lee. 2012. "The Brighton treatment wetlands." Ecological Engineering 47, no. : 56-70.
Two demonstration treatment wetland systems were studied for over four years. Both consisted of sedimentation basins, followed by wetland cells. The Imperial, CA system had four wetland cells totaling 4.7 ha, 25% vegetated with bulrushes (Schoenoplectus californicus), and the Brawley, CA system had two wetland cells totaling 1.8 ha, also 25% vegetated with bulrushes. Imperial received irrigation runoff water at 30 cm/day, and Brawley received New River water at 11 cm/day, both with moderately high levels of nutrients, sediments and pathogens. The systems seeped 40–60% of the incoming water. The hydraulic efficiencies of the systems were high because of compartmentalization and high aspect ratios. Concentration reductions of TN, TP and TSS were 50%, 39%, and 97% at Imperial, and 73%, 50% and 96% at Brawley. Imperial achieved about 1.5 log10 reductions in total coliforms, fecal coliforms and Escherichia coli, while Brawley achieved about 2.7 log10 reductions. The sedimentation basins settled most of the incoming TSS, as well as the algal solids that were generated in the basins. Algal uptake removed nutrients in the basins, which were supersaturated with oxygen. The wetlands were effective in denitrification, and trapped the remaining and generated TSS. Removal rate constants, corrected for infiltration, were at the high end of those reported for other wetlands.
Robert H. Kadlec; Sujoy B. Roy; Ronald K. Munson; Stephen Charlton; William Brownlie. Water quality performance of treatment wetlands in the Imperial Valley, California. Ecological Engineering 2010, 36, 1093 -1107.
AMA StyleRobert H. Kadlec, Sujoy B. Roy, Ronald K. Munson, Stephen Charlton, William Brownlie. Water quality performance of treatment wetlands in the Imperial Valley, California. Ecological Engineering. 2010; 36 (8):1093-1107.
Chicago/Turabian StyleRobert H. Kadlec; Sujoy B. Roy; Ronald K. Munson; Stephen Charlton; William Brownlie. 2010. "Water quality performance of treatment wetlands in the Imperial Valley, California." Ecological Engineering 36, no. 8: 1093-1107.
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).
Robert H. Kadlec; Linda A. Zmarthie. Wetland treatment of leachate from a closed landfill. Ecological Engineering 2010, 36, 946 -957.
AMA StyleRobert H. Kadlec, Linda A. Zmarthie. Wetland treatment of leachate from a closed landfill. Ecological Engineering. 2010; 36 (7):946-957.
Chicago/Turabian StyleRobert H. Kadlec; Linda A. Zmarthie. 2010. "Wetland treatment of leachate from a closed landfill." Ecological Engineering 36, no. 7: 946-957.
Constructed treatment wetlands have served the City of Columbia, MO, for fourteen years. Four free water surface wetland units in series, comprised of 23 cells, are an addition to the activated sludge wastewater treatment plant, for the purpose of added biochemical oxygen demand (BOD) and total suspended solids (TSS) control. The system operates year-round, and supplies water to the Eagle Bluffs Conservation Area for wetland maintenance. The cattail wetlands processed an average of 57,000 m3/d, at a water depth of 20 cm. The resulting detention time was approximately 2 days, and the hydraulic loading was 13 cm/d. Water temperatures were warm leaving the treatment plant and in the wetlands in winter, because of the short detention. The period of record average carbonaceous biochemical oxygen demand (CBOD) leaving the wetlands was 5.0 mg/L, and the TSS was 14.7 mg/L. Dissolved oxygen was depressed in summer, likely because of the high sediment demand. Nutrient concentrations were only minimally reduced, total nitrogen (TN) by 22% and total phosphorus (TP) by 6%. However, load reductions were maximal, 98 t/yr for nitrogen, and 3.6 t/yr for phosphorus. Fecal coliforms were reduced by 98%, and E. coli by 95%. First order rate coefficients were high for CBOD (64 m/yr), nitrate (61 m/yr) and organic nitrogen (42 m/yr), but relatively low for ammonia (8 m/yr) and phosphorus (5.7 m/yr). Nitrogen removal was strongly affected by vegetative uptake. Sediment accretion in the wetland inlets was substantial, at 1.6 cm/yr in the inlets to the upstream wetland units. Muskrats caused vegetation damage, and waterfowl use was high in winter, causing TSS excursions.
Robert H. Kadlec; Craig Cuvellier; Trent Stober. Performance of the Columbia, Missouri, treatment wetland. Ecological Engineering 2010, 36, 672 -684.
AMA StyleRobert H. Kadlec, Craig Cuvellier, Trent Stober. Performance of the Columbia, Missouri, treatment wetland. Ecological Engineering. 2010; 36 (5):672-684.
Chicago/Turabian StyleRobert H. Kadlec; Craig Cuvellier; Trent Stober. 2010. "Performance of the Columbia, Missouri, treatment wetland." Ecological Engineering 36, no. 5: 672-684.
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.
Robert H. Kadlec. Nitrate dynamics in event-driven wetlands. Ecological Engineering 2010, 36, 503 -516.
AMA StyleRobert H. Kadlec. Nitrate dynamics in event-driven wetlands. Ecological Engineering. 2010; 36 (4):503-516.
Chicago/Turabian StyleRobert H. Kadlec. 2010. "Nitrate dynamics in event-driven wetlands." Ecological Engineering 36, no. 4: 503-516.
R.H. Kadlec. The Houghton Lake wetland treatment project. Ecological Engineering 2009, 35, 1285 -1286.
AMA StyleR.H. Kadlec. The Houghton Lake wetland treatment project. Ecological Engineering. 2009; 35 (9):1285-1286.
Chicago/Turabian StyleR.H. Kadlec. 2009. "The Houghton Lake wetland treatment project." Ecological Engineering 35, no. 9: 1285-1286.
Lagoon-treated wastewater was discharged to a natural peatland to remove nutrients. For thirty consecutive years, an average of 600,000 m3 of treated water was discharged to the Porter Ranch peatland near the community of Houghton Lake, Michigan. This discharge was seasonal, commencing no sooner than May 1 and ending no later than October 31. During the winter half-year, treated wastewater was stored at the lagoon site. This water contained 3.5 mg/L of total phosphorus, and 7 mg/L of dissolved inorganic nitrogen. Other wastewater quality parameters were CBOD5 = 15 mg/L, TSS = 34 mg/L, and fecal coliforms at 66 cfu/100 ml. The peatland was large, about 700 ha, but the zone that provided wastewater polishing was approximately 100 ha. Outflows from the larger peatland showed no effects of the discharge, and maintained concentrations of 40 μg/L of phosphorus, and 85 μg/L of ammonia nitrogen. Nutrients were stored in the 100-ha irrigation area, which removed 94% of the phosphorus (53 metric tons) and 95% of the dissolved inorganic nitrogen. All other constituents were also removed in the irrigation area, except for pass-through substances such as chloride. Phosphorus was stored in new biomass, increased soil sorption, and accretion of new soils and sediments, the last being dominant. A simple growth and uptake model described the removal of phosphorus, with an uptake rate coefficient that did not change over time. Thus, rates in this system were stable over time, and the P-removal capacity did not diminish. The irrigation area underwent large changes in ecosystem structure. There was an initial fertilizer response, characterized by much larger standing crops of vegetation. There was also a plant community shift, from the initial sedge-willow cover type to a cattail-dominant cover type. This new cattail patch became a floating mat.
Robert H. Kadlec. Wastewater treatment at the Houghton Lake wetland: Hydrology and water quality. Ecological Engineering 2009, 35, 1287 -1311.
AMA StyleRobert H. Kadlec. Wastewater treatment at the Houghton Lake wetland: Hydrology and water quality. Ecological Engineering. 2009; 35 (9):1287-1311.
Chicago/Turabian StyleRobert H. Kadlec. 2009. "Wastewater treatment at the Houghton Lake wetland: Hydrology and water quality." Ecological Engineering 35, no. 9: 1287-1311.
This paper describes the vegetation responses in a very long-running study of the capacity of a natural peatland to remove nutrients from treated wastewater. Data are here presented and analyzed from three decades of full-scale operation, during which large changes in the plant communities occurred. An average of 600,000 m3 year−1 of treated wastewater was discharged seasonally (May 1–October 31) to the Porter Ranch peatland near the community of Houghton Lake, Michigan. This discharge was seasonal, commencing no sooner than May 1 and ending no later than October 31. During the winter half-year, treated wastewater was stored at the lagoon site. This water contained 3.5 mg/L of total phosphorus, and 7 mg/L of dissolved inorganic nitrogen (DIN). Nutrients were stored in the 100 ha irrigation area, which removed 94% of the phosphorus (53 metric tons) and 95% of the dissolved inorganic nitrogen. Phosphorus was stored in new biomass, increased soil sorption, and accretion of new soils and sediments, with accretion being dominant. The irrigation area underwent large changes in ecosystem structure, in which the original plant communities were displaced by Typha spp. There was an initial fertilizer response, characterized by much larger standing crops of vegetation, at about triple the crop in control areas. Increased biomass was accompanied by increases in tissue nitrogen and phosphorus content, by factors of two and three, respectively. The plant community shift, from the initial sedge-willow and leatherleaf-bog birch cover types to a cattail-dominant cover type, progressed to a 83-ha area over the 30-year period of record (POR). The interior portion of this new cattail patch became a floating mat. There were large gradients in stem densities and stem heights within the impacted area. The response times of the vegetative community shifts were on the order of 10 years for 63% of the final impact zone development. The grow-in time for development of a new larger standing crop in the discharge zone was also 10 years. The impacted area was stable at the 30-year time, without any further moving fronts. Around the cattail zone, there were fringe areas that contained a mixture of the original cover types intruded by relatively small amounts of cattail.
Robert H. Kadlec; Frederick B. Bevis. Wastewater treatment at the Houghton Lake wetland: Vegetation response. Ecological Engineering 2009, 35, 1312 -1332.
AMA StyleRobert H. Kadlec, Frederick B. Bevis. Wastewater treatment at the Houghton Lake wetland: Vegetation response. Ecological Engineering. 2009; 35 (9):1312-1332.
Chicago/Turabian StyleRobert H. Kadlec; Frederick B. Bevis. 2009. "Wastewater treatment at the Houghton Lake wetland: Vegetation response." Ecological Engineering 35, no. 9: 1312-1332.
This paper describes the sediment and soils responses in a very long-running study of the capacity of a natural peatland to remove nutrients from treated wastewater. Data are here presented and analyzed from three decades of full-scale operation (1978–2007), during which large changes in the wetland soils occurred. An average of 600,000 m3 y−1 of treated water was discharged each warm season to the Porter Ranch peatland near the community of Houghton Lake, Michigan. This discharge was seasonal, commencing no sooner than May 1 and ending no later than October 31. During the winter half-year, treated wastewater was stored at the lagoon site. This water contained 3.5 mg/L of total phosphorus, and 7 mg/L of dissolved inorganic nitrogen. Nutrients were stored in the 100 ha irrigation area, which removed 94% of the phosphorus (53 t) and 95% of the dissolved inorganic nitrogen. Phosphorus was stored in new biomass, increased soil sorption, and accretion of new soils and sediments, with accretion being dominant. Peat probings, water level increases and topographical surveys established quantitative measures of soil accretion. Over 30 cm of new soil developed, in which nutrient storage occurred. Phosphorus concentrations in the new soil were approximately 2000 mg P/kg, and the nitrogen concentration was 2–3%DW. The removal of TSS was effective, but minor in comparison to the internal generation and cycling of produced particulates. Later in the project history, the interior portion of impacted area became a floating mat. Sedimentation processes then occurred with no exposure to above-mat detrital processes. Trace element analyses showed no appreciable accumulation of heavy metals, other than the calcium and iron that characterized the antecedent wetland and the incoming water. Biomass cycling models were found to produce reasonable estimates of the measured nutrient accumulations. The light loadings of nutrients to this system produced dramatic effects in the ecosystem, but were lower than the range seen in some other treatment wetlands. Insufficient nitrogen was added to support the new biomass, and nitrogen fixation was identified as a possible compensatory mechanism.
Robert H. Kadlec. Wastewater treatment at the Houghton lake wetland: Soils and sediments. Ecological Engineering 2009, 35, 1333 -1348.
AMA StyleRobert H. Kadlec. Wastewater treatment at the Houghton lake wetland: Soils and sediments. Ecological Engineering. 2009; 35 (9):1333-1348.
Chicago/Turabian StyleRobert H. Kadlec. 2009. "Wastewater treatment at the Houghton lake wetland: Soils and sediments." Ecological Engineering 35, no. 9: 1333-1348.
This paper describes the temperatures in surface water and soils in a very long-running study of the capacity of a natural peatland to remove nutrients from treated wastewater. Two zones were found, an adaptation zone near the discharge to the wetland, and a background zone comprised of areas more than about 100 m from the discharge. The discharge zone was transformed to a floating mat during the 30-year course of the project. Strong diurnal cycles in surface water temperatures were measured, with a median daily swing of about 6–10 °C. Pumped water was a few degrees warmer than the wetland background, and was reduced in temperature by passage through the adaptation zone. The time constants for adaptation (63% of change) were approximately one-half to 1 day. Soil temperatures followed a cyclic pattern, with decreasing amplitude with depth, and a time delay increasing with depth. The seasonal surface maximum was about 18 °C. The irrigation season started on May 1, with water at 10 °C, and ended in early October, with water at 10 °C. The soil conduction model was used to infer cyclic surface temperatures, with a smoothed result compared to synoptic temperature measurements in surface water. Background zone fitting parameters were the Julian day of surface maximum temperature (196), mean temperature (7.9 °C), surface amplitude (10.3 °C), and penetration depth (1.0 m). Soil heat fluxes were vertically downward during the warm season, and back up toward the surface with maxima of 1.4 MJ/m2 d in the discharge zone. This vertical soil heat flux was of small importance to the summer energy budget, which was dominated by solar radiation and evaporative cooling.
Robert H. Kadlec. Wastewater treatment at the Houghton Lake wetland: Temperatures and the energy balance. Ecological Engineering 2009, 35, 1349 -1356.
AMA StyleRobert H. Kadlec. Wastewater treatment at the Houghton Lake wetland: Temperatures and the energy balance. Ecological Engineering. 2009; 35 (9):1349-1356.
Chicago/Turabian StyleRobert H. Kadlec. 2009. "Wastewater treatment at the Houghton Lake wetland: Temperatures and the energy balance." Ecological Engineering 35, no. 9: 1349-1356.
The two most prevalent types of treatment wetland, especially during the early history of the technology, are free water surface (FWS) and horizontal subsurface flow (HSSF) wetlands. The several factors involved in the choice of which alternative to choose include size, cost, operability, together with health and nuisance issues and ancillary benefits. Contaminant removal performance differs by constituent, with the advantage to FWS for moderate to high biochemical oxygen demand (BOD), TSS, ammonia, total nitrogen and phosphorus. HSSF are more effective for tertiary BOD levels, nitrate and pathogens. Superpositions of the loading data show that the respective data clouds overlap virtually entirely for HSSF and FWS wetlands. There is little or no performance difference when they are compared on this areal basis. In general, there is little or no advantage of HSSF for space saving. In cold climates, HSSF systems are less cold sensitive, and easier to insulate for winter operation. The use of winter storage enables FWS to be used in freezing conditions, but the cost makes that option comparable to the more expensive HSSF. In general, economics do not favor the choice of HSSF wetlands. Factors other than reduction performance are also important in the selection process. Other principal reasons for selecting the HSSF option over the FWS option are prevention of human health contact problems, mosquito control and minimization of wildlife interactions.
R.H. Kadlec. Comparison of free water and horizontal subsurface treatment wetlands. Ecological Engineering 2009, 35, 159 -174.
AMA StyleR.H. Kadlec. Comparison of free water and horizontal subsurface treatment wetlands. Ecological Engineering. 2009; 35 (2):159-174.
Chicago/Turabian StyleR.H. Kadlec. 2009. "Comparison of free water and horizontal subsurface treatment wetlands." Ecological Engineering 35, no. 2: 159-174.
This paper reports data and models for nitrogen processing for the demonstration-scale Tres Rios, Arizona, wetlands. Four field-scale wetlands of approximately 1 ha each were operated under varying conditions at a site west of the City of Phoenix. The water supply was partially nitrified effluent from a City wastewater treatment plant. Total nitrogen was reduced by about 60%, from an inflow concentration between 6 mg/L and 8 mg/L. Speciation of the inflow was approximately 25% organic nitrogen, 25% ammonium nitrogen and 50% nitrate nitrogen. Typical outflow concentrations were about 1.2 mg/L organic, 0.5 mg/L ammonium, and 0.0–2.5 mg/L nitrate. Two wetlands were reconfigured with channelization parallel to flow, and the other two lost vegetation. This paper compares the before and after performance for both changes. Rate constants for nitrate and total nitrogen were decreased by the changes. For loss of vegetation, nitrate k20-values decreased from 76 m/yr to 23 m/yr, and total nitrogen k20-values decreased from 54 m/yr to 11 m/yr. For reconfiguration, nitrate k20-values decreased from 83 m/yr to 47 m/yr, and total nitrogen k20-values decreased from 49 m/yr to 32 m/yr. Rate constants were found to be temperature sensitive. It is concluded that the reconfiguration and loss of vegetation both markedly lessened the ability of the wetlands to process nitrogen. Further, reconfiguration was ineffective for mosquito control.
R.H. Kadlec. The effects of wetland vegetation and morphology on nitrogen processing. Ecological Engineering 2008, 33, 126 -141.
AMA StyleR.H. Kadlec. The effects of wetland vegetation and morphology on nitrogen processing. Ecological Engineering. 2008; 33 (2):126-141.
Chicago/Turabian StyleR.H. Kadlec. 2008. "The effects of wetland vegetation and morphology on nitrogen processing." Ecological Engineering 33, no. 2: 126-141.
Twelve research wetlands were operated under varying conditions at a site west of the city of Phoenix. These were constructed as a triplicated design, with zero, one, two and three internal deep zones, all containing an inlet distribution and an outlet collection deep zone, together comprising 12.5–35% of the wetland areas. The water supply was partially nitrified effluent from a city wastewater treatment plant. Total nitrogen was reduced by about 50%, from inflow concentrations between 6 and 8 mg/L. Speciation of the inflow was approximately 25% organic nitrogen, 25% ammonium nitrogen and 50% nitrate nitrogen. Typical outflow concentrations were about 1.2 mg/L organic, 0.5 mg/L ammonium and 0.0–2.5 mg/L nitrate. Rate constants for total nitrogen were 15–20 m/year at 20 °C, and 20–30 m/year for nitrate, which agree well with other project reports. Temperature factors averaged 1.100 for total nitrogen, and 1.184 for nitrate. There were no differences in the internal hydraulics with deep zone numbers. Deep zone numbers in the wetlands did not affect nitrogen treatment performance. No differences with deep zone numbers were found for temperature, dissolved oxygen, pH, or nitrogen removals or rate constants. In conjunction with other reported results, there appears to be no large treatment benefit or detriment of incorporating internal deep zones in free water surface wetlands.
R.H. Kadlec. The effects of deep zones on wetland nitrogen processing. Water Science and Technology 2007, 56, 101 -108.
AMA StyleR.H. Kadlec. The effects of deep zones on wetland nitrogen processing. Water Science and Technology. 2007; 56 (3):101-108.
Chicago/Turabian StyleR.H. Kadlec. 2007. "The effects of deep zones on wetland nitrogen processing." Water Science and Technology 56, no. 3: 101-108.
Muskrat grazing can change treatment wetlands from being densely vegetated to a patchwork of open and emergent areas. Muskrats consume a portion of the annual net primary productivity, primarily rhizomes, but their mounds represent a greater share of this production. Densities of 20 or more animals per ha have been found, which can destroy the majority of the macrophyte standing crop in a given year. At such an exacerbated scale, muskrat herbivory may be termed as an “eatout,” and is evidenced by the removal of essentially all emergent plant parts. Destruction of the wetland vegetative infrastructure may create an attendant loss of some water quality functions, but may not harm others. The integrity of berms may be threatened by burrowing. Impacts on wetland hydraulics are also possible. In all cases, loss of the emergent vegetation has been viewed with dismay by owners, wetland practitioners, regulators and the general public. Several case histories are reviewed to illustrate the breadth and severity of muskrat damage. Muskrat control is given scant attention in existing treatment wetland literature, which provides very limited information on potential muskrat problems, or on the means to control them. Controls include trapping, shooting, poisoning, hazing, and exclusion in order to protect the wetland from excessive vegetation destruction by these rodents. This paper summarizes available muskrat controls, as well as their effectiveness. While many of these approaches have had a limited effect on deterring these industrious creatures, there are some methods that have proven to be effective over the long run, and should be considered in wetland design.
Robert H. Kadlec; John Pries; Heather Mustard. Muskrats (Ondatra zibethicus) in treatment wetlands. Ecological Engineering 2007, 29, 143 -153.
AMA StyleRobert H. Kadlec, John Pries, Heather Mustard. Muskrats (Ondatra zibethicus) in treatment wetlands. Ecological Engineering. 2007; 29 (2):143-153.
Chicago/Turabian StyleRobert H. Kadlec; John Pries; Heather Mustard. 2007. "Muskrats (Ondatra zibethicus) in treatment wetlands." Ecological Engineering 29, no. 2: 143-153.
This paper reviews and summarises the theory and techniques used when conducting hydraulic tracer tests in treatment wetlands, with particular attention paid to the practical issues to be considered during the planning and implementation phases. Typically, a single-shot impulse of tracer is introduced at the inlet and the concentration tracked at the outlet or other internal point in order to uncover information about the hydraulic characteristics of the wetland. The following aspects are discussed: the range of commonly used tracer substances, the mass of tracer to be added, and planning of the sampling regime. A range of graphical and statistical tools are described for interpreting the data from a tracer study, with example data from an impulse tracer study used to demonstrate the required computational procedures. It is recommended that a standardised approach be adopted for presenting tracer study data in order to allow the direct comparison of data from different wetland systems.
Thomas R. Headley; Robert H. Kadlec. Conducting hydraulic tracer studies of constructed wetlands: a practical guide. Ecohydrology & Hydrobiology 2007, 7, 269 -282.
AMA StyleThomas R. Headley, Robert H. Kadlec. Conducting hydraulic tracer studies of constructed wetlands: a practical guide. Ecohydrology & Hydrobiology. 2007; 7 (3-4):269-282.
Chicago/Turabian StyleThomas R. Headley; Robert H. Kadlec. 2007. "Conducting hydraulic tracer studies of constructed wetlands: a practical guide." Ecohydrology & Hydrobiology 7, no. 3-4: 269-282.
This paper reviews the types of tracer testing that have been used in treatment wetlands, and summarizes example studies and collections of results. Impulse tests typically produce outlet gamma distributions, characterized by N tanks in series (TIS) and a volumetric efficiency (eV) calculated from the mean tracer detention time. TIS values center on N = 4 for FWS and N = 6 for SSF wetlands; while median eV values are 77% for FWS and 89% for SSF systems. When used in conjunction with inert tracers, reactive material behavior may be better understood via spike additions. Thus dual additions of an inert, such as bromide, accompanied by a spike of a target substance, such as a pathogen, can provide easy interpretation of the removal rate. Sample results from 32P and 15N studies are shown to yield valuable insights into internal processes and their speeds. Wetland sediment storages build slowly, but the progress of accretion can sometimes be followed via radioisotopes such as 137Cs and 210Pb.
Robert H. Kadlec. Tracer and spike tests of constructed wetlands. Ecohydrology & Hydrobiology 2007, 7, 283 -295.
AMA StyleRobert H. Kadlec. Tracer and spike tests of constructed wetlands. Ecohydrology & Hydrobiology. 2007; 7 (3):283-295.
Chicago/Turabian StyleRobert H. Kadlec. 2007. "Tracer and spike tests of constructed wetlands." Ecohydrology & Hydrobiology 7, no. 3: 283-295.
The Everglades Nutrient Removal Project (ENRP) was one of the largest treatment wetlands ever built. In North America, it has been exceeded only by the Stormwater Treatment Areas, the designs for which it was developed to support. The five cells of the ENRP contained varying mixtures of submerged, emergent and floating vegetation, and produced concomitantly variable phosphorus (P) removal. The range of first–order settling rates for total P (TP) removal was from 12 to 73 m/year for the individual cells, compared to a range of 13–23 m/year for Boney Marsh, Water Conservation Area 2A, and Orlando Easterly Wetlands. The mean TP settling rate in the ENRP of 23 m/year compares well to a mean of 16 m/year for 77 other wetland systems. No seasonal trends were detected in the ENRP, but there was ±50% variability for outlet TP concentrations. The ENRP operated at the low end of the spectrum of P concentrations and loadings for treatment marshes in general, with a mean inlet TP of about 100 μg P/L, while producing 21 μg P/L in the effluent over a 6-year period of record. Consequently, vegetation density and P content were low compared to other wetland systems. The biogeochemical cycle in the ENRP resulted in accreting residuals that had about 1000 mg P/kg dry weight. The project was built economically, but large sums were spent on research. The regulatory concept of a TP 12-month rolling average was initiated for the first time. The project fulfilled its goal of confirming and refining the information from earlier prototype systems. In turn, much of the ENRP design has been replicated in the full-scale STAs, with moderate success.
Robert H. Kadlec. Free surface wetlands for phosphorus removal: The position of the Everglades Nutrient Removal Project. Ecological Engineering 2006, 27, 361 -379.
AMA StyleRobert H. Kadlec. Free surface wetlands for phosphorus removal: The position of the Everglades Nutrient Removal Project. Ecological Engineering. 2006; 27 (4):361-379.
Chicago/Turabian StyleRobert H. Kadlec. 2006. "Free surface wetlands for phosphorus removal: The position of the Everglades Nutrient Removal Project." Ecological Engineering 27, no. 4: 361-379.
This paper reports data and models for temperatures and energy flows for the Tres Rios surface flow wetlands. Treatment wetlands are solar powered ecosystems, resulting in annually cyclic temperatures. There is also a daily cycle in wetland water temperature of several degrees amplitude. The timing of individual daily measurements may therefore bias the result to values different from the daily mean. The energy balance is dominated by radiation to and from the wetland, heat transfer from air, and evaporative losses. Transpiration causes energy dissipation from the canopy, while evaporation causes energy loss from and cooling of the surface water. Transpiration was found to dominate the water loss. Downstream daily average water temperatures are cooler than daily average air temperatures at all times of the year, due to evaporative cooling. Water cools as it passes from inlet to outlet. The excess sensible heat is dissipated during travel through the inlet region of the wetland. For long detention times, longer than about five days, water temperature reaches a balance condition. Up to that time, sensible heat from the source water also influences evaporation and water temperature. Balance water temperatures ranged from 3.9 °C in winter to 27.2 °C in summer, while mean daily air temperatures ranged from 5.3 to 37.2 °C. Diel variations were found to range up to 6 °C. Stochastic variability produced a band width of ±5 °C. Energy balance models provide a good representation of these phenomena, but are subject to large sensitivity to input variables, especially air temperature, humidity and wind. Evapotranspiration was higher than that predicted for a balance condition, because of the warmth of the incoming water. It was less than that predicted for a grass crop.
Robert H. Kadlec. Water temperature and evapotranspiration in surface flow wetlands in hot arid climate. Ecological Engineering 2006, 26, 328 -340.
AMA StyleRobert H. Kadlec. Water temperature and evapotranspiration in surface flow wetlands in hot arid climate. Ecological Engineering. 2006; 26 (4):328-340.
Chicago/Turabian StyleRobert H. Kadlec. 2006. "Water temperature and evapotranspiration in surface flow wetlands in hot arid climate." Ecological Engineering 26, no. 4: 328-340.
Nitrogen processing in treatment wetlands was investigated by use of the stable isotope 15N introduced as ammonium. Two small field-scale, gravel-bed wetlands with horizontal subsurface-flow (SSF) received primary meat processing water. Four SSF cascade mesocosms, each comprising five tanks in series, received primary meat processing water, primary dairy water, secondary dairy water or aerated secondary dairy water. The mesocosms and one of the field-scale wetland contained well-established bulrushes (Schoenoplectus tabernaemontani), and the other field-scale wetland remained unvegetated. The systems were operated at steady inflows, with a nominal detention times of 4–5 days. The incoming ammonium nitrogen ranged from 18.5 to 177 g m−3, and removals ranged from 15 to 90% for the various feed waters. Each system was dosed with a single pulse of 15N ammonium mixed into the feed wastewater, and the fate and transport of the isotopic nitrogen were determined. The 15N pulses took 120 days to clear the heavily loaded field-scale wetlands. During this period small reductions in 15N were attributable to nitrification/denitrification, and a larger reduction due to plant uptake. Mesocosm tests ran for 24 days, during which only 1–16% of the tracer exited with water, increasing with N loading. Very little tracer gas emission was found (∼1%). The majority of the tracer was found in plants (6–48%) and sediments (28–37%). These results indicated a rapid absorption of ammonium into a large sediment storage pool, of which only a small proportion was denitrified during the period of the experiment. Plant uptake claimed a fraction of the ammonium, determined mainly by the plants requirement for growth rather than the magnitude of the nitrogen supply. A rapid return of ammonium to the water was also found, so that movement of 15N through the wetland mesocosms was comprised of a spiral of uptake and release along the flow path. A two compartment model was found to reasonably represent the isotope progress through the wetlands. First order exchanges and removals were employed in dynamic mass balances on water and solids. It is concluded that interpretation of nitrogen dynamics in wetlands must include the nitrogen spiral through the wetland, as well as plant uptake. This greatly increases the N residence time in treatment wetlands relative to the hydraulic detention time, resulting in long delays of treatment system response to changes in N loading and attenuation of short-term fluctuations in loading.
Robert H. Kadlec; Chris C. Tanner; Vera M. Hally; Max M. Gibbs. Nitrogen spiraling in subsurface-flow constructed wetlands: Implications for treatment response. Ecological Engineering 2005, 25, 365 -381.
AMA StyleRobert H. Kadlec, Chris C. Tanner, Vera M. Hally, Max M. Gibbs. Nitrogen spiraling in subsurface-flow constructed wetlands: Implications for treatment response. Ecological Engineering. 2005; 25 (4):365-381.
Chicago/Turabian StyleRobert H. Kadlec; Chris C. Tanner; Vera M. Hally; Max M. Gibbs. 2005. "Nitrogen spiraling in subsurface-flow constructed wetlands: Implications for treatment response." Ecological Engineering 25, no. 4: 365-381.