Field Application of a Renewable Constructed Wetland Substrate for Phosphorus Removal1

Rosenquist, Shawn E., W. Cully Hession, Matthew J. Eick, and David H. Vaughan, 2011. Field Application of a Renewable Constructed Wetland Substrate for Phosphorus Removal. Journal of the American Water Resources Association (JAWRA) 47(4):800‐812. DOI: 10.1111/j.1752‐1688.2011.00557.x Abstract: Phosphorus (P) is typically the best target to prevent eutrophication in freshwater, a biological process associated with water quality degradation. Constructed wetlands (CW) and other practices that include P removal by sorption processes in substrates can provide economical treatment of stormwater, but have limitations (e.g., large land requirements, loss of removal over time, lack of P recovery). Over the last three years, a multi‐study research program addressed these limitations with a new P management concept. This concept minimizes CW size with a rejuvenation cycle (or rejuvenation) that renews P‐sorption capacity in the CW substrates and enables P recovery for productive use. This study, conducted in Blacksburg, Virginia (July‐September 2009), tested the efficacy of rejuvenation in the field. Methods included replicate cells of two sand substrates monitored for P removal during prerejuvenation and postrejuvenation filtration runs. One substrate contained cast iron filings as a repository for sorption capacity. Results support the following conclusions: (1) P removal is likely dependent on multiple factors including influent P concentration, previous substrate/solution equilibrium, pH, and time; (2) rejuvenation is capable of releasing P adsorbed during stormwater filtration; (3) inclusion of cast iron in substrate promotes additional P removal and enables further removal after rejuvenation; but (4) inclusion of cast iron may limit release of P during rejuvenation.     

Stormwater Runoff Quality and Quantity From Traditional and Low Impact Development Watersheds1

Abstract: The quality and quantity of residential stormwater runoff from a control, traditional, and low impact development (LID) watershed were compared in a paired watershed study. A traditional neighborhood was built using typical subdivision standards while a LID design was constructed with best management practices including grass swales, cluster housing, shared driveways, rain gardens, and a narrower pervious concrete‐paver road. Weekly, flow‐weighted, composite samples of stormwater were analyzed for nitrate + nitrite‐nitrogen (NO₃ + NO₂‐N), ammonia‐nitrogen (NH₃‐N), total Kjeldahl nitrogen (TKN), total phosphorus (TP), and total suspended solids (TSS). Monthly composite samples were analyzed for total copper (Cu), lead (Pb), and zinc (Zn). Mean weekly storm flow increased (600x) from the traditional watershed in the postconstruction period. Increased exports of TKN, NO₃ + NO₂‐N, NH₃‐N, TP, Cu, Zn, and TSS in runoff were associated with the increased storm flow. Postconstruction storm flow in the LID watershed was reduced by 42% while peak discharge did not change from preconstruction conditions. Exports were reduced from the LID watershed for NH₃‐N, TKN, Pb, and Zn, while TSS and TP exports increased.     

Review of Urban Stormwater Quality Models: Deterministic,Stochastic, and Hybrid Approaches1

Abstract: The growing impact of urban stormwater on surface‐water quality has illuminated the need for more accurate modeling of stormwater pollution. Water quality based regulation and the movement towards integrated urban water management place a similar demand for improved stormwater quality model predictions. The physical, chemical, and biological processes that affect stormwater quality need to be better understood and simulated, while acknowledging the costs and benefits that such complex modeling entails. This paper reviews three approaches to stormwater quality modeling: deterministic, stochastic, and hybrid. Six deterministic, three stochastic, and three hybrid models are reviewed in detail. Hybrid approaches show strong potential for reducing stormwater quality model prediction error and uncertainty. Improved stormwater quality models will have wide ranging benefits for combined sewer overflow management, total maximum daily load development, best management practice design, land use change impact assessment, water quality trading, and integrated modeling.     

Water Quality Functions of a 15-Year-Old Riparian Forest Buffer System1

Newbold, J. Denis, Susan Herbert, Bernard W. Sweeney, Paul Kiry, and Stephen J. Alberts, 2010. Water Quality Functions of a 15-Year-Old Riparian Forest Buffer System. Journal of the American Water Resources Association (JAWRA) 46(2):299-310. DOI: 10.1111/j.1752-1688.2010.00421.x Abstract: We monitored long-term water quality responses to the implementation of a three-zone Riparian Forest Buffer System (RFBS) in southeastern Pennsylvania. The RFBS, established in 1992 in a 15-ha agricultural (row crop) watershed, consists of: Zone 1, a streamside strip (∼10 m wide) of permanent woody vegetation for stream habitat protection; Zone 2, an 18- to 20-m-wide strip reforested in hardwoods upslope from Zone 2; and Zone 3, a 6- to 10-m-wide grass filter strip in which a level lip spreader was constructed. The monitoring design used paired watersheds supplemented by mass balance estimates of nutrient and sediment removal within the treated watershed. Tree growth was initially delayed by drought and deer damage, but increased after more aggressive deer protection (1.5 m polypropylene shelters or wire mesh protectors) was instituted. Basal tree area increased ∼20-fold between 1998 and 2006, and canopy cover reached 59% in 2006. For streamwater nitrate, the paired watershed comparison was complicated by variations in both the reference stream concentrations and in upslope groundwater nitrate concentrations, but did show that streamwater nitrate concentrations in the RFBS watershed declined relative to the reference stream from 2002 through the end of the study in early 2007. A subsurface nitrate budget yielded an average nitrate removal by the RFBS of 90 kg/ha/year, or 26% of upslope subsurface inputs, for the years 1997 through 2006. There was no evidence from the paired watershed comparison that the RFBS affected streamwater phosphorus concentration. However, groundwater phosphorus did decline within the buffer. Overland flow sampling of 23 storms between 1997 and 2006 showed that total suspended solids concentration in water exiting the RFBS to the stream was on average 43% lower than in water entering the RFBS from the tilled field. Particulate phosphorus concentration was lower by 22%, but this removal was balanced by a 26% increase in soluble reactive phosphorus so that there was no net effect on total phosphorus.     

Simulation of Temperature Mitigation by a Stormwater Detention Pond1

Abstract: A numerical model has been developed to simulate the hydraulic and heat transfer properties of a stormwater detention pond, as part of a simulation tool to evaluate thermal pollution of coldwater streams from stormwater runoff. The model is dynamic (unsteady) and based on principles of fluid mechanics and heat transfer. It is driven by hourly weather data, and specified inflow rates and temperatures. To calibrate and validate the pond model field data were collected on a commercial site in Woodbury, Minnesota. The relationship between pond inflow and outflow rates to precipitation was effectively calibrated using continuously recorded pond levels. Algorithms developed for surface heat transfer in lakes were found to be applicable to the pond with some modification, resulting in agreement of simulated and observed pond surface temperature within 1.0°C root mean square error. The use of an unshaded pond for thermal mitigation of runoff from paved surfaces was evaluated using the pond model combined with simulated runoff from an asphalt parking lot for six years of observed rainfall events. On average, pond outflow temperature was 1.2°C higher than inflow temperature, but with significant event‐to‐event variation. On average, the pond added heat energy to runoff from an asphalt parking lot. Although the pond added total heat energy to runoff, it did reduce the rate of heat outflow from the pond by an order of magnitude due to reductions in volumetric outflow rate compared with the inflow rate. By reducing the rate of heat flow, the magnitude of temperature impacts in a receiving stream were also reduced, but the duration of impacts was increased.     

人工湿地控制非点源污染的应用

随着点源污染的有效管理和控制,非点源污染已成为水环境污染的主要原因。人工湿地作为一种控制水环境非点源污染的有效工具,已被世界上很多国家所认可。本文首先简述了非点源污染的危害,其次对人工湿地的概念和类型进行了介绍,论述了人工湿地对非点源污染中氮、磷、重金属和农药等主要污染物的去除机理,最后对人工湿地处理系统的附属设施、水力因素、表土层以及植物收割等应用问题进行了探讨。     

A Side‐by‐Side Comparison of Pervious Concrete and Porous Asphalt1

Welker, Andrea L., James D. Barbis, and Patrick A. Jeffers, 2012. A Side‐by‐Side Comparison of Pervious Concrete and Porous Asphalt. Journal of the American Water Resources Association (JAWRA) 48(4): 809‐819. DOI: 10.1111/j.1752‐1688.2012.00654.x Abstract: This article compares the performance of two permeable pavements, pervious concrete and porous asphalt, that were installed side‐by‐side in fall 2007. Because the pavements are located directly adjacent to one another, they experience the same vehicle loads, precipitation, and pollution loads. These permeable pavements are part of an infiltration stormwater control measure (SCM). This article focuses on the comparison of water quality parameters, maintenance and durability, and user perception. Eleven different water quality parameters were analyzed at this site for 19 different storm events over a one year period: pH, conductivity, total suspended solids, chlorides, total nitrogen, total phosphorus, total dissolved copper, total dissolved lead, total dissolved cadmium, total dissolved chromium, and total dissolved zinc. Results from the two pavement types were compared using the Mann–Whitney U‐test. The only parameter that was found to be statistically different between the two pavements was pH. Periodic inspection of the two pavement types indicated that after two years of use both pavements were wearing well. However, there was some evidence of clogging of both pavements and some evidence of surface wear. A survey of users of the lot indicated that the perception of these permeable pavements was favorable.     

潜流人工湿地在景观水系水质维持中的应用

以上海金地格林世界高尔夫公园生态景观水体水质维持系统工程为例,探讨了建立以FILSYS潜流人工湿地工艺为核心的住宅区生态景观水体水质维持系统,以及FLSYS潜流人工湿地工艺的应用特点和效果,并对其经济效益进行了分析。     

MODELING THE BUILDUP AND WASHOFF OF POLLUTANTS ON URBAN WATERSHEDS1

ABSTRACT: A model for urban stormwater quality was developed in this study. The basis for the model is the process by which pollutants build up on the watershed surface. For the wet climate of the study site, it was assumed that there exists an interval of time over which the pollutant buildup equals the pollutant washoff (no accumulation of pollutant). The buildup model was represented by a linear function of the antecedent dry time. The buildup function was then linked with a pollutant washoff model represented by a power function of the storm runoff volume. Various time intervals for no net accumulation were tested to calibrate the model. The model was calibrated to observed data for two small urban basins in Baton Rouge, Louisiana, and model results were used to analyze the behavior of phosphorus concentrations in storm runoff from these basins over a long period of time.     

A Multilevel Model of the Impact of Farm‐Level Best Management Practices on Phosphorus Runoff1

Abstract: Multilevel or hierarchical models have been applied for a number of years in the social sciences but only relatively recently in the environmental sciences. These models can be developed in either a frequentist or Bayesian context and have similarities to other methods such as empirical Bayes analysis and random coefficients regression. In essence, multilevel models take advantage of the hierarchical structure that exists in many multivariate datasets; for example, water quality measurements may be taken from individual lakes, lakes are located in various climatic zones, lakes may be natural or man‐made, and so on. The groups, or levels, may effectively yield different responses or behaviors (e.g., nutrient load response in lakes) that often make retaining group membership more effective when developing a predictive model than when working with either all of the data together or working separately with the individuals. Here, we develop a multilevel model of the impact of farm level best management practices (BMPs) on phosphorus runoff. The result of this research is a model with parameters which vary with key practice categories and thus may be used to evaluate the effectiveness of these practices on phosphorus runoff. For example, it was found that the effect of fertilizer application rate on farm‐scale phosphorus loss is a function of the application method, the hydrologic soil group, and the land use (crop type). Further, results indicate that the most effective method for controlling fertilizer loss is through soil injection. In summary, the resultant multilevel model can be used to estimate phosphorus loss from farms and hence serve as a useful tool for BMP selection.     

Regulating Industrial Stormwater: State Permits,Municipal Implementation,and a Protocol for Prioritization1

Abstract:  This research evaluated the effectiveness of regulations for stormwater pollutants originating from industrial facilities. Industrial facilities discharging stormwater are subject to General Permits implemented by state and federal agencies, which require facility operators to identify themselves and to implement pollution prevention measures. An overlying system of permits require Municipal Separate Storm Sewer System operators to identify and inspect facilities in their jurisdictions capable of discharging substantial pollutant loads into stormwater conveyances, introducing more active regulation and strategic prioritization, but with unequal implementation in different urban regions. This research evaluated the interaction between the regulations and ways in which the regulations succeed, or fail, at protecting water quality. The research evaluated potential for pollutant discharges at 136 industrial facilities in Pinellas County, Florida, using telephone interviews; off-site facility visits; and on-site facility inspections, targeting four industrial categories: wood products; stone, clay, glass, and concrete products; fabricated metal products; and electronic products. Results documented that a large proportion of facilities subject to General Permits conduct few or no activities likely to produce stormwater pollutants, indicating that the regulations’ equal treatment of all facilities may constitute overregulation. The research developed a methodology to assess facilities using intensity of industrial activities exposed to stormwater, a rational measurement that could regularize municipal agencies’ requirements and prioritize implementation toward facilities with the potential to impact receiving water quality.     

WATER QUALITY CONCERNS AND REGULATORY CONTROLS FOR NONSTORM WATER DISCHARGES TO STORM DRAINS1

ABSTRACT: Nonstorm water discharges to municipal separate storm sewer systems (MS4s) are notable for spatial and temporal variability in volume, pollutant type, pollutant concentration, and activity of origin. The objective of this paper was to determine whether current technical knowledge and existing U.S. policy support an improved regulatory approach. The proposed policy would use type of discharge as a regulatory basis, merging the concepts of allowability of de minimis discharges and type-based statewide consistent rules. Specific research objectives were to comprehensively identify discharge types, characterize their prevalence in California, analyze relevant local and regional regulatory guidelines, and systematically evaluate opinions of experts about potential water quality impacts. Results demonstrate nonstorm water discharges were widespread in at least one sector, industrial facilities subject to a state permit; one discharge for every four facilities was reported in 1995, even though the permit explicitly prohibits such discharges. Clear consensus exists for minimal water quality concern for some discharge types when considering both municipal guidelines and experts’ opinions. In particular, condensate from a wide range of equipment and discharges from fire fighting equipment testing were found to be of low concern. Discharge types with consensus high concern were largely limited to discharges prohibited under other regulations, such as wastewater and hazardous waste management controls. Some discharge types where no consensus was identified, such as landscape irrigation, nevertheless generated concern for water quality impacts and appear to be relatively widespread. Available information supports technical feasibility of the proposed policy because at least some discharge types show strong consensus for de minimis impacts among regulatory guidelines and opinions of technical experts.     

Contaminant Retention Potential of Forested Filter Strips Established as SMZs in the Piedmont of Georgia1

Abstract: It is common practice in the United States and elsewhere to maintain vegetated filter strips adjacent to streams to retain contaminants in surface runoff. Most research has evaluated contaminant retention in managed agricultural field strips, while relatively few studies have quantified retention in forested filter strips, particularly for dissolved contaminants. Plot‐scale overland flow experiments were conducted to evaluate the efficiency of natural forested filter strips established as streamside management zones (SMZs) for retaining phosphorus (P), atrazine, and picloram transported in runoff. Retention was evaluated for five different slope classes: 1‐2, 5‐7, 10‐12, 15‐17, and 20‐22%; two cover conditions: undisturbed forest floor (O horizon intact) and forest floor removed by raking; and two periods with contrasting soil moisture conditions: summer‐dry and winter‐wet season. Surface flow was collected at 0, 2, 4, 6, and 10 m within the filter strip to evaluate changes in solution concentration as it moved through the O horizon and the surface soil horizon mixing zone. On average, a 10 m length of forested SMZ with an undisturbed forest floor reduced initial solution concentration of total dissolved P by 51%, orthophosphate P by 49%, atrazine by 28%, and picloram by 5%. Percentages of mass retention through infiltration of water plus concentration reductions in runoff were 64% for total dissolved P, 62% for orthophosphate P, 47% for atrazine, and 28% for picloram for undisturbed forest floor conditions. Lower retention occurred following forest floor removal, particularly for P. Average dissolved P retention was 16% lower following forest floor removal. For undisturbed sites, differences in retention were more closely related to forest floor depth than to slope or antecedent soil moisture. These results indicate that forested SMZ filter strips provide a significant measure of surface water protection from dissolved P and herbicide delivery to surface water.     

Performance Assessment of Rain Gardens1

Abstract: The most widely used approach for evaluating the performance of stormwater best management practices (BMPs) such as rain gardens is monitoring, but this approach can involve a long time period to observe a sufficient number and variety of storm events, a high level of effort, and unavoidable uncertainty. In this paper, we describe the development and evaluation of three approaches for performance assessment of rain gardens: visual inspection, infiltration rate testing, and synthetic drawdown testing. Twelve rain gardens in Minnesota underwent visual inspection, with four determined to be nonfunctional based on one or more of the following criteria: (1) presence of ponded water, (2) presence of hydric soils, (3) presence of emergent (wetland) vegetation, and (4) failing vegetation. It is believed that these rain gardens failed due to a lack of maintenance. For the remaining eight rain gardens, an infiltrometer was used to determine the saturated hydraulic conductivity (K_sat) of the soil surface at several locations throughout each basin in what is termed infiltration rate testing. The median K_sat values for the rain gardens ranged from 3 to 72 cm/h. Synthetic drawdown testing was performed on three rain gardens by filling the basins with water to capacity where possible and recording water level over time. The observed drain times for two of those rain gardens were in good agreement with predictions based on the median of the infiltrometer measurements. The observed drain time for the third rain garden was much greater than predicted due to the presence of a restrictive soil layer beneath the topsoil. The assessment approaches developed in this research should prove useful for determining whether the construction of the rain garden was performed properly, a rain garden is functioning properly, and for developing maintenance tasks and schedules.     

A MODELING APPROACH FOR STORM WATER QUANTITY AND QUALITY CONTROL VIA DETENTION BASINS1

ABSTRACT: Storm water detention basins have historically been employed for quantity (i.e., flooding) control only. However, recently it has been suggested that these basins may also provide a practical means of storm water quality control. This paper presents the formulation of a mathematical modeling approach which may be used by professionals to simultaneously design detention basins for the dual purpose of storm water quantity and quality control. Model simulations demonstrate that for a given basin, pollutant removal increases as storm frequency increases. The importance of particle size distribution and settling velocity for net pollutant removal is illustrated, The design procedure is demonstrated, and pollutant loading diagrams for estimating pollutant removal as a function of storm size are developed.     

Hydrologic and Phosphorus Export Behavior of Small Streams in Commercial Poultry‐Pasture Watersheds1

Romeis, J. Joshua, C. Rhett Jackson, L. Mark Risse, Andrew N. Sharpley, and David E. Radcliffe, 2011. Hydrologic and Phosphorus Export Behavior of Small Streams in Commercial Poultry‐Pasture Watersheds. Journal of the American Water Resources Association (JAWRA) 1‐19. DOI: 10.1111/j.1752‐1688.2011.00521.x Abstract: Few watershed‐scale studies have evaluated phosphorus export in streamflow from commercial poultry‐pasture operations. Continuous streamflow and mixed‐frequency water quality datasets were collected from nine commercial poultry‐pasture (AG) and three forested (FORS) headwater streams (2.4‐44 ha) in the upper Etowah River basin of Georgia to estimate total P (TP) loads and examine variability of hydrologic response and water quality of storm and nonstorm‐flow regimes. Data collection duration ranged from 18 to 22 months, and approximately 1,600 water quality samples were collected. Significant (p < 0.1) inverse relationships were detected between peak flow response variables and both drainage area and fraction of forest cover. Order‐of‐magnitude differences in TP and dissolved reactive P (DRP) concentration were observed between AG and FORS sites and among AG sites. TP yields of FORS sites ranged from 0.01 to 0.1 kg P/ha. Yields of AG sites ranged from 0.031 to 3.17 kg P/ha (median = 0.354 kg P/ha). With 95% confidence intervals, AG yields ranged from 0.025 to 13.1 kg P/ha. These small‐watershed‐scale yields were similar to field‐scale yields measured in other studies in other regions. TP yields were significantly related to area‐weighted Mehlich‐1 soil test P concentrations (p = 0.0073) and base‐flow water sample P concentrations (p ≤ 0.0005). Water quality sampling during base‐flow conditions may be a useful screening tool for P risk‐based management programs.     

A Benefit‐Cost Analysis of Total Maximum Daily Load Implementation1

Abstract: Total Maximum Daily Load (TMDL) implementation generates benefits and costs from water quality improvements, which are rarely quantified. This analysis examines a TMDL written to address bacteria and aquatic‐life‐use impairments on Abrams and Opequon Creeks in Virginia. Benefits were estimated using a contingent valuation survey of local residents. Costs were based on the number and type of best management practices (BMPs) necessary to achieve TMDL pollution reduction goals. BMPs were quantified using watershed‐scale water quality simulation models (Generalized Watershed Loading Function and Hydrological Simulation Program‐FORTRAN). Based on our projections, the costs to achieve TMDL induced pollution reduction goals outweigh the estimated benefits. Benefit‐cost ratios ranged between 0.1 and 0.3.