Browsing by Author "Natarajan, Poornima"

Now showing 1 - 18 of 18

Assessing and Improving Pollution Prevention by Swales
(St. Anthony Falls Laboratory, 2014-08) Gulliver, John S.; Ahmed, Farzana; Natarajan, Poornima; Weiss, Peter T.; Nieber, John L.
Roadside swales are drainage ditches that also treat runoff to improve water quality, including infiltration of water to reduce pollutant load. In the infiltration study, a quick and simple device, the Modified Philip Dunne (MPD) infiltrometer, was utilized to measure an important infiltration parameter (saturated hydraulic conductivity, Ksat) at multiple locations in a number of swales. The study showed that the spatial variability in the swale infiltration rate was substantial, requiring 20 or more measurements along the highway to get a good estimate of the mean swale infiltration rate. This study also developed a ditch check filtration system that can be installed in swales to provide significant treatment of dissolved heavy metals and dissolved phosphorous in stormwater runoff. The results were utilized to develop design guidelines and recommendations, including sizing and treatment criteria for optimal performance of the full-scale design of these filters. Finally, the best available knowledge on swale maintenance was combined with information obtained from new surveys conducted to develop recommendations for swale maintenance schedules and effort. The recommendations aim toward optimizing the cost-effectiveness of roadside swales and thus provide useful information to managers and practitioners of roadways. The research results and information obtained from this study can thus be used to design swale systems for use along linear roadway projects that will receive pollution prevention credits for infiltration. This will enable the utilization of drainage ditches to their full pollution prevention potential, before building other more expensive stormwater treatment practices throughout Minnesota and the United States.
Assessing and Improving Pollution Prevention by Swales
(Center for Transportation Studies, University of Minnesota, 2014-08) Ahmed, Farzana; Natarajan, Poornima; Gulliver, John S.; Weiss, Peter T.; Nieber, John L.
Roadside swales are drainage ditches that also treat runoff to improve water quality, including infiltration of water to reduce pollutant load. In the infiltration study, a quick and simple device, the Modified Philip Dunne (MPD) infiltrometer, was utilized to measure an important infiltration parameter (saturated hydraulic conductivity, Ksat) at multiple locations in a number of swales. The study showed that the spatial variability in the swale infiltration rate was substantial, requiring 20 or more measurements along the highway to get a good estimate of the mean swale infiltration rate. This study also developed a ditch check filtration system that can be installed in swales to provide significant treatment of dissolved heavy metals and dissolved phosphorous in stormwater runoff. The results were utilized to develop design guidelines and recommendations, including sizing and treatment criteria for optimal performance of the full-scale design of these filters. Finally, the best available knowledge on swale maintenance was combined with information obtained from new surveys conducted to develop recommendations for swale maintenance schedules and effort. The recommendations aim toward optimizing the cost-effectiveness of roadside swales and thus provide useful information to managers and practitioners of roadways. The research results and information obtained from this study can thus be used to design swale systems for use along linear roadway projects that will receive pollution prevention credits for infiltration. This will enable the utilization of drainage ditches to their full pollution prevention potential, before building other more expensive stormwater treatment practices throughout Minnesota and the United States.
Assessing Iron-Enhanced Swales for Pollution Prevention
(2015-09) Natarajan, Poornima; Gulliver, John S.
The treatment of dissolved phosphorus and metals in runoff requires specialized filtration media, which, however, is not accounted for in the typical swale ditch check designs currently employed. In this project, ditch checks with iron-enhanced sand filter insert were developed to increase the retention of phosphate and dissolved metals in roadside swales and ditches. The iron-enhanced swale ditch checks were designed and installed as part of roadway projects of the Minnesota Department of Transportation (MnDOT) and City of Roseville. The effectiveness of the ditch checks was investigated by field testing using synthetic runoff, and field monitoring during natural rainfall events in Fall 2014 and from Spring to Summer 2015. A ditch check containing no enhanced media was also monitored for comparison. The MnDOT iron-enhanced ditch check provided consistent phosphate mass reductions during 15 rainfall events (33% mean; 37% median). The cumulative phosphate mass removal was 35%. Metal reductions were largely negative, possibly due to leaching of metals from the filter media. The Roseville iron-enhanced ditch check exhibited 47%, 43%, 26% phosphate removal and 14% zinc removal under different field testing scenarios. The ditch check without the iron-enhanced sand filter insert showed no phosphate removal but retention of metals in the top soil cover. Since the iron-enhanced ditch check monitoring excluded the effect of top soil, it can be presumed that an iron-enhanced ditch check will retain metals in the soil covering the ditch check and retain phosphate in the filter section. The project results were utilized to develop typical design recommendations for future applications of the iron-enhanced ditch check.
Assessment of Internal Phosphorus Loading in Swimming Pool Pond and Point of France Pond, City of Edina
(2019-03) Natarajan, Poornima; Gulliver, John S.
Assessment of Internal Phosphorus Release and Treatment with Iron Filings in five RPBCWD Ponds
(University of Minnesota, College of Science and Engineering, 2022-06) Natarajan, Poornima; Gulliver, John S.
Five ponds, Aquila Pond (in Bloomington), Pond BC-P4.10C (in Chanhassen), Bren Pond (in Eden Prairie), Pond 849_W (in Minnetonka) and Pond 42 (in Shorewood), were evaluated in this two-part study. a) In the first part of the study, the potential anoxic sediment phosphorus release was evaluated using laboratory sediment cores. A moderately-high flux of phosphate was measured under anoxic conditions, which was supported by high sediment oxygen demand and high organic matter content in the sediments. A low oxic flux was observed only for Pond BC-P4.10C and Bren Pond sediments, indicating mobilization of organic P by bacteria. Detailed sediment phosphorus characterization revealed low to moderate concentrations of mobile P (redox-P + labile organic P) mass, which is releasable under low oxygen conditions and by microbacterial degradation under both oxic and anoxic conditions. The relative mobile P mass (as % of the total sediment phosphorus mass) was 53% in Aquila Pond, 43% in Pond BC-P4.10 C, 47% in Bren Pond, 41% in Pond 42, and 63% in Pond 849_W, highlighting the importance of mobile phosphorus in driving internal phosphorus loading during anoxia in the ponds. b) In situ monitoring of surface to bottom DO and temperature profiles in the ponds were indicative of a stratified water column that was anoxic from top to bottom during much of the summer period. The observation of pervasive anoxia was common in Pond BC-P4.10C, Bren Pond, Pond 849_W, and Pond 42 during all three field seasons, as indicated by the relatively high summer anoxic factor (AF) for these ponds. Aquila Pond appeared to partially mix intermittently although bottom DO was still low during certain periods. c) All five pond sites had floating vegetation (duckweed and watermeal) that had a dense surface coverage (nearly 100%) from June to September. We have found strong evidence of duckweed cover influencing the DO dynamics in several ponds and have observed a strong pattern between summer anoxic factor and duckweed cover in our pond research projects. It is possible that the effect of duckweed may be exacerbated in dry years (like 2021) when stormwater inputs to provide direct mixing are less frequent. d) The application of iron filings was utilized to reduce phosphate release from the pond sediments. Ponds BC-P4.10C and 849_W were treated with iron filings in February 2020 and Bren Pond was treated in February 2020. Aquila Pond can be used as a control for the RPBCWD region, where surface water TP was seen to increase greatly from 2019 to 2020, and then stayed about the same in 2021. In Pond BC-P4.10C, the average TP went up after treatment with iron filings in February 2020, but not as substantially as the Aquila Pond. In Bren Pond, the average TP had a slight reduction in all three years. In Pond 849_W, the average TP went up in 2020 but then reduced in 2021. A similar reduction can be seen in comparing average TP for Shoreview Commons Pond (a fourth iron-treated pond located in the Ramsey Washington Metro Watershed District) to the Alameda Pond (located in v Roseville), where Shoreview Commons had a reduced average TP in 2021 after iron filings addition and the Alameda Pond, with no iron filings addition, did not. e) The analysis of the iron-treated sediments from Pond BC-P4.10C, Pond 849_W, and Bren Pond showed an increase in the iron-bound P mass and a concomitant decrease in the mass of labile organic P and loosely-bound P after iron filings application to the sediments, suggesting the partial or full movement of phosphate from the organic P form and loosely- bound P to iron-phosphate minerals in the sediments. The iron-treated sediment cores from Bren Pond exhibited an anoxic phosphate flux that was significantly lower than the phosphate flux from untreated sediments. f) While the column studies confirmed that sediment phosphate flux was controlled after iron addition, the reduction in internal phosphorus loading in the ponds was not directly assessed. The post-treatment water quality data showed reductions in SRP levels (surface and epilimnion) at the three iron-treated ponds but did not conclusively show reductions in TP levels, specifically in ponds BC-P4.10C and 849_W. The interpretation and assessment of treatment effectiveness is complicated by the year-to-year variation in pond water quality driven by rainfall patterns and runoff inputs among other factors, especially in ponds BC- P4.10C and 849_W, which have pretreatment data for only one year before iron filings were applied. Treatment of the ponds will likely require a combination of remediation techniques such as sealing the sediments from phosphate flux, aeration to enhance mixing and watershed-based phosphorus control actions to reduce the inflow of TP. Aeration may work well in Pond 849_W, which has a small amount of inflow or outflow.
Characterization of Runoff Quality from Paved Low-Volume Roads and Optimization of Treatment Methods
(Minnesota Department of Transportation, 2020-09) Natarajan, Poornima; Weiss, Peter T.; Gulliver, John S.
Vehicular traffic contributes a large fraction of the pollutant load in stormwater runoff from roadways. While runoff concentrations have historically been characterized for urban roads with high average daily traffic (ADT), the runoff quality from paved rural roads that have relatively low ADT is largely unknown. In this study, runoff from low-volume roads (ADT < 1500) in Minnesota was monitored at 10 locations during 174 rainfall events in 2018 and 2019. The initial concentrations of total suspended solids (TSS), total phosphorus (TP), nitrate+nitrite, and heavy metals in the runoff, and the relationship between measured concentrations and site-specific conditions were analyzed. Concentrations were strongly influenced by the surrounding land use and soil type. Sites with agricultural lands had higher mean TSS, TP, and zinc concentrations, and lower nitrite+nitrate concentrations than wooded sites, which can be related to the type of soil that would get transported onto the roadways. When compared to existing urban runoff quality data, the estimated event mean concentrations (EMCs) in rural road runoff were substantially lower for copper and zinc and marginally lower for TSS, TP and nitrate+nitrite. Based on detailed cost-benefit analysis of various roadside treatment options, roadside drainage ditches/swales are recommended for cost-effective treatment of runoff from low-volume roads over ponds, sand filters and infiltration basins. Example road widening projects were also modeled to determine how stormwater management requirements can be achieved using drainage ditches/swales.
Characterization of Runoff Quality from Paved Low-Volume Roads and Optimization of Treatment Methods
(2020-09) Gulliver, John S.; Natarajan, Poornima; Weiss, Peter T.
Vehicular traffic contributes a large fraction of the pollutant load in stormwater runoff from roadways. While runoff concentrations have historically been characterized for urban roads with high average daily traffic (ADT), the runoff quality from paved rural roads that have relatively low ADT is largely unknown. In this study, runoff from low-volume roads (ADT < 1500) in Minnesota was monitored at 10 locations during 174 rainfall events in 2018 and 2019. The initial concentrations of total suspended solids (TSS), total phosphorus (TP), nitrate+nitrite, and heavy metals in the runoff, and the relationship between measured concentrations and site-specific conditions were analyzed. Concentrations were strongly influenced by the surrounding land use and soil type. Sites with agricultural lands had higher mean TSS, TP, and zinc concentrations, and lower nitrite+nitrate concentrations than wooded sites, which can be related to the type of soil that would get transported onto the roadways. When compared to existing urban runoff quality data, the estimated event mean concentrations (EMCs) in rural road runoff were substantially lower for copper and zinc and marginally lower for TSS, TP and nitrate+nitrite. Based on detailed cost-benefit analysis of various roadside treatment options, roadside drainage ditches/swales are recommended for cost-effective treatment of runoff from low-volume roads over ponds, sand filters and infiltration basins. Example road widening projects were also modeled to determine how stormwater management requirements can be achieved using drainage ditches/swales.
Data for: Internal Loading in Stormwater Ponds as a Phosphorus Source to Downstream Waters
(2019-04-15) Taguchi, Vinicius J; Olsen, Tyler A; Natarajan, Poornima; Janke, Benjamin D; Gulliver, John S; Finlay, Jacques C; Stefan, Heinz G; ; taguc006@umn.edu; Taguchi, Vinicius J; University of Minnesota - St. Anthony Falls Laboratory - Stormwater Research Group
Stormwater ponds remove phosphorus through sedimentation before releasing captured water downstream. Internal loading can impair net phosphorus removal but is understudied in these highly modified systems. Using a combination of methods, we assessed the prevalence and potential causes of sediment phosphorus release in urban ponds. In a three-year, 98-pond dataset, nearly 40% of ponds had median water column total phosphorus concentrations exceeding the 95% confidence interval for runoff values (0.38 mg/L), suggesting widespread internal loading. In a subsequent intensive monitoring study of four ponds, strong stratification prevented spring and summer diurnal mixing, resulting in persistent hypolimnion anoxia (<1 mg/L dissolved oxygen). Incubated sediment cores from seven ponds demonstrated high anoxic phosphorus release. Sediment analysis revealed high labile organic and redox-sensitive phosphorus fractions with release potential at anoxia onset. Our analyses suggest phosphorus accumulated in stormwater ponds is highly sensitive to internal loading, reducing net removal and contributing to downstream eutrophication.
Detecting phosphorus release from stormwater ponds to guide management and design
(2021-01) Janke, Benjamin D.; Natarajan, Poornima; Shrestha, Paliza; Taguchi, Vinicius T.; Finlay, Jacques C.; Gulliver, John S.
Detecting phosphorus release from stormwater ponds to guide management and design
(2021-02-23) Finlay, Jacques C; Gulliver, John S; Janke, Benjamin D; Natarajan, Poornima; Taguchi, Vinicius; Shrestha, Paliza; janke024@umn.edu; Janke, Ben D; University of Minnesota - St. Anthony Falls Laboratory - Stormwater Research Group
There is growing concern that aging stormwater retention ponds may become net sources of phosphorus (P) to receiving waters. Release of P previously deposited in sediments (i.e. internal loading) is a major contributor to eutrophication in lakes. Stormwater ponds often have high external P loading, and other characteristics that may increase the likelihood of internal loading as ponds age. However, stormwater ponds have received comparatively little research attention, even though they are widely used with the intended goal of permanent immobilization of phosphorus. The ability of these systems to retain phosphorus over their lifespan is essentially unknown. The proposed research will build understanding necessary to assess the capacity of stormwater ponds to retain or release phosphorus in Minnesota’s stormwater pond infrastructure. The projects aim to develop methods for rapid and efficient identification of pond phosphorus release, to guide management of existing ponds, and to reveal factors that underlie poor performance for P removal. The results of this project will be used to inform and improve pond maintenance, pond design and decision making around construction of new ponds, and to ultimately improve the water quality of our lakes, rivers and wetlands.
Golden Lake Phosphorus Release and Alum Dosing Feasibility Study
(2020-06) Natarajan, Poornima; Gulliver, John S.
Internal Phosphorus Load Reduction with Iron Filings
(2017-09) Natarajan, Poornima; Gulliver, John S.; Arnold, William A.
Iron-Enhanced Swale Ditch Checks for Phosphorus Retention
(Minnesota Department of Transportation, 2019-07) Natarajan, Poornima; Gulliver, John S; Weiss, Peter T
Iron-enhanced ditch checks in roadside swales were developed specifically for capturing dissolved phosphorus and dissolved metals from roadway runoff in both urban and agricultural environments. One iron-enhanced ditch check constructed along CR 15 (formerly TH 5) in Stillwater, Minnesota, was monitored during 40 storm events from 2016 to 2018. The iron-enhanced sand filter insert generally captured phosphate, yielding lower phosphate concentrations and mass load reductions that varied between 22% and 50% during several events. However, the cumulative phosphate retention in the filter insert decreased from 42% in 2015 to 30% in 2016, 25% in 2017, and 23% in 2018. The filter insert was not an effective retention device for dissolved copper and zinc. The overall ditch check’s performance, although unexceptional in 2016 and 2017, appeared to improve in 2018. Sampling issues likely contributed to the low performance measured until 2017. The 2018 water sample collection method provided a better estimate of the ditch check’s performance and roughly matched that of the filter insert. Synthetic runoff testing supported the level of treatment achieved during storm events. Phosphate load from the degrading topsoil and the overutilization of the bottom filter media most likely affected overall treatment performance. Design improvements and recommended maintenance actions were developed based on the lessons learned from field monitoring. The iron-enhanced ditch check can improve net phosphate retention through roadside swales, as long as the recommended maintenance actions are performed as scheduled.
St. Cloud Pond 52: Assessment of Pond Sediments After Iron Filings Treatment
(2022-01) Natarajan, Poornima; Gulliver, John S.
Stormwater Pond Maintenance, and Wetland Management for Phosphorous Retention
(Minnesota Department of Transportation, 2023-06) Janke, Benjamin D.; Natarajan, Poornima; Gulliver, John S.; Finlay, Jacques C.
Reduction in phosphorus is critical because phosphate, a dissolved form of phosphorus, sustains algal and cyanobacteria growth and causes a wide range of water-quality impairments in the ponds and downstream waters including algal blooms, excess floating plants, taste, and odor problems. Many stormwater ponds and wetlands that treat stormwater appear to be less effective than expected or originally intended in phosphorus retention, a key function of these ponds in urban environments. There is evidence that many old ponds are releasing phosphorus from bottom sediments at high rates and likely exporting phosphorus to downstream surface water bodies. A major outcome of this project is a pond Assessment Tool to assess the risk of high phosphorus concentrations in ponds and sediment release of phosphorus. The tool is based on 20 ponds with detailed water quality and phosphorus release measurements and a meta-analysis of 230 ponds in the Twin Cities metro area. Other outcomes included a working definition of a constructed stormwater pond and a wetland treating stormwater in the framework of water-body regulations, the development of recommendations for stormwater pond maintenance and wetland management, and an update to the sections on the constructed stormwater ponds section of the 2009 Stormwater Maintenance BMP Guide.
Stormwater Pond Maintenance, and Wetland Management for Phosphorus Retention
(Minnesota Department of Transportation, 2023-06) Janke, Benjamin D.; Natarajan, Poornima; Gulliver, John S.; Finlay, Jacques C.
Reduction in phosphorus is critical because phosphate, a dissolved form of phosphorus, sustains algal and cyanobacteria growth and causes a wide range of water-quality impairments in the ponds and downstream waters including algal blooms, excess floating plants, taste, and odor problems. Many stormwater ponds and wetlands that treat stormwater appear to be less effective than expected or originally intended in phosphorus retention, a key function of these ponds in urban environments. There is evidence that many old ponds are releasing phosphorus from bottom sediments at high rates and likely exporting phosphorus to downstream surface water bodies. A major outcome of this project is a pond Assessment Tool to assess the risk of high phosphorus concentrations in ponds and sediment release of phosphorus. The tool is based on 20 ponds with detailed water quality and phosphorus release measurements and a meta-analysis of 230 ponds in the Twin Cities metro area. Other outcomes included a working definition of a constructed stormwater pond and a wetland treating stormwater in the framework of water-body regulations, the development of recommendations for stormwater pond maintenance and wetland management, and an update to the sections on the constructed stormwater ponds section of the 2009 Stormwater Maintenance BMP Guide.
Wet Pond Maintenance for Phosphorus Retention
(Minnesota Department of Transportation, 2022-06) Taguchi, Vinicius J.; Janke, Benjamin D.; Herb, William R.; Gulliver, John S.; Finlay, Jacques C.; Natarajan, Poornima
This report considers the outcomes of the pond maintenance strategies of sediment treatment to reduce internal loading of phosphorus, mechanical aeration, alteration of pond outlet to pull water off the bottom, reduction of wind sheltering, dredging, outlet treatment by iron enhanced sand filtration and reduction of phosphorus loading from the watershed. The strategies were analyzed with the model CE-QUAL-2E, where inputs to the model were initial conditions, morphology, inflow rate and total phosphorus and soluble reactive phosphorus concentrations, sediment oxygen demand, sediment release of phosphate, and meteorological conditions. The model as applied in this research simulates stratification, wind mixing, outflow and vertical profiles of temperature, dissolved oxygen, chloride, soluble reactive phosphorus, and total phosphorus. The model is calibrated on data from Alameda pond, verified on data from the Shoreview Commons pond, and applied to maintenance and remediation strategies for the Alameda, Shoreview Commons, Langton, and Minnetonka 849W ponds. Costs of maintenance or remediation strategies are estimated and the cost per reduction in total phosphorus release is calculated.
Wet Pond Maintenance for Phosphorus Retention: LRRB 2019 KB 03 MnDOT Agreement No. 1034035
(2022-06) Taguchi, Vinicius J.; Janke, Benjamin D.; Herb, William R.; Gulliver, John S.; Finlay, Jacques C.; Natarajan, Poornima

University Digital Conservancy

Browse by Author

Browsing by Author "Natarajan, Poornima"