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2008
Author(s): Bratieres, K., T.D. Fletcher, A. Deletic, and Y. Zinger.
Title: “Nutrient and Sediment Removal by Stormwater Biofilters: A Large-Scale Design Optimization Study”
Journal (Issue): Water Research, 42(14): 3930-3940.
Study Type: Laboratory
Description: 125 large columns of varying plant species, filter media, filter depth, filter area, and pollutant inflow concentrations were tested to measure the performance of biofilters to remove sediment, nitrogen, and phosphorus. The results showed that vegetation selection was critical for nitrogen performance. Phosphorus removal was consistently very high. Phosphorus removal was reduced for the filter media with added organic matter. According to this research, biofilters could be optimally designed to remove nutrients and TSS (up to 70% for nitrogen, up to 85% for phosphorus, and over 95% for TSS). The optimal biofilter was at least 2% of its catchment area, and was constructed with a sandy loam filter media. C. appressa and M. ericfolia were the most effective plants used in this study. This study took place in Melbourne, Australia.
Author(s): Davis, A.P.
Title: “Field Performance of Bioretention: Hydrology Impacts”
Journal (Issue): Journal of Hydrologic Engineering, 13(2): 90-95.
Study Type: Field
Description: Study took place in College Park, Maryland. It introduced 3 new metrics to compare hydrologic performance of bioretention to LID hydrology goals for undeveloped land. It provided target values for these LID hydrology goals. The 3 metrics are for: (1) 24 hour flow volume reduction, (2) peak flow reduction, and (3) peak delay. Two lined cells were studied and they had media depths of 0.9 m and 1.2 m, where the deeper cell included an anoxic sump. The water quality data for these sites are available in Davis (2007).
Author(s): Emerson, C.H., and R.G. Traver.
Title: “Multiyear and Seasonal Variation of Infiltration from Storm-Water Best Management Practices”
Journal (Issue): Journal of Irrigation and Drainage Engineering, 134(5): 598-605.
Study Type: Field
Description: Two infiltration stormwater BMPs have been continuously monitored in Southeastern Pennsylvania at Villanova University campus to determine long-term and seasonal variations of engineered infiltration of stormwater runoff. There has been no evidence of decrease in performance to date, but they both show considerable seasonal variation. The seasonal variation is mostly explained by temperature dependency of the viscosity of water. The two monitored systems are a pervious concrete infiltration basin (constructed in 2002) and the bio-infiltration traffic island (constructed in 2001). Essentially no maintenance has been performed on either BMP. While the time period studied is short compared to the life expectancy of the BMP, there is no evidence of decrease in performance. The importance of proper design, siting, pre-treatment, construction, and maintenance is emphasized to continue function as intended.
Author(s): Hatt, B.E., T.D. Fletcher, and A. Deletic
Title: “Hydraulic and pollutant removal performance of fine media stormwater filtration systems”
Journal (Issue): Environmental Science and Technology, 42(7), 2535-2541
Study Type: Laboratory
Description: An overall assessment on hydraulic and pollutant removal behavior was done on soil and sand stormwater filters. The impacts of time, cumulative inflow sediment and water volume, wetting and drying, and compaction were investigated. The formation of a clogging layer at the surface was the main cause of hydraulic failure. Sediment and heavy metals were effectively captured and retained; however, leaching of nitrogen and phosphorus occurred for the soil-based systems. Significant accumulations of all pollutants occurred in the top 20% of the filter profile. Based on the results of this study, the authors recommend removing the top 2-5 cm of filter media every 2 years to prevent hydraulic failure and to avoid excessive accumulation of heavy metals.
Author(s): Hunt, W.F., J.T. Smith, S.J. Jadlocki, J.M. Hathaway, and P.R. Eubanks.
Title: “Pollutant Removal and Peak Flow Mitigation by a Bioretention Cell in Urban Charlotte, NC”
Journal (Issue): Journal of Environmental Engineering, 134(5): 403-408.
Study Type: Field
Description: Study took place in an ultra-urban location – Charlotte, NC. Data are available on fecal coliform, E. coli, metals, nitrogen, phosphorus, total suspended solids, and flow (peak flows). Bioretention was shown to effectively reduce peak runoff from small and mid-sized events, and it showed potential to reduce indicator species of pathogenic bacteria.
Author(s): Li, H., and A.P. Davis.
Title: “Urban Particle Capture in Bioretention Media. I: Laboratory and Field Studies”
Journal (Issue): Journal of Environmental Engineering, 134(6): 409-418.
Study Type: Laboratory and Field
Description: Column studies and field observations showed that media stratification occurs with runoff percolation due to particulate deposition, so periodic surface media replacement could be an effective measure in bioretention maintenance. The filter media are clogging limited, as opposed to breakthrough limited, so media clogging will always occur before TSS penetration. Depth/cake filtration significantly contributes to urban particle capture. Column tests showed incoming suspended solids could not significantly penetrate below 5 to 10 cm, where field observations exhibited penetration to depths up to 20 cm. The controlling effect on media clogging is the clay-sized components in the incoming suspended solids. The results suggest that removing the top 20 cm of media is sufficient in maintenance procedures to remove particles captured in runoff.
Author(s): Li, H., and A.P. Davis.
Title: “Urban Particle Capture in Bioretention Media. II: Theory and Model Development”
Journal (Issue): Journal of Environmental Engineering, 134(6): 419-432.
Study Type: Modeling
Description: A 3-layer model was developed to describe particulate capture in bioretention media. The 3 layers include: pristine zone (bottom), working zone (middle), and cake zone (top). The mechanisms for depth filtration and cake filtration are examined through mass balances. The model predicts effluent TSS and media hydraulic conductivity. With proper assumptions, the model can be used to predict frequency of media replacement. The authors discuss that fauna and vegetation can play a role in loosening the media structure and maintaining media permeability, so laboratory tests may underestimate media permeability prediction.
Author(s): Li, H., and A.P. Davis.
Title: “Heavy Metal Capture and Accumulation in Bioretention Media”
Journal (Issue): Environmental Science & Technology, 42(14): 5247-5253.
Study Type: Field and Modeling
Description: This study examined capture and accumulation of various heavy metals (lead, copper, and zinc) in bioretention media using a 1-dimensional filtration equation for particulate metals, advection/dispersion/adsorption transport equations for dissolved metals, and sequential extractions. Based on a simple risk evaluation, the limiting metal in bioretention accumulation is lead. The results of this study suggest that shallow design (20-40 cm) is sufficient for systems focused on metal capture.
Author(s): Lloyd, S., and T. Wong.
Title: “Paired Catchment Storm Event Monitoring: Assessing the Performance of a Bioretention System (Rain Garden)”
Journal (Issue): Australian Journal of Water Resources, 12(1): 133-141.
Study Type: Field
Description: Runoff characteristics from a landscaped bioretention system were compared to a conventional concrete pipe system in a residential development in Victoria, Australia. The results showed that the extent of function depended on design characteristics, storm size, in-situ geology, and antecedent moisture conditions. Runoff volumes and peak flows were lower in the bioretention systems. The small, frequent storms were completely captured by the bioretention system. Consequently, pollutant loads were reduced through runoff retention and physical and/or chemical treatment processes. Pollutant load calculations made for 10 events showed reductions of gross pollutants (100%), TSS (68%), total phosphorus (68%), and total nitrogen (57%).
Author(s): Lucas, W.C., and M. Greenway.
Title: “Nutrient Retention in Vegetated and Non-vegetated Bioretention Mesocosms”
Journal (Issue): Journal of Irrigation and Drainage Engineering, 134(5): 613-623.
Study Type: Laboratory
Description: Retention of dissolved nutrients by bioretention was studied using 30, 240 L bioretention mesocosms. Media used in the mesocosms were sandy loam, loamy sand, and pea gravel with loamy sand. Half of the mesocosms were vegetated and the rest were barren. The systems were loaded with synthetic stormwater and then tertiary effluent. When loaded with synthetic stormwater, retention of total phosphorus and total nitrogen were higher in the vegetated systems and higher with the sandy loam. The same results held true with the tertiary effluent. There was a substantial increase in total phosphorus and total nitrogen retention in the vegetated systems, higher than the uptake rates for plants, so other processes were likely involved.
Author(s): Muthanna, T.M., M. Viklander, and S.T. Thorolfsson.
Title: “Seasonal Climatic Effects on the Hydrology of a Rain Garden”
Journal (Issue): Hydrologic Processes, 22(11): 1640-1649.
Study Type: Field
Description: Two small-scale rain gardens in a small residential watershed in Trondheim, Norway, were studied to examine performance and winter hydrology in a cold climate. One rain garden was studied for 20 months and the other, which was used as the control, was only studied for 7 months. Hydraulic detention, lag time, and peak flow reduction were measured and compared seasonally. There was no significant difference between lag time. For 44 storms, the average peak flow reduction was 42%, but was only 27% during the winter season. A strong positive correlation between time since last wetting event and lag time was found. There was also a correlation between air temperature and hydraulic detention. Key parameters for hydraulic performance of rain gardens in cold climates are time between events and seasonal air temperatures. As a side note, the rain gardens weren’t used for snow storage areas.
Author(s): Muthukrishnan, S., and M. Oleske.
Title: “Effects of Lime Amendment on the pH of Engineered Soil Mix for the Purposes of Bioretention”
Journal (Issue): Journal of Irrigation and Drainage Engineering, 134(5): 675-679.
Study Type: Laboratory
Description: pH strongly influences pollutant attenuation behavior of bioretention systems. For native acidic soils, lime amendment can be a useful and easy technique to raise pH to aid in improving heavy metal sorption capacities. By adding 0.5% lime to the selected soil with pH of 4.8, the 7 day laboratory study showed that the pH exceeded the target range. Previous studies showed a range of 5.5 to 7 is appropriate for sorption of heavy metals.
Author(s): Pitt, R., S. Chen, S.E. Clark, J. Swenson, and C.K. Ong.
Title: “Compaction’s Impacts on Urban Storm-Water Infiltration”
Journal (Issue): Journal of Irrigation and Drainage Engineering, 134(5): 652-658.
Study Type: Field
Description: Showed how the degree of compaction can greatly affect the steady-state infiltration rates for both sand and clay soils and for varying antecedent moisture conditions. Compaction in disturbed urban soils has a major impact on reduced infiltration. A major component in urban runoff models is soil infiltration, so understanding the effect of compaction is necessary to accurately predict stormwater runoff and bioretention outflow.
Author(s): Read, J., T. Wevill, T. Fletcher, and A. Deletic
Title: “Variation among plant species in pollutant removal from stormwater in biofiltration systems”
Journal (Issue): Water Research, 42(4-5), 893-902
Study Type: Laboratory
Description: The impact of how different vegetation improves pollutant removal efficiency was studied using semi-synthetic stormwater passing through a soil filter medium. Twenty Australian plant species were tested. TSS, Al, Cr, Cu, Pb, Zn, N species, and P in effluent were measured. Presence of plants improved effectiveness of biofilters, but a variation in pollutant removal was observed for the different plant species. Variation in pollutant removal, by up to 20-fold, indicates that plant selection could have substantial influence on biofilter effectiveness. Some of the variation was explained by plant size.
Author(s): Thompson, A.M., A.C. Paul, and N.J. Balster.
Title: “Physical and Hydraulic Properties of Engineered Soil Media for Bioretention Basins”
Journal (Issue): Transactions of the ASABE, 51(2): 499-514
Study Type: Laboratory
Description: Physical and hydraulic characteristics were measured for a variety of engineered bioretention media mixes. Infiltration, bulk density, and moisture holding capacity were measured for different composite mixtures of sand, soil, and compost. The effects of compaction were measured by its impact on bulk density, moisture holding capacity, and saturated hydraulic conductivity. A total of 11 mixtures were evaluated, with sand, sandy or silt loam soil, and organic compost ranging from 30-70%, 0-20%, and 20-70%, respectively.
Author(s): Zhang, W., G.O. Brown, and D.E. Storm.
Title: “Enhancement of Heavy Metals Retention in Sandy Soil by Amendment with Fly Ash”
Journal (Issue): Transactions of the ASABE, 51(4): 1247-1254.
Study Type: Laboratory and modeling
Description: Batch sorption and column leaching experiments were run to determine sorption of heavy metals (copper, lead, and zinc) in 3 soils (Dougherty sand, Teller loam, and Slaughterville loam), fly ash, and fly ash/sand mixtures. The mixture with the highest metals retention was fly ash, and the lowest was Dougherty sand. When fly ash was added to the Dougherty sand, the metals retention increased. A linear equilibrium, convection-dispersion transport model was used in conjunction with parameters determined from the laboratory columns to model heavy metals transport. The results of this showed a 1 m deep filter media of pure sand could remove heavy metals from stormwater for only 10 years, but when sand was mixed with 5% fly ash, metals removal would continue on for over 900 years.
Author(s): Zhang, W., G.O. Brown, D.E. Storm, and H. Zhang.
Title: “Fly Ash Amended Sand as Filter Media in Bioretention Cells to Improve Phosphorus Removal”
Journal (Issue): Water Environment Research, 80(6): 507-516.
Study Type: Laboratory
Description: Fly ash, 2 expanded shales, peat moss, limestone, and 2 common Oklahoma soils (Teller and Dougherty) were tested to identify materials with high phosphorus sorption capacity. Peat moss was a source of phosphorus. The 2 soils, limestone, and 1 of the expanded shales had modest sorption capacities. The other expanded shale and fly ash had significant sorption capacity. In its pure form, fly ash is not suitable due to its low permeability. With the addition of small amounts of fly ash to the sand, phosphorus sorption was increased significantly. Transport simulations were run to determine treatment capacities and lifetimes of the systems.
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