A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item IMPROVING STORMWATER QUALITY USING A NOVEL PERMEABLE PAVEMENT BASE MATERIAL(2018) OSTROM, TRAVIS Kyle; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A novel stormwater treatment media has been developed using expanded shale aggregate, Al-based water treatment residual (WTR), and psyllium-based binder. The media (HPMM) has sufficient structural capacity and hydraulic conductivity to serve as a permeable pavement base material and demonstrated effective phosphorus (P) retention in lab- and field-scale studies. Long-term adsorption capacity is projected to exceed 600 years of useful life before P saturation under conditions typical of urban stormwater in Maryland (i.e., 0.20 mg/L dissolved P (DP) influent and 100 cm of direct rainfall per year). A dynamic model was developed to describe DP adsorption onto the media based on lab testing and verified under field monitoring. The model predicted 62% DP concentration reduction and 65% DP mass load reduction. Actual reductions from 17 months of monitoring in a field pilot study were 67% for DP concentration and 69% DP mass load. Total Cu and Zn were also removed from stormwater in lab and field studies. Percent concentration reductions of 59-69% for Cu and 78-90% for Zn were shown in lab studies using synthetic stormwater. Mass load was reduced in field monitoring by 32 and 21% for Cu and Zn, respectively. WTR in the media was shown to be a potential source of nitrogen (N). An internal water storage (IWS) zone was established in a 5-cm permeable pavement base layer to mitigate N export by promoting denitrification. The IWS was shown to effectively lower N concentrations in simulated stormwater when carbon (C) was available in excess (~10 mg/L total C as C). Elevated Al concentrations were found in some filtrate samples from the field study, resulting from washout of fines from the media. Improved HPMM mix preparation methods have been developed and are critical to prevent Al washout and export. This research resulted in development of the first known enhanced stormwater treatment media to retain DP in a permeable pavement base layer. With appropriate N and Al control, the novel media can be an effective tool and can enhance permeable pavements to improve urban stormwater quality.Item Nutrient Leaching from Leaf-and-Grass Compost Addition to Stormwater Submerged Gravel Wetlands(2016) Mangum, Kyle Robert; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Submerged Gravel Wetlands (SGWs) are subsurface-flow wetlands, and are effective stormwater control measures (SCM). Compost addition has many properties beneficial to SGWs but may also lead to leaching of nitrogen (N) and phosphorus (P). To investigate nutrient leaching effects of leaf-and-grass compost addition in SGWs, mesocosm studies were conducted using bioretention soil media (BSM) mixed with 30% and 15% compost, by volume. Synthetic stormwater was applied to mesocosms and effluent analyzed for N and P. Compost-added mesocosms were found to leach N and P. Maximum N concentrations of 16 and 6.4 mg-N/L were reached after 1.7 and 3.0 cm of rainfall for 15% and 30%, respectively. Maximum P concentrations of 2.9 and 0.52 mg-P/L were both reached after 2.5 cm for 30% and 15%, respectively. Particulate P was the dominant P species found in effluent samples, while N species were mixed. Although compost addition led to leaching of N and P, treatment of both nutrients was achieved, with the 15%, reaching a net-zero export of P after the equivalent of 20 cm of rainfall. Nitrogen treatment was attributed to denitrification and plant and microbial uptake. Phosphorus treatment was attributed primarily to adsorption.Item Nutrient Leaching from Bioretention Amended with Source-Separated Compost(2016) Owen, Dylan; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bioretention has been noted to be an effective stormwater control measure (SCM). Compost addition to bioretention could be beneficial, but could also act as a source for excess nutrients. This project analyzed possible nitrogen (N) and phosphorus (P) leaching from bioretention soil media (BSM) amended with source-separated compost. Columns were mixed with compost and BSM at volumes of 30%, and 15%. A final column had 15% compost and an additional 4% water treatment residual (WTR). Synthetic stormwater was applied to each column and the effluent was analyzed for N and P. The 30% column increased the mass exported for both nutrients. Both 15% columns had a net zero effect on nitrogen, but the 15%+WTR column reduced the exported phosphorus load. All compost columns discharged more nutrients than standard BSM. Compost addition should be minimized in bioretention, less than 15% by volume, and WTR should be added to control phosphorus leaching.Item Management of Ammoniacal Nitrogen in Stormwater Runoff(2016) Khorsha, Golnaz; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Nitrogen in stormwater runoff plays a dominant role in the eutrophication of receiving waters. The challenge in treating nitrogen lies in its diverse speciation and biological cycling. This work aimed to improve removal of influent and mineralized ammonium through the use of sorption media and nitrification in preparation for subsequent denitrification. Two media, clinoptilolite (ZT) and hydrous-aluminosilicate (CA), were characterized in a series of batch and sorption column experiments, which indicated superior performance of ZT because of its higher capacity (206 months life-expectancy) and faster kinetics (60 min). Competition with Ca2+ and K+ resulted in smaller and slower sorption for both media. Removed ammonium in ZT was highly extractable, signifying its potential bioavailability. Sorption columns exhibited high removal during influent NH4+ increases, desorption with influent concentration drops, and lower ammonium removal upon rewetting/saturateting. Nitrification in bio-active sorptive media enhanced removal efficiency, particularly for alternating wet/saturated-dry/unsaturated conditions, with smaller desorption occurring. ZT application in filtration-based stormwater control measures is recommended.Item Understanding Urban Stormwater Denitrification in Bioretention Internal Water Storage Zones(2016) Igielski, Sara Jasmine; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Free-draining bioretention systems commonly demonstrate poor nitrate removal. In this study, column tests verified the necessity of a permanently saturated zone to target nitrate removal via denitrification. Experiments determined a first-order denitrification rate constant of 0.0011 min-1 specific to Willow Oak woodchip media. A 2.6-day retention time reduced 3.0 mgN/L to below 0.05 mg-N/L. During simulated storm events, hydraulic retention time may be used as a predictive measurement of nitrate fate and removal. A minimum 4.0 hour retention time was necessary for in-storm denitrification defined by a minimum 20% nitrate removal. Additional environmental parameters, e.g., pH, temperature, oxidation-reduction potential, and dissolved oxygen, affect denitrification rate and response, but macroscale measurements may not be an accurate depiction of denitrifying biofilm conditions. A simple model was developed to predict annual bioretention nitrate performance. Novel bioretention design should incorporate bowl storage and large subsurface denitrifying zones to maximize treatment volume and contact time.