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 NUTRIENT MOVEMENT IN A VEGETATED COMPOST BLANKET AMENDING A VEGETATED FILTER STRIP ON A HIGHWAY SLOPE(2022) Forgione, Erica Rose; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Excess stormwater runoff caused by rapid urbanization and exacerbated by climate change generates many challenges for public safety and the environment. Large runoff volumes contribute to flooding and pollutants in stormwater runoff pose risks to human and environmental health, including toxicity to the aquatic environment caused by heavy metals and nutrient pollution leading to eutrophication, the cause of harmful algal blooms. An effort is being made to improve the efficiency of existing highway stormwater control systems which have limited performance in terms of volume reduction and pollutant removal. To address this issue, amendment of highway Vegetated Filter Strips (VFS) with a Vegetated Compost Blanket (VCB), a layer of seeded compost placed on an established slope, has been proposed. Compost has high water holding capacity and organic matter content which can immobilize contaminants of concern. However, the high nutrient content of compost poses a threat to net beneficial performance since excess nutrient leaching occurs after application. This research has posed the question: Can a VCB be used as a stormwater control measure (SCM) while avoiding excessive nutrient leaching?The VCB/VFS system was assessed through lab-scale, greenhouse-scale, and field-scale experiments. Hydrologic performance was evaluated in field and greenhouse experiments through evaluation of dynamic flow modification, event volume storage, and cumulative volume retention. Water quality performance was assessed through analysis of Total Suspended Solids (TSS), Nitrate + Nitrite (NOx), Total Kjeldahl Nitrogen (TKN), Total Nitrogen (TN), Total Phosphorus (TP), filtered and total Copper, and total Zinc concentrations. Nitrogen (N) and phosphorus (P) in compost are naturally transformed from organic to inorganic, soluble forms through the microbially-mediated process of mineralization. Nutrient removal occurs through adsorption as compost leachate passes through the VFS soil layer. To further investigate nutrient movement, small scale laboratory experiments were completed to determine the N and P compost mineralization rates and theoretical soil adsorption capacities. Nutrient data from greenhouse and field experiments were empirically evaluated using the lab-obtained mineralization data. Nutrient release was simulated and compared to experimental field data using a new open-source software, OpenHydroQual, which combines hydraulic and water quality modeling. VCBs were found to have a significant impact on both flow and volume reduction, though at the highest flowrates, VCBs were unable to significantly reduce flow and instead acted as conveyance. A useful design estimate for representative storage capacity using the saturated moisture content and wilting point of both the VCB and VFS was determined. Significant TSS removal was observed in both the field and greenhouse studies and particulate metals were largely removed; however dissolved copper leaching was observed in the field experiment, as has been observed previously for some compost in stormwater systems. Highly elevated concentrations of nutrients (as high as 100 mg/L TN and 12 mg/L TP) were observed in the effluent of both field and greenhouse experiments, resulting in net nutrient leaching and concentrations above recommended EPA freshwater limits even after 1-2 years. Additionally, mass loading rates at the field site (as high as 41 kg/ac/yr for TN and 14 kg/ac/yr for TP) were 1-2 magnitudes higher than observed influent mass loading rates (~3.8 kg/ha/yr for TN and ~0.47 kg/ha/yr for TP). Through laboratory mineralization studies, N and P mineralization rates were found to differ between compost batches, with initial nutrient content and age/leaching of compost being important factors. Adsorption experiments indicated increasing P adsorption from compost leachate with increasing soil Al+Fe content. Comparisons to greenhouse and field data showed differences in N speciation, likely due to differences in moisture content and temperature causing differing amounts of nitrification and volatilization. OpenHydroQual modeling showed modest results, with varying levels of accuracy for storm hydrograph simulation and mass release. VCBs are not currently recommended for use due to the risk of nutrient and metals pollution, especially in nutrient and metals sensitive watersheds. However, several impactful factors were identified that may reduce nutrient leaching, including compost composition, compost age/leaching, and VFS soil type.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 ENERGY-POSITIVE METHODS OF WASTEWATER TREATMENT-- AN EXAMINATION OF ANAEROBIC DIGESTION & BIO-ELECTROCHEMICAL TECHNOLOGY(2013) Gregoire, Kyla Patricia; Tender, Leonard; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The results presented here demonstrate plausibility of a hybrid Anaerobic Digester-Microbial Fuel Cell (AD-MFC) system for anaerobic primary (AD) and secondary (MFC) treatment and resource recovery from high-strength wastewater. We empirically determine the treatment efficiencies and energy densities achieved by the AD and MFC processes, both separately and when integrated as primary and secondary unit operations. On the basis of current production, undigested wastewater yielded an stable anodic current of 131 A/m3 when continuously fed to triplicate MFCs (chronoamperometry, Ean, -0.200V vs. Ag/AgCl). Substrate limitations in digested sludge reduced anodic current--36 A/m3, 17 A/m3, and 9 A/m3 were achieved from 6d, 13d, and 21d digestate, respectively. Cathodic limitations severely limited power/energy production by the MFC, with maximum power output of 11 W/m3 (69 mW/m2). Presumably, this was due to mass transport of oxygen reduction intermediates. When AD and MFC processes are de-coupled (i.e. each fed with undigested wastewater), the energy realized from AD (as biogas) was, on average, 29.6 kJ per m3 wastewater treated (8.2 Wh/m3), whereas the MFC produced, on average, 2.1 kJ per m3 wastewater treated (0.58 Wh/m3). On the basis of COD removal, AD separately generated 9,110 kJ per kg COD removed (2,530 Wh/kg COD) whereas MFC separately generated 0.18 kJ per kg COD removed (0.05 Wh/kg COD). When combined as primary and secondary unit processes with a 6-d digestion period (reaction period which yielded the highest net energy production), the energy output from AD (as biogas) was 23.9 kJ per m3 wastewater; the energy output from MFC (as electrical power) was 2.1 kJ per m3 wastewater. MFC treatment rates exceeded 90% COD removal, 80% VS removal and 80% TS removal, likely owing to the upflow, baffled reactor design that maximized interaction between wastewater and the anodic biofilm. Results indicate an inverse logarithmic relationship between digester retention time and subsequent MFC current production, i.e. maximal MFC current production is achieved with undigested waste, and an inverse linear relationship between digester retention time and subsequent COD/VS removal in MFCs. Breakthroughs must be made to address cathodic limitations of MFCs, before scaling is practically or economically viable.Item Examination of a GIS-Based Water Quality Model using USGS Gaged Watersheds in Maryland(2007-06-13) Shivers, Dorianne E.; Moglen, Glenn E; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Water quality models are important tools used by the Maryland Department of the Environment (MDE) in developing Total Maximum Daily Loads (TMDLs), which serve as water quality standards. The MDE tool, which spatially interpolates output from the Chesapeake Bay Program Watershed Model (WSM), is often used because it requires little time, data, or training. In contrast, the WSM requires extensive time, data, and training to run. This study examines if the MDE tool provides accurate estimates of pollutant loads and whether the mid-level complexity model AVGWLF provides comparatively more accurate estimates. The accuracy of the models was assessed based on qualitative comparisons, t-tests, and Nash-Sutcliffe coefficients. The MDE tool was found to more accurately predict total nitrogen and total sediment loads and the AVGWLF model was found to more accurately predict total phosphorus loads. The study also found that a consistent method for calculating observed loads needs to be developed.