A. James Clark School of Engineering
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item REMOVAL OF STORMWATER DISSOLVED ORGANIC NITROGEN MODEL COMPOUNDS THROUGH ADSORPTION AND BIOTRANSFORMATION(2019) Mohtadi, Mehrdad; Davis, Allen P.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bioretention systems are stormwater control measures designed to reduce nitrogen and phosphorus transferred by stormwater to water resources. They are, however, not effectively designed to remove dissolved organic nitrogen (DON). This study concentrated on improvement of bioretention design to remove stormwater DON. Batch adsorption of eight organic nitrogenous compounds onto several adsorbents showed that coal activated carbon (AC) could be a reliable adsorbent for removal of organic nitrogenous compounds such as pyrrole and N-acetyl-D-glucosamine (NAG). The adsorption capacity of pyrrole and NAG on coal AC were 0.4 mg N/g (at equilibrium concentration, Ce = 0.02 mg N/L) and 0.71 mg N/g (at Ce = 1 mg N/L), respectively. These eight nitrogenous compounds were also tested for continuous column adsorption on a media mixture of coal AC + quartz sand, and only pyrrole showed an appreciable adsorption performance; the breakthrough and exhaustion depths for pyrrole were 88 and 499 m, respectively, at the fixed superficial velocity of 61 cm/h and influent DON concentration of 1 mg N/L. Pyrrole adsorption was also minimally affected by superficial velocity (DON removal efficiency stayed > 91% for all tested superficial velocities, 7 to 489 cm/h). Because the adsorption process was successful for removal of only one (pyrrole) out of eight examined compounds, biological treatment was also investigated for removal of organic nitrogenous compounds. Biotransformation alongside adsorption demonstrated benefits such as ammonification of bio-recalcitrant organic nitrogen compounds, e.g., pyrrole, and bioregeneration of the adsorbent (coal AC). According to the results, ammonifiction might be considered as a possible reliable mechanism for stormwater DON removal at low temperatures > 4°C. Under intermittent wetting/draining conditions, the effluent DON was less than 0.1 mg N/L after the applied depth of 48 m, indicating that DON was successfully removed through simultaneous adsorption/ammonification, although generated ammonium in the effluent must be properly addressed. Overall, based on the results from the current study, some DON types were strongly adsorbed by adsorbents, e.g., adsorption of pyrrole on coal AC, some were more bioavailable, e.g., ammonification of leucine, and some were barely adsorbable and bioavailable, e.g., Aldrich humic acid on coal AC. Accordingly, both adsorption and biotransformation should be considered to enhance stormwater DON removal as much as possible.Item Evaluation of Nutrients and Suspended Solids Removal by Stormwater Control Measures Using High Flow Media(2017) Landsman, Matthew Robert; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)High Flow Media (HFM) is able to treat large runoff volumes using small- footprint systems. Seven full-scale HFM Stormwater Control Measures (SCMs) in a residential area were monitored over 11 months to assess the removal of Total Suspended Solids (TSS), Nitrogen, and Phosphorus in First Flush (FF) stormwater runoff. Excellent removal of TSS and particulate-bound nutrients was noted, but, in most SCMs, removal of dissolved species was limited. Sorption of dissolved P occurred, although most likely on captured and suspended sediment and not on the HFM itself. Mineralization and nitrification of dissolved N species during dry periods led to nitrate export. HFM grain size and organic content did not significantly impact TSS or P removal, but higher organic content was associated with higher N removal. FF was present in TSS (strongest), TN, and TP (weakest). Optimal HFM SCM design incorporates sedimentation before filtration.Item MULTI-CRITERIA VEGETATION SELECTION FOR MARYLAND BIORETENTION, WITH NITROGEN FOCUS(2015) Muerdter, Claire; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Stormwater is a leading source of nutrient pollution in natural waters. Bioretention cells can mitigate stormwater pollution. This study examines the role of vegetation in bioretention. In a bioretention field study; of Eutrochium dubium, Solidago rugosa, and Erigeron sp.; E. dubium had the thickest root and tallest aboveground biomass. The root length of the three species averaged 29.1 cm. A greenhouse bioretention mesocosm study examined three plant species: Eutrochium dubium, Iris versicolor, and Juncus effusus. Only J. effusus created significant nitrate (NO3-) removal from synthetic stormwater influent, 0.21 mg to 0.066 mg NO3--N L-1, only in low-density plantings. However, all planted treatments prevented nitrogen export vis-à-vis the unplanted treatment in two storms. J. effusus had the greatest average biomass growth of the three species, 29-fold vis-à-vis 1.3- and 2.7-fold. J. effusus is the most highly recommended plant for Maryland bioretention in this study. E. dubium is cautiously recommended.Item FIELD EVALUATION OF ENHANCED PHOSPHORUS AND NITROGEN REMOVAL IN STORMWATER CONTROL MEASURES(2014) Liu, Jiayu; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This project evaluates two innovative stormwater control measures (SCMs) installed on the University of Maryland campus in College Park, Maryland. One project retrofitted an existing bioretention cell with 5% (by mass) aluminum-based water treatment residual (Al-WTR) to enhance phosphorus removal (P1 site). The other combined a porous parking area with underground anoxic vaults to promote nitrogen removal (N1 site). At the P1 site, the net reduction of the total runoff was 40% and the volume reduction ratios ( ) were lower than before the retrofit. The total suspended solids (TSS), total phosphorus (TP), and particulate phosphorus (PP) concentrations were significantly reduced by the bioretention cell, due to the filtration of the particulate matter, while TP export occurred before WTR retrofit. Soluble reactive phosphorus (SRP) and dissolved organic phosphorus (DOP) concentrations in the stormwater runoff were not obviously changed compared to the system effluent. The near constant outflow of SRP and DOP concentrations suggest an equilibrium adsorption treatment mechanism. Mass loads were reduced for TSS and all P species. WTR incorporation decreased the bioretention media phosphorus saturation index (PSI) from approximately 0.075 to approximately 0.041, which stayed relatively constant during the two year study period, even with the media P continually increasing, indicating a significant increase in media P sorption capacity. At the N1 site, the flow management achieved nearly zero runoff discharge due to infiltration from the vaults during dry weather. With regard to the porous pavement, approximately 34% of the total nitrogen (TN) (4.7 kg/ha-yr) was mitigated by filtration processes; 6.5 kg/ha-yr particulate organic nitrogen (PON) and 1.8 kg/ha-yr ammonium nitrogen ( ) were removed, and 4.0 kg/ha-yr oxidized nitrogen (NOx) were created. In the denitrification vaults, approximately 26% of the TN (3.7 kg/ha-yr) was decreased by system reaction, mostly due to the decrease in NOx (3.8 kg/ha-yr). PON was reduced slightly, by 0.2 kg/ha-yr. The small amount of DON and produced likely resulted from leaching from the wood logs. As a result, the N mass reduction that occurred was not only due to volume reduction, but also to system reactions (60%).Item Advanced Denitrification in Bioretention Systems Usinging Woodchips as a Primary Organic Carbon Source(2013) Peterson, Ian James; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bioretention systems still lack the ability to effectively mitigate nitrogen concentrations from urban stormwater. Column tests were conducted to evaluate the effect of nitrate concentration, stormwater retention time, limestone addition, and woodchip species, size, and mass percentage on the bioretention denitrification process. Denitrification of artificial stormwater appeared to follow pseudo-first-order kinetics. A 0.8 day average retention time showed the highest nitrate removal percentage of 82.4 + 0.4%. Longer retention times correspond to greater removal efficiency. Willow Oak and Red Maple woodchips resulted in the highest total nitrogen removal efficiencies at 61.9 + 0.8% and 61.8%, respectively. Smaller woodchips and higher woodchip mass percentage corresponded to greater nitrate removal efficiencies, but also higher organic nitrogen leaching. Media containing 4.5% 5 mm Willow Oak woodchips by mass represented optimum conditions with a pseudo-first-order denitrification rate of 4.1 + 4.6 day-1 with nitrate concentrations of 1.5 to 4.5 mg/L N.