Theses and Dissertations from UMD
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Item PREVENTION AND TREATMENT OF PERSISTENT ORGANIC POLLUTANTS IN STORMWATER AND SEDIMENT(2023) Yuan, Chen; Kjellerup, Birthe V; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Polycyclic aromatic hydrocarbons (PAHs) and Polychlorinated biphenyls (PCBs) are two groups of persistent organic pollutants (POPs) with toxicity, carcinogenicity, and teratogenicity. Those compounds are harmful to human health and wildlife. Stormwater is one of the important sources of PAHs and PCBs to aquatic environments. Stormwater control measures (SCMs) have already been used to remove PAHs and PCBs from stormwater, however traditional SCMs can remove PAHs and PCBs in the particle phase, but there still are dissolved PAHs and PCBs in the outflow of SCMs. This study focused on reducing the influence of PAHs and PCBs in stormwater on the environment by 1) improve the treatment performance by adding a polishing treatment procedure after traditional SCMs, and remove the PAHs and PCBs accumulated in the polishing treatment media by bioaugmentation of Pseudomonas putida ATCC 17484 and Paraburkholderia xenovorans LB400 and 2) dechlorination of PCBs in the sediment of aquatic environments by biofilm Dehalobium chlorocoercia DF1 inoculum. The results of polishing treatment showed that all black carbon materials, namely biochar, granular activated carbon (GAC), and regenerated GAC (RAC), were effective to remove dissolved PAHs with removal > 95%. However, all materials had lower removal efficiency on PCBs with removal > 84%, By the comparation of cost and lifetime under the condition that 50% polishing media are used in the polishing treatment facility. RAC which has a lifetime>147 years based on the precipitation of Maryland and Washington and cost <3.79 $-m3-yr-1, was the best material for polishing treatment. Results of treatment train with a traditional SCM media column and polishing treatment column indicated that average removal of PAHs can be improved from 94.56% of BSM columns to 99.61% of polishing treatment columns, and removal of PCBs can be improved from 84.61% to 95.16%. Results of bioaugmentation of polishing treatment media showed no biodegradation took place in the mesocosms with polishing media. However, the liquid mesocosms showed P.putida degraded 97.9% of pyrene. The bacteria colony on plates after the biodegradation experiment showed that there were less P.putida and P.xenovorans colony of polishing media mesocosms than liquid mesocosms. Therefore, the limitation of biodegradation of polishing media mesocosms may cause by the limited bioavailability and less active inoculated bacteria. The results of dechlorination by Dehalobium chlorocoercia DF1 biofilm shows that there were native bacteria, such as Gemmatimonadetes, Actinobacteria, Proteobacteria and Firmicutes in the sediment that can dechlorinate PCBs. The three treated mesocosm groups (addition of biochar, bioaugmentation with DF1 biofilm and liquid DF1 culture) all can improve dechlorination, of 28.09%, 21.30%, and 17.10%, respectively. Those three groups had dechlorination extent higher than negative control (4.60%), and abiotic control (-1.02%). The microbial community analysis indicated that biofilm inoculation improved abundance of DF1 and had a more stable influence on the community than liquid inoculation. Overall, biofilm inoculation and addition of biochar dechlorinate PCBs in sediment efficiently, and polishing treatment is an efficient approach to improve traditional SCMs, while treating the polishing media with bioaugmentation need further study.Item Interactions and Treatment of Metals in Urban Stormwater(2023) Croft, Kristen; Kjellerup, Birthe V; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Increasing urbanization and a changing climate will only exacerbate the magnitude of pollution entering our waterways, threatening our drinking water source and aquatic ecosystems. Urban stormwater contains a cornucopia of pollutants that pose direct toxicity risks (e.g., metals, organics, pathogens) and indirect adverse effects (e.g., sediments, nutrients) to aquatic life. Metals, specifically copper (Cu) and zinc (Zn), are both ubiquitous in the urban environment and detrimental to aquatic ecosystems at low concentrations (approximately 10 ppb). Targeting this growing source of pollution upstream is critical in providing necessary environmental protections, especially as the intensifying effects of climate change and urbanization are imminent. This leads to the main research question – how can Cu and Zn loads in stormwater be reduced to protect aquatic ecosystems?Bioretention is a stormwater control measure (SCM) that mimics natural systems to take advantage of the natural filtering processes. In addition to hydrologic benefits, bioretention provides removal of particulate matter (PM) through filtration and sedimentation, and potential removal of dissolved constituents through chemical and biological processes. Studies including characterization of stormwater, road-deposited sediments (RDS), and performance of a mature bioretention cell were performed to determine treatability, mobility, and bioavailability of Cu and Zn in stormwater and through bioretention treatment. Both metals accumulated in the finest (<25 μm) fraction of RDS samples, however particulate bound (PB) Zn concentrations were enriched in stormwater compared to finer fractions of RDS, while PB-Cu was not. This indicated that PB-Zn is more mobile than PB-Cu, likely due to different sources of these metals in urban environments. The PM and PB metal loads were reduced by 82% and 83%, respectively, showing that mature bioretention cells are effective at reducing PM and PB contaminant loads. However, dissolved constituents were essentially unchanged through bioretention treatment, and concentrations of dissolved metals were measured at levels that potentially cause aquatic toxicity. Thus, alternative media amendments were investigated for further reduction of dissolved metal contents. Black carbon (BC) media including biochar, granular activated carbon (GAC), regenerated activated carbon (RAC), and a natural mineral sorbent, clinoptilolite zeolite, were tested in continuous columns, and in up-scaled modular treatment columns. The four tested BC media performed similarly for Cu and Zn removal, with Zn having an earlier breakthrough compared to Cu. This technology is predicted to provide reduction of dissolved Cu for up to 60 years with current rainfall predictions. Modular treatment columns showed that traditional bioretention soil media (BSM) provided effective removal of dissolved Zn (71%) and ineffective removal of Cu (17%). The subsequent BC polishing module was effective for Cu removal (40%), and zeolite showed potential for Zn removal. Overall, dissolved metals in stormwater are the most mobile, bioavailable, and difficult to remove through traditional filtration-based SCMs. This research has shown that fresh BSM can provide effective removal of dissolved Zn, and BC amendments are a potential solution for removal of dissolved Cu in stormwater. Refreshing the top few centimeters of an existing bioretention with fresh BSM can provide treatment of dissolved Zn. Retrofitting bioretention to include a polishing module either layered or in series with a mix of BC and zeolite can further reduce dissolved Cu and Zn loads in stormwater.Item Occurrence and Removal of Polychlorinated Biphenyls (PCBs) in Urban Stormwater(2020) Cao, Siqi; Kjellerup, Birthe V.; Davis, Allen P.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Polychlorinated biphenyls (PCBs) are a group of chlorinated organic compounds. They are persistent in the environment and can threaten the health of humans and wildlife. Urban stormwater runoff is considered as an important source of PCBs to aquatic environments. The objective of this study is to provide information on the occurrence and removal of PCBs in stormwater; specifically, the occurrence, concentrations, and biological transformations of stormwater PCBs were studied together with their removal. Concentrations of 209 PCB congeners were determined in surface stormwater sediments collected from various roadway sites and bioretention media. The total PCB concentrations ranged from 8.3 to 57.4 ng/g dry weight (dw), with a mean value of 29.2 ng/g dw. Land use had an impact on the concentration of PCBs, where higher stormwater sediment PCB concentrations were found in dense urban areas (average: 39.8 ± 10.5 ng/g) compared to highways passing through greenspace (average: 18.0 ± 0.4 ng/g). PCB sorption tended to increase with the concentration of total organic carbon (TOC) and smaller particle size (< 75 µm) of stormwater particulate matter. In bioretention core samples, PCB concentrations decreased with bioretention media depth (from 30.0 ± 2.0 ng/g at the surface to 21.2 ± 4.8 ng/g at 40 cm depth), and with distance from the stormwater entrance (from 38.4 ± 2.3 ng/g at the entrance to 33.2 ± 2.9 ng/g at 3 m distance). A non-Aroclor congener, PCB 11, was detected in all samples, likely originating from yellow road paint. Putative organohalide respiring bacteria within Chloroflexi and aerobic PCB degrading bacteria containing the functional genes encoding for biphenyl dioxygenase (bphA) and ring cleavage (bphC) were detected in some of the stormwater sediments and bioretention media. The presence of such bacteria and a higher level of ortho-chlorinated biphenyls indicated the potential of PCB biotransformation in these samples. The performance of an on-campus bioretention indicated that bioretention is effective in removing PCBs from stormwater, with 64–92% reduction of dissolved PCB concentrations. Overall, urban stormwater is an important environmental source of PCBs. Bioretention has the potential to remove PCBs from stormwater via adsorption and biotransformation.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 IMPACT OF PERIODIC HIGH CONCENTRATIONS OF SALTS ON BIORETENTION NUTRIENTS PERFORMANCE(2018) McManus, Meigan; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bioretention is a stormwater control measure commonly used to remove pollutants, including nitrogen (N) and phosphorus (P), from urban runoff. This project seeks to evaluate the impacts of high concentrations of sodium chloride (NaCl) deicer on bioretention N and P removal performances. Bioretention mesocosm studies were conducted to examine N and P removal efficiencies following periodic 2,000, 5,000, and 10,000 mg/L NaCl salt applications. Episodic washouts of TSS, N and P, likely due to ion exchange with the sodium and chloride ions, were observed for all three columns and mass export of P was observed for the 2,000 and 5,000 mg/L NaCl columns after 26 m and 7 m applied water, respectively. No mass N export was observed. Based on a mass balance of N and P, it is recommended to limit the use of deicers to prevent long-term P export.Item Bioretention Media for Enhanced Permeability and Phosphorus Sorption from Synthetic Urban Stormwater(2017) Yan, Qi; Davis, Allen Porter; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bioretention systems have been proven as effective urban stormwater control measures (SCMs), and are commonly used to improve both quantity and quality (pollutant removal) aspects of urban runoff. A promising media modification process is developed to simultaneously achieve both high infiltration rate and improved P removal in bioretention systems, Bioretention soil media (BSM) and a sandy ‘high flow medium’ (HFM) were modified with three Al-based amendments: water treatment residual (WTR), alum, and partially hydrolyzed aluminum (PHA), 10% by dry mass, respectively. The sorption of adenosine monophosphate (AMP) and myo-Inositol hexakisphosphate (IHP), two forms of organic phosphorus, and inorganic phosphate by modified media mixtures were studied. Compared with unmodified BSM and HFM, the sorption of AMP was increased by a factor of 26 and 80 for media with alum and PHA, respectively. Similarly, the IHP removal capacity were increased by factors of 7 and 8, respectively. Alum and PHA modified media mixtures can reduce P concentrations to <0.01 mg P/L within a contact time < 1 min. Adsorption and chemical precipitation are two predominated mechanisms for P removal using modified media mixtures. HFM modified with HFM and WTR showed high permeability and excellent P removal relative to other media mixtures and most importantly, it requires simplified modification conditions and is recommended for use in bioretention and related SCMs.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 BIORETENTION/CISTERN/IRRIGATION TO ELIMINATE STORMWATER RUNOFF AT THE UNIVERSITY OF MARYLAND(2015) Doan, Loc Nguyen; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Water quality of parking lot (~1,858 m2) stormwater runoff and its treated effluent flow were analyzed for total phosphorus (TP), total nitrogen (TN), total suspended solids (TSS), electrical conductivity (EC), copper, lead and zinc. The novel system under investigation, located at the University of Maryland, College Park, Maryland, includes a standard bioretention facility, underdrained to a cistern to store treated stormwater, and pumped to a vegetable garden for irrigation. The site abstraction, the average bioretention abstraction, and bowl volumes were estimated to be 8500, 4378, and 895 L, respectively; this indicates that rain events of more than 0.45 cm are necessary to produce runoff and more than 0.75 cm will produce system overflow. The cistern water quality indicates good-to-excellent treatment by the system. Compared to local tap water, cistern water has lower concentrations of TP, TN, EC (non-winter), copper, and zinc, indicating a good water source for irrigation.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 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.