No description available.

No description available.

Contamination of natural waters due to nitrogenous wastes has become a crucial environmental problem due to deterioration of water quality and eutrophication in aquatic eco-systems. Thus, the reduction of nitrogen accumulation in the natural environment is vital to maintain a healthy eco-system. Bipolar membrane electrodialysis (BMED) is a promising technology for selective ammonia separation from high-strength wastewater, such as liquid digestates of food waste or wastewater sludge. This technology was recently studied for reducing membrane scaling problems associated with conventional electrodialysis (ED) systems due to the water splitting mechanism in the BPM interface. A bench-scale BMED stack was built using 5 pairs of cation exchange membranes (CEMs) and bipolar membranes (BPMs). Using the BMED stack, a simulated food liquid digestate solution was examined to separate ammonia with different voltage applications and inter-membrane distances. The highest ammonia recovery was obtained at a cell pair voltage of 5.83 V (81% separation). Experiments on investigation of optimal inter-membrane distance of BMED operation suggested that the inter-membrane distance could be increased up to 2.46 mm without a significant decrease in nitrogen recovery. The residual Ca2+ and Mg2+ in the CIP (clean-in-place) solution which explains the degree of the scaling problem in the BMED was observed consistently below 2% of the initial mass introduced to the system, indicating that BMED design and regular CIP were effective in scaling control. The ammonia loss through CEMs to the feed cell by back diffusion was minimized due to high pH in the base cell since uncharged free ammonia was dominant over ammonium cation in the base cell. The energy required for BMED operation was comparatively low; 1.93-6.93 kWh/kg-N within 90 mins. Therefore, BMED can be considered as a sustainable candidate for selective ammonia recovery at high energy efficiency with successful scaling control. / Thesis / Master of Civil Engineering (MCE)

Algal blooms in Lake Erie have worsened in severity, extent, and duration due to agricultural phosphorus (P) loading. Science, policy, and community action are needed to identify and implement feasible solutions for freshwater protections. To improve conservation action for P-reduction in the Lake Erie watershed, we must understand landscape drivers that enhance P runoff across agricultural regions with seasonal and spatial variation. The goals of this thesis were to assess landscape determinants of seasonal P variations in the understudied Canadian Lake Erie watershed, and to develop tools to amplify community stream monitoring and environmental engagement. A seven-year dataset revealed that P loading has significantly increased on an annual basis (2012 – 2019) in the late-winter-early-spring (February, March, April) in three separate Lake Erie tributaries (the East Sydenham River, the Thames River, and the Grand River). I demonstrated that year-over-year increases in tile drainage area on farms explained 23 – 49% of the year-over-year increases in P loading; however, I found the effects of tile drainage were moderated by differences in soil texture, land use/land cover, regional climate, and urban point sources. Using a nested-watershed approach for one year in 13 monitoring stations of the mixed-use Grand River watershed, I determined that row crop area was a strong predictor of P concentration in the Grand River when fields are bare, soils exposed, and nutrient assimilation by biota nonexistent. I recommend the use of year-round field cover by cover crops as a conservation measure to attenuate P-enrichment in the Grand River since sub-watersheds with increased cover crop proportion had reduced P concentrations and turbidity throughout the year. In another one-year study of 13 sub-watersheds across a gradient row crop and tile-drained sub-watersheds of the East Sydenham River and Grand River, I provided quantitative evidence of the negative effects of intensively row crop and tile-drained sub-watersheds on soluble reactive P export during late-winter-early-spring, and particulate loss during the growing season. To engage agricultural communities in monitoring P export from farms, I developed a bioassay that uses stream algae to determine P concentration in low-order streams. This method involving substrate rods (i.e., Peristix) is cost-effective, requires very little training, and yielded data that were significantly related to P concentrations in agricultural streams in the growing season. I recommend that environmental agencies and landowners use this bioassay to identify areas to implement conservation measures to reduce P export from the Lake Erie watershed. For greater application of community-science tools, I created the CommunityFIRST framework, which emphasizes feasible community collaborations, inclusive volunteerism involving a range of abilities and knowledge systems, using tools developed in this thesis that are relevant to the community’s environmental issues and carried out in a supportive and trusting environment between researchers and community members. My research integrates science and community methods to advance our understanding of agricultural land management and seasonal P loading from the Canadian Lake Erie watershed. / Thesis / Doctor of Philosophy (PhD) / After decades of improvement, Lake Erie eutrophication continues to be a water-quality issue in the Great Lakes Basin. Year after year, algae blooms cover the lake and call scientists, politicians, and communities to action. Phosphorus runoff from agricultural activities is at the core of this issue, and a better understanding of phosphorus runoff is needed across all Lake Erie watersheds and during all seasons of the year. The goals of this thesis were to assess landscape determinants of seasonal variations in phosphorus in the understudied Canadian Lake Erie watershed, and to develop tools to amplify community stream monitoring and environmental engagement. Spanning three major Canadian Lake Erie tributaries, I analyzed the effects of agricultural intensity, agricultural management practices, and changing seasonality on phosphorus export. I determined critical periods and specific landscape characteristics and compositions that can enhance phosphorus runoff from agricultural fields, and I offered recommendations to guide management decisions in the Canadian Lake Erie watershed. At the local scale, I developed a feasible stream monitoring tool for community-science initiatives. My research integrates science and community methods to advance the overall understanding of agricultural land management and seasonal phosphorus export from the Canadian Lake Erie watershed.

No description available.

No description available.

No description available.

Excess nutrient pollution and eutrophication are widespread problems that must be solved at watershed scales, and stream restoration is increasingly implemented as a solution. Yet few studies evaluate the cumulative effects of multiple individual restoration projects on watershed-scale nutrient loading. We constructed a HEC-RAS model of stream restoration implemented throughout a generic 4th order watershed typical of the Piedmont physiographic province of the eastern USA. We simulated restoration of hyporheic exchange as one increasingly popular technique that receives dissolved nitrate-nitrogen (NO3--N) mitigation credit under the Chesapeake Bay TMDL. We populated the model with hyporheic exchange (0.3% of surface flow per hyporheic-exchange inducing in-stream restoration structure) and NO3--N removal (supply-limited denitrification removes all NO3--N that enters the hyporheic zone) values from prior literature on in-stream structures and related restoration techniques. We then varied the percentage of stream channels in the watershed in which restoration occurred. For watersheds with less than 100% of stream channels restored, we also varied where in the watershed (i.e. stream order) that restoration occurred. We found that hyporheic restoration in our 4th order watersheds has the potential to reduce NO3--N loading to downstream waterbodies by up to 83%, but that a maximum of <100% reduction exists given certain watershed characteristics. Model results revealed a nonlinear relationship between percent of stream channels restored and percent NO3--N loading reduction that occurred at the watershed outlet. This indicates that the effects of individual projects are not linearly additive, and must be evaluated in the context of how much of the watershed has already been restored. We also found that restoration was more effective at reducing NO3--N loading when it occurred in higher order streams (e.g., 3rd and 4th order), yielding load reductions upward of 30% compared to < 10% in lower order streams (e.g., 1st and 2nd order). Thus, the location of an individual restoration project within a watershed is important in determining its effect on NO3--N. Overall, our results indicate that hyporheic restoration can have significant effects on watershed NO3--N loading to downstream waterbodies, yet the watershed must be viewed as a whole to understand the potential impacts of any particular project under consideration. / Master of Science / Nutrient pollution and harmful algal blooms are widespread problems that must be solved at watershed scales, and stream restoration is increasingly implemented as a solution. Yet few studies evaluate the cumulative effects of multiple individual restoration projects on watershed-scale nutrient loading. We constructed a HEC-RAS model of stream restoration implemented throughout a generic watershed typical of the mid-Atlantic USA. We simulated restoration of nutrient-reducing groundwater flow cells along a stream corridor (hyporheic exchange) as one increasingly popular technique that is emphasized under the Chesapeake Bay TMDL. We populated the model with hyporheic exchange and nitrate-nitrogen (NO3--N) removal values from prior literature on in-stream structures and related restoration techniques. We then varied the percentage of stream channels in the watershed in which restoration occurred. For watersheds with less than 100% of stream channels restored, we also varied where in the watershed (i.e. stream order) that restoration occurred. We found that hyporheic restoration in our watershed has the potential to reduce NO3--N loading to downstream waterbodies by up to 83%, but that a maximum of less than 100% reduction exists given certain watershed characteristics. Model results revealed a nonlinear relationship between percent of stream channels restored and percent NO3--N load reduction that occurred at the watershed outlet. This indicates that the effects of individual projects are not linearly additive, and must be evaluated in the context of how much of the watershed has already been restored. We also found that restoration was more effective at reducing NO3--N loading when it occurred in larger streams, yielding load reductions upward of 30% compared to less than 10% in smaller streams. Thus, the location of an individual restoration project within a watershed is important in determining its effect on NO3--N. Understanding the maximum possible degree of NO3--N reducing hyporheic exchange is an important step for practitioners and policy-makers in choosing the most effective location for a stream restoration based on a project's goals, and cannot be done without analyzing the watershed as a whole. With more watershed-scale planning and a better understanding of certain physical characteristics, we can choose restoration locations and strategies that will ultimately work more efficiently toward reaching a nutrient reduction goal.

Several Florida lakes with different documented trophic state indices were selected for sediment analysis. Vertical sections of the sediment were taken at depths of .1, .5, 1, 2, 3, 4, 5, 6, 10 and l5 centimeters below the surface of the sediment-water interface. Total Phosphorus analysis was done on each section. The profile presented was then evaluated and was found that the profiles best fit the equation Y = X/ (A + BX), where Y is the Phosphorus Concentration in ppm and X is the sediment depth in cm. Correlation between the trophic state and the profiles characteristics are presented. A hypothesis as to how the sediment profile changes as the lake experiences increased Phosphorus loading is presented, and is used to evaluate the lake studied. This discussion expresses phosphorus dynamics within the sediments in terms of adsorption, chemical changes, biological activity, and molecular and eddy diffusion.

Anthropogenic eutrophication of freshwater lakes due to land use change is a growing global problem with economic consequences, such as a reduction in shoreline property value. Managing eutrophication is of utmost importance in Maine, USA due to the large number of inland fresh waterbodies and their economic importance for fisheries, recreation, and real estate. This thesis investigates the relationships between water quality and catchment land use. Agricultural land use is a large driver of excess nutrient export to lakes, including in Maine, and can result in toxic cyanobacterial blooms, decreased water clarity, and fish kills. I developed a statistical relationship to quantitatively link agricultural intensity in the catchment and resultant water quality outcomes in Maine lakes. I observe a strong statistical relationship between water quality and anthropogenic activity in the catchment, as expected. Interestingly, I found that the effects of anthropogenic activity were most closely related to a five-year lag in water quality, which is between 0.8 to 4.71 years longer than the lake residence times. My results suggest that changes in land use may have long-term effects on water quality that last for far longer than would be expected. The analysis presented in this paper is novel for directly linking long term observational agricultural and biological datasets and presents a new way to quantitatively link water quality and anthropogenic intensity in the catchment area. / Master of Science / Worsening water quality of freshwater lakes due to land use change is a growing global problem with economic consequences, such as a reduction in shoreline property value. Managing water quality is of utmost importance in Maine, USA due to the large number of inland fresh waterbodies and their economic importance for fisheries, recreation, and real estate. This thesis investigates the relationships between water quality and lakeside land use. Agricultural land use is a large driver of lowered water quality in lakes, including in Maine. I developed a statistical relationship to mathematically link agriculture near the lake and resultant water quality outcomes in Maine. I observe a strong statistical relationship between water quality and human activity in the catchment, as expected. Interestingly, I found that the effects of human activity were most closely related to a five-year lag in water quality, which is between 0.8 to 4.71 years longer than the lake residence times. My results suggest that changes in land use may have long-term effects on water quality that last for far longer than would be expected.