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Master of Science / Department of Biological & Agricultural Engineering / Stacy L. Hutchinson / To understand the region-specific effects of biota on function of bioretention cells, a lysimeter study was conducted at Kansas State University to determine how earthworms and native Kansas grasses impact runoff treatment and hydraulic function of a bioretention cell. This study also employed the Comprehensive Bioretention Cell (BRC) model to demonstrate how three seasons of growth could impact bioretention cell function. The model results of the first season of growth were then compared to field data. Results indicate that the interaction of plant roots and soil macrofauna over one growing season improved several aspects of bioretention cell function. The greatest increase in saturated hydraulic conductivity was in the treatment that included both plants and macrofauna. The presence of vegetation reduced ponding effects and increased water storage. Earthworm treatments had a lesser ability to store water. All treatments were effective in reducing the concentration of P in effluent. A large amount of N was released during all events from all treatments probably because of a high initial N content of the bioretention media. No treatment performed significantly better in improving water quality, indicating that macropore flow in the earthworm treatments did not induce a higher rate of pollutant transport.

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<p> As reuse of municipal water resource recovery facility (WRRF) effluent becomes vital to augment diminishing fresh drinking water resources, concern exists that conventional barriers may prove deficient and the upcycling of contaminants of emerging concern (CECs) could prove harmful to human health and aquatic species if more effective and robust treatment barriers are not in place. </p><p> There are no federal Safe Drinking Water Act (SDWA) regulations in place specifically for direct potable reuse (DPR) of WRRF effluent. Out of necessity, some states are developing their own DPR reuse regulations. Currently, reverse osmosis (RO) is the default full advanced treatment (FAT) barrier for CEC control. However, the potential exists for tight thin-film composite (TFC) nanofiltration (NF) membranes to provide acceptable CEC rejection efficacies for less capital, operations and maintenance (O&amp;M), energy, and waste generated. </p><p> Recognizing the inherent complexity of CEC rejection by membranes, this research program was designed to elucidate the vital predictive variables influencing the rejection of 96 CECs found in municipal WRRF effluents. Each of the CECs was cataloged by their intended use and quantitative structure activity relationship (QSAR) properties, and measured in secondary effluent samples from WRRFs in Texas and Oklahoma. These secondary effluent samples were then processed in bench-scale, stirred, dead-end pressure cells with water treatment industry-specified TFC NF and RO membranes. </p><p> A multi-level, multi-variable model was developed to predict the probable rejection coefficients of CECs with the studied NF membrane. The model was developed from variables selected for their association with known membrane rejection mechanisms, CEC-specific QSAR properties, and characteristics of the actual solute matrix. R statistics software version 3.1.3 was utilized for property collinearity analysis, outlier analysis, and regression modeling. The Pearson correlation method was utilized for selection of the most vital predictor variables for modeling. The resulting Quantitative Molecular Properties Model (QMPM) predicted the NF rejection CECs based on size, ionic charge, and hydrophobicity. Furthermore, the QMPM was verified against a CEC rejection dataset published by an independent study for a similar commercially available TFC NF membrane.</p>

Resin and fatty acids (RFAs) are the major toxic constituents of pulp and paper mill effluent. RFAs are toxic to aquatic life at low concentrations (2 ppm). The concentration and type of RFAs in the wastewater vary with wood source and mill process. The E-stage effluent contributes only 5-10% of the total plant wastewater discharges, yet most of the total wastewater toxicity and color is attributed to the E-stage. The focus of this research project was to determine which of four Advanced Oxidative Processes (Ozone, Ozone with Hydrogen Peroxide, Ozone with Ultraviolet 254nm light, Ozone with Hydrogen Peroxide and UV254nm light) produces the highest reduction of toxicity for a simulated E-stage wastewater. The treated water was characterized by UV absorbance scans, total organic carbon analysis, Gas Chromatography/Mass Spectroscopy and Microtox toxicity. The highest reduction of toxicity was achieved by 94.4 mg/L (30 minutes contact time) of Ozone transferred.

<p> Over the past decade, there has been a revival in algal research and attempts at large scale cultivation for bioenergy production. Among various types of microalgae culturing systems, Open Raceway Ponds (ORP) are considered as an economic system for large-scale microalgae cultivation. In order to improve the algal growth and productivities in ORPs, it is very important to understand the effects of design parameters and operating conditions on mixing and light distribution patterns. The goal of this dissertation was to develop computational tools and experimental techniques to assess key variables that affect algal growth and productivity, and to improve microalgal cultivation in ORPs. The effects of major parameters on growth, were investigated and the optimum C. vulgaris growth condition was determined at 52 W/m2, 24&deg;C, and pH of 7.4, using Response Surface Methodology. The C. vulgaris grown in swine wastewater with 102 mg/L nitrogen and 76 mg/L phosphorus at the optimum environmental condition achieved the average growth rate of 0.16 g/L/day, compared to 0.19 g/L/day for its growth in the modified Bold's medium with 100 mg/L nitrogen and 53 mg/L phosphorus, at the same condition. Results indicated that at NC weather conditions, C. vulgaris grown in swine wastewater in a pond with 0.3 m medium depth, can reach a biomass and lipid productivity of 80 and 20 tons/hectare/year, respectively, at the harvesting cell density of 0.1 g/L. However, the algal productivity decreased significantly with the increase of harvesting cell density. A specific growth rate model of C. vulgaris was generated as a function of light intensity, temperature and pH. A Computational Fluid Dynamics (CFD) model was developed to simulate the multiphase flow in ORPs to investigate the effects of operational conditions on biomass concentration and light intensity distribution. Operating large scale ORPs at 0.2 m/s inlet velocity resulted in a significant decrease in dead zone areas in comparison with 0.1 m/s. However, further increase in velocity to 0.3 m/s did not make significant changes. CFD models were then integrated with the growth kinetic model to simulate the dynamic growth of C. vulgaris in ORPs. The predicted algal growth and productivity well agreed with those measured values. The predicted average algal productivities for the 3-week cultivation of C. vulgaris in the lab-scale ORPs were 7.34, 7.4, and 7.46 g/m2/day for medium depths of 0.20, 0.25, and 0.30 m, respectively, which well agreed with the measured values of 6.78, 7.23 and 7.39 g/ m2/day for medium depths 0.20, 0.25, and 0.30 m, respectively. Simulations were conducted to study different harvesting methods. The average algal productivity for the 3-week cultivation in the ORP with 0.2 m depth by harvesting 50% algae at the target 0.2 g/L cell density was 10.5 g/m2/day, which was 54.7% higher than 6.78 g/ m2/day for the 3-week cultivation under the same condition without harvesting. The average algal productivity decreased with the increase of harvesting cell density.</p>

<p> Precipitation and land cover in the West African Sahel have changed dramatically over the past 50 years. Region-wide data on land cover change in the Sahel, however, have been sparse or unreliable. I present a new 30 meter 2000&ndash;2016 annual resolution land cover dataset for the West African Sahel. The product is built from hand-classified land cover maps using random forest machine learning methods with Landsat, precipitation, and topography features. The resulting maps confirm the widespread extensification of agriculture in the region over this time period. Contrary to the common narrative of desertification, this increase in agriculture has not been accompanied by an increase in bare soil or sandy area. Land cover change volatility is shown to be spatially heterogeneous, both at local and regional scales. In addition to the new land cover dataset, I present spatial and temporal analyses of precipitation during the recent years of increased variability in the West African Sahel. I examine seasonal trends, interannual variability, and differences among datasets representing precipitation in the Sahel. Region-wide spatial organization of precipitation is identified using the self-organizing mapping pattern recognition technique. The number of days spent in the monsoon transition period is strongly negatively correlated with annual precipitation anomaly` indicating a tradeoff with the peak monsoon period, a result that supports the upped-ante hypothesis of precipitation in the Sahel.</p><p>

A two-dimensional laboratory simulator was designed and assembled to investigate removal of dense non-aqueous phase liquid (DNAPL) contaminants from ground water by water flooding and neutral buoyant co-solvent flooding. Preliminary experiments indicated that optimum DNAPL removal was achieved during water flooding for viscous-to-capillary scaling ratios between 0.00075 and 0.001. The simulator was used to investigate effects of the direction of gradient flow on DNAPL removal efficiency by neutral buoyant co-solvent flooding. Results indicated that approximately 90 percent DNAPL was removed when injection was performed either in the direction of gradient flow or against it. However, injection in the direction of gradient flow was more efficient in terms of time and total co-solvent needed. Nevertheless, during injection in the direction of the flow more contamination occurred downstream due to dispersion. Results also indicated that size of the plume does not play an important role in the recovery efficiency of this system / acase@tulane.edu