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Algae are a prolific source of biochemicals with economic importance, including nutraceuticals, biofuels, animal feed, etc. The general aim of this study was to establish how the hydrodynamic conditions generated within specific types or designs of photobioreactors determine their respective algae growth. The specific objectives of this study were: (1) To determine and compare key hydrodynamic parameters in the Air Accordion photobioreactor and the conventional bubble column, including Residence Time, Vessel Dispersion Number, Bodenstein Number, Mixing Time and oxygen liquid mass transfer coefficient (kla); and, (2) To test how differences in the hydrodynamic conditions would result in significant difference in growths of the green alga Scenedesmus obliquuus between the photobioreactors. The results of the study showed that: (1) The Residence Time of 566 s for the Air Accordion significantly exceeded by 28% that of 444 s for the bubble column, signifying greater liquid mixing in the Air Accordion; (2) The Vessel Dispersion Number for the Air Accordion of 0.168 significantly exceeded that for the bubble column of 0.166, indicating greater degree of mixing in the Air Accordion than in the bubble column; (3) The Mixing Time in both the Air Accordion and the bubble column declined as the air flow rate increased, indicating that the tracer ions in both photobioreactors mixed more quickly. For each of the flow rates tested, however, the mixing time for the bubble column significantly exceeded that for the Air Accordion, indicating that liquid mixing in the Air Accordion occured significantly quicker than in the bubble column. At 1.0 LPM, the bubble column's Mixing Time of 10 s exceeded by 25% that of the Air Accordion of 8 s; (4) The oxygen liquid mass transfer coefficients in both photobioreactors increased as the air flow rate increased, indicating that the transfer of oxygen from the air bubbles into the liquid within the photobioreactors gained efficiency. For each of the air flow rates tested, however, the oxygen liquid mass transfer coefficient for the Air Accordion significantly exceeded that for the bubble column, indicating a significantly more efficient oxygenation of the liquid in the Air Accordion occurring than in the bubble column. At 1.0 LPM, the Air Accordion's oxygen liquid mass transfer coefficient of 0.00138 s⁻¹ exceeded by 48% that of the bubble column of 0.000931 s⁻¹; and (5) The growth of Scenedesmus obliquus in the Air Accordion significantly exceeded that in the bubble column for both 0.1 LPM and 1.0 LPM. The final algae density of 0.25 g DW/L in the Air Accordion significantly exceeded by 31% that of 0.18 g DW/L in the bubble column at 0.1 LPM. Similarly, the final algae density of 0.37 g DW/L in the Air Accordion significantly exceeded by 19% that of 0.31 g DW/L in the bubble column at 1.0 LPM. Thus, the growth of Scenedesmus obliquus in the Air Accordion photobioreactor -- with significanlty more favorable hydrodynamic characteristics in terms of Residence Time, Vessel Dispersion Number, Mixing Time and oxygen liquid mass transfer coefficient -- significantly exceeded algae growth in the bubble column of the same volume and under the same environmetal conditons.

Evapotranspiration (ET) is a key parameter for irrigation planning and management, and it is a crucial factor for water conservation practices considering the challenges associated with agricultural water availability. Field ET determination is the most accurate, but remains to be expensive and limited in scope. On the other hand, remote sensing is becoming an alternative tool for the estimation of ET. Operational ET algorithms, like the Moderate Resolution Imaging Spectroradiometer (MODIS)-based ET, are now successful at generating ET estimates globally at 1km resolution, however their intent is not management of agriculture irrigation. This research was done to develop an integrated method for downscaling MODIS ET appropriate for farm-level applications using geostatistical and remote sensing techniques. The proposed methodology was applied in the Wellton-Mohawk Irrigation and Drainage District of Yuma, Arizona. In a first effort, ET data was downscaled from standard 1-km-MODIS to a medium 250-m-spatial resolution via cokriging using Land Surface Temperature and Enhanced Vegetation Index as covariates. Results showed consistent downscaled ET with a variance greater than the variance of the coarse scale input and nearly similar mean values. This 250m product can serve larger irrigation districts in developed countries, where plot size is fairly large and regular. However, the size and shapes of most farms in developing countries makes the 250m ET challenging. For this reason, the second part of this work was done to downscale global scale 1km ET to 30m farm level application for irrigation use. This approach involved the generation of daily vegetation indices (VI) at 30m in order to support the downscaling of MODIS 1km ET. Landsat and MODIS reflectances were combined with the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) algorithm and the resulting VI data was used as a covariate to downscale ET with the cokriging approach. The results showed that the MODIS ET data seriously underestimates ET over irrigated areas. To correct this problem the MODIS data was then adjusted using field measured values to make it useful for operational purposes. The proposed geospatial method was applied to different growth stages of cotton and results were validated with actual ET from The Arizona Meteorological Network (AZMET) and published consumptive use of water for the area. The adjusted downscaled ET was comparable to these two published data (maximum error of 33%). This methodology is a practical alternative in areas where there is no ancillary data to estimate ET and it is expected to help in the planning of irrigation agriculture that will lead to improved agricultural productivity and irrigation efficiency.

Slow sand filters (SSF) have been used to treat surface water to drinking water standards for over a century. Today many cities, including London still treat surface waters to drinking water standards, however because there are viruses that are not efficiently removed by a slow sand filter and are not killed by chlorine, communities have turned to the use of micro filtration and/or reverse osmosis to provide safe drinking water. These technologies are much more efficient if organics are removed and turbidity reduced to less than 1 Nephelometric Turbidity Units (NTU). The greenhouse industry is another potential user of slow sand filters. They are not able to recycle irrigation drainage water without it being treated to reduce bacteria, virus, and fungi. The objective of this research was to develop management strategies for SSF that specifically meet the needs of entities using SSF for pretreatment of potable water or use in a greenhouse. This data was used to test a scour system that resulted in scouring 80 percent of the organic layer in the filter and suspending the solids for 40 minutes. A conceptual design was done for a full scale SSF that took advantage of the scour and suspension data to clean the SSF at the end of a run cycle. SSF were able to consistently produce water with a turbidity less than 1 (NTU) and with the infiltration capacity of 0.27 m³m⁻². For greenhouse effluent a 1,000 square meter greenhouse that is discharging 3,600 L d⁻¹ of drainage water would require a 12.6 m² SSF, and the SSF for the community requiring treatment of 4.7 million liters per day of raw water was 730 m². The innovative cleaning system based on an air/water jet was developed to clean the SSF. Experiments were run to determine the amount of time that the solids were suspended and a scour system developed to exceed these times. The entire time for cleaning and recovery of the SSF was an average of 118 minutes for the greenhouse system and 170 minutes for the SSF serving a small community.

Microalgae have now been widely considered as a promising bio-energy feedstock. The current microalgae harvesting methods used, such as centrifugation, sedimentation and flocculation, have been shown to be effective but are costly, representing between 35 % to 50 % of the total production cost. The aims of this study were: (1) to investigate the effectiveness of two electrocoagulation processes, electroflocculation and electroflotation, as algae pre-harvesting processes; and (2) to design, test and optimize a cost-effective and efficient filtration-based harvesting mechanism for micrioalgae. The principal results of the study showed that: (1) The mean final concentration for electroflocculation of 17.94 gL⁻¹ significantly exceeded (p = 0.0416) that for electroflotation of 9.51 gL⁻¹, indicating electroflocculation to be the more effective process; (2) Microscope images of the algae showed that, for the level of power applied (1 A, 40 V max), electrocoagulation did not appear to have produced any effect on the algae that was significantly different from that by centrifugation and that neither method appeared to have caused any significant cell wall damage or rupture; (3) The most effective configuration for the harvester prototype -- resulting in higher throughput rate (0.303 gh⁻¹), higher efficiency (233.33 gL⁻¹), as well as a lower energy consumption (143.46 kWhm⁻³) -- corresponded with higher concentration of the incoming biomass (21.5 gL⁻¹), lower belt velocity (0.05 ms⁻¹), higher inclination angle (25°) and lower pressure (0 Psi); and (4) The total energy consumption for the harvester prototype, when combined with a preceding pre-harvesting process, of 4.95 kWhm⁻³ was comparable to those reported by others for filtration-based harvesting. The new efficient harvesting mechanism proposed showed significant potential in successfully reducing algae production cost and make biofuels from microalgae economically feasible in the mid to long term in view of the prototype having achieved high output biomass concentration, low energy consumption per unit volume, high throughput rate, and facility of implementation.

Scenedesmus obliquus is a freshwater microalga which has high lipid content and biomass productivity. It is regarded as a promising species for production of biodiesel and other valuable organic compounds. Given the high cost of using potable water and commercial fertilizers, the use of municipal wastewater as algal growth medium is attractive in view of its constituent organic carbon and inorganic nutrients, including nitrogen and phosphorus. Investigating the mixotrophic cultivation of S. obliquus in an imitation municipal wastewater, the results of this study showed that: (1) The unmodified imitation wastewater by itself as expected yielded poor S. obliquus growth owing to its pH significantly decreasing to 3.5 as caused by the presence of Ammonium Chloride in the wastewater, inhibiting cell growth; (2) Adding either Acetic Acid or Sodium Acetate to the wastewater medium maintained its pH at 6.5 to 7.0, and its algae biomass on day 6 increased significantly by 212% and 194%, respectively; (3) Adding either Acetic Acid or Sodium Acetate to the wastewater medium maintained its pH at 6.5 to 7.0, and its algae biomass during exponential phase (day 4) significantly exceeded that in the MF control by 220.6% and 165.8%, respectively, while its algae biomass during saturation (day 6) significantly exceeded that in the MF control by 60.8% and 51.5%, respectively; and (4) Addition of NaNO₃ to the wastewater to match the level of N in the MF medium improved the algae biomass by 10%. This study developed ways for how the successful mixotrophic cultivation of S. obliquus in municipal wastewater could be achieved.

The specific aim of this study was to advance the development of the Minimally Structured & Modular Vertical Farm (MSM-VF), an original concept developed at The University of Arizona, by designing a specific modular unit made of a transparent-walled modified standard shipping container for use in climate locations represented by Los Angeles and New York City. The conclusions of the study included: (1) A workable range of temperatures (15 to 30°C) for cultivating tomato in Los Angeles and New York City could be achieved in a transparent-walled MSM-VF shipping-container modular unit by using a cover material of low density polyethylene (LDPE) and a heating, ventilating and air conditioning (HVAC) system with an airspeed of 2 m/s, inlet angle at 60° and outlet position located at the top of the back wall; (2) A workable range of temperatures (15 to 27°C) for cultivating lettuce in Los Angeles and New York City could be achieved by using a cover material of LDPE and an HVAC system with an air speed of 4m/s, inlet angle at 60° and outlet position located at the bottom of the back wall; (3) The annual energy demands of the plastic-walled MSM-VF shipping-container modular unit were far less than those for the opaque-walled control plant-factory unit in all cases, except in the one case of growing tomato in New York City. Still, in this one exception, the annual energy demand of growing tomato in New York City in the plastic-walled MSM-VF shipping-container modular unit of 557.65 kWh/m² (versus 325.34 kWh/m² for the opaque-walled control plant-factory unit) was significantly lower than that of 711.91 kWh/m², which was the average for 164 greenhouses occupying a total of 16444 m² operated by the Cornell University Agricultural Experiment Station (CUAES) in the state of New York (CUAES Greenhouses); and, (4) The annual energy demands of the plastic-walled MSM-VF shipping-container modular unit were either significantly lower or for one case approximately the same (773.84 kWh/m²) as that of the 711.91 kWh/m² for the New York greenhouses. By contrast, the annual energy demands of the opaque-walled control plant-factory unit significantly exceeded that of the 711.91 kWh/m² for the New York greenhouses by 170% for Los Angeles and by 126% for New York City, both for growing lettuce. The foregoing results provided significant and reasonable basis for the practicability of Minimally Structured & Modular Vertical Farms made of plastic-walled shipping-container modular units in Los Angeles and New York City as well as in many other mega-cities around the world with similar climates.

With a continued worldwide trend in population shift from rural to urban areas predicted to increase, new approaches to agricultural production must be considered and implemented. Little academic interest has been applied to determining economically viable urban agriculture crop production sites for business investment. A feasibility model to aid investors in selecting appropriate sites for the development of urban agriculture food production within population centers was created. Lettuce crop trials were performed from August 2015 to December 2015 at the University of Arizona Controlled Environment Agriculture Center to validate the productivity of a unique high density hydroponic system designed for the rooftop environment. The feasibility model is based on this system and with a minimal number of inputs, ranging from size of growing space to growing media costs, determines a wide range of useful outputs. These outputs include crop productivity within the facility, material inputs and a cost breakdown of starting a new agricultural venture. The model utilizes multiple sheets within one excel document to give the user a clear and organized financial perspective of a hypothetical growing operation in the main sheet. With this model, investors into urban agriculture will have a means to gain an objective view of financial considerations before substantial investment is completed.

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The current study expands on the body of knowledge associated with water distribution system security. The three main chapters focus on 1) the effectiveness of an incomplete mixing model (AZRED-I) with respect to multi-objective sensor placement decisions; 2) risk assessment as a tool for evaluating vulnerability and making sensor placement decisions; and 3) experimental verification of a combined axial-dispersion and incomplete-mixing water quality model (AZRED-II). The study concludes that water quality models do impact sensor placement decisions, especially in highly interconnected networks; that risk assessment is a valuable evaluation tool for providing information concerning a system's vulnerability to contamination and also information that can affect sensor placement decisions; and that AZRED-II is superior to other water quality models at predicting the spatiotemporal pattern of a pulse through a distribution network with cross junctions under laminar flow. The other sections of the study describe the connection that exists between water distribution security and water quality models.