Water

The objective of this thesis is to develop a new experimental method to characterize
the diffusion of water in polymer resins, based on the evolution in the volume of water
droplets as a function of time. A finite element model is established to model the mass
transport of water droplet through evaporation and diffusion processes. Diffusivity of water
into polymer resins is then extracted by matching the volume variation of the simulated
water droplet to the experimental results. Capability of this method is demonstrated by
determining the diffusivity of water into void-free epoxy and epoxy samples with voids.
Diffusion coefficient value obtained from this method agrees with data from conventional
water immersion method. The significantly small scale of the water droplet (less than 10
microliter) allows rapid characterization of diffusivity in hours instead of months as
typically required by the conventional immersion method. The method developed here provides a useful tool for rapid and effective characterization of diffusivity of water in
polymer substrates and can be extended to other substances as well.

The influence of voids on the moisture uptake of epoxy has been studied. Specimens with void contents from 0 to about 50% were prepared. Void geometry and content were analyzed using microscopy and density methods. Void containing dry samples were characterized by Differential Scanning Calorimetry and Dynamic-Mechanical Analysis which verified consistency of chemistry of the epoxy network. The moisture uptake of specimens immersed in distilled water at 40 °C was monitored. The rate of absorption and saturation moisture content increased with increasing void content. The moisture uptake of void-free and void containing specimens was non-Fickian. The Langmuir model provided good fits to the experimental results for specimens with low to medium void content, although the moisture uptake of the high void content specimens showed substantial deviations from the Langmuir diffusion model. The moisture diffusivity agreed reasonably with predications from the Maxwell inclusion model over a range of void contents from 0 to 50%. The state of sorbed water was examined using mass balance calculations and DSC analysis. Only 6-8% of the void volume is occupied by water at saturation. Absorbed water may be classified as free and bound water. For void-free specimens, only bound water was found. The medium and high void content specimens contained water in three states: free water, freezable bound water, and non-freezable bound water. The DSC results show that the proportions of free water and freezable bound water increase with increasing void content, while the content of non-freezable bound water decreased. Moisture induced swelling decreased with increasing void content. The swelling is attributed to the content of non-freezable bound water.

This paper presents the results of the spike tests performed in the alternative water supply pilot testing program for the City of Pembroke Pines. It establishes the effectiveness of a protocol that can be used to gain further insight on the rejection capacities of RO membranes. An in-depth study of the molecular descriptors affecting rejection by RO membranes is presented and used in the development of a discriminant function analysis. This analysis proved to be an effective way to predict the passage of Emerging Substances of Concern (ESOCs) through RO membrane. Further, a principal component (PC) analysis was performed to determine which factors accounted the largest variation in RO permeability. Additionally, this paper defines the groundwork for a discriminant analysis model that, if further developed, could serve as an important tool to predict the rejection capabilities of RO treatment when handling with ESOCs.

A landfill is in a reserved space on land used for the disposal of refuse by utilizing the principles of engineering to confine the refuse to the smallest practical area to prevent the creation of nuisances to public health or safety (Andersen et al. 1967). However, because landfills are open to the atmosphere, rainfall can saturate them, resulting in a liquid called leachate. Leachate generated within the landfill contains suspended solids, soluble components of the waste and by-products from the degradation of the waste by various micro-organisms. Treatment of leachate is an emerging area of need. In this manuscript the main purpose is to investigate a laboratory scale batch reactor that is able to detoxify and treat leachate by using an advanced oxidation process (i.e. TiO2). Based on the results obtained from this ground breaking research, it appears that the process investigate has the potential to radically change the way landfill leachate is treated. Scale up may provide direction that can be used to improve the efficiency of the different stages of toxicity of leachate during the entire life of a landfill.

Pigment-based chemotaxonomy uses relative amounts of photosynthetic pigments (biomarkers) within algae samples to determine the algal class composition of each sample. Chemotaxonomy has been applied successfully to phytoplankton communities, but its efficacy for periphyton has not yet been established. This study examined the ability of simultaneous linear equations (SLE), CHEMTAX, and the Bayesian Compositional Estimator (BCE) to determine algal class composition in Florida Everglades periphyton. The methods were applied to artificial datasets, mixed lab cultures of known composition, and Everglades periphyton samples for which microscopic biovolume data was available. All methods were able to return accurate sample compositions for artificial data and mixed lab cultures. Correlation between pigment methods and microscopic results for natural periphyton samples was poor. SLE and CHEMTAX returned similar results for all samples while BCE performed less well.

The analysis and modeling of the coastal farfield behavior of inlet discharge plumes is the key to understanding the fate of pollutants discharged into the ocean. These plumes disperse in chaotic and unpredictable patterns. Theoretical models are based on the average conditions and calibrated to the results of tracer studies. Data and models for freshwater discharges in coastal ocean systems are limited because of the lack of adequate tracers. On February, 2007, a tracer study was conducted on the Boynton Inlet, Florida, using sulfur hexafluoride (SF6) tracer. The objective of this study is to provide methods of analysis for the sample data collected during the experiment. The detected tracer concentrated in a bolus that migrated north of the inlet at velocities lower than predicted by the current data. The plume was successfully modeled with a Gaussian plume model, with 90% of the SF6 predictions having less than 4.6 pptr error.

Phosphorus (P) is required for all living organisms. Fully oxidized pentavalent (+V) is the principal form in organisms, however studies on Desulfotignum phosphitoxidans show the enzymatic metabolism of reduced P oxyanions. Thus a natural source of reduced P is expected. Geothermal waters are naturally occurring reducing environments and ion chromatography has been used for the detection of submicromolar concentrations of P, yet the detection of reduced oxyanions is complicated by fluoride and hydrogen carbonate with similar elution times as hypophosphite(+I) and phosphite(+III) respectively. Studies had shown that simplifying the matrix through pretreatment with silver and sulfonic acid cartridges improves IC limits of detection (LODs). The effects of pretreatment are dependant upon the total concentration of ions in solution. The purpose of this study is to determine IC phosphorous oxyanion LODs and to maximize signals by analyzing the relationship between filtering techniques, effective concentration of P oxyanions, and total ions in the matrix.