As a result of the EPA?s Disinfection Byproduct Rule, the Northeast Mississippi Regional Water Supply District requested that the Environmental Technology and Applications Laboratory at Mississippi State University conduct a study to develop techniques to comply with new TOC regulations. This study involved the use of jar testing and Enhanced Coagulation in a laboratory setting over a period of twelve months to optimize the various coagulants evaluated in this study. Iron (III) sulfate, aluminum sulfate, aluminum chloride, aluminum chlorohydrate, and a number of polyaluminum chlorides were evaluated in this study. Coagulants were evaluated on both a treatment effectiveness and economical basis. It was determined that an acidified alum solution performed best at meeting EPA standards for total organic carbon reduction, as well as being economically feasible.

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This report has been prepared with the idea of briefly summarizing the most important principles underlying the coagulations/flocculation process as it applies to water and wastewater treatment. The production of potable water from a supply which has been contaminated by naturally-occurring or man-made pollutants has been an object of concern throughout history. Several broad aspects have been considered in the report, such as the history, the nature and physical chemistry of colloidal particles, the theories of and the factors affecting coagulation/flocculation, and control of the coagulation/flocculation process. It is advisable for those persons engaged in the dynamic environmental sciences to occasionally review the basic principles having to do with the processes being employed. In this light, this report provides a cursory review of pertinent literature with regard to the history, the stoichiomentry and physical mechanisms involved, the techniques of process control and an assessment of the state-of-the-art of the coagulation/flocculation process. Of course, this discussion could have been written more extensive detail, but the volume of such an enterprise would be excessive. For those desiring further information, and extensive bibliography of references has been appended.

Coagulation factor XI plays an important role in the consolidation phase of blood coagulation. Previous studies from our laboratory and others have demonstrated that zymogen factor XI (FXI) binds to heparin with moderate (KD~110 nM) affinity via residues (K252, K253 and K255) located in the apple 3 (A3) domain of the molecule. In contrast, the enzyme, factor XIa (FXIa), was shown to bind to heparin with significantly higher affinity (~1.5 nM by ELISA) via residues (K529, R530 and R532) within the catalytic domain (CD). The interaction between heparin and FXIa potentiates the inhibition of FXIa by protease nexin-2 by 10-fold. In addition, related polyanions heparin and dextran sulfate inhibit the catalytic activity of FXIa. The present study was designed to determine the relative contributions of positively charged residues as well as the dimeric structure of FXI in heparin binding. During this project, wtFXI, FXIR504A, FXIK505A, FXIR507A, FXIR529A, FXIR530A, FXIR532A, and FXIR586A have been expressed and purified. All mutants were homogenous and identical to wtFXI on SDS-PAGE, clotting assays and 1G5 monoclonal antibody binding studied by SPR. In addition, monomeric FXI C321S/K331A was expressed and purified. Utilizing an ELISA assay, no difference in the affinity for heparin between FXIa and FXI was found. Surface plasmon resonance (SPR) data collected for FXI clearly indicate a complex interaction which does not conform to a simple 1:1 Langmuir binding model making it difficult to obtain quantitative information. The complexity of FXI interactions with heparin is likely to arise from the multivalent nature of the binding, in which both protein and heparin have multiple binding sites. Two positively charged residues in the FXI catalytic domain, FXIR507A and FXIR532A, were found to be particularly important for interaction with heparin. The FXIR507A and FXIR532A mutants demonstrated ~ 65% and ~50% decreases respectively in total number of heparin binding sites based on ELISA. Also, the apparent dissociation constants for FXIR507A (KDapp ~13 nM) and FXIR532A (KDapp ~21 nM ) were 6 and 10-fold increased respectively compared with 2.1 nM for the wtFXI. Mutant FXIR586A also demonstrated a defect in affinity (KDapp ~ 13 nM) without an effect on the Bmax. The monomeric FXIC321S/R331A was also characterized for its ability to bind heparin compared with wtFXI. Surprisingly, the monomeric FXI displayed defective binding to heparin according to ELISA (KDapp ~ 30 nM) and SPR methods. Thus, the unique homodimeric structure of FXI in addition to the residues both in its catalytic and A3 domain chains are necessary for high-affinity heparin binding. / Biochemistry

Gas bubbles that form within water treatment plants can disrupt drinking water treatment processes. Bubbles may form whenever the total dissolved gas pressure exceeds the local solution pressure, a condition termed dissolved gas "supersaturation." This project investigated how bubble formation affects conventional drinking water treatment and examined factors that can reduce these problems. Gas bubbles attached to coagulated floc particles can reduce settling efficiency and create "floating floc." In laboratory experiments, bubbles formed on the surface of the mixing paddle, since this was the location of minimum pressure within the system. The formation and stability of floating floc was dependent on many different factors including the amount and type of dissolved gas supersaturation and surface chemistry of the mixing paddle. The intensity and duration of rapid mixing also controlled the amount of floating floc. Bubbles forming in filter media can block pore spaces and create headloss, a process popularly termed "air binding." During benchscale filtration experiments, bubbles were released upwards from the media in a burping phenomenon, and bubbles could also be pushed downwards by fluid flow. Burping is beneficial since it partly alleviates the bubble induced headloss, but the media disruptions might also decrease filter efficiency (particle capture). Bubble formation within filters can be reduced by increasing the pressure inside the filter via greater submergence (water head above the media), lower hydraulic flow rate, or use of a more porous media. The mode of filter operation (declining or constant flow rate) will also affect the local filter pressure profile. Dissolved gas supersaturation and bubble formation are detected in on-line turbidity devices and particle counters causing spurious measurements. The use of bubble traps usually reduced these problems, but one device worsened turbidity spikes. Flow disturbances may also release bubbles upstream of the on-line turbidimeter, which can cause spikes in turbidity readings. / Ph. D.