Corrosion of household copper plumbing infrastructure can cause pipe failure and lead to elevated levels of copper in drinking water which can exceed the USEPA health based standard for copper in drinking water of 1.3 mg/L Cu. The purpose of this study was to determine taste thresholds of copper in different types of water, analyze how copper chemistry can affect tasting, determine if common disinfectants influence the taste of copper and evaluate genetic links to copper sensitivity. A one-out-of-five test was used to define thresholds, evaluate disinfectant influences, and examine copper chemistry differences. A difference from control test was used to analyze soluble copper tasting and a one solution test with visual classification was used to discriminate 6-n-propylthiouracil (PROP) taster status. Solutions containing copper sulfate (0.05 – 8 mg/l Cu) were prepared in distilled water, mineral water of varying pH and mineral water with disinfectant added. Geometric mean copper taste thresholds were 0.48 mg Cu/l and 0.41mg Cu/l in distilled and mineral water pH 7.4 respectively. Logistic regression copper taste thresholds were 1.50 mg Cu/l and 1.96 mg Cu/l in distilled and mineral water pH 7.4 respectively. Soluble copper was readily tasted while particulate copper was poorly tasted. Chlorine and chloramines dosed at typical tap water levels had no significant effect on panelists' tasting abilities for water containing 1 mg/l total copper. Geometric mean copper thresholds values did not correlate with (PROP) status so PROP sensitivity would not be a good indicator for copper sensitivity. / Master of Science

Chlorine dioxide (ClO₂) was included in the Spring Hollow Water Treatment Plant (Roanoke County, Virginia) to oxidize manganese and iron, prevent tastes and odors, and avoid the formation of excessive halogenated disinfection by-products. A state-of-the-art, gas:solid ClO₂ generation system manufactured by CDG Technology, Inc. was installed at the plant and is the first full-scale use of this technology in the world. The ClO₂ generator produces a feed stream free of chlorine, chlorite ion (ClO₂⁻), and chlorate ion (ClO₃⁻), resulting in lower by-product concentrations in the treatment system The objectives of this project were to study ClO₂ persistence and by-product concentrations throughout the treatment plant and distribution system and to evaluate granular activated carbon (GAC) columns for removing ClO₂⁻ from the finished water. The ClO₂ dosages applied during this study were relatively low (<0.75 mg/L), and, as a result, ClO₂⁻ concentrations never approached the maximum contaminant level (MCL) (1.0 mg/L). Likewise, the plant effluent ClO₂ concentration never approached the maximum residual disinfectant level (MRDL) (0.80 mg/L), but concentrations as high as 0.15 mg/L reformed in the distribution system by ClO₂⁻ reaction with chlorine. Chlorate ion was monitored despite the fact that no ClO₃⁻ MCL has been proposed, and concentrations were quite low (never greater than 0.10 mg/L) throughout the treatment plant and in the distribution system. The reasons for the low concentrations are that ClO₃⁻ is not produced by the gas-solid generator used at the facility and ClO₂⁻ concentrations in the clearwell prior to chlorination were uniformly low. The average ClO₂⁻ reduction upon passage of treated water through the GAC contactor was approximately 64 percent, but the GAC effectiveness was declining over the six-month study period. Apparently, GAC effectiveness, as shown by others, is short-lived, and if higher ClO₂ dosages are ever applied at the Roanoke County facility, the ClO₂⁻ concentrations will have to be reduced by either ferrous coagulants or reduced-sulfur compounds. Regenerated ClO₂ concentrations in the distribution system were below 0.2 mg/L, but concentrations as low as 0.03 mg/L were found at homes of customers who complained of odors. During this study, twelve complaints were received from eight customers, and each complainant had recently installed new carpeting, which has been shown to contribute volatile organics that react with ClO₂ to produce odors similar to kerosene and cat urine. While meeting the Cl₂ MCL likely will be no problem if the ClO₂ dose at the plant remains below 1.0 mg/L, the problem of offensive odors in the distribution system will likely continue as long as any ClO₂ is in the finished water when chlorine is present. / Master of Science

Interactions between copper and chlorine disinfectants were examined from the perspective of disinfectant decay and copper pitting corrosion. Sparingly soluble cupric hydroxide catalyzed the rapid decay of free chlorine, which in turn, led to production of less soluble and more crystalline phases of cupric hydroxide. The catalytic activity of the cupric hydroxide was retained over multiple cycles of chlorine dosing. Experiments with chloramine revealed that copper species could also trigger rapid loss of chloramine disinfectant. In copper pipes, loss of free chlorine and chloramine were both rapid during stagnation. Reactivity of the copper to the disinfectants was retained for weeks. Phosphate tended to decrease the reactivity between the copper pipe and chlorine disinfectants. A novel, inexpensive and real-time test to monitor copper pitting corrosion was developed. In a normal pipe, it is not possible to measure the electron flow or pitting current from the pit anode to the cathode. But a new method was developed that can form an active pit on the tip of a copper wire, which in turn, allows the pitting current to be measured. Preliminary experiments presented herein have proven that this technique has promise in at least one water condition known to cause pitting. The method also quickly predicted that high levels of orthophosphate could stop pitting attack in this water, whereas low levels would tend to worsen pitting. Future research should be conducted to examine this technique in greater detail. / Master of Science

In an effort to maintain compliance with current and future United States Environmental Protection Agency regulations governing haloacetic acids (HAAs) and trihalomethanes (THMs), the Blacksburg, Christiansburg, VPI (BCVPI) Water Authority in Radford, Virginia elected to eliminate prechlorination and replace it with preoxidation using chlorine dioxide (ClO2). Prior to full-scale application at the BCVPI Water Treatment Plant, jar testing was done to determine the effects of ClO2 on the formation of HAAs and THMs. Jar testing results showed a significant reduction in THM formation potential when 2.0 mg/L ClO2 was applied to raw water and chlorination was delayed. Chlorine dioxide doses less than 2.0 mg/L were statistically insignificant in the reduction of THM formation potentials below samples that were prechlorinated according to the BCVPI Water Treatment Plant's current practice. Likewise, ClO2 did not alter HAA formation potentials in such a way that statistical differences could be detected between ClO2 pretreatment and prechlorination, even at a dose of 2.0 mg/L ClO2. The two inorganic byproducts of ClO2, chlorite and chlorate, were also measured following jar tests. Chlorite concentrations increased with an increased ClO2 dose, but remained below 1.0 mg/L. Chlorate was formed in all jar-test samples. / Master of Science

An ideal drinking water distribution system (DWDS) must supply safe drinking water with free chlorine residual (FCR) in the form of HOCI and OCIֿ at a required concentration level. Meanwhile the FCR is consumed in the bulk liquid phase and at the DWDS pipes wall as the result of chemical reactions. Because of these, an optimized chlorine dosing for the DWDS using model-based predictive control (MBPC) is developed through the steps of modelling the FCR transport along the main pipes of the DWDS, designing chlorine dosing and implementing a multiple-input multiple-output system control scheme in Matlab 7.0.1 software. Discrete time-space models (DTSM) that can be used to predict free chlorine residual (FCR) concentration along the pipes of the DWDS over time is developed using explicit finite difference method (EFDM). Simulations of the DTSM using step and rectangular pulse input show that the effect of water flow rate velocity is much stronger than the effect of chlorine effective diffusivity coefficient on the FCR distribution and decay process in the DWDS main pipes. Therefore, the FCR axial diffusion in single pipes of the DWDS can be neglected. Investigating the effect of injection time, initial chlorine distribution, and overall chlorine decay rate constant involved in the process have provided a thorough understanding of chlorination and the effectiveness of all the parameters. This study proposed a model-based chlorine dosing design (MBCDD) based on a conventional-optimum design process (CODP) (Aurora, 2004), which is created for uncertain water demand based on the DTSM simulation. / In the MBCDD, the constraints must be met by designing distances between chlorine boosters and optimal value of the initial chlorine distribution in order to maintain the controlled variable (CV), i.e. FCR concentration with a certain degree of robustness to the variations of water flow rate. The MBCDD can cope with the simulated DWDS (SDWDS) with the conditions; the main pipe is 12 inch diameter size with the pipe length of 8.5 km, the first consumers taking the water from the point of 0.83 km, the assumed pipe wall chlorine decay rate constant of 0.45 m/day, and the value of chlorine overall decay rate constants follow Rosman's model (1994), by proposing a set of rules for selecting the locations for additional chlorine dosing boosters, and setting the optimal chlorine dosing concentrations for each booster in order to maintain a relatively even FCR distribution along the DWDS, which is robust against volumetric water supply velocity (VWS) variations. An example shows that by implementing this strategy, MBCDD can control the FCR along the 8.5 km main pipe of 12 inch diameter size with the VWS velocity from 0.2457 to 2.457 km/hr and with the assumed wall and bulk decay constants of 0.45 and 0.55 m/day, respectively. An adaptive chlorine dosing design (ACDD) as another CODP of chlorine dosing which has the same concept with the MBCDD without the rule of critical velocity is also proposed in this study. The ACDD objective is to obtain the optimum value of initial chlorine distribution for every single change in the VWS. Simulation of the ACDD on the SDWDS shows that the ACDD can maintain the FCR concentration within the required limit of 0.2-0.6 mg/1. / To enable water quality modelling for studying the effectiveness of chlorine dosing and injection in the form of mass flow rate of pure gaseous chlorine as manipulated variable (MV), a multiple-input multiple-output (MIMO) system is developed in Simulink for Matlab 7.0.1 software by considering the disturbances of temperature and circuiting flow. The MIMO system can be used to design booster locations and distribution along a main pipe of the DWDS, to monitor the FCR concentration at the point just before injection (mixing) and between two boosters, and to implement feedback and open-loop control. This study also proposed a decentralized model-based control (DMBC) based on the MBCDD-ACDD and centralized model predictive control (CMPC) in order to optimize MV to control the CV along the main pipe of the DWDS in the MIMO system from the FCR concentration at just after the chlorine injection (CVin) to the FCR concentration (CVo) before the next chlorine injection with the constraints of 0.2-0.6 ppm for both the CVin and CVo. A comparison of the performances of decentralized PI (DPI) control, DMBC and CMPC, shows that the performances of the DMBC and CMPC in controlling the MIMO system are almost the same, and they both are significantly better than the DPI control performance. In brief, model-based predictive control (MBPC), in this case a decentralized model-based control (DMBC) and a centralized predictive control (CMPC), enable optimization of chlorine dosing for the DWDS.

<p>The hypothetical assumption that chloride is conservative in the soil has been debated for the last decade. The results of the recent years of study in chlorine biogeochemistry show that chloride is non-conservative but rather participates in complex biogeochemical reactions in the soil. These interactions in nature inform the development of simplified hydrochemical model of chloride dynamics in the soil that is driven on soil routine component of HBV hydrological model. This novel attempt affords the opportunity to explore chlorine biogeochemistry further by evaluating the biological processes such as microbial biomass that predominate chlorine cycles in the same order of magnitude as earlier studied abiotic factors. Data from soil lysimeter experiment with different inputs treatments were used in the calibration and validation of both the hydrological and biogeochemical model. The results show that (1) model efficiency reduces with decreasing water residence and with increasing soil organic matter. (2) Longer water residence time (low water input), high chloride and high nitrogen input loads relatively enhance maximum biomass accumulation in a shorter time span. (3) Chloride retention time reduces with increasing chloride loads under short water residence. (4) Microbial biomass growth rate is highest under high chloride input treatments. (5) Biomass death rates shows reducing trend under short water residence (High water input). Further researches are therefore suggested for possible model expansion and to make the results of this model plausible under field conditions.</p>

The hypothetical assumption that chloride is conservative in the soil has been debated for the last decade. The results of the recent years of study in chlorine biogeochemistry show that chloride is non-conservative but rather participates in complex biogeochemical reactions in the soil. These interactions in nature inform the development of simplified hydrochemical model of chloride dynamics in the soil that is driven on soil routine component of HBV hydrological model. This novel attempt affords the opportunity to explore chlorine biogeochemistry further by evaluating the biological processes such as microbial biomass that predominate chlorine cycles in the same order of magnitude as earlier studied abiotic factors. Data from soil lysimeter experiment with different inputs treatments were used in the calibration and validation of both the hydrological and biogeochemical model. The results show that (1) model efficiency reduces with decreasing water residence and with increasing soil organic matter. (2) Longer water residence time (low water input), high chloride and high nitrogen input loads relatively enhance maximum biomass accumulation in a shorter time span. (3) Chloride retention time reduces with increasing chloride loads under short water residence. (4) Microbial biomass growth rate is highest under high chloride input treatments. (5) Biomass death rates shows reducing trend under short water residence (High water input). Further researches are therefore suggested for possible model expansion and to make the results of this model plausible under field conditions.

As algae-derived biofuel is a promising renewable energy source, it is well-established that micro-algae have the potential to make a significant contribution to transportation fuel demand. Although it has many advantages including high areal productivity, there are many negative factors. One of these factors is the predation of algae by amoebas, protozoans, ciliates and rotifers, particularly in open pond systems. For example, the rotifer Brachionus plicatilis, is able to eat as much as 12,000 algae cells per hour and can be responsible for an entire pond crash within days. Thus, these higher organisms need to be controlled in order to satisfy large-scale algae crop and biofuel production demand. One method of predation control involves the introduction of a toxic chemical to an algal culture that the predator has a higher sensitivity to with respect to algae. Ideally, predation could be minimized or eliminated without a substantial effect on the algal culture growth. Chlorella kessleri was used as the algal culture and Brachionus calyciflorus as the source of predation. Research was conducted in five stages. First, chlorine dissipation tests were carried out using spring water, distilled water, Bolds Basal Medium (BBM), and three different dry weights of algal suspension in order to analyze the dissipation rate of the residual chlorine. The results showed that chlorine in distilled water and spring water rarely dissipated while chlorine concentration in algal suspension rapidly decreased by a maximum of 90% within the second hour. Second, acute chlorine toxicity tests were conducted in order to find the 24-hr LC50 of B. calyciflorus. The 24-hr LC50 of the test animal was 0.198 mg Cl/L. Third, chlorine toxicity tests were conducted in order to find the LC50 of Chlorella kessleri. The 24-hr LC50 of C. kessleri was 0.321 mg Cl/L. Based on these results, the test animal was more sensitive to chlorine than the test algae; therefore chlorine may be used to avoid algae pond crashes by B. calyciflorus. Fourth, C. kessleri and B. calyciflorus were combined into one test to determine how long it would take to observe an algal culture crash. The result demonstrated that the higher the population of predators in algal suspension, the faster it crashed. Finally, chlorine, C. kessleri, and B. calyciflorus were combined into one test to determine what chlorine concentration and dosing interval was needed to significantly reduce predation without significantly reducing algae growth. The results of the fifth experiment showed that the effective intermittent chlorine concentration was between 0.45 and 0.60 mg Cl/L, and a short interval of chlorine dosing was effective in inhibiting rotifers in algal suspension. Even though the rotifers in algal suspension were inhibited by 0.45 to 0.60 mg Cl/L, algae growth was greatly inhibited by chlorine. In this respect, future work is needed to reduce the effect on algae by chlorine or alternative chemicals.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1973. / Bibliography: leaves [293]-300. / xvi, 300 l illus., tables

Magister Pharmaceuticae - MPharm / This study was based on Dioxy MP 14 (DMP), a brand of stabilized chlorine dioxide (SCD). The active pharmaceutical ingredient (API) of DMP is chlorine dioxide (CD) which is a potent oxidant and biocide. These properties have proved invaluable for various applications. The main goals of this study were: to evaluate the effectiveness of DMP for disinfecting Mycobateria tuberculosis (TB) contaminated medical instruments, devices, floors and surfaces; to investigate the stability of DMP; and to explore possibilities for medical application of DMP. Evaluation of disinfectant activity of DMP on TB was performed using the spectrophotometric method, a modification of the European suspension test, EN 14348. M. bovis BCG was employed as surrogate in this test. Results were as follows: The minimum inhibitory concentration (MIC₉₀) = 12.5 ppm; the minimum bactericidal concentration (MBC) = 15.4 ppm; the Mycobactericidal Effect (ME) = 8.8log reduction; and the minimum inhibitory concentration (MIC₉₀) x minimum exposure time (CT) = 12.5 ppm.s. The long term stability study of DMP was performed by monitoring the rate of degradation of DMP stored in the fridge (2-8 °C), in the oven (40 °C), and under ambient conditions (15-30 °C). Analytical methods of assessing DMP concentration was by Iodometric titration method. The shelf life of DMP stored in a transparent bottle at room temperature was 9.8 weeks, as opposed to 52.7 weeks when stored in an amber colored reagent bottle at the same temperature. Both oven samples had an expiry date of about 20 weeks and the fridge samples about 70 weeks. Foam formulations for a vaginal douche (VGD), mouth rinse (MRF), and foot/sit bubble bath (F/SBB)], were developed in the laboratory. DMP and the formulated concentrate were designed to be mixed just prior to administration. During foam evaluation studies, a mechanical overhead stirrer was used to generate foam. Foamability was assessed by quantifying the amount of foam generated. The stability of foams were assessed by: 1) determining the rate of foam decay and the rate of foam drainage observed concurrently from foam loaded in a measuring cylinder; and 2) determining the life span of single bubbles of each foam system i.e. the bubble breaking time (BBT). The density of each foam system was also determined. Potentiometric acid base titration was used to select suitable adjuster alkali, and to show the benefits of employing a buffer. Concentrate development was initiated by a simple mixture of all the ingredients followed by stirring and observing the deviations from desired quality attributes of the product. The subsequent five processes were improvements designed to circumvent the shortcomings of the initial procedure to arrive at the optimized method E. Prototype formulations were employed to optimize excipient quantities to eventually arrive at an optimized master formula. In foam evaluation, it was found that sodium lauryl sulphate/ammonium lauryl sulphate/cocoamidopropyl betaine/cetostearyl alcohol (SLS/ALS/CAPB/CSA) foam system was the most appropriate to use in the formulation. NaOH was selected as the adjuster solution and KHP as the buffer. The dosage formula (DF) of the VGD and F/SBB was determined to be MDF = 5 ml of 50 ppm DMP + 5 ml concentrate + 40 ml water = 50 ml and that of MRF as MDF = 19 ml diluted concentrate + 1 ml of 50 ppm DMP. In conclusion, DMP was found to be a highly effective disinfectant against Mycobacteria. DMP has reasonable shelf life if stored appropriately. Pharmaceutical formulation from DMP was found to be delicate due to the narrow pH window of DMP stability, but is feasible.