In potable water preparation, chlorination is the last step before the potable water enters the distribution network. Umgeni Water Wiggins Waterworks feeds the Southern areas of Durban. A reservoir at this facility holds treated water before it enters the distribution network. To ensure an adequate disinfection potential within the network, the free chlorine concentration in the water leaving the reservoir at the Umgeni Water Wiggins Waterworks should be between 0.8 and 1.2 mg/L. The aim of this study was to develop an effective strategy to predict and control the chlorine concentration at the exit of the reservoir. This control problem is made difficult by the wide variations in flow and level in the reservoirs, together with reactive decay of the chlorine concentration. A Computational Fluid Dynamic study was undertaken to gain understanding of the physical processes operating in the reservoir (FLUENT software). As this kind of modelling is not yet applicable for real-time control, compartment models have been created to simulate the behaviour of the reservoir as closely as possible, using the results of the fluid dynamic simulation. These compartment models were initially used in an extended Kalman filter (MATLAB software). In a first step, they were used to estimate the kinetic factor for chlorine consumption and in a second step, they predicted the chlorine concentration at the outlet of the reservoir. The comparison between predictions and data, allowed the validation of the compartment models. A predictive control strategy was developed using a Dynamic Matrix Controller, and tested offline on the compartment models. The controller manipulated the chlorine concentration in the inlet of the reservoir in order to control the chlorine concentration in the outlet of the reservoir. Finally, the simplest compartment model was implemented on-line, using the Adroit SCADA system of the plant, in the form of a Kalman filter to estimate the chlorine decay constant, as well as a predictive model, using this continuously-updated decay parameter. The adaptive Dynamic Matrix Controller using this model was able to control the outlet chlorine concentration quite acceptably, and further improvements of the control performance are expected from ongoing tuning. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

The progress in the computing and communication industries together with the fast evolution of the semiconductor industry has made possible advances in the communications field. These advances have been used by other related applications to improve the services that they bring about. On the other hand, business crimes have increased three digits orders of magnitude in one decade, making from 20% to 30% of small businesses fail. These conditions demand new solutions to make security systems more reliable and efficient. The present work combines ISDN as a network with a security system to create a security network (SECNET). It will create intelligent and distributed security devices that communicate information from different places to a main security office by using the ISDN lines available at the premises. This work also introduces a new idea of individual equipment protection.

This problem was undertaken to determine the potentialities of chlorine dioxide as an algaecide and as an agent for the removal of tastes and odors from fresh water.

Little information is available regarding the applicability of various disinfectants to the control of microbial growths within water distribution systems, especially in relation to "nuisance" organisms. With regards to microbially mediated iron precipitation, an isolated heterotrophic iron precipitating bacterium was identified. An investigation of free chlorine, chloramines, and chlorine dioxide was undertaken to examine their applicability in the control and/or elimination of this type of deterioration in water quality. Environmental conditions were then varied to determine their effects on the disinfectant's efficiencies. The isolated bacterium was identified as Pseudomonas cepacia. It was determined that chlorine dioxide offered a serious challenge to chlorine as a secondary disinfectant on the basis of its biocidal capabilities and stability. Solution pH affected free chlorine's efficiency the greatest, while chloramine's poor efficiency suggested that its use should be avoided in areas of microbial iron precipitation. Water temperature and turbidity showed a minimal effect on the rate of inactivation of P. cepacia for all the disinfectants under consideration. / Master of Science

In anticipation of government mandates regulating the quantity of the toxic mutagen, 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone, which can be released into potable waters or from industrial facilities, technologies for monitoring the concentration, reducing the quantity, and inhibiting the formation of this compound were investigated. Adsorption of the chlorinated hydroxyfuranone from laboratory systems (pH 7.2, 22°) utilizing the non-polar, polymeric resin, Amberlite XAD-4, was successful. As these system conditions are comparable to those present in drinking water treatment facilities, application of this resin to such systems should be investigated. However, typical concentrations of the chlorinated mutagen released from such facilities are some 100 times less then those employed in laboratory experiments. As such, highly sensitive analytical technology, such as fluorescent spectroscopy, would be required for direct detection of the mutagen in these aqueous systems. Since development of a fluorescent adduct of the mutagen, through either Schiff's base or halogen replacement reactions, failed, application of the adsorption methodology was not investigated. Approaching the problem in a different manner lead to ° investigations aimed at reducing the formation of the mutagenic compound. Since the mutagen is formed upon chlorination of waters containing lignin derived materials, lignification in intact growing plants, and the effects of modified substrates on this process, were investigated. All modified substrates tested increased the uptake of a C¹⁴ labelled lignin precursor into the lignin containing fraction of a living poplar stem. Research continues in this area to determine through what mechanism these compounds are affecting lignification. / Master of Science / incomplete_metadata

MSc. (Applied Chemistry) / Remediation of POPs particularly the chlorinated compounds in water is therefore crucial. This research work describes the modification of polyethersulfone (PES) thin-film membrane composite (TFC) with functionalised carbon nanotubes (f-CNTs) using the phase invasion method. The oxidised CNTs were successfully decorated with Zero-Valent (ZV) Fe/Ni nanoparticles for the adsorption and degradation studies of polychlorinated organic pollutants (in this case the dichlorodiphenyltrichloroethanes (DDTs)). The in situ modification procedure was carried out using different quantities (0.04 wt%, 0.1 wt% and 0.2 wt%) of Fe/Ni-f-CNTs nanohybrids dispersed in a DMAc solution and dipping the polyethersulfone powder into a suspension containing the Fe/Ni-f-CNTs to form a nano-composite membrane. The formed composite membrane characteristics were investigated with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle (CA) and X-ray diffraction spectroscopy (XRD). The incorporation of nanohybrid in the PES membrane was found to increase the surface smoothness and the hydrophilicity of the composites. In addition, there was an increase in the adsorption of DDTs with increase in the nano-hybrid loading as indicated by the adsorption studies using the Langmuir isotherm and Freundlich isotherm studies. The data obtained from the batch studies closely fitted with the Langmuir isotherm based on the characteristic parameter RL found to lie within the standard range 0 < RL < 1 .

Granular activated carbon (GAC) pretreatment was evaluated for the removal of trihalomethane (THM) precursors from a surface water supply, the Occoquan Reservoir, in northern Virginia. The carbon contactors were operated in the upflow mode at flow rates of 2, 4, and 6 gpm which provided empty bed contact times (EBCT) of 26, 13, and 6.6 minutes, respectively. Reservoir raw water quality data was collected to determine what relationship existed between these measurements and the trihalomethane formation potential (THMFP) of the reservoir water. The results indicated that THM precursors, as measured by total organic carbon (TOC) and THMFP, could be removed from an untreated surface water supply by GAC contact. The degree to which THM precursors were removed was directly related to EBCT, the most effective being 26 minutes (2 gpm). GAC contact appeared to be selective for the removal of those precursors responsible for instantaneous THM concentrations i.e., those produced within a thirty minute chlorine-contact period. Those precursors responsible for THM concentrations produced after thirty minutes and for up to seven days thereafter (herein designated THMFP) appeared to be associated either with particulate matter in the raw water or with larger molecular weight organic substances which were not well adsorbed by the carbon. There were no discernible direct correlations between THMFP and the turbidity, color, TOC, chlorophyll-a concentration and algal populations in the raw water. Runoff from a rainstorm late in the period of study resulted in increases in raw water color, turbidity, and TOC concentrations, but it was impossible to determine which of these factors was responsible for the increased raw water THMFP that occurred at the same time. / Master of Science

Up-coming regulations on chlorine dioxide in drinking water treatment require low level measurement of chlorite ion (CI0₂-) and chlorate ion (CI0₃-). This research investigated analysis of CI0₂- and CI0₃-; in drinking water by flow injection analysis with iodometric detection (FIA) and ion chromatography with conductivity detection (IC). Both the FIA and IC methods were accurate for the determination of CIO₂-; and CIO₃-; in reagent water. The IC method was accurate in drinking water, however, FIA responded to chloramines and other oxidants present in drinking water causing inaccurate analysis of CIO₂-; and CIO₃-; by FIA. The two IC eluants investigated, a carbonate/bicarbonate mixture and a borate/boric acid mixture, performed well. By taking advantage of the slightly different separation abilities of each eluant, the IC method can be modified to maximize resolution of CIO₂-; and CIO₃-; in different drinking water matrices. Chlorite was unstable in chlorinated drinking water but was stable for up to three days when sodium oxalate was added and stable up to eighteen days when ethylene diamine was added as a preservative. Chlorate was stable in drinking water for up to eighteen days with or without a preservative. The propagation of errors method for determining detection limits yielded limits of detection for CIO₂- (mg/L) of 0.05 for FIA, 0.03 for the IC carbonate eluant and 0.01 for the IC borate eluant. For CIO₃- the limits of detection (mg/L) were 0.24 for FIA; 0.11 for the IC carbonate eluant and 0.02 for the borate eluant. / Master of Science

Past research regarding complexed iron has focused on the resistance to and kinetics of oxidation by O₂(aq) and the extent of stabilization. The 0.45 um filter was typically used to differentiate between dissolved and particulate iron. This research investigated Fe(II) oxidation by free chlorine and ClO₂ in the presence of DOC by varying the pH, DOC to Fe ratios, DOC sources, oxidant dosages, and contact time. Complexed iron removal by alum coagulation with and without oxidant addition was also examined. Particulate, colloidal, and soluble iron were differentiated by the use of 0.2 um filters and 100K ultrafilters. Ultrafiltration and oxidation studies revealed that, at the DOC-to-iron ratios used for this research, not all of the Fe(II) in solution was actually complexed. Thus, oxidation studies represented the oxidation of uncomplexed Fe(II) to Fe(III), which was then complexed by the higher molecular weight DOC. Results indicated that particulate iron formation (as defined as retention by a 0.2 um filter) was a function of the DOC source and oxidant used for testing. The formation of colloidal iron (as defined by retention on 100K ultrafilter) due to oxidation was dependent upon the initial DOC-to-iron ratio and the DOC source. A correlation between DOC adsorption to iron oxide solids and the solution pH, initial DOC-to-iron ratio, and the oxidant used was also evident. Complexed Fe(II) was removed from solution by alum coagulation. Oxidant addition to alum coagulation was necessary to effectively remove uncomplexed Fe(II) (in the presence of DOC) from solution. / Master of Science

The major objectives of this study were to investigate the effects of seasonal changes in Lake Manassas and its watershed (late winter to late summer), the impoundment of Broad Run, and the stratification of Lake Manassas on trihalomethane (THM)-precursors in Broad Run, upstream and downstream of the reservoir, and in Lake Manassas. An additional objective was to determine the molecular-size distributions of the dissolved organic carbon, and the THM precursors of the organic carbon pool in Lake Manassas during stratification. Raw water samples were collected from March through August on Broad Run immediately upstream of the reservoir, at two sites in the reservoir-- one approximately 0.27 miles from the dam and the second, at a more central location, 0.73 miles from the dam, and on Broad Run 2.81 miles below the dam. During stratification two samples were collected from each lake site-- one from the epilimnion, and the second from the hypolimnion. All of the samples were size fractionated by ultrafiltration and chlorinated for determination ofTHMFP. The differences in THMprecursor characteristics were determined by assessing the differences in the total organic carbon (TOC) concentrations and THM-formation potentials (THMFPs) of the various size fractions. The TOe and THM concentrations generally increased from late winter to late summer at all stations. The concentrations in Lake Manassas and in Broad Run below the dam were consistently higher than those observed in Broad Run upstream of the lake, indicating that impoundment causes an increase in levels of THM precursors. In addition, during stratification higher THM yields were produced by the predominantly low-molecular-weight precursors « 5,000) in the epilimnion of Lake Manassas, while the predominantly high-molecular-weight precursors (> 5,000 daltons) were low-yielding-THM precursors. / Master of Science