Chlorine is the primary method for disinfection of drinking water in the United States; however, growing concerns about the potential hazards associated with carcinogenic chlorine disinfection by-products have resulted in increased efforts to develop alternative methods of water disinfection. In addition, it is sometimes difficult to maintain an adequate concentration of free chlorine throughout a drinking water distribution system due to intrusion events and the presence of biofilms.Silver and copper are widely used as environmental biocides and as clinical antimicrobial agents. Copper has been extensively used as an algaecide for many years, and is reported to be one of the most toxic metals to heterotrophic bacteria in aquatic environments. In this study, silver and copper, both individually and in combination, were able to significantly reduce the numbers of the bacterial pathogens Salmonella typhimurium, Escherichia coli, Listeria monocytogenes, and Mycobacterium fortuitum in aqueous solutions. Silver and copper together could potentially be used as a secondary disinfectant in water treatment because their residual effect is long lasting and no harmful byproducts are generated.Besides water, produce can also be a source of microbial pathogens. Fruits and vegetables are the third leading source in microbial foodborne outbreaks, accounting for more than 10,000 cases of foodborne illness in the U.S. between 1990 and 2001. Alternative produce sanitizers in addition to chlorine were evaluated against foodborne pathogens inoculated onto lettuce. Overall, Fit® (citric acid, grapefruit oil extract) and chlorine yielded the greatest reductions of the study organisms.A large number of compounds are available for use as disinfectants; however, some are highly toxic, corrosive and produce harmful by-products. Natural antimicrobial products are another possible alternative. The efficacy of a natural peptide-based antimicrobial, Absolute Fx, was assessed against bacteria and viruses. Absolute Fx effectively inactivated the study organisms.

Cast iron pipes were installed broadly in North American water utilities. Many of these cast iron pipes are corroded and are continuous sources of Fe(II) ions in drinking water distribution systems. Recent studies have reported that soluble or particulate iron decreases water quality in distribution systems. In this study, an array of bench scale experiments were conducted to evaluate the impact of most common water parameters (e.g., pH, PO4, Cl2, and DOM) on the oxidation rate of Fe(II) ions, and on the formation of iron suspense in synthetic water samples. This was accomplished using a 24 full factorial design approach at a 95% confidence level. This study demonstrated that a lower content of iron suspension color, turbidity, and smaller particle size would appear to be obtained in presence of a phosphate based corrosion inhibitor at a pH value of 6.5 compared to a pH value of 8.5. To investigate the impact of Fe(II) ions, phosphate, pH and reaction time, and their interaction on DBPs formation in water samples, this study was conducted following an experimental design approach. Considering all the significant (α = 0.05, p < 0.05) factors, mathematical models for HAAs and THMs prediction were developed using 80 experiments. The models’ adequacy was checked thorough the statistical and graphical diagnostics. Different sources of natural water samples collected from three main water treatment plants in Halifax, Canada, were used to validate the models. This study suggested that the models’ performance were found to be excellent under a wide range of studied variables. Consequently, the most predominant iron oxides (goethite and magnetite) were used to investigate their impact on chlorine decay and DBPs formation study. Goethite and magnetite were also used for the adsorption of DBPs precursor (DOM). The DOM adsorption data illustrated to fit well with the Langmuir adsorption isotherm, indicating monolayer coverage. Molecular weight (MW) distributions of DBPs precursor (DOM) revealed that the higher molecular weight fractions adsorbed preferentially onto goethite followed by magnetite surface. The change of MW distribution of DOM was found to be in reasonable agreement with the change of DBPs formation in iron-water systems.

South Africa is fast approaching an era where its electrical energy demand will surpass the generating capacity of it's primary utility. The reason for this is due to the fact that over the past 10 years, the economic growth in South Africa has increased considerably and has become very energy intensive. South African electrical energy consumption is currently estimated to be growing at a rate of around 1 000 MW per year. Due to the electrical energy demand being the greatest during peak-times, Eskom has introduced various "time of use" tariff structures, such as Megaflex and Ruraflex. These two tariff structures differentiate between standard, peak and off-peak periods of the day, as well as different seasons of the year. The tariffs for these different scenarios are adjusted such that the consumers are persuaded into avoiding unnecessary electrical energy consumption during peak periods. It has been identified that electrical energy consumption can be split into two categories. One of the categories considers sectors where there are a large number of electrical energy consumers, each utilising a negligible amount of power. The other category considers sectors where there are few electrical energy consumers, each utilising large amounts of power. This therefore means that the consumers in the latter category have a great potential in implementing more efficient ways of consuming power. In order to try and control the electrical energy demand problem in South Africa, Eskom has implemented a DSM (Demand Side Management) programme in order to help the larger energy consumers in shifting their peak-time loads to off-peak periods. If the client wishes to shift their load to off-peak periods, Eskom will assist by funding all costs to carry out such a project. According to Eskom's monitoring and verification team, Eskom's DSM initiative has proven to be highly successful. Since the inception of Eskom's DSM programme in 2003, up until the end of 2005, an accumulated total load reduction of 296.3 MW has successfully been realised. At present, most water distribution schemes have been developed without making use of Eskom's DSM initiative. As these schemes consume considerable amounts of electrical energy, they are prime candidates for an initiative such as Eskom's DSM initiative. It had previously been identified that the Vaal Gamagara Water Scheme, situated in Delportshoop, was a prime candidate for Eskom's DSM initiative. Presented in this dissertation are the findings of the DSM investigation. Although the project has yet to be implemented, the proposed intervention methodology was manually tested, where a 3 MW load shift in the evening peak and a 3.6 MW load shift in the morning peak was achieved. If the current intervention methodology is maintained, the annual savings will be in the region of R 830,000.00. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2008.

South Africa is fast approaching an era where its electrical energy demand will surpass the generating capacity of it's primary utility. The reason for this is due to the fact that over the past 10 years, the economic growth in South Africa has increased considerably and has become very energy intensive. South African electrical energy consumption is currently estimated to be growing at a rate of around 1 000 MW per year. Due to the electrical energy demand being the greatest during peak-times, Eskom has introduced various "time of use" tariff structures, such as Megaflex and Ruraflex. These two tariff structures differentiate between standard, peak and off-peak periods of the day, as well as different seasons of the year. The tariffs for these different scenarios are adjusted such that the consumers are persuaded into avoiding unnecessary electrical energy consumption during peak periods. It has been identified that electrical energy consumption can be split into two categories. One of the categories considers sectors where there are a large number of electrical energy consumers, each utilising a negligible amount of power. The other category considers sectors where there are few electrical energy consumers, each utilising large amounts of power. This therefore means that the consumers in the latter category have a great potential in implementing more efficient ways of consuming power. In order to try and control the electrical energy demand problem in South Africa, Eskom has implemented a DSM (Demand Side Management) programme in order to help the larger energy consumers in shifting their peak-time loads to off-peak periods. If the client wishes to shift their load to off-peak periods, Eskom will assist by funding all costs to carry out such a project. According to Eskom's monitoring and verification team, Eskom's DSM initiative has proven to be highly successful. Since the inception of Eskom's DSM programme in 2003, up until the end of 2005, an accumulated total load reduction of 296.3 MW has successfully been realised. At present, most water distribution schemes have been developed without making use of Eskom's DSM initiative. As these schemes consume considerable amounts of electrical energy, they are prime candidates for an initiative such as Eskom's DSM initiative. It had previously been identified that the Vaal Gamagara Water Scheme, situated in Delportshoop, was a prime candidate for Eskom's DSM initiative. Presented in this dissertation are the findings of the DSM investigation. Although the project has yet to be implemented, the proposed intervention methodology was manually tested, where a 3 MW load shift in the evening peak and a 3.6 MW load shift in the morning peak was achieved. If the current intervention methodology is maintained, the annual savings will be in the region of R 830,000.00. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2008.

Water supply and distribution infrastructures are vital for current life. They have a significant role in public health, providing safe water for drinking and human consumption as well as for essential non-potable uses such as fire fighting. These diverse objectives create challenges for everyone who must address in some way the actual performance of the system. This research critically evaluates all common objectives of conventional design approaches and evaluates the advantages and drawbacks of various performance measures. New ideas for a more realistic and comprehensive approach to the design, operation assessment of WDS are proposed. A new approach, called a Risk-based Performance Assessment, for hydraulic performance evaluation is tentatively proposed. It is based on integration of reliability, resiliency, and vulnerability as three basic operational indices in the operation of WDS. Furthermore, the Total Life-cycle Cost evaluation approach is tentatively proposed based on considering all major costs of a WDS.

Water supply and distribution infrastructures are vital for current life. They have a significant role in public health, providing safe water for drinking and human consumption as well as for essential non-potable uses such as fire fighting. These diverse objectives create challenges for everyone who must address in some way the actual performance of the system. This research critically evaluates all common objectives of conventional design approaches and evaluates the advantages and drawbacks of various performance measures. New ideas for a more realistic and comprehensive approach to the design, operation assessment of WDS are proposed. A new approach, called a Risk-based Performance Assessment, for hydraulic performance evaluation is tentatively proposed. It is based on integration of reliability, resiliency, and vulnerability as three basic operational indices in the operation of WDS. Furthermore, the Total Life-cycle Cost evaluation approach is tentatively proposed based on considering all major costs of a WDS.

With advances in technology and the increasing use of power electronic components in the design of household and industrial equipment, harmonic distortion has become one of the major power quality problems in power systems. Identifying the harmonic sources and quantifying the contributions of these harmonic sources provides utility companies with the information they require to effectively mitigate harmonics in the system. This thesis proposes the use of observers for harmonic estimation and harmonic source identification. An iterative observer algorithm is designed for performing harmonic estimation in measured voltage or current signals taken from a power distribution system. The algorithm is based on previous observer designs for estimating the power system states at the fundamental frequency. Harmonic estimation is only carried out when the total harmonic distortion (THD) exceeds a specified threshold. In addition, estimation can be performed on multiple measurements simultaneously. Simulations are carried out on an IEEE distribution test feeder. A number of scenarios such as changes in harmonic injections with time, variations in fundamental frequency and measurement noise are simulated to verify the validity and robustness of the proposed iterative observer algorithm. Furthermore, an observer-based algorithm is proposed for identifying the harmonic sources in power distribution systems. The observer is developed to estimate the system states for a combination of suspicious nodes and the estimation error is analysed to verify the existence of harmonic sources in the specified node combinations. This method is applied to the identification of both single and multiple harmonic sources. The response of the observer-based algorithm to time varying load parameters and variations in harmonic injections with time is investigated and the results show that the proposed harmonic source identification algorithm is able to adapt to these changes. In addition, the presence of time delay in power distribution system measurements is taken into consideration when identifying harmonic sources. An observer is designed to estimate the system states for the case of a single time delay as well as multiple delays in the measurements. This observer is then incorporated into the observer-based harmonic source identification algorithm to identify harmonic sources in the presence of delayed measurements. Simulation results show that irrespective of the time delay in the measurements, the algorithm accurately identifies the harmonic sources in the power distribution system.

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Smart inverters have been considered the primary fast solution for voltage regulation in power distribution systems. Optimizing the coordination between inverters can be computationally challenging. Reactive power control using fixed local rules have been shown to be subpar. Here, nonlinear inverter control rules are proposed by leveraging machine learning tools. The designed control rules can be expressed by a set of coefficients. These control rules can be nonlinear functions of both remote and local inputs. The proposed control rules are designed to jointly minimize the voltage deviation across buses. By using the support vector machines, control rules with sparse representations are obtained which decrease the communication between the operator and the inverters. The designed control rules are tested under different grid conditions and compared with other reactive power control schemes. The results show promising performance. / With advent of renewable energies into the power systems, innovative and automatic monitoring and control techniques are required. More specifically, voltage regulation for distribution grids with solar generation is a can be a challenging task. Moreover, due to frequency and intensity of the voltage changes, traditional utility-owned voltage regulation equipment are not useful in long term. On the other hand, smart inverters installed with solar panels can be used for regulating the voltage. Smart inverters can be programmed to inject or absorb reactive power which directly influences the voltage. Utility can monitor, control and sync the inverters across the grid to maintain the voltage within the desired limits. Machine learning and optimization techniques can be applied for automation of voltage regulation in smart grids using the smart inverters installed with solar panels. In this work, voltage regulation is addressed by reactive power control.