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No description available.

No description available.

Water is the most abundant substance in nature and vital for life activities. The major water sources for use are surface water bodies such as rivers and lakes, and underground aquifers and pore spaces down the water table (Ring, 2003). Water derived from these sources is not necessarily pure since it contains dissolved inorganic and organic substances, living organisms (viruses, bacteria, etc). For these reasons, water intended for domestic uses should be free from toxic substances and microorganisms that are of health significance (WHO, 2005). The availability and quality of water always have played an important role in determining the quality of life. Water quality is closely linked to water use and to the state of economic development (Chennakrishnan et al., 2008). Ground and surface waters can be contaminated by several sources. In urban areas, the careless disposal of industrial effluents and other wastes may contribute greatly to the poor quality of water (Mathuthu et al., 1997). In most developing countries, most areas are located on the watersheds which are the end points of effluents discharged from various industries (Oberholster and Ashton, 2008). South Africa, as a developing country, is experiencing rapid demographic changes due to urbanization, industrialization and population growth. The country has also been identified as being water-scarce, which can lead to a challenge of meeting the increasing water demand due to industrialization and urbanization. Such population growth increase may result in an increase in wastewater output, especially around urban areas.

Thesis (DTech (Electrical Engineering))--Cape Peninsula University of Technology, 2009 / The problem for effective and optimal control of wastewater treabnent plants is very important recently because of the increased requirements to the qualitY of the effluent The activated sludge process is a type of wastewater process characterized with complex dynamics and because of this proper control design and implementation strategies are necessary and important for its operation. Since the early seventies, when a major leap forward was made by the widespread introduction of dissolved oxygen control, little progress has been made. The most critical phase in the solution of any control problem is the modelling stage. The primary building block of any modem control exercise is to construct and identify a model for the system to be controlled. The existing full Activated Sludge Model 1 (ASM1) and especially University of Cape Town (UCT) models of the biological processes in the activated sludge process, called in the thesis biological models, are highly complex because they are characterised with a lot of variables that are difficult to be measured on-line, complex dependencies and nonlinear interconnections between the biological variables, many kinetic parameters that are difficult to be determined, . different time scales for the process dynamics. The project considers reduction of the impact of the complexity of the process model over the methods for control design and proposes a solution to the above difficulties by development of a reduced model with small number of variables, but still with the same characteristics as the original full model for the purposes of real time.

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Graduation date: 1997

Groundwater resources have become seriously threatened due to improper use by industrial, municipal, and even public sectors. Widespread contamination of aquifer systems has jeopardized human health and the environment and methods for restoring these systems are needed. Biological and chemical in situ remediation, where contaminants are degraded within the natural system, has become the foremost technique for cleaning up affected sites. However, before in situ remediation can be implemented, studies of the sites' physical, chemical, and biological characteristics must be done. Physical aquifer models (PAM's) were constructed for use in evaluating groundwater remediation strategies in porous media. The PAM's offer a unique approach for work of this kind, the most important of which are opportunity for conducting large-scale transport experiments under controlled conditions, and maintaining geometric, dynamic, and reactive similitude. The PAM's consist of aluminum reactors, 4.00 m (length) x 2.00 m (width) x 0.20 m (height), supported by a steel framework. Reservoirs at each end of the reactor permit adjustment of hydraulic gradient across its length. An array of 40 fully-penetrating wells allows versatility in sampling, injection, or extraction of solutes. Experiments can be performed under confined or unconfined, steady-state or transient conditions where temperature, pressure, and hydraulic gradient can be controlled. Plumbing design, well design, sampling protocol, and media-packing procedure were developed and tested in dye and bromide tracer experiments. The results of dye experiments in a water-filled PAM demonstrated the effectiveness of the inlet and outlet port design and construction of the wells. This was evident through control of a symmetrical plume that developed within a uniform flow field. Protocols for sampling, injection, and extraction using the well array were also effective based on observed dye plume development and bromide concentration contour plots. A new approach for packing sand was used to create a statistically equivalent homogeneous and isotropic porous media. Results of bromide tracer experiments indicate that this condition of homogeneity and isotropy was achieved. The PAM's worked well for creating the desired experimental conditions needed for studying transport of solutes (non-reactive in this case) in porous media. Additional experimental work will be done to develop and expand more of their capabilities (e.g. transient flow, confined conditions, heterogeneic media) for which they were designed. Remediation strategies will be investigated using the developed PAM's and it is hoped that results obtained from these studies will be successfully applied to field situations. / Graduation date: 1993

Phosphorus (P) is an important pollutant of concern in wastewater that causes eutrophication and algal blooms in water body. On the other hand, P is a valuable natural resource for agricultural and industrial use. With the rapid depletion of mineral phosphorus on earth, there is a need to recover phosphorus from wastewater. In this study, a new chemical and biological process facilitated with iron dosing has been developed for P removal and recovery during wastewater treatment. The system consists of a main stream identical to the conventional activated sludge process in an aerobic sequencing batch reactor (SBR) for P removal and a side stream of sludge recirculation through an anaerobic SBR (AnSBR) for P release and recovery from the P-rich sludge. In the aerobic SBR treating a synthetic domestic wastewater, Fe(III) (FeCl3) was dosed to remove P by precipitation and adsorption. Fe(III) dosing at a Fe/P molar ratio of 1.5:1 could reduce the P concentration from more than 10 mg/L to below 1 mg/L in the final effluent. Compared to other dosing periods, dosing Fe(III) right before the SBR settling could achieve the best result in sludge flocculation and P removal. Meanwhile, organic removal was well maintained as 90% of the chemical oxygen demand (COD) was degraded in the aerobic SBR. In the AnSBR, phosphate precipitated with ferric iron in the sludge was released owing to microbial Fe(III) reduction, and a positive correlation was found between the phosphate and ferrous iron concentrations in the sludge suspension. Chemical tests showed that significant P release from Fe(III)-P occurred only if the acidic condition and the reducing condition were combined. For the AnSBR sludge, a higher organic loading, lower pH and higher biomass concentration resulted in a higher level of Fe(III) reduction and P release. Organic acidogenesis prevailed in the reactor and lowered the pH to ~4.5, which facilitated the P release from the solid phase into the liquid phase. With a solids retention time (SRT) of 10 days, the anaerobic supernatant contained a phosphate concentration of up to 70 mg/L, while the settled sludge was returned to the aerobic SBR. The phosphate could be readily recovered from the supernatant with Fe-induced precipitation by aeration and pH adjustment, and the overall P recovery could be achieved at about 70%. In addition to the treatment performance, the speciation of P in the aerobic sludge and the anaerobic sludge also was investigated. A significant change in the immediately available P and the redox-sensitive P was found in the sludge through the aerobic-anaerobic cycle. Such chemical transformation is believed to be crucial to the P removal and recovery during the wastewater treatment process. / published_or_final_version / Civil Engineering / Master / Master of Philosophy