No description available.

Self-cycling fermentation (SCF) control was applied to a semi-continuous, aerobic, fixed-film reactor for the treatment of simulated and real brewery wastewater. The simulated wastewater was treated at 25°C. After approximately 3 hrs, 86% to 96% of the soluble BOD (SBOD) was removed, producing an effluent with a SBOD between 169 mg/L and 412 mg/L. The treatment of real brewery wastewater was undertaken at 25°C and 35°C, and was operated under ammonia-nitrogen deficient condition. 83% to 92% of the total BOD (TBOD) was removed after 3 hrs at 25°C, and after 1.5 to 2 hrs at 35°C. The treated effluent produced had a TBOD between 120 and 438 mg/L. The suspended solids in the treated effluent contributed between 63% and 71% of the TBOD. Hence, better treatment efficiency would have been possible if an efficient clarifier was installed, or the suspended solids were removed from the brewery wastewater prior to treatment.

Three systems for filtering polluted river water for use in subsurface irrigation have been designed, operated and evaluated. One system consisted of filtering the water through filter basins covered with grass. The second system used geotextiles in filter basins. The third system consisted of flooding a section of a field. In this system, the water was filtered as it moved through the soil towards the subsurface drainage/irrigation drain pipes. / It was found that grass filter basins are very efficient in removing sediment from river water. Grass filter basins having drain pipes placed in trenches 30 cm wide backfilled with sand gave the best results. More than 90% of sediments were removed from the river water. From the outflow measurements, it was found that less than 0.2% of the field to be irrigated needs to be devoted to the filtration system. / Important filter design parameters, namely filtration rates per unit area of filter basin and per unit length of filter trench and drain pipe, were determined. / Due to the fast clogging of the geotextile, filtration of river water through basins covered with geotextile was found to be impractical and expensive, as compared to filtration using water tolerant grasses as a basin cover. / Flooding a section of the crop land combined with controlled drainage was found to be an efficient way of irrigating maize crop. The yields obtained with this system were comparable with those obtained with conventional subsurface irrigation. Flood irrigation combined with controlled drainage would be particularly commendable on relatively flat fields which have subsurface drains.

High voltage treatment technology has been developed in this thesis and had initially shown promise in its effectiveness in reducing microorganisms found in water supplies. Initial testing found that the high voltage could destroy over 99.9% of the bacteria S. marcescens (a 3-log reduction). Cited literature on the effects of high voltage pulsed electric fields (PEFs) on various microorganisms have shown that high destruction rates of up to 9-log can be achieved. Thus by increasing the electric field strength or exposure time, or by improving the design of the electrode flow chamber, better results should be achieved using high voltage on water. However, contrary to this, upon further design improvements the 99.9% destruction threshold was rarely increased. The initial slow flow device of one litre-per-minute (1 LPM) was scaled up to flows of 10 LPM and 33 LPM. However, these faster flow devices were even less effective in the destruction of bacteria, destroying only 99% of S. marcescens (2-log reduction). No physical or technical design parameters could account for this low performance. One possible reason for these low results was in the preparation of the bacteria themselves. It was discovered that the growth stage of bacteria prepared for experiments had a large effect on the results. Bacteria harvested in the early growth stage could be nearly all destroyed by the high voltage (greater then 4-log reduction), whereas those harvested in the late stationary stage were much more resistant (less than 0.5-log reduction). Bacteria naturally occurring in water supplies will mostly be in a non-metabolising state. This implies that they will be more resistant to high voltage exposure than bacteria grown in a laboratory under standard testing procedures. Thus standard testing procedures for this device do not give accurate results. Further research into the mechanism behind the bacterial resistance is required to improve the performance of high voltage devices. A combination of different technologies may also prove effective in overcoming the resistance mechanism. These improvements are required before high voltage treatment can be properly developed and commercially exploited.

Fischer-Tropsch Reaction Water (FTRW) is a high organic strength wastewater produced as a by-product in Sasol’s Fischer-Tropsch Reactors. Typically it has an organic load of 18000 mgCOD/L and is highly acidic with a pH of approximately 3.8. It is deficient in nutrients (N and P and other micronutrients). This dissertation deals with the biological and physico-chemical model development of a dynamic anaerobic digestion model, and explores two different approaches to representing the physico-chemical processes that complement and interact with the bioprocesses. The performances of the resultant two dynamic models (ADFTRW1 & AD-FTRW2) were compared in order to assess to what extent the more detailed and rigorous ionic speciation modeling in AD-FTRW2 addressed the shortcomings attributed to the simplified physicochemical modeling in AD-FTRW1. The ionic speciation model used in AD-FTRW2 uses a classic equilibrium formulation along the same lines as in the UCTADM2 model for anaerobic digestion of municipal wastewater sludges (Brouckaert et al., 2010), while AD-FTRW1 uses a simplification of the approach developed by Musvoto et al. (2000) in order to represent short chain fatty acid (SCFA) dissociation and the weak acid base chemistry of the inorganic carbon system. A 44 day extract from a 700 day laboratory-scale dataset (Van Zyl et al. 2008) was used as the basis for comparing the models. During this period the membrane bio-reactor was subjected to varying flow and load conditions. To validate the models, the experimentally measured and model predicted process variables of reactor alkalinity, reactor pH, biogas production and effluent SCFA concentration were compared. It was found that AD-FTRW2 provided superior agreement with pH data, but predictions of alkalinity, gas production rate and effluent short-chain fatty acids were not significantly improved in AD-FTRW2 relative to AD-FTRW1. This outcome was hypothesized since pH is strongly dependent on physico-chemical processes such as ionic interactions in solution and gas exchange which were the components to the models (AD-FTRW1 versus AD-FTRW2) which differed most significantly. Alkalinity, which is also highly influenced by physico-chemical model representations showed substantial improvement however statistical analysis could not show this improvement to be significant. The other two variables that were compared, biogas production and effluent SCFA concentration, displayed very similar agreement with experimental data. These variables depend more on mass balance effects and biological kinetics and were therefore not significantly altered by the more rigorous handling of aqueous chemistry in AD-FTRW2. It was concluded that AD-FTRW2 constitutes an improvement in model predictive power over AD-FTRW1 at a small cost in computing time. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2013.

No description available.

The international year of fresh water represents the opportunity to look back at the seemingly irresistible movement toward privatization and at the devolution of State responsibilities in water and wastewater services. The welfare State appears to be increasingly ill-adapted to times dominated by globalisation and efficiency, while the market and the private corporations are presented as a panacea for solving the water crisis. But expectations of the market have not been met. This thesis analyses the debate over privatization of these services and the fondamental impacts on public values of introducing a market philosophy into this industry. Rather than witnessing a retreat of the State, its role is evolving although direct service provision is superseded by heavy regulation of the industry. In criticizing the neoclassical approach to the public good and regulation, the thesis argues that individualizing the process of valuing the public good fosters a culture of conflict and complexity that ultimately undermines our ability to formulate and achieve common goals. This creates an important accountability deficit. The need for environmental efficiency and democracy in an era of uncertainty requires that we search for means of expanding the reach of public values and thus suggests an even deeper reshaping of our governance structures, public and private.

In this thesis, a combination of laboratory experimentation under well defined conditions coupled with a kinetic modelling approach is used to verify the existence and respective kinetic rates of previously unconfirmed or postulated mechanisms that drive and limit dark Fenton (Fe(II)/H2O2) - mediated As(III) oxidation at pH 3 and 8 and dark Cu(II) - H2O2 - mediated As(III) oxidation at pH 8. Dark Fenton - mediated oxidation of As(III) at pH 3 is first examined and the effects of the variation in the concentration of reactants (As(III), Fe(II) and H2O2), oxygen, phosphate and organics (2 - propanol, formate, and citrate) are reported and analysed. The kinetic models developed for these systems show high applicability to full scale water treatment application and key mechanistic findings include the significance of the cycling of Fe(II) / Fe(III) via HO2 ???/O2 ??????, the effects of As(IV) termination reactions in the absence of oxygen and the retarding effects of phosphate due to the postulated formation of a Fe(III) - phosphate complex (at a derived rate constant of 2.2 x 106 M-1s-1, that also appears to have negligible kinetic activity in terms of reduction to Fe(II) by HO2 ???/O2 ??????). The work also demonstrates the significance of the free radical by products of formate and citrate oxidation by ???OH (HCOO???/CO2 ?????? and 3HGA???2???). The examination of the dark Cu(II) - H2O2 - mediated oxidation of As(III) at pH 8 with variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate and organics (2 - propanol, formate and citrate) demonstrated for the first time the high applicability of this system to the pre - oxidation of As(III) in water treatment and mechanistically that ???OH and CO3 ?????? are the dominant As(III) oxidants in this system. The As(III) oxidant CO3 ??????, is suggested to be generated by the interaction of ???OH and O2 ?????? with the carbonate matrix, at the respective rate constants of 4.9 x 107 M-1s-1 and 5.5 x 106 M-1s-1. Examination of the dark Fenton - mediated oxidation of As(III) at pH 8 and the effects of variation in the concentration of reactants (As(III), Fe(II) and H2O2), carbonate, organics (2 - propanol, formate and citrate) and Cu(II) demonstrates the varied potential mechanistic pathways in relation to the generation of As(III) oxidants from the Fenton reaction, Fe(II) + H2O2 such as Fe(IV) and CO3 ?????? and the previously dismissed ???OH, due to the presence of Fe(II) - citrate complexes. This work also demonstrates and models the enhancement of As(III) oxidation in the presence of an additional transitional metal ion, Cu(II).

Thesis (D.P.H.)--University of Michigan, 1994.

Thesis (D.P.H.)--University of Michigan, 1994.