A magnesium-plus-lime coagulation process, incorporating magnesium recovery by sludge carbonation, recently developed for water treatment has been tested for its application to the decolourization of kraft mill effluents. Total bleached kraft mill effluent (BKME), after biological treatment and effluent from the first caustic extraction stage of a conventional bleachery (E₁ or T-20 effluent) were examined in the laboratory. It was shown that a combination of low magnesium and low lime dosages can achieve better decolourization of kraft mill effluents than 3-5 times as much lime alone, (i.e.: 30-60 mg/1 Mg⁺⁺ plus 375-475 mg/1 lime (as Ca0) at pH ≃11.1 for BKME; and 150-300 mg/1 Mg⁺⁺ plus 1875-3750 mg/1 lime (as Ca0) at pH ≃12.1 for T-20 effluent.) Colour removals of 90-95% were achieved using either fresh or recycled magnesium. Results of the study showed that greater than 90% magnesium recovery can be attained by operating the sludge carbonator to a final pH ≃7.5, with complete mixing and a good C02 diffuser system provided. (Key words: magnesium, lime, kraft mill effluent, decolourization, colour removal, Magnesiurn Carbonate Process.) / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Feasibility of the biodegradation of neutralized-caustic potato peel waste by aerobic-thermophilic fermentation was examined. Fermentation temperature, pH, rate of solids utilization, dissolved oxygen and total organic nitrogen were characterized with respect to the fermentation process. Examination of these parameters showed distinct characteristic behaviour, though the parameter magnitude varied between the trials. The naturally occurring flora of thermophilic microorganisms of the potato was sufficient as an inoculum, with their propagation creating the fermentation characteristics. The solids content of the potato waste was reduced by the thermophilic fermentation with a noticeable improvement in the nitrogen content in the remaining residue. Protein and amino acid analyses supported the feasibility of using the remaining residue as animal feed. Increases in the nitrogen content of the substrate was assumed to be due to the conversion of atmospheric nitrogen by nitrogen-fixing microorganisms within the fermentation. Microbial identification indicated that these organisms belonged to the species Bacillus coagulans. No strains within this species have been previously reported to fix atmospheric nitrogen. It was concluded that an aerobic-thermophilic fermentation can be utilized as a waste treatment process for caustic potato peel waste. Besides the numerous advantages of an aerobic-thermophilic fermentation, the validity for the utilization of this fermentation process in the treatment of potato peel waste is the near total disposal of the waste. / Land and Food Systems, Faculty of / Graduate

The equilibrium phase diagram for the system sodium sulfate-methanol/water-sulfuric acid at 35° was determined. The nucleation, and growth characteristics of sodium sulfate have been studied in a laboratory scale crystallizer (Mixed Suspension Mixed Product Removal 'MSMPR') under carefully controlled conditions of supersaturation, temperature, agitation rate and residence time. From a statistical analysis of the data it was found that supersaturation, temperature, the interactions of supersaturation with temperature and agitation rate with temperature had positive effects on growth and nucleation rates, while agitation rate, residence time, the interactions of agitation rate with supersaturation, residence time with supersaturation had negative effects on growth and nucleation rates. The 'order' of the nucleation process, b, defined by B = K[sub= N]S[sup= B] was about 5. The growth rate, defined by G = K[sub= G]S[sup= c] Was first order (C = 1). For both processes the activation energy varied from 12 to 15 kcal/mol. The growth process was considered to be surface integration controlled for the various conditions tested. The nucleation rate was considered essentially to be homogeneous nucleation. A non-linear mathematical relationship was developed for both growth rate and nucleation rate in terms of the three factors, temperature, supersaturation and residence time. In both the growth and nucleation rate models the measured data fit poorly. This indicates that the model (a reaction rate type) poorly represents the data for crystallization found in this study. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Includes bibliographical references / The trade in and management of electronic waste in Nigeria is significant because of the volumes of e-waste generated from second-hand electrical and electronic equipment (EEE) imports. Current and future e-waste discourse advocate the need for, not only an effective legislative approach, but also a sustainable approach towards e-waste management, best encapsulated through a concept known as the 'Extended Producer Responsibility (EPR)' approach. The EPR approach, which is based on the Polluter Pays Principle (PPP) places legal, financial, informative and physical(including environmental) responsibility on producers of EEE, from 'cradle-to-cradle.'The thesis groups this classification into a general term - the 'EPR Matrix,' which is utilised throughout the thesis to analyse the realistic implementation and enforcement of these responsibilities on a producer in a developing country context. Although the shipment of e-wastes between developed and developing countries is regulated under the Basel Convention 1989 and the Bamako Convention 1991, both treaties, however, do not prohibit it. The efforts of Conference of Parties (CoP) to both Conventions reveal a cognizant change in perception which is aligned with the ideals of the EPR approach to e-waste management. The realistic implementation of this approach in a developing country context is investigated, because the importer, rather than the producer is the key actor in the EEE chain. The identification of this circumstance requires that the EPR approach be extended to include the importer and other actors in the EEE chain, sharing applicable responsibilities proposed by the EPR Matrix. The thesis explores the legitimacy of this premise, by evaluating the relative success of mandatory and voluntary EPR schemes on e-waste in South Africa. Although empirical investigation reflected in the thesis reveals that voluntary industry approaches on e-waste are effective and complementary to the regulatory model, this thesis also identifies a three-tier voluntary model for effective e-waste management in South Africa, and the scope of its application. Current e-waste legislation in Nigeria reflects the adoption of the EPR approach, but in essence, the provisions are ineffective, with the absence of requisite institutions to implement its provisions. This thesis suggest that Nigerian e-waste legislation be reconsidered, with a formalization of informal e-waste markets to reflect a more resolute approach towards illegal e-waste imports and management. The certainty of a successful, and effective EPR approach in Nigeria requires a synergy of both voluntary and mandatory approaches to e-waste in that jurisdiction, and an extension of the EPR concept to include other stakeholders in industry - producers, importers, retailers, consumers and government. This thesis thus recommends the adoption of both voluntary and mandatory approaches to e-waste management in Nigeria, including an institutionalized approach, which requires the establishment of collection centres for e-waste recycling, the establishment of an EEE registry/database and proper regulation of the informal sector.

Against a background of a chemical engineering degree and a few years of industrial experience, I undertook this M.Sc. degree with the conviction that chemical engineering skills have a unique role to play in addressing environmental problems of pollution generated by industrial activity. Moreover, given that, of industrial activity, it is chemical processing industries (CPI) and mining industries which are the major contributors to generation of waste, hazardous waste in particular, it is appropriate that the chemical engineering profession, which populates such industry activities, should assume such responsibility. In response to increasingly vociferous demands for more stringent environmental control over industrial activity, and regulatory compliance with stricter constraints on emissions of pollutants, there is a tendency to rely on readily available end-of-pipe solutions to resolve environmental management problems. This strategy is embodied in current practices in South Africa at effluent treatment- and landfill disposal facilities. Yet this is a costly solution in the long term, with implications for increasing operating costs, investment costs for development of new facilities, as well as closure and potential liability costs for old facilities. Furthermore, this strategy fails to address problems of resource depletion and the potential for resource recovery from materials considered to be "waste". Waste minimisation offers an alternative waste management strategy which seeks to reduce the generation of waste before end-of-pipe management is required, and to recover resources for reuse, thereby reducing resource consumption. The Department of Environment Affairs in the South African government has recommended that there should be research in the application of waste minimisation. While clearly there is a need for fundamental research into particular technological problems (such research is being undertaken at some institutions), the approach I adopted was to investigate potential for effecting meaningful waste minimisation solutions using procedures and techniques which constitute popular waste minimisation assessment methodologies. I focused specifically on small and medium scale industry operators which traditionally do not employ chemical engineering skills and which need a practical tool to improve in-house environmental management capability.

Includes bibliography. / This thesis attempts to resolve some of the major problems associated with lime treatment in waste water reclamation. The contribution to knowledge is briefly outlined below. One of the major problems associated with lime treatment is the instability of lime-treated effluent, which may result in serious calcium carbonate scale formation problems. In the thesis this instability is attributed to two fundamental causes, (1) Incomplete precipitation, i.e. a kinetic problem. (2) The unintentional absorption of carbon dioxide from the air by the highly alkaline lime-treated effluent, i.e. a contamination problem. Calcium carbonate and magnesium hydroxide precipitation are time dependent. As a consequence of this time dependency unstable effluent may be produced under reaction conditions commonly encountered in practice. An exhaustive study identified the major factors affecting the precipitation kinetics. Reaction system conditions required for producing a stable effluent are, (1) Lime slurry and sludge, in that sequence, must be thoroughly mixed with the waste water, preferably by means of in-line static mixers, before discharge to a completely stirred tank reactor. (2) A completely stirred tank reactor with a minimum mean residence time of two minutes must be provided for the dissolution and precipitation reactions to go as near to completion as possible. (3) The reactor contents must have a sludge concentration of the order of 10 000 mg l⁻¹.

In 2010 the city of Cape Town partnered with the Department of Environmental Affairs to initiate a project to investigate and evaluate the possible re-opening and licensing of Historic and Old landfill sites. The project to reassess these landfill sites is due to the fact that the three main operating landfill sites in Cape Town are nearing capacity. This calls for the city to re-imagine its waste management infrastructure. Meanwhile, within the urban areas of Cape Town, there exists a network and constellations of informal waste pickers working in conjunction with buy-back centres and recyclers to form an economically, environmentally and socially sustainable solution that diverts volumes of recyclable waste from landfills. These informal waste pickers contribute to filling in a gap within the formal recycling system but there is no infrastructure supporting these individuals on whom the formal recycling industry depends on. Most of the waste pickers sleep 'on the streets' with little access to amenities such as water, toilets and washing facilities. The spaces they occupy/sleep make it hard to store their pickings and hence they are forced to sell as soon as they collect. It also forces them to make multiple trips to the buy-back centres whom they are always at the mercy of, particularly when the ever changing price of recyclable waste is low. This project aims at creating a productive landscape that uses waste as a vehicle to enhance the livelihoods of informal waste pickers and encourage local communities to see the economic and environmental value of recycling waste. By providing secure storage and sorting, safe/hygienic sleeping and cleaning spaces coupled with social and productive areas; the project seeks to unlock the potential of recycling using a suitable architectural intervention that is self-sustaining.

The objective of this thesis is twofold - (1) to design the unit processes for treating the waste from a specific industrial plant using the best practicable technology, and (2) to critically examine the theory of these unit processes for utilization in design. The industrial waste was derived from a synthetic button and textile trimmings factory producing polyester and casein buttons. The effluent has a high pH and COD; contains metallic poisons; and is highly coloured. It exceeds the limitations for effluent quality promulgated by the Cape Town Municipality before discharge to the sewers. A certain measure of pretreatment before discharge to the sewers was therefore required. The treatment process eventually selected consists of neutralization; flocculation; sedimentation; sand filtration of the sludge; and atmospheric drying of the sludge.

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The main focus of the project is to tell the story of waste - to improve awareness and to help people grasp the colossal problem of landfill space running out! Currently, only 5% of the 3 million tons of waste, produced by Tshwane per year, is being recycled at landfill sites and yet 80% of the waste is recyclable! (Dekker, F. 2012) Where will we go with all of our waste when there’s no space left for landfill sites? What would happen if landfill sites start to take over our parks and green open spaces?! We need to start thinking green and recycle in order to prevent this from happening. The idea behind the design is to change the visitors’ perception of waste by allowing the visitors to go through a process of discovery in order to experience and become aware of the problem and value of waste in a fun and exciting way. The project is multifaceted with a variety of activities and spaces that contribute to the story of waste being told - educating the visitors about the endless possibilities of recycled waste and how they can make a difference by recycling and using waste as a resource. / Mini Disserration (ML(Prof))--University of Pretoria, 2013. / Architecture / unrestricted