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University of the Witwatersrand (2011)

A decision support system for assessing the feasibility of implementing wastewater reuse in South Africa

Rotimi, Adewumi James

Titre : A decision support system for assessing the feasibility of implementing wastewater reuse in South Africa

Auteur : Rotimi, Adewumi James

Université de soutenance : University of the Witwatersrand

Grade : Doctor of Philosophy 2011

South Africa is a semi-arid country with low volumes of rainfall (average of 500 mm per annum) and high evaporation (approximately 85 percent of mean annual precipitation). The highly variable and spatial distribution of rainfall across the country adds to the sparse availability of fresh water. Stream flows in most South African rivers are at relatively low levels for most of the year, and the infrequent high flows that do occur happen over limited and often unpredictable periods. Coupled with this problem is continuous pollution of surface water with wastewaters generated from domestic, institutional and industrial activities. Community concerns about environmental pollution resulting from the quality of wastewater disposed to sensitive environments have led to pressures on the water industry to treat wastewater to higher qualities before discharging to water. As a result of the above, wastewater reuse for potable and non-potable uses increases globally. In South Africa, the shortage of water can significantly abated by the reuse of treated municipal wastewater through dual water reticulation systems. However, it is very likely that a water reuse project may fail if all the factors governing its implementation are not well addressed prior to its implementation. To achieve this goal, there is need to develop a decision support tool that would enable a balance between the social, economic, technical and environmental attributes involved in implementing wastewater reuse via dual reticulation. The aim of this research work is to develop a Decision Support System (DSS) for assessing the feasibility of implementing wastewater reuse systems for non-potable uses in South Africa. The DSS is classified into quantitative and qualitative modules. The quantitative modules consist of technical and economic assessment criteria while qualitative modules consist of environmental and social assessment criteria. Under quantitative assessment, technical assessment starts with the estimation of the volume of non-potable water needed for agricultural irrigation, urban, domestic, mining and industry and in other uses. This module therefore, provides the basis to justify a reuse project economically by quantitative estimation of the volume of recycled water needed for various activities. Other quantitative assessments include pollutant removal efficiency to meet reuse water quality, capital and O&M costs of the 33 unit processes from which the DSS can form a diversity of wastewater treatment trains. Treatment train qualitative is classified into technical (i.e. reliability, adaptability to upgrade, varying flow rate, change in water quality, ease of O&M and ease of construction) and environmental (i.e. power and chemical requirements, odour generation and impact on groundwater) criteria. The social qualitative module of the DSS contains simplified questionnaires that were developed based on the implications of the results obtained from the application of the Theory of Planned Behaviour (TPB) for potential domestic and institutional users at Limpopo (Capricorn and Vhembe) and Cape Town (City of Cape Town) provinces to determine factors influencing intention to accept/reject wastewater reuse for non-potable water uses. The Triple Bottom lines of sustainability (TBL) were also used to investigate the ability of the service providers to manage reused facilities successfully.


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