A desalination guide for South African municipal engineers

Abstract

Municipalities need to develop Water Services Development Plans (WSDPs) as a first requirement in their budgetary process, and need to be made aware of the options that are available to provide more than basic services. While 25ℓ/person·d has been set as the minimum basic water supply and while many consumers receive far in excess of this amount, there are areas of the country where water of acceptable quality is not available for household use. However, in many areas adequate quantities of saline water may be, or are, readily available. This is especially the case for coastal cities and towns. The cost of treating water is only part of the total cost of making drinking water available to the consumer. This together with the fact that membrane technology is becoming more affordable and that energy can be recovered, makes the desalination of water viable for domestic purposes. A desk study, funded by the Department Water Affairs and Forestry and managed by the Water Research Commission, was undertaken to identify treatment options for desalinating seawater from both the Indian and Atlantic oceans or brackish water from boreholes. The specific objectives of the project were to compile a Guide on the technologies that can be implemented in South Africa to treat saline water to drinking water standards, to identify the pretreatment that is necessary, and to present guidelines on operational, maintenance, management and environmental aspects relevant to the selection and use of these technologies. An important aspect was also to quantify the capital and operating costs for planning purposes of the different components needed to successfully bring the water to the accepted standards for potable and domestic use. Of particular importance for the South African application was to identify the level of skills required for daily operation of the desalination plants, the level of skills required to provide technical back-up and advice, and to identify and advise on the competencies, training needs and capacity building required at operator and management levels. Lastly, the relevant local environmental legislations governing desalination were also identified.