A comparative life cycle assessment (LCA) of water treatment plants using alternative sources of water (seawater and mine affected water).

Abstract

Water is a replenishing, yet at times scarce resource that is necessary for the growth and development of all organisms and plant life. In South Africa, the situation is challenging due to competing demands for limited fresh water reserves. Thus, the search for technological solutions is necessary to alleviate water shortages. Two of the potential measures to increase available water supply are desalination and reuse of water. As with any industrial operation, potable water production involves several processes which inherently impact the environment. These need to be taken into consideration in the design and management of water treatment operations. The purpose of the study was to conduct an environmental Life Cycle Assessment (LCA) of two water treatment membrane plants that use alternative feed sources namely seawater and mine affected water. The first plant will be located in the Southern area of the eThekwini Municipality and will utilise seawater reverse osmosis (SWRO) to produce 150 Mℓ/d of potable water. The second is a case study based on an existing mine water reclamation plant in Mpumalanga that is designed around a two stage ultrafiltration-reverse osmosis (UF-RO) process used to treat 15 Mℓ/d of mine affected water. The LCA guidelines, which were established by the International Organisation for Standardisation, were utilised for the purposes of this study. Design data was collected for both the construction and operation phases of the plants while SimaPro was used as the LCA analysis software with the application of the ReCiPe Midpoint method. The key findings from the assessment reveal that electricity production and consumption is responsible for the majority of environmental impacts that stem from the respective plants. A further analysis indicated that the South African electricity mix has greater environmental impacts than other energy sources such as photovoltaic and wind power. The integration of these energy systems with alternative water treatment processes has been proven to reduce environmental loads to levels associated with conventional water technologies. Based on these results, it is recommended that focus should shift towards energy minimisation techniques and the use of renewable energy sources in order to advance the environmental performance of water treatment processes.