Life cycle assessment of a secondary water supply (2003)

This study aims to assess the environmental burdens due to abstracting, treating, distributing, collecting and disposing (including recycling) water in an urban context. As such it intends to calculate and present the environmental burdens for a terrestrial pathway of the water cycle, i.e. from the abstraction of water from rivers through to the return of the same water (after it was used) to the sea. This project should be seen as a logical continuation of the work done for another WRC project (project No 1077) entitled The Use of Life Cycle Assessment in the Selection of Water Treatment Processes.

In addition to the global environmental impacts used by the LCA methodology this study also incorporates research on salination. This is an environmental impact which is important to the local context and which is related to the decrease of water quality in the water pathway under study. For South Africa it is important because salination requires additional treatment of water with consequent financial and environmental implications. It is considered one of the major environmental problems related to water in this country.

In the context of sustainable development, life-cycle assessment (LCA) is emerging as one of the tools of cleaner production. It is the only tool which has a cradle-to-grave approach and by this it avoids positive ratings for measurements which only consist in the shifting of (environmental) burdens (Kloepffer, 1997). Therefore, it provides a holistic view of the environmental impacts due to a product, service or activity. The LCA methodology enables the calculation of environmental burdens in a systematic and scientific way by regarding all the inputs and outputs of a system. Hence, it allows for comparison on environmental grounds. Due to these unique characteristics, this tool was used to assess the environmental burdens resulting from the abstraction, production and distribution of potable water as well as from the collection, treatment and disposal of wastewater. For each of these processes a particular case was investigated.

For the abstraction of raw water the Inanada Dam was used as a case study and a simplified LCA was performed. As such it looked at the major inputs and outputs from the construction of the dam as well as from operation. In addition aspects like change in land use and social impacts, not covered by LCA were investigated. For the treatment of raw water the two major water treatment plants (Wiggins and Durban Heights Waterworks) in the eThekwini Municipality were used as case studies. Environmental LCA scores have been calculated for both of them and an average LCA score for the eThekwini Municipality. For the distribution and collection of potable water and wastewater one particular network in a delimited area was used. Environmental scores have been calculated for the movement of one kiloliter of water/wastewater in this network. For the treatment of wastewater the Southern Wastewaterworks and the nearby Durban Water Recycling Plant were investigated. LCA scores have been calculated for the processes involved. The disposal to sea used as a case study the Southern Wastewater Works Outfall and additional toxicity tests have been performed not only for the outgoing wastewater but also for different effluent streams within the treatment works.