10 20 Time [d]
Chapter 7 Conclusions and Recommendations
7.2. Key questions revisited
bottled water. In that instance it was better to provide a potable water supply to all consumers than to separately provide bottled water for drinking purposes only. This was due mainly to the large burden associated with the production of the bottles.
One of the most important outcomes of this thesis is the development of a framework for the sustainable expansion of a water and sanitation system. This framework serves as an addition to the existing framework for 'Appropriate Solutions For Water Supply and Sanitation'. This addition allows decision makers to include sustainability criteria when considering expansion options.
7.1.2. Important limitations of these conclusions
While LCA is a valuable environmental tool it is not the right tool for evaluating all environmental impacts. For the analysis of the dam environmental impact assessment is probably a better tool as LCA neglects impacts such as changes in bio-diversity and downstream river morphological effects. For the other water and wastewater treatment process LCA provides a good representation of their environmental impact. The use of LCA in water treatment processes is well documented and its focussing ability is a valuable tool.
The use of a non South African database to calculate the magnitude of the impacts results in some inaccuracies. However for the important emissions from the generation of power these measurements are close enough to the GaBi database to be used.
occur during the construction phase of a project (e.g. Inanda Dam). These impacts are hard to quantify but were presented in order to provide a more complete picture.
The results of the LCA in Chapter 6 showed that in terms of South Africa's environmental total environmental profile, the contribution from water and sanitation is small (less than 1%).
Therefore in the global .scheme of things water and sanitation should not be prioritised as being a sector with a large environmental burden and targeted for emissions reduction. However, with the current pressure on cities to ensure that their growth is sustainable it is important that future expansion to water and sanitation infrastructure be done in accordance with the sustainability framework developed in Chapter 6.
Regarding the social impacts, the social impact of not providing proper water and sanitation facilities is undoubtedly high and this was not considered by this study as it was taken as a given that water and sanitation services will be expanded. The impacts of the different sanitation methods were investigated. It was found that on-site sanitation methods had the lowest burden, however, this cannot be used in an urban environment. In an urban environment where sewer bourne sanitation is used it was revealed that the majority of the environmental burden could be traced to the activated sludge units due to the high electricity use. Therefore this unit should be the subject of an improvement analysis.
What are the main contributors to this?
The main contributions to the environmental impacts come from the use of electricity during the operations phase of each the system. For the social impacts the main impacts occur during the construction phase and in particular from the health impacts associated with the generation of electricity. This led to the development of an electricity index which can be used to measure environmental performance.
Are there ways of reducing this load and if so by how much?
An improvement analysis was carried out in Chapter 3 to see how the existing system could be improved. This analysis showed that large environmental savings (up to 80 percent for some sub-systems) could be achieved by making modifications which made the processes more energy efficient. Examples of some units that were targeted for improvement were the ozonation and activated sludge unit. In the case of the ozonation unit it was found that by limiting the airflow to the thermal destruct unit a 70% reduction in electricity usage could be achieved without compromising the performance of the unit.
The operating parameters of the activated sludge unit were investigated and the unit modelled to see the effect of changes. By optimising parameters such as sludge age, wastage rate, aeration levels and recycle rate it was shown how the environmental performance of the unit could be improved.
When examining the system as a whole in Chapter 6 two basic steps for improving the environmental performance were suggested. These are an efficiency analysis and a water demand management program.
How can the water and sanitation service levels be increased? What is the most environmentally friendly way of doing this?
If one had to rank the best way of increasing the water and sanitation levels in a municipality one would first implement a review of how the system is operated and then, if possible, try to maximise the use of existing assets. The second step would be the introduction of water recycling schemes. These schemes can be for the provision of industrial and potable grade water, however it should be noted that where possible the quality of supply should be tailored to the needs of the consumer. Finally the construction of new infrastructure should be considered.
In Chapter 6 a framework for municipalities expanding there provision of water and sanitation services was developed. This outlines how water and sanitation service levels can be increased in a sustainable manner.
What is the net effect of providing recycled water in Durban? Is this the best way of increasing the water supply? The results of the scenario analysis (Figure 6-9) show that it is clear that for both scenarios A and B (waterborne and onsite sanitation), Option 2, the recycling option is the best. Option 2 has already been implemented in the eThekwini Municipality and the results are based on operational data. The results prove that the addition of the recycling plant has reduced the environmental impact of water and sanitation provision in the eThekwini Municipality. An important aspect that the study highlighted in the investigation of Option 3 (new infrastructure option) is the importance of proper planning when constructing a dam. Dams should only be constructed if there is sufficient demand for the water that they can supply otherwise they act as greenhouse emitters for no return. Thus one should always aim to use a dam to its maximum capacity to get the greatest return for the environmental damage being caused.
The question of whether recycling water is socially acceptable is not relevant to this study as the recycled water is only utilised for industrial use and these users are mainly concerned with the
price and quality of the water rather than the source. The social impacts of the provision of recycled water were analysed in Chapter 4. The analysis showed that overall recycling had a small impact when compared to the impacts associated with the construction of new infrastructure such as dams.