Water Journal : Water Journal May 2011
my point of view Ted Gardner's approach will be necessary for us to effectively disseminate the operating knowledge gained from them. Therefore, while small-scale distributed systems may have significant potential benefits, they still face significant challenges and have not yet been widely implemented. Instead, large-scale reuse systems and desalination plants have been used to address the shortfall in supplies. Desalination Plants The case of seawater desalination plants is interesting with respect to sustainable water systems, as the energy required for production makes this water energy intensive. However, the greenhouse gas emissions from Australian desalination plants are largely offset by green energy sources, and if we are willing to accept this as a valid approach to reducing greenhouse gases, then the greenhouse gas emissions associated with this water are similar to that of dam waters or from inter-basin transfers. Furthermore, these plants do not always operate. For instance, the Sydney desalination plant operates intermittently, shutting down when the reservoirs are full and only producing water when the reservoirs are low. Such an approach to operation reduces overall energy use, but also leads to underutilisation of the asset. Similar operating protocols are also in place for the indirect potable reuse scheme in Brisbane, which only delivers water to the drinking water system when reservoirs are low and community acceptance is higher. The flexibility of these systems to deliver water only when required comes at the expense of redundancy in the system, increasing costs. Such redundancy may also be present in small-scale water systems, for example, the use of potable water as backup for rainwater tanks or stormwater systems. Therefore, perhaps the need for redundancy in the system is something that requires an effective communication campaign as an outcome of moving towards systems that are more sustainable, cost being a trade-off for lower energy use and water security. Future Strategies So what does this mean for the future of water systems in Australia? We currently have seawater desalination and large-scale water recycling plants for another 20--30 years, and small-scale distributed systems still have significant challenges before they can claim to outperform large-scale systems. They also need to compete against demand management and peak levelling approaches in areas requiring significant augmentation of their networks. However, the potential for lower-energy water transport that exists for distributed systems, and their ability to address stormwater discharges, still makes them interesting to consider. Perhaps we should use the time before the next renewal phase of our large systems to ascertain if the potential of distributed systems can be realised and how other strategies can be implemented in a more sustainable way.
Water Journal April 2011
Water Journal July 2011