Water Journal : Water Journal December 2012
refereed paper small water & wastewater systems water DECEMBER 2012 67 during the life of the Master Plan. Instead, 10 case studies were selected from the 34 filtered opportunities for more detailed analysis to represent a cross- section of sources and project scales. Multi-criteria analysis was undertaken to assess each case study scheme according to financial and other criteria, both quantitative and qualitative. Financial analysis Financial analysis estimated the cost of building, operating and maintaining each case study scheme from the perspective of both a water service provider and whole of society perspective. A comparison of estimated capital costs, operating costs and business costs was summarised within preliminary business case analysis undertaken for each case study, with the results presented in Figure 9. The costs are compared against the potential recycled water supply capacity of each scheme. Figure 10 compares estimated levelised costs (i.e . the present value of recycled water in cost per kL). It is important to note that levelised costs for the purpose of comparing the case studies in the MCA are whole-of-society costs, but exclude business costs and revenue as these were difficult to estimate accurately. Multi-criteria analysis The City of Sydney invited a range of stakeholders to participate in the development of assessment criteria and weightings for Multi-Criteria Analysis (MCA) to be used to compare conceptual options. The MCA results clearly show the need to consider multiple supply sources and local considerations. Sewer mining and stormwater suggested preferences are comparable, however, for very different drivers. For example, carbon intensity values support stormwater and thermal desalination, and network intensity supports sewer mining and thermal desalination (due to the volumes of demand that can be satisfied). Table 2. Case study summary. Name Demand GL/yr Key Infrastructure Sewer Mining 1.1b 0.4 1.2ML/day wastewater treatment plant Sewer Mining 1.2b 8.1 3 advanced wastewater treatment plants with a combined capacity of 22ML/day Sewer Mining 1.2e 3.1 8.5ML/day advanced wastewater treatment plant Sewer Mining 1.2h 0.8 2.2ML/day advanced wastewater treatment plant which may be co-located with the proposed trigeneration plant Sewer Mining 1.5c 2.1 5.7ML/day advanced wastewater treatment plant which would be co-located within the Green Square development. Stormwater Harvesting 2.3a 0.5 12ML surface storage pond with treatment suitable for internal and external use Stormwater Harvesting 2.7a 0.5 8ML sub-surface storage with treatment suitable for internal and external use Stormwater Harvesting 2.8a 0.5 Existing and proposed storages with treatment suitable for supplying the surrounding Alexandria Canal area. Roof Water Harvesting 3.2a 0.1 8.5ML sub-surface storage main running the length of the facility providing both storage and pre-treatment and distribution of the harvested roof water. Thermal Desalination 5.1a 2.0 Extraction of raw seawater from Sydney Harbour and delivery to a 5.6ML/day thermal desalination plant Figure 9. Case study cost comparison. Figure 10. Levelised cost (whole of society perspective).
Water Journal February 2013
Water Journal November 2012-1