Water Journal : Water Journal April 2011
water APRIL 2011 133 water supply options Most options were considered flexible and able to be upgraded. The decentralised system scored lower as the pipes would be sized for individual system requirements and not for additional capacity. New users to a decentralised scheme would also require new infrastructure. Safety was assessed in terms of water quality and operability. Water quality was assessed quantitatively using industry and published data on typical characteristics. Centralised systems also scored higher than localised, as it is easier to manage safety on a single site. Environmental impacts (qualitative & quantitative) The volume of waste generated was estimated quantitatively based on the likely liquid or solid residual production. Option 29 ranked highest due to its closed loop nature and low use of sewage. Option 21 and 18 scored well as the water was largely groundwater and the only waste stream was brine concentrate. The footprint score was based on treatment infrastructure requirements which were similar for all options, except Option 29 which was smallest, and pipeline easements. Options using WTP water ranked lowest due to 23km of pipeline from WTP to ATP. Options 3 and 15 scored slightly better for approvals as the consent for the Altona Recycling Plant may be utilised, and therefore no new land is required and the ATP is zoned for this use type. The main issue for Options 3 and 15 would be consent for the WTP to ATP pipeline. The impact on local ecology was based on discharges. The impact on groundwater was based on the volume of groundwater being extracted with respect to the estimated volume of groundwater available. Social/community impacts (quantitative & qualitative) Heritage maps were used to locate areas of heritage and cultural significance in the Altona area, and identify which options overlapped these, and how significantly. The aesthetics took into account noise, odour and plant appearance. The appearance considered size, as all plants would be designed to blend with the surroundings. Options using raw sewage scored lower than other options due to the likely generation of odour. Traffic disruption considered the number of major road crossings. The localised options fared better in this criterion, due to having no major road crossings. Options using WTP scored lower due to the 23km pipeline. Community and social acceptance was based on the perception of the operators and the public. While use of recycled water is preferable to potable water, the use of sewage has not always been seen favourably in the past. However, these issues can typically be addressed through community engagement and education. The community education category considered this. Energy use (quantitative analysis) Energy use was based on the operational requirements of the pumps and treatment plants. The numbers were estimated using CPES (CH2M HILL's Proprietary Cost Estimation Tool) which has a GHG calculator function. Multi-Criteria Analysis Results The top five options identified through MCA are presented in Figure 2. Option 3 scored well in most of the categories, as did Option 2, whereas Options 19 and 11 scored particularly well in the water supply criteria. Cost-Benefit Analysis (CBA) Capital and annual operating costs were developed using CPES. Net Present Value (NPV) utilising these numbers was then developed. The NPV was based on Capital Cost expenditure spread evenly over two years, and Operating Costs from Year 3, a plant life of 35 years and 5.1% per year discount rate using the City West Water NPV calculation model. Table 3: Summary of key and sub-criteria and weightings. Key criteria Primary weighting (%) Sub-criteria Sub weighting (%) Water supply 40% Water quality 50% Water quantity (yield) and security of supply 50% Operability 20% Proven technology 35% Ease of operation 35% System flexibility/ability to upgrade and extend 15% Safety 15% Environmental impacts 15% Volume of waste generated 20% Footprint of plant and infrastructure 20% Approvals required and transfer of land use 30% Impact on local ecology 20% Impact on groundwater 10% Social/ community 15% Heritage sites (non-cultural) 15% Aboriginal and cultural heritage 20% Aesthetics 15% Traffic disruption 20% Community/social acceptance 15% Community education opportunities 15% Energy use 10% Energy requirements 50% Greenhouse gas (GHG) emissions 50% TOTAL 100% Figure 2: MCA results for alternative water supply options.
Water Journal March 2011
Water Journal May 2011