Water Journal : Water Journal December 2011
water resources technical features 64 DECEMBER 2011 water • The significance of a number of environmental issues identified in this study demonstrates that greenhouse gas emissions are not an adequate proxy for the range of important environmental externalities associated with urban water system operations. • LCA provides a number of impact models that may enhance a broad- spectrum environmental analysis of urban water systems. A number of areas were identified where current LCA methodology for urban water systems analysis could be improved. Notably, LCA models should be extended to consider the significance of phosphorus recovery in the context of global minerals resource depletion challenges. • Similarly, regarding nutrient balances for any land application of biosolids and wastewater, existing LCA models suggest a potential for significant nutrient transfers to adjacent waterways. The likelihood and implications of achieving lower artificial fertiliser use also need to be considered. Quantifying fertiliser offsets and nutrient fluxes is subject to large uncertainties, and LCA in this area would be enhanced by guidance on best practice approaches to doing so in a regional context. • Other than Human Toxicity Potential, the impacts considered in this study associated with infrastructure construction are likely to be of secondary concern. This applied even for the relatively materials- intensive rainwater tank and 'third pipe' water recycling reticulation systems. • Wastewater treatment operations are the biggest source of most of the impacts considered, and may offer the greatest potential for reducing the overall environmental burden of the urban water system. Therefore, debates on the environmental implications of urban water system planning decisions need to have a wider focus than just the choice between water supply alternatives. • Wastewater and biosolids pollutants (chlorine, metals and organics) are the major source of potential ecotoxicity across the infrastructure lifecycle. Discerning the relative importance of these different contaminants is constrained by limitations with the available contaminant data, and the available LCA toxicity models. In this regard, further discussion of the LCA ecotoxicity models applied can be found in the full report from this study (Lane et al., 2011). • One of the benefits of the using the LCA approach is that indirect contributions to impact potentials can be tracked. Examples are transport (e.g. fuel use for biosolids and chemicals), mining and manufacturing (e.g. for treatment chemicals), which are responsible for substantial indirect contributions to the overall ecotoxicity potential associated with an urban water system. • Where direct water recycling systems (i.e. 'third pipe' or similar) and household scale rainwater tanks are under consideration, quantitative comparisons of urban water supply alternatives (such as by LCA) should include sensitivity testing for different end-use demand levels and system configurations. The results in our study suggest that assumptions on the supply-demand balance for these systems could be critical to their ranking in comparative assessment of different water supply options. Acknowledgements This paper is a condensed version summarising the outcomes of a research project funded by the Urban Water Security Research Alliance (UWSRA) in Queensland. The final report is available through UWSRA. For more information visit the website at: www. urbanwateralliance.org.au/. This paper is published with the permission of the Director of UWSRA. Assistance with data collection and review from a number of individuals, particularly those within the former Gold Coast Water (now Allconnex Water, Southern Region) and SEQWater (Water Secure), is gratefully acknowledged. The Authors Dr David de Haas (email: david. email@example.com) is an engineering technologist with GHD Pty Ltd (Brisbane) and also worked part-time as a researcher at the Advanced Water Management Centre, University of Queensland for the duration of this project. Joe Lane is an engineer and PhD Candidate at the Advanced Water Management Centre, University of Queensland. Paul Lant is Professor and Head of School, Chemical Engineering, at the University of Queensland. References Beal C, Stewart RA, Huang T & Rey E, 2011: SEQ Residential End Use Study. Water Journal 38 (1), pp 92--96. 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Institute for Sustainable Futures, UTS, Sydney. Talebour MR, Stewart RA, Beal C, Dowling B, Sharma A & Fane S, 2011: Rainwater Tank End Usage and Energy Demand: A pilot study. Water Journal 38(1), pp 85--89. Vieritz A, Gardner T & Baisden J, 2007: Rainwater TANK Model Designed for Use by Urban Planners. AWA Ozwater'07 Conference, 4--8 March 2007, Sydney. Willis R, Stewart RA & Emmonds S, 2009: Pimpama-Coomera dual reticulation end use study: baseline situational context and post commission end use prediction. Paper presented at Reuse09 Conference, 20--25 September 2009, Brisbane.
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Water Journal November 2011