Sustainable subdivisions - Construction Innovation

Factors affecting technology selectionOccupancyHousehold occupancy patterns infl uence the volumes ofpotable water consumed and wastewater produced. Keyfactors when selecting water-servicing options are:• Per-capita mains water consumption andwastewater generation decrease with increasingoccupancy levels.• Trends are for lower occupancy per dwelling andhigher dwelling density per land area. Averagehousehold size in SEQ of 2.6 persons in 2001 isdeclining to estimates of 2.45 by 2011, and 2.29 by2026 (SEQ Offi ce of Urban Management 2005).Socio-economics and regulatory environmentOther factors which can infl uence the adoption ofparticular technologies include socio-economic andregulatory infl uences. For example, the perceivedbenefi ts of particular technologies, the direct costs andongoing costs relative to centrally supplied water, thelevel of government subsidies and legislative ease ofimplementation, can all affect technology uptake.Implementation and management strategyManagement strategies adopted infl uence theprobability of successful implementation of moresustainable water services. Currently, stormwater,wastewater and mains water supply are largelyseparately planned. This acts as a barrier toimplementing integrated water services (Mitchell 2004).Mitchell found successful projects often involve a highlevel of public involvement and strong partnerships,alliances or project champions providing impetusto see the project through to completion. Hence,implementation of alternative water services requiresattention to existing, as well as new, managementstrategies.Technology assessmentThere are a wide range of alternative water-servicingtechnologies available, including systems for thecollection and use of rainwater and stormwater, andthe treatment and use of greywater and wastewater.The task of assessing which type of technology isappropriate is a complex task and is not the focus ofthis report. The suitability of any particular technologywill be infl uenced by a number of factors includingthe scale of application (e.g. from household tosubdivisional level) as well as the performance requiredand operational and maintenance needs. This reportfocuses on the benefi ts of the technology in terms ofthe urban water cycle and on operational, practical andassociated issues associated with implementation.There are a number of methods which can be used togive a thorough and detailed assessment of the differenttechnologies and aid in technology selection. Tools thathave been used previously for assessment of optionsinclude:•••••water balance analysiscontaminant balance analysislife cycle costing (LCC)life cycle assessment (LCA) covering energy,materials and emissionsrisk assessment and management.Water and contaminant balance assessment oftechnologies should consider impacts on the entireurban water cycle, particularly with regard to waterfl ows and quality. This sort of assessment can evaluatethe ability of a technology to meet IUWM objectives,such as reduction in mains water usage or return ofsurface fl ows to pre-development conditions.LCC is a process to determine the sum of all thefi nancial costs associated with a technology, includingacquisition, installation, operation, maintenance,refurbishment and disposal.LCA is an objective process to evaluate theenvironmental burdens associated with a product,process or activity from ‘cradle to grave’. This is doneby identifying energy and materials used and wastesreleased to the environment.There are many risk assessment and managementprocesses which are applied to urban water systems.The assessment of health, environmental, social,institutional and political risks should also be includedin an IUWM process.5