Life cycle impacts of the Gold Coast urban water cycle

Quantitative life-cycle assessment (LCA) was used to consider the environmental burdens associated with the urban water cycle of the Gold Coast, Queensland, Australia. Detailed inventories were collected for all the major infrastructure types involved, in order to assess performance across a range of environmental and resource-use impacts. An analysis of the existing water cycle infrastructure shows that it is the wastewater management (collection, treatment and disposal) step that makes the biggest contribution to most of the environmental impacts. Across the whole water cycle, chemicals use should be included with electricity use and fugitive gas emissions as the biggest concerns from a greenhouse gas risk mitigation perspective. The results suggest that the ecotoxicological implications of agricultural biosolids reuse, and of marine effluent discharge, warrant further consideration. The irrigation disposal pathway made a lesser contribution to the toxicity results, and the contribution of metals far outweighed that of organic micropollutants in all water cycle flows. Both rainwater tanks and Class A+ recycling showed increased overall impacts (Global Warming Potential, Fossil Fuel Extraction, Toxicity) compared with the low energy dam supplies that are the norm. Reduced freshwater extraction is the key benefit from recycling and rainwater tanks, although the Class A+ model did not deliver any substantial benefits beyond those available from a rainwater tank. This finding is dependent on the low household water demand profile used, and might be different under other circumstances. The relevance of key data uncertainties is noted. In particular, fugitive greenhouse gas emissions, rainwater tank energy burdens, and the implications of nutrient land application, should be considered carefully in the water cycle planning process.