A set of indicators for the assessment of temporal variations in the sustainability of sanitary systems

The sustainability of an urban water system was studied by application of a set of indicators that focuses on environmental issues and the efficiency and performance of the technical system. Temporal variations of indicators reflecting freshwater resources, drinking water, wastewater and by-products, were investigated for the water and wastewater system in Göteborg. Extended time series of precise data were available for quantitative indicators such as water consumption, energy use and discharge loadings. Qualitative indicators such as drinking water quality, sewage sludge quality and ecosystem status were more difficult to assess, a situation complicated by variations in criteria set in different countries. Although large urban water systems are often considered unsustainable, the set of indicators demonstrate that the water and wastewater system in Göteborg has moved towards a more sustainable status; recycling of nutrients to agriculture remains, though, a major concern.