Relative sustainability assessment of five European projects aiming to reduce rainwater volume in sewer systems

Excess rainwater in sewer systems creates problems including sewer overflow leading to flooding, inefficient wastewater treatment, overloading of wastewater treatment plants, production of large amounts of sludge, high energy demands and non-replenishment of groundwater. These effects are a problem in areas where rainwater, runoff and sewage are collected in the same system, and are likely to be exacerbated by the effects of climate change and traditional methods of new development. The ‘No Rainwater In Sewers’ (NORIS) project comprises pilot studies in Sweden, Netherlands, Germany, Belgium and the UK, all of which attempt in different ways to return the hydrological cycle to a more natural state at a local level by adaptation of existing sewerage systems. The aim of the work presented here is to determine the relative contribution of the chosen techniques to sustainable development. The research illustrates the difficulties faced in urban water of addressing all sustainability principles equally and gives details on the development of a structured framework that will compare the water management options chosen and inform stakeholders of how decisions are made, which is not only necessary under the auspices of the European Water Framework Directive, but is also more rational in terms of sustainable development.