UN World Water Day 2023: How municipalities can accelerate the water transformation

The last summers of persistent heat and drought have shown that the water transformation must also gain momentum in Germany. Scientists at ISOE – Institute for Social-Ecological Research are investigating how sustainable water supply can be achieved in municipalities, for instance through the consistent use of service water in the building sector, including existing buildings and not just newly built ones.

The sustainable use of water is one of the central goals that the UN wants to achieve by 2030. And due to the increasing pressure on water resources time is pressing. Bottlenecks in the availability of good quality water in sufficient quantities are becoming ever more frequent, not only in drier regions of the world. Even in water-rich countries like Germany, drinking water sometimes becomes scarce regionally, especially in phases of prolonged heat and drought. “The economically use of drinking water is becoming increasingly important in view of climate change and is already practized in many areas,” says ISOE researcher Martina Winker. “We cannot, however, speak of sustainable water use as long as high-quality drinking water, which is treated at great expense of resources, is still used in large amounts on a daily basis for flushing toilets.”

Crucial for the water transformation, she says, is that the drinking water tap is not turned on for all kinds of purposes, be it in the industry, in commercial, public or residential buildings. “We have to get to the point where so-called service water can be used depending on the quality required,” says Winker. Service water is obtained from rainwater or from only slightly polluted household water and is suitable for example for flushing toilets.

“Municipalities can accelerate the water transformation if they promote the consistent use of service water in public and domestic buildings as well as in trade and industry.” To achieve consistency, we need apartments with piping systems that allow service water to be treated and used separately from drinking water. It is technically feasible and already being done in new construction areas and should become standard, also in existing buildings. “The transformation of water infrastructures in existing buildings is certainly a challenge for municipalities, but implementable in the long term,” says Winker.

Sustainable water use through the transformation of infrastructures in existing buildings

Forcing the use of service water in new building areas alone is not an option for the water researcher, because this would not constitute a sufficient contribution to change. However, Martina Winker also knows: “A transformation to service water systems in existing buildings faces many hurdles and resistance, because it sensitively targets the status quo.” Conventionally, all wastewater from households is piped together to a central sewage treatment plant, regardless of whether it is heavily contaminated toilet water or slightly polluted water from the kitchen or bathroom. At the treatment plants it is purified at great expense before it is discharged into the water bodies. “A sustainable water supply means turning away from the costly follow-up treatment of wastewater. Not only is this saving drinking water, but it can also be less energy-intensive to separate different water flows and qualities that are already in the building and to treat them in a way that is adapted to the structural situation,” says Winker.

In several research projects, Winker has determined the potential and environmental effects of the use of service water and found a high level of acceptance among users. “The preconditions for the transformation of water infrastructures are already in place, and the alternative solutions have long been technologically feasible, even in existing buildings. What is missing are municipalities that take courageous decisions and bring innovation to a wider public.” In a recent study, Martina Winker and her colleague at ISOE Engelbert Schramm looked at the need for research and development that could accompany and promote such decisions. This includes further studies concerning pipeline systems that keep the costs and effort involved in conversion as low as possible, or studies on environmental performances.

Winker and Schramm also see the need for information tools that enable political decision-makers in the municipalities to identify good windows of opportunity for the conversion of existing buildings. To obtain a good basis for decision-making, they also recommend for municipalities to draw up a water management master plan concerning the operational water supply for their municipality or city.

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