EU researchers say cities could cut freshwater withdrawals by up to 60% by fixing leaks, reducing household demand and reusing treated wastewater, as parts of Europe face increasing pressure on water supplies.
Around 40% of the EU population is affected by water scarcity, the European Commission noted in a release on Tuesday.
Managing the risk of municipal water supplies running low is particularly relevant in heavily populated urban areas, it added.
European water policy is based on the Water Framework Directive, and the European Commission has set out a 2025 Water Resilience Strategy that promotes water security and a more circular approach to managing water, according to the Commission’s environment department.
A study summarised by Science for Environment Policy examined how urban water utilities could reduce the amount of freshwater they withdraw from sources such as rivers and groundwater aquifers.
It said many utilities still operate “flow-through” — or open-loop — systems, where water is taken from nature, delivered to customers, wastewater is treated, and then discharged back into local water bodies without being recycled for further use.
The researchers built a simulation model based on a hypothetical city in a high-income country, comparing a baseline open-loop system with several circular options, including cutting leakage, lowering residential water use through education measures, and turning treated wastewater into potable — drinkable — water.
Reusing treated wastewater makes the biggest difference
In the baseline scenario, the model assumed households used 200 litres of water per person per day, leakage was 30% between the raw-water intake and customers, and non-residential demand was 100,000 cubic metres, the Commission informed.
Combining three measures — reducing leakage to 10%, lowering household demand from 200 to 130 litres per person per day, and reusing 60% of treated wastewater as potable water over longer timescales — reduced freshwater withdrawals by up to 60% compared with the baseline.
System-wide costs were also lower than the open-loop system, despite spending needed on infrastructure repairs and upgrades.
Recycling treated wastewater had a larger effect than focusing only on reducing demand and leakage.
The Commission described potable reuse as a shift towards a closed-loop system, in which some water entering the network does not leave it.
Adding a desalination plant — taking 200,000 cubic metres of seawater per day to produce 100,000 cubic metres of potable water — reduced raw-water extraction by a further 14%, bringing the total reduction to 74%.
Costs rose by 3% compared with the open-loop system, and the researchers said desalination may not be needed in many locations.
The study also noted that desalination uses large amounts of energy, generates greenhouse gas emissions and other air pollutants, and produces brine that can harm marine ecosystems if discharged to the sea.
Researchers cautioned that utilities often lack location-specific data to estimate losses and costs at each point in the network, and said upgrade costs may need to be passed on to households and non-residential users, potentially requiring public information campaigns.
The study was published as “The economics of a circular urban water system” by Dale Whittington and Meena Chandrasekaran in "Environmental Research Letters."
