Wetlands already work alongside grey infrastructure — the hurdle is maintenance, IWA panel hears

Treatment wetlands are already working alongside conventional “grey” water infrastructure — the bigger obstacle to nature-based solutions is that they are often treated as needing no upkeep at all, a panel at the IWA World Water Congress in Glasgow heard.

About 70% of the treatment wetlands recorded in the UK and Ireland by the Constructed Wetland Association are integrated with conventional plant rather than standing alone, said Dr Gabriela Dotro, an ecological engineer who leads NBS Future. She described aerated wetlands that fully nitrified effluent after a rotating biological contactor, and a 2015 system at Cowdenbeath in Scotland that treats storm overflows rather than simply storing them. Adding a small wetland for amenity and biodiversity to a septic-tank upgrade cost a tiny fraction of the scheme’s whole-life cost and stayed competitive with the conventional option, she said. “Imagine if we could design for biodiversity, all the good that we could do.”

From the physical to the digital

Lauren Roth Venu of Roth Ecological Design described Follow the Drop, an app paid for by the City of Honolulu and free to residents, which sizes rainwater and sustainable drainage measures for a property, lets owners submit them to the utility and then tracks rainfall captured, heat-island reduction and carbon. A study of the city’s direct-install programme found costs of pennies per gallon captured — “100 to 1,000 times less cost than putting in something end of pipe”, she said. Developers still need incentives: “if there’s not a dangling incentive, like, it’s just not going to happen.”

Moderator Nick Schreiner of Biomatrix Water showed floating treatment wetlands retrofitted onto lagoons, aeration lanes and clarifiers without structural changes, including a disused aeration lane at Cheddar owned by Wessex Water. Water infrastructure need not be a fenced-off grey site, he said: “It could be a haven for biodiversity, it could be a place that people want to visit.” Biomatrix founder Galen Fulford named storm tanks and reservoirs as obvious early opportunities.

Low maintenance, not no maintenance

Questions from the floor kept returning to upkeep. Dotro said UK wetlands have often been installed and then neglected: “we put them in and we abandon them because they’re so resilient”, until problems become expensive to fix. A delegate who said he had built about 200 constructed wetlands in India reported the same pattern: “Most people mistake them for no maintenance.”

Sarah Jenner of United Utilities offered the other side: an operator at one of the company’s reed-bed sites values it so much for its wildlife that “he has his lunch there every day”, with no detention tank to desilt. Dotro said a new innovation-fund project, Community Water Enterprises, will develop training and micro-accreditation for maintaining this kind of infrastructure, and that winning over sceptics means overcoming bad past experiences: “it’s education, but it’s also re-education.”

Recorded at a press session at the IWA World Water Congress, Glasgow, 6 October 2026.

Written with AI assistance from the session recording. Every quotation was checked against the recording; filler words and repetitions were removed. Corrected on 11 October 2026: two quotations were amended after a second check against the recording. Approved for publication by Inese Pritchard.