Constructed Wetlands

22/09/2026

The floating island that we delivered and installed together with our Estonian colleagues at the end of last summer has turned beautifully green! It is located on Lake Pormujärv in southern Estonia.

21/09/2026

Event photos from Iridra, one of the main sponsors.

15/09/2026

At the IWA Wetland Systems for Water Pollution Control International Conference on Wetland Systems for Water Pollution Control (ICWS 2026) in Chania, Crete, Prof. Yujie Feng from Harbin Institute of Technology presented the keynote:

“Low-carbon wastewater treatment and near-natural ecological restoration: experiences from China”

The keynote connected several directions of Feng’s research, from low-carbon wastewater treatment and microbial electrochemical systems to enhanced nature-based solutions, ecological floating beds and restoration of polluted urban waters.

One particularly interesting direction was the use of functional materials and bioelectrochemical processes to strengthen specific treatment mechanisms. Her group has investigated conductive carbon materials, iron-carbon substrates and electroactive microbial communities, including applications where nitrogen removal is constrained by a low C/N ratio. Here, the substrate is no longer considered only as support or sorption media. Its chemical and electrochemical properties, and its interaction with the microbial community, become part of the process design.

The presentation also showed the progression from fundamental studies of microorganisms and material interfaces towards pilot and field-scale systems. Feng reported applications of enhanced nature-based solutions in 25 water ecological restoration projects, including black-odorous urban waters, together with long-term monitoring of restored systems. Ecological floating beds coupled with microbial electrochemical processes are another relevant development, with published work showing substantially intensified nitrogen removal compared with conventional floating beds.

Another strong point was the interpretation of low-carbon treatment beyond electricity consumption alone. Aeration requirements, sludge production, resource recovery and direct emissions of CO₂, CH₄ and N₂O were considered together. Low operational energy by itself does not necessarily mean a low overall climate impact.

Perhaps the most interesting direction for our field is the increasing attention given to the plant–microorganism–material interface. We understand much more today about what happens around the roots and inside the media than we did when many of our wetland systems were first developed.

The challenge now is not to put every new material or mechanism into a wetland. It is to find out which ones still make a difference after several years in the field, under changing loads, seasons and real maintenance conditions. That is where promising research becomes useful wetland engineering.

14/09/2026

Forty years of making the French System

Some very valuable lessons from Dirk Esser’s keynote at IWA Wetland Systems for Water Pollution Control ICWS 2026 in Chania: “The making of the French System: Forty years of technical development, insights and subsequent innovations, and some mistakes to be avoided.”

The French System did not start with a perfect design. It developed through decades of experiments, observations, successes and, importantly, failures.

One early influence was Kickuth’s rootzone method. In the 1980s, horizontal flow wetlands using cohesive soil seemed a very promising idea. The soil offered good adsorption properties and an active environment for roots and microorganisms. But there was a problem. Water still has to move through the filter. Low hydraulic conductivity, clogging and preferential flow showed that good treatment properties are of little use if the hydraulics fail.

Some of the most important lessons came from research on intermittent sand filters. A vertical filter needs periods of feeding and resting. A dose infiltrates, air moves through the pore space, the filter drains and atmospheric oxygen can enter again. This is particularly important for nitrification. The filter effectively needs to breathe.

There are many practical consequences. Most bacterial activity may occur within approximately the upper 15 cm of sand, but a deeper layer is needed to prevent preferential pathways. Around 30 cm was recommended as a practical minimum, while depths beyond about 40 cm bring relatively little additional improvement for many treatment parameters, except notably pathogen removal.

Sand selection is critical. During operation, hydraulic conductivity in the upper layer can decrease by two orders of magnitude. Therefore, we should not design according to the hydraulic conductivity of clean sand. We need to think about what that sand will look like after years of wastewater loading. Poor sand selection has been one of the common causes of failure.

These lessons gradually contributed to what became the French vertical flow treatment wetland. One of its great advantages is that raw municipal wastewater can be applied to the first stage without conventional primary settling. Solids accumulate at the surface, while alternating feeding and resting allows them to dewater and mineralize.

The development shown in the presentation is impressive. In 1999 there were only 42 municipal treatment wetlands in France. Today the number presented is around 6,000, serving communities from roughly 40 to 4,000 people.

Perhaps the best lesson from these forty years is a simple one. Constructed wetlands may look simple, but reliable treatment is not just about putting plants into sand or gravel. Hydraulics, oxygen transfer, media selection, loading and resting are all part of the treatment process.

And sometimes understanding why a wetland failed teaches us more than another successful installation.

Photos from Dirk Esser’s keynote at ICWS 2026, Chania, Greece.

13/09/2026

IWA Wetland Systems for Water Pollution Control event has started! Wonderful pre-conference workshop with professors from Austria about modelling constructed wetlands already has passed. Now some Cretan food and gathering together with people from all around the world!

08/08/2026

What if a single solution could help an island community battle water scarcity, wildfires, and floods all at once? On the Greek island of Skiathos, the NURISH project is pioneering an integrated approach to severe climate challenges, turning to nature-based solutions that blend seamlessly with its landscape and culture.

Facing increasing water scarcity, flash floods, and wildfires, the island is implementing engineered wetlands. These systems are designed not just for urban wastewater treatment and reuse, but also combined with photovoltaic systems for energy self-sufficiency. They additionally capture and store rainwater and flood runoff, creating vital reserves for both agriculture and critical firefighting needs.

This holistic strategy highlights the incredible versatility of thoughtfully designed ecological infrastructure. It’s a powerful example of how constructed wetlands can be multifunctional assets, offering sustainable water treatment, enhancing water availability for various uses, and building robust climate resilience. It showcases the blend of ecological design with robust engineering.

How do you see such integrated, nature-based solutions shaping the future of water management in vulnerable regions worldwide?

Source: https://cordis.europa.eu/article/id/466726-reimagining-water-and-resilience-on-a-greek-island-in-the-aegean-sea

Skiathos is emerging as a key resilience hub under the NURISH project, with nature-based solutions that combat water scarcity, wildfires...

08/08/2026

Did you know nearly 40% of the EU population faced water scarcity in 2019? This critical challenge is sparking innovation, even in unexpected places like zoos. An EU-backed initiative, LIFE4ZOO, is tackling this head-on by testing pioneering water reuse systems in facilities like Zoo Liberec in Czechia and Zoo Barcelona in Spain. The goal is clear: treat and reuse wastewater on-site to drastically cut water consumption and reduce carbon footprint.

What's truly exciting is the integrated approach being used. These systems combine advanced processes like ultrafiltration and disinfection with nature-based features – notably, engineered constructed wetlands and floating vegetation islands. This blend allows zoos to manage their significant water needs sustainably, transforming wastewater into a valuable resource rather than a discharge.

This project isn't just about zoos; it's a powerful demonstration of how ecological engineering can address critical issues like water scarcity and environmental impact on a larger scale. By adopting such circular water management, these facilities are setting a model that could be adapted for other water-intensive sites globally. How do you see similar nature-based solutions reshaping water management in urban environments?

Source: https://www.brusselstimes.com/eu-affairs/2258190/european-zoos-test-water-reuse-systems-as-eu-sounds-scarcity-alarm

Water consumption at one zoo is set to drop 50%, saving 40,000 cubic metres annually. A new EU-funded project demonstrates scalable solutions for Europe's water crisis.

07/08/2026

Imagine spending billions to restore what was once deliberately drained. That's the story unfolding in Florida, where vast sections of the Everglades were engineered away for development. Now, the multi-billion-dollar Comprehensive Everglades Restoration Plan is actively reversing decades of ecological transformation, aiming to bring vitality back to this crucial wetland.

A cornerstone of this monumental effort is the Everglades Agricultural Area Reservoir, featuring an impressive 6,500-acre constructed wetland with three treatment cells. These wetlands are designed to naturally purify water and remove nutrient pollution. This project powerfully illustrates how ecological engineering and nature-based solutions blend human ingenuity with natural processes for water quality improvement.

The project's expedited completion to 2029 underscores a vital model for sustainable water management. It demonstrates that even extensive environmental damage can be thoughtfully addressed through a powerful partnership with nature. What major challenges could benefit from such large-scale ecological engineering initiatives?

Source: https://en.as.com/latest_news/florida-spent-decades-draining-a-vast-wetland-now-billions-of-dollars-are-being-spent-to-restore-it-f202608-n/

The southern half of Florida was once a massive wetland, but it has been reduced to less than half its original size. Work is underway to repair the damage.