The project is part of a broader initiative undertaken by the City of Łódź aimed at improving the management of stormwater and meltwater. The existing open tank at Liściasta Street no longer met the requirements regarding the volume of retained water or the quality of its treatment.
Effective stormwater treatment is essential due to runoff from the nearby residential area, which flows through the stormwater drainage system. Until now, partially treated water was discharged directly into the tank and the Sokołówka River, which runs through the area.
The installation of a new tank employing environmentally friendly technologies improves both retention efficiency and water treatment quality, benefitting the surrounding environment.
The total project cost amounted to PLN 5.1 million gross.
The project, titled “Nature Supported by Technology – A Retention Tank with a Hydrofit Pre-Treatment System at Liściasta Street in Łódź”, was implemented by Ecol-Unicon and received 1st Prize in the “Environmental Protection” category at the Smart City Poland Award 2024 competition.
Moreover, the project has been included on the map of good practices in Interreg Europe – a program co-funded by the European Union. Its aim is to facilitate the exchange of knowledge and experiences in sustainable and innovative solutions across Europe.
Scope of work
- Design of the stormwater pre-treatment facility modernization
- Demolition of existing pre-treatment structures
- Construction of a retention tank with a total capacity of 900 m³
- Construction of the hydrofit pre-treatment system
- Installation of pre-treatment devices, including sedimentation tanks, separators, and tanks
- Construction of process pipelines
- Installation of control, automation, and water pre-treatment measurement systems
- Construction of fencing, access roads, pedestrian pathways, and surface hardening for pre-treatment facility maintenance
How does the implemented solution work?
In the newly constructed facility in Łódź, we implemented the HYDROZONE BENEFIT retention tank, one of the most advanced solutions available. It enables not only water retention but also its reuse, achieved through pre-treatment devices and the operation of a hydrofit system with appropriately selected vegetation.
How does it work? The retention tank, with a total capacity of 900 m³, collects stormwater, which is pre-treated as it flows through a series of devices that remove suspended solids and floating contaminants. Hydrocarbon substances are eliminated using a lamella separator. Additionally, organic pollutants are filtered out in the hydrofit section, thanks to the planted vegetation and gravel layer. To keep the retained water fresh, aeration and flushing jets have been installed. These devices supply oxygen to the tank, preventing water stagnation and decomposition.
The retention tank installed by Ecol-Unicon is divided into three sections:
- Operational Section (0.5 m height, 150 m³ capacity) – The water collected here is reused for municipal purposes, such as street cleaning, channel flushing, green space irrigation, and sewer maintenance. Additionally, it supplies water to the hydrofit section during dry periods. In such cases, the water circulates in a closed loop, flowing through the filtration layer and back into the tank to ensure continuous plant irrigation.
- Working Section (1.5 m height, 450 m³ capacity) – This section retains incoming stormwater, which is subsequently pumped into the hydrofit system for treatment of organic pollutants.
- Emergency Section (1.0 m height, 300 m³ capacity) – This section provides overflow retention in case the working section reaches its capacity, for instance, during pump system failures.
Ecol-Unicon was also responsible for surface development around the pre-treatment facility. The area surrounding the tank and the Sokołówka River serves as a recreational space for the residents of Łódź, making the visual aspect of the project equally important.
The investment at Liściasta Street in Łódź demonstrates a comprehensive approach to stormwater retention. The project focuses not only on water storage but also on pre-treatment, enabling its reuse for municipal purposes and green space irrigation.
Such technological solutions reflect the latest global trends, which, in the face of climate change, aim not only to retain water but also to reuse it for other purposes.
An implementation on this scale is truly innovative and paves the way for future projects. It can be successfully applied in urban areas dominated by concrete surfaces and other sealed city squares, offering a much-needed introduction of greenery to such spaces.
The use of a prefabricated tank significantly shortened the installation time, allowing the project to be completed within the planned schedule. The project was carried out in a city park with limited available space, which required careful intervention in the existing tree stand. We selected construction methods that minimized tree felling to the necessary minimum. The earthworks were conducted in the Sokołówka River valley, where the groundwater level was high. Here, the use of concrete and the weight of prefabricated components proved advantageous, counteracting buoyant forces and facilitating assembly onto the foundation slab.
Przemysław Dębski, Service Department Director, Ecol-Unicon