An online Site Visit has been successfully celebrated on the last 29^th of January, addressed to AQUARES partnership. The meeting aimed to provide a detailed presentation and deeper knowledge about the good practice of Lodzkie Region (Poland) has been presented during the site visit, entitled ‘The Sequential Sedimentation-Biofiltration System (SSBS)’ built on the Sokolowka river in Lodzkie region (Poland), as a treatment method for urban rivers supplied by stormwater runoff.

The system was constructed to purify a small urban river whose hydrological regime is dominated by stormwater and meltwater. The practice is situated in the capital of Lodzkie Region, whose hydrographic network consists of several small streams or rivers. One of these waterways is the Sokolowka river, flowing in the north-western part of the city.

The results indicate that the sedimentation zone played a fundamental role in the removal of Total Suspended Solids and nutrients. Its performance can be improved by the implementation of structures such as concrete and lamellar systems, which support the sedimentation process and lower the inlet flow velocity. Post-investment management of this zone, including regular monitoring and removal of sediments excess, should provide high efficiency and extend the operating time of the system.

The SSBS ensured efficient nitrogen transformation, resulting in significant reduction of TN and NO3. The inflow concentrations of N compounds were below the Polish Water Quality Standards (2014), so the system could be adjusted to improve the reduction of the main pollutants (TSS and phosphorus), which were exceeded at the inflow.

The system reduced chloride concentration, but further studies are needed to understand its circulation in CWs and to assess the impact of Cl on purification processes. The results indicate that it possible to create efficient working multi-zone CWs such as monitored SSBS based on ecohydrological principles for removing pollutants in urban areas with limited space.