Pollution Treatment on the Glinščica, Slovenia
Year of issue
2025
Summary
Installed in 2006 by Limnos Ltd., the innovative ecoremediation (ERM) system on a polluted tributary of the Glinščica combines a sedimentation pond (to settle coarse particles and reduce flow velocity), a vegetated sand-filled drainage ditch with reeds, and a short meandered channel. Early monitoring (2008–2009) reported strong reductions in nutrients and suspended matter, with effectiveness sustained by routine maintenance (including sediment removal in 2008). The facility remains in place and in use, is maintained by the City of Ljubljana, and is incorporated into local educational activities; project managers confirm it has not been amended. Since installation, additional nature-based solutions for flood retention and stormwater management have been implemented elsewhere in the Glinščica catchment - most notably the Brdnikova dry retention reservoir and works at Podutik - which have helped mitigate recent heavy-rain events. In the technical literature the site is also referenced within a broader “Multifunctional Water Reservoir (MWR) Ljubljana,” where upgrades commissioned in 2014 enhanced ecological and educational functions without changing the ERM’s treatment role.
Photo Gallery
Location
46.0761, 14.45249
Project
NWRM
National ID
Slovenia_02
Sector
Hydromorphology
Installation Date
2006-01
Implementation status
Completed
Contact
REC
Overview
Location of the project
This is just off Podutiška cesta near the historic Kavšek Bridge over the Glinščica. Parcels listed in the thesis: KO Glince 668, 667/1, 660/1.
Country
Slovenia
NUTS2 Code
Zahodna Slovenija
Sponge measures implemented in the case study
Ponds and scrapes
Swales
Infiltration Trenches
Objectives
Clean the polluted inflow using a chain of a sedimentation pond → vegetated sand-filled drainage ditch (with reeds) → short meandered channel, while slowing flow, reducing erosion, and enhancing biodiversity; also to serve education/awareness (integration in a water learning trail). No explicit numeric targets were found ex-ante, but subsequent monitoring documents substantial nutrient reductions.
Involved partners
| Authority type | Authority name | Authority role |
|---|---|---|
| — | Limnos ltd. | — |
| Local water authority | MOL-Municipality of the Ljubljana | Financing |
Site Information
Climate Zone
Cool temperate moist
Precipitation
1343.00 mm
Temperature (°C)
9.70 °C
Elevation range
300 m
Slope range
0-1% Average channel gradient reported as 0.006
Vegetation class
On-site treatment vegetation is emergent wetland macrophytes dominated by common reed (Phragmites australis) in the vegetated drainage ditch; the municipal page notes planting with marsh plants.
WFD Ecological status
Good
WFD Chemical status
Failing to achieve good
Water quality status
Increased pollution/toxicity in Glinščica linked to leaking septic tanks/sewer overflows, stormwater runoff, and nearby agricultural non-point sources. The Podutik reservoir/Glinščica system is affected by these inputs.
Design and Implementation
Project scale
Micro
Project scale specifications
a site-specific intervention on a small tributary (sedimentation pond + vegetated ditch + short meandered reach; ERM length ~70 m), addressing local water quality/hydromorphology.
Size
225.00
Size unit
m2
Financing
Total cost
166723.00 €
Total cost information
€166,723 for the project “Ekoremediacijski objekt na Glinščici”
€23,000 in 2011 for maintenance/monitoring and flood-related repairs at the ERM.
€23,000 in 2011 for maintenance/monitoring and flood-related repairs at the ERM.
Costs capital information
The cost was 100 Euro/m2 for investment
Costs operation maintenance information
Operation is about 30-50 Euro/m2/year
Compensations
Non
Policy and Governance
Policy description
Riparian development, pollution incident. a polluted tributary where urban stormwater (meteorna kanalizacija) meets a small brook carrying agricultural non-point pollution; the ERM was built to treat this inflow and restore local habitat.
Policy targets
Runoff control
Pollutants Removal
Improved Biodiversity
Oher Societal Benefits
Part of a wider plan
Non
Public consultation
Oui
Consultation activities
| Activity type |
|---|
| Improved public acces |
Has contractual arrangements
Non
Impacts and Monitoring
Monitoring System
Monitoring requirements
Limnos monitored 2006–2009 for nutrients, physico-chemistry, toxicity and biota, demonstrating substantial nutrient reductions when maintenance was performed.
Monitoring parameters
Multi-season programme covered BOD₅, organic N, NH₄⁺, NO₂⁻, NO₃⁻, total N, total P, plus pH, salinity, oxygen balance, temperature, specific (non-)synthetic pollutants, water/sediment toxicity, reed productivity, and plant diversity. Hydromorphology noted quantity & dynamics of flow and substrate conditions. Reported removal in the third season: NO₂⁻ 84%, NO₃⁻ 68%, total N 40%, etc.
Upstream station
The water level was measured at Inflow and at additional 6 sampling points in the VDD.
Downstream station
Outflow of the VDD and the outflow of the RBM
Maintenance
Maintenance requirements
Regular municipal maintenance like mowing, debris/sludge removal and conveyance upkeep (with a key pond desilt in 2008) keeps the ERM effective.
Impact Assessment Methodology
Performance impact assessment method
Catchment outlet
Performance impact estimation information
pH, EC, DO and T were measured with portable meters WTW Multiline P4 according to Standard Methods. Hydraulic residence time (HRT) was measured with the tracer test with CaCl on 25.7.2007 and 26.7.2007. And statistical analyses.
Socio-economic Impacts
Direct benefits
Education & access: The City plans the ERM as part of a water learning trail; information boards and improved public access are listed measures.
Biophysical impacts: Hydrology
Retained water
118.70
Information on retained water
Creation of a sedimentation pond, a vegetated drainage ditch and a short meandered channel (≈70 m). The City states the ERM slows flow, mitigates erosion and retains water; this can help during dry periods (no volumes given). 118.7m3
Biophysical impacts: Biodiversity
Information on improved biodiversity
System planted with common reed (Phragmites); the City reports 49 plant species recorded on the ERM and notes increasing biodiversity. (RiverWiki’s macrophyte results are marked “inconclusive”.)
Biophysical impacts: Water & Soil Quality
Water quality overall improvements
Positive impact-WQ improvement
Information on water quality overall
The results showed efficient removal of BOD5 (9%), organic N (24%), ammonia (7%), nitrites (84%), nitrates (68%), total N (40%) and total P (3%) in the entire ERM system in the third season. Vegetated ditch was efficient in removal of ammonia (38%), nitrites (91%) and nitrates (63%) and meandered stream was efficient in removal of total P (10%). With the exception of suspended and dissolved solids, pollutants concentrations at the end of the ERM system stayed within the permitted levels for outflow. The results showed the entire ERM system to be more efficient in removal of nitrites and ammonia in season 2008/2009 compared to previous year. Removal of sediments from the pond proved to be essential for efficiency of vegetated ditch, since the ditch reached higher efficiency for almost all parameters after maintenance work in the summer 2008
Water quality improvements - Phosphorus (P)
3.00
Water quality improvements - Phosphorus (P) - Unit
% reduction pf pollutant
Water quality improvements - Nitrogen (N)
40.00
Water quality improvements - Nitrogen (N) - Unit
% reduction pf pollutant
Information on water quality improvements (TSS)
SS increased
Soil quality overall improvements
Negative impact-SQ deterioration
Biophysical impacts: Others
Ecosystem impact climate regulation
Not relevant for the specific application
Information on other biophysical impacts
Microclimate/drought buffering: Municipality notes water retention can play an important role in dry periods (adaptation benefit). No site-specific data on evapotranspiration, greenhouse gases or carbon.
Lessons Learned
Key lessons
Regular maintenance is decisive. Performance jumped after desilting the sedimentation pond in July 2008, showing that the ERM’s efficiency depends on routine sludge/debris removal and vegetation upkeep.
The combined design works. A staged chain—sedimentation pond → vegetated drainage ditch (VDD) → meandered reach—delivered marked nutrient reductions (e.g., NO₂⁻ −84%, NO₃⁻ −68%, TN −40%) and is a sound option for polluted run-off with variable flows. This aligns with the case’s stated lesson that a regularly maintained ERM can efficiently decrease pollutants and that the VDD+meander combo is promising.
Hydromorphology requires attention. While water-quality improved, RiverWiki notes a deterioration signal for “quantity & dynamics of flow” and “substrate conditions,” reminding practitioners to track morphology alongside chemistry and adapt the layout/operations if needed.
Long-term anchoring helps. Municipal ownership, budgeting and use as an educational stop kept the installation active and cared for years after commissioning, an underrated enabler of continuity.
Highly fluctuating inflows shape processes. Monitoring found even distribution of the denitrification narG gene across the VDD under flashy hydraulics, useful insight for similar small urban/agri catchments.
The combined design works. A staged chain—sedimentation pond → vegetated drainage ditch (VDD) → meandered reach—delivered marked nutrient reductions (e.g., NO₂⁻ −84%, NO₃⁻ −68%, TN −40%) and is a sound option for polluted run-off with variable flows. This aligns with the case’s stated lesson that a regularly maintained ERM can efficiently decrease pollutants and that the VDD+meander combo is promising.
Hydromorphology requires attention. While water-quality improved, RiverWiki notes a deterioration signal for “quantity & dynamics of flow” and “substrate conditions,” reminding practitioners to track morphology alongside chemistry and adapt the layout/operations if needed.
Long-term anchoring helps. Municipal ownership, budgeting and use as an educational stop kept the installation active and cared for years after commissioning, an underrated enabler of continuity.
Highly fluctuating inflows shape processes. Monitoring found even distribution of the denitrification narG gene across the VDD under flashy hydraulics, useful insight for similar small urban/agri catchments.
Drivers
| Driver type | Driver role | Comments |
|---|---|---|
| Organisation committed to it | Main driver | Dedicated municipal role (Mestna občina Ljubljana) with ongoing care and public-facing use (learning trail). |
Success factors
| Success factor type | Success factor role | Comments |
|---|---|---|
| Existing technical standards | Main factor | Timely maintenance, especially the 2008 desilt that restored treatment efficiency. |
| Attitude of relevant stakeholders | Secondary factor | Structured monitoring (2008–2009) enabling adaptive management and evidencing results. |
Transferability
Highly transferable to small, mixed-pollution tributaries and stormwater outfalls. Success hinges on routine O&M (esp. desilting the pond), capacity to manage flashy inflows, and space for a pond-VDD-meander chain. Watch solids loads, upstream sewer/agri pressures, and potential hydromorphology trade-offs; keep monitoring nutrients/physico-chemistry to adapt.
Sources
Sources