Where Denmark’s wastewater goes
Treatment plants, sewer overflows and rainwater outlets, municipality by municipality, as the utilities report them to the national database. It also shows how much of what is reported about overflows was actually measured.
Pick a municipality
2024 discharges plant by plant and outlet by outlet, and the municipality’s totals since 2010.
Danmarks Statistik, table VANDUD. A gap means Danmarks Statistik shows no figure for that year.
Treatment plants, 2024
Treatment as coded in PULS: M mechanical, B biological, N nitrification, D denitrification, K chemical phosphorus removal; further letters are extra steps.
Largest overflows of combined sewage, 2024
Outlet codes as registered by the utility. Types: OV overflow structure, OS with storage basin, OF with detention basin, OK with both, Bypass at a treatment plant, UR untreated wastewater. Level is the calculation level reported for the figure (section 02).
Measured or calculated?
Every overflow figure in PULS carries a calculation level. Most are calculated from rainfall, catchment area and pipe models.
From standard values to measurement
Uncertainty on discharged amounts as stated in Miljøstyrelsen’s technical instruction for rain-dependent discharges. Level 0 has none stated. The level is read from the method text each utility enters, as written.
Most overflows are modelled, not measured
Measured outlets tend to be the big ones, so levels 4 and 5 cover 48 % of the volume from only 13 % of the outlets. For 3,635 overflows, the reported volume is a calculation with a stated uncertainty of up to ±135 %. The totals are the best available estimate, not a measurement. That is the same question we ask of any forecast or signal: what was actually observed, and what was assumed?
Measured water, fixed nitrogen
The level describes how the water volume was found. The nitrogen figure is often that volume times one fixed concentration.
Overflows with at least 10,000 m³ in 2024. Nitrogen counts as fixed when it is within 0.5 kg of the water volume times 12 or 10 mg/l. That describes how the figure was made, not whether it is wrong: a fixed value can be a sensible standard. The data does not say where the values come from.
Check it without trusting us
Every figure here can be traced to an open source, and the totals are checked against Miljøstyrelsen’s national report.
Data and code
The downloaded files, their hashes, the method and the script that builds this page. CI recomputes it on every change.
The repository →Danmarks Statistik
Table VANDUD: water, nitrogen, phosphorus and organic matter by municipality and source.
VANDUD →The national check
Plant by plant and outlet by outlet, the 2024 layers add up exactly to the national totals in Punktkilder 2024.
Punktkilder 2024 →PULS, via two open doors
Utilities, municipalities and Miljøstyrelsen report discharges to PULS at Danmarks Miljøportal. PULS needs a login, so this page uses two open publications of the same data:
- Danmarks Statistik’s municipal totals.
- Miljøministeriet’s map layers for the water plans, with one row per plant and per outlet for 2024.
What this can’t show
A discharge into a small stream matters more than the same amount into the open sea. That isn’t assessed here. Plant and outlet detail is for 2024 only. Utilities fill in the method field differently. Nothing here is a verdict on any utility or municipality.
And the rest of the nitrogen? NEW
Wastewater is about a tenth of the nitrogen reaching the sea. We tried to check farming’s share with open measurements only, method locked first. The direction is clear. The size is not.
Farming’s share of the nitrogen →This is the same habit we bring to validating trading signals: separate what was measured from what was assumed, and show where every number comes from.