Urban waste water treatment per province and river basin district

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Regions Urban waste water treatment plants Capacity pollution equivalents by type Total capacity pollution equivalents (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Mechanical treatment (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Trickling filters (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Aeration tanks (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Oxidation tanks (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Oxidation ditches (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Carrousels (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Discontinuous systems (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Parallel installations (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Multi-stage installations (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Compact installations (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Membrane bioreactor (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Nereda granular sludge reactor (1 000 pollution equivalent) Urban waste water treatment plants Capacity pollution equivalents by type Hybrid Nereda - active sludge system (1 000 pollution equivalent) Influent waste water Quantities Pollution Equivalents (1 000 pollution equivalent) Discharge of waste water (effluent) Quantities Pollution Equivalents (1 000 pollution equivalent)
Nederland 30,019 0 54 10,101 4,363 1,194 9,934 91 1,478 1,502 91 0 849 363 26,382 2,130
Noord-Nederland (LD) 3,369 0 54 651 375 81 1,318 40 322 97 91 0 0 340 2,600 251
Oost-Nederland (LD) 6,724 0 0 1,488 1,684 404 2,268 0 580 115 0 0 162 23 6,109 433
West-Nederland (LD) 13,368 0 0 4,586 1,861 95 4,805 51 575 927 0 0 468 0 11,642 895
Zuid-Nederland (LD) 6,557 0 0 3,375 443 615 1,543 0 0 363 0 0 218 0 6,031 551
Groningen (PV) 1,017 0 0 180 110 13 260 40 17 56 0 0 0 340 784 100
Fryslân (PV) 1,336 0 54 0 170 16 828 0 136 41 91 0 0 0 1,069 90
Drenthe (PV) 1,016 0 0 471 95 51 230 0 169 0 0 0 0 0 748 60
Overijssel (PV) 2,157 0 0 865 632 290 218 0 16 90 0 0 22 23 1,878 138
Flevoland (PV) 715 0 0 0 65 0 650 0 0 0 0 0 0 0 635 27
Gelderland (PV) 3,851 0 0 623 986 113 1,400 0 564 25 0 0 140 0 3,596 268
Utrecht (PV) 2,110 0 0 185 108 0 1,365 0 0 19 0 0 432 0 1,831 118
Noord-Holland (PV) 4,547 0 0 1,929 1,039 79 779 51 424 246 0 0 0 0 4,181 319
Zuid-Holland (PV) 5,913 0 0 1,838 714 16 2,618 0 65 662 0 0 0 0 5,145 396
Zeeland (PV) 799 0 0 634 0 0 43 0 86 0 0 0 36 0 485 62
Noord-Brabant (PV) 4,506 0 0 2,892 16 615 620 0 0 363 0 0 0 0 4,183 364
Limburg (PV) 2,051 0 0 484 427 0 922 0 0 0 0 0 218 0 1,848 186
The river Eems 1,134 0 0 366 102 0 270 0 0 56 0 0 0 340 867 109
The river Rijn (North Rijn) 1,520 0 54 0 178 44 918 40 153 41 91 0 0 0 1,211 105
The river Rijn (East Rijn) 6,775 0 0 1,481 1,742 385 2,775 0 185 90 0 0 92 23 5,987 414
The river Rijn (Central Rijn)
The river Rijn (West Rijn) 13,083 0 0 4,245 1,897 143 4,241 51 1,053 952 0 0 502 0 11,684 883
The river Maas 6,205 0 0 2,904 427 606 1,686 0 0 363 0 0 218 0 5,636 505
The river Schelde 1,302 0 0 1,105 16 16 43 0 86 0 0 0 36 0 998 114
Source: CBS.
Explanation of symbols

Table explanation


This table presents the most significant results of the annual survey Public treatment of urban waste water. The results are presented per province and river basin district (Rijn, Maas, Eems and Schelde) and include:
- number and capacity of the urban waste water treatment plants by type of treatment;
- the volume and concentration of organic matter, nutrients and heavy metals in the waste water running into waste water treatment plants (influent) and the volume of treated waste water (effluent). As of 2017, data on heavy metals are only inventoried for even years.
- the volume and destination of the sludge released, with nutrients and heavy metals. As of 2017, sludge data are only inventoried for even years.
Additional data on urban waste water treatment plants, process technology, energy consumption, generation of energy and sludge dewatering can be accessed on the Dutch version of StatLine.

Data available from: 1981

Status of the figures:
The figures in this table are definitive.

Changes as of 29 May 2026:
The figures of 2024 has been added.

When will new figures be published?
New figures on 2025 will be published by March 2027.

Description topics

Urban waste water treatment plants
The number and capacity of urban waste water treatment plants in the Netherlands where nearly all domestic waste water and waste water from the private sector is treated. The plants are all operated by regional water quality control authorities.
Capacity pollution equivalents by type
Capacity urban waste water treatment plant:
A value that indicates how much organic pollution theoretically can be treated by a waste water treatment plant.

The pollution equivalent is the official unit that quantifies the pollution in waste water; one pollution equivalent = 150 g TOD (Total Oxygen Demand).
One pollution equivalent is the daily quantity of oxygen-demanding material in the waste water of one person. The degree of pollution in the waste water produced by the private sector is also expressed in pollution equivalents.
This unit is used as of 2010, so for previous years no values are available.
Total capacity pollution equivalents
Mechanical treatment
Installation where suspended matter is extracted from waste water by settlement.
Trickling filters
Waste water is sprinkled over a layer of porous stones covered with bacteria (biofilm). Thus, organic compounds in the waste water are degraded.
Aeration tanks
Pre-settled waste water runs through an intensively aerated basin containing active sludge (bacteria). Organic pollutants are degraded by oxygen and active sludge. The treatment process takes up only a short period of time and the sludge load is high which is typical of aeration basins.
Oxidation tanks
Operates by the same principle as the aeration tank but the sludge load is significantly lower. The resulting sludge is highly mineralised and will therefore decompose more slowly.
Oxidation ditches
In oxidation ditches, waste water is directed through a aeration circuit several times. The process takes up 2 or 3 days. Consequently, the sludge load is extremely low.
Carrousels
This technology is chiefly applied in large installations. Typical of carrousels are the depth (between 2 to 4 metres) and the aeration method.
Discontinuous systems
Oxidation basins and oxidation ditches. Waste water is let in batch-controlled.
Parallel installations
Various combinations of treatment systems (so-called 'streets') are applied in one installation.
Multi-stage installations
A serial process consisting of two systems, for instance, a trickling filter and an aeration basin. The waste water runs through both stages.
Compact installations
A system consisting of a basin subdivided into four segments. Waste water flows into the aeration segment. Subsequently, the sludge is separated in the central aeration zone. Then part of the sludge is conditioned in the reaeration zone and led back into the aeration zone. The other part (surplus sludge) is stabilised in the sludge mineralisation zone and subsequently removed.
Membrane bioreactor
A system where the sludge is separated from the waste water by using a membrane.
Nereda granular sludge reactor
In the Nereda granular sludge reactor the wastewater is purified by micro-organism clogged in natural granular structures of high density. These granules have a high biological activity and make it easy to separate the micro-organisms from the treated wastewater.

As from 2019 this new treatment type is distinghuished separately in Statline. In the period 2011-2018 already 4 Nereda systems became operational. Until 2019, these installations were classified as oxidation tanks and/or discontinous systems.
Hybrid Nereda - active sludge system
System consisting of a parallel operated Nereda granular sludge reactor and activated sludge system.

In the Nereda granular sludge reactor the wastewater is purified by micro-organism clogged in natural granular structures of high density. These granules have a high biological activity and make it easy to separate the sludge from the treated wastewater.

In activated sludge systems the wastewater is treated in bassins with flocculated sludge . This sludge clumps exists of microorganisms that feed on the the organic pollution in wastewater.

As from 2019 this new treatment type is distinghuished separately in Statline. In the period 2013-2018 already 2 hybrid Nereda - activated sludge sytems became operational. Until 2019, these installations were classified as parallel installations.
Influent waste water
Data on concentrations and quantities of pollutants in the waste water running into urban waste water treatment plants (influent).
Quantities
Pollution Equivalents
The pollution equivalent is the official unit that quantifies the pollution in waste water; one pollution equivalent = 150 g TOD (Total Oxygen Demand).
One pollution equivalent is the daily quantity of oxygen-demanding material in the waste water of one person. The degree of pollution in the waste water produced by the private sector is also expressed in pollution equivalents.
This unit is used as of 2010, so for previous years no values are available.
Discharge of waste water (effluent)
Data on concentrations and quantities of pollutants in treated waste water (effluent) discharged from urban waste water treatment plants.
Quantities
Pollution Equivalents
The pollution equivalent is the official unit that quantifies the pollution in waste water; one pollution equivalent = 150 g TOD (Total Oxygen Demand).
One pollution equivalent is the daily quantity of oxygen-demanding material in the waste water of one person. The degree of pollution in the waste water produced by the private sector is also expressed in pollution equivalents.
This unit is used as of 2010, so for previous years no values are available.