Urban waste water treatment per province and river basin district

Urban waste water treatment per province and river basin district

Periods Regions Urban waste water treatment plants Numbers by type Total number (number) Urban waste water treatment plants Numbers by type Mechanical treatment (number) Urban waste water treatment plants Numbers by type Trickling filters (number) Urban waste water treatment plants Numbers by type Aeration tanks (number) Urban waste water treatment plants Numbers by type Oxidation tanks (number) Urban waste water treatment plants Numbers by type Oxidation ditches (number) Urban waste water treatment plants Numbers by type Carrousels (number) Urban waste water treatment plants Numbers by type Discontinuous systems (number) Urban waste water treatment plants Numbers by type Parallel installations (number) Urban waste water treatment plants Numbers by type Multi-stage installations (number) Urban waste water treatment plants Numbers by type Compact installations (number) Urban waste water treatment plants Numbers by type Membrane bioreactor (number) Urban waste water treatment plants Numbers by type Nereda granular sludge reactor (number) Urban waste water treatment plants Numbers by type Hybrid Nereda - active sludge system (number) 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) Urban waste water treatment plants Capacity inhabitant equivalents by type Total capacity inhabitant equivalents (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Mechanical treatment (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Trickling filters (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Aeration tanks (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Oxidation tanks (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Oxidation ditches (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Carrousels (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Discontinuous systems (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Parallel installations (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Multi-stage installations (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Compact installations (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Membrane bioreactor (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Nereda granular sludge reactor (1 000 inhabitant equivalents) Urban waste water treatment plants Capacity inhabitant equivalents by type Hybrid Nereda - active sludge system (1 000 inhabitant equivalents) Influent waste water Quantities Volume waste water (1 000 m3) Influent waste water Quantities Pollution Equivalents (1 000 pollution equivalent) Influent waste water Quantities Chemical oxygen demand (COD) (1 000 kg) Influent waste water Quantities Biochemical oxygen demand (BOD) (1 000 kg) Influent waste water Quantities Nitrogen compounds as N (total) (1 000 kg) Influent waste water Quantities Phosphorus compounds as P (total) (1 000 kg) Influent waste water Quantities Copper (kg) Influent waste water Quantities Chromium (kg) Influent waste water Quantities Zinc (kg) Influent waste water Quantities Lead (kg) Influent waste water Quantities Cadmium (kg) Influent waste water Quantities Nickel (kg) Influent waste water Quantities Mercury (kg) Influent waste water Quantities Arsenic (kg) Discharge of waste water (effluent) Quantities Volume waste water (1 000 m3) Discharge of waste water (effluent) Quantities Pollution Equivalents (1 000 pollution equivalent) Discharge of waste water (effluent) Quantities Chemical oxygen demand (COD) (1 000 kg) Discharge of waste water (effluent) Quantities Biochemical oxygen demand (BOD) (1 000 kg) Discharge of waste water (effluent) Quantities Nitrogen compounds as N (total) (1 000 kg) Discharge of waste water (effluent) Quantities Phosphorus compounds as P (total) (1 000 kg) Discharge of waste water (effluent) Quantities Copper (kg) Discharge of waste water (effluent) Quantities Chromium (kg) Discharge of waste water (effluent) Quantities Zinc (kg) Discharge of waste water (effluent) Quantities Lead (kg) Discharge of waste water (effluent) Quantities Cadmium (kg) Discharge of waste water (effluent) Quantities Nickel (kg) Discharge of waste water (effluent) Quantities Mercury (kg) Discharge of waste water (effluent) Quantities Arsenic (kg) Sewage sludge Wet sewage sludge by destination Total wet sludge (1 000 kg) Sewage sludge Wet sewage sludge by destination Agriculture (1 000 kg) Sewage sludge Wet sewage sludge by destination Wet oxidation (1 000 kg) Sewage sludge Wet sewage sludge by destination Composting (1 000 kg) Sewage sludge Wet sewage sludge by destination Landfill (1 000 kg) Sewage sludge Wet sewage sludge by destination Incineration (1 000 kg) Sewage sludge Wet sewage sludge by destination Cement industry (1 000 kg) Sewage sludge Wet sewage sludge by destination Co-incineration at power plants (1 000 kg) Sewage sludge Wet sewage sludge by destination Other destinations (1 000 kg) Sewage sludge Dry solids by destination Total dry solids (1 000 kg) Sewage sludge Dry solids by destination Agriculture (1 000 kg) Sewage sludge Dry solids by destination Wet oxidation (1 000 kg) Sewage sludge Dry solids by destination Composting (1 000 kg) Sewage sludge Dry solids by destination Landfill (1 000 kg) Sewage sludge Dry solids by destination Incineration (1 000 kg) Sewage sludge Dry solids by destination Cement industry (1 000 kg) Sewage sludge Dry solids by destination Co-incineration at power plants (1 000 kg) Sewage sludge Dry solids by destination Other destinations (1 000 kg) Sewage sludge Nutrients and heavy metals Ashes (1 000 kg) Sewage sludge Nutrients and heavy metals Nitrogen compounds as N (1 000 kg) Sewage sludge Nutrients and heavy metals Phosphorus compounds as P (1 000 kg) Sewage sludge Nutrients and heavy metals Copper (kg) Sewage sludge Nutrients and heavy metals Chromium (kg) Sewage sludge Nutrients and heavy metals Zinc (kg) Sewage sludge Nutrients and heavy metals Lead (kg) Sewage sludge Nutrients and heavy metals Cadmium (kg) Sewage sludge Nutrients and heavy metals Nickel (kg) Sewage sludge Nutrients and heavy metals Mercury (kg) Sewage sludge Nutrients and heavy metals Arsenic (kg)
1981 Nederland 505 47 81 57 35 121 73 47 10 25 9 0 . . . . . . . . . . . . 20,034 1,855 2,200 7,325 668 826 3,803 54 596 2,690 17 0 1,247,035 . 694,973 284,775 60,630 17,365 132,300 63,965 469,650 141,352 2,745 49,449 892 2,435 1,247,035 . 144,177 39,901 33,388 10,064 39,690 25,586 140,895 56,541 1,098 34,614 268 1,217 3,622,102 1,407,656 0 450,225 1,719,789 34,763 0 0 9,669 179,616 69,101 0 39,285 64,946 5,351 0 0 933 74,866 8,471 4,216 88,636 36,332 312,411 81,582 1,518 13,919 587 1,179
1985 Nederland 487 30 62 63 51 121 80 32 9 34 5 0 . . . . . . . . . . . . 22,676 1,755 1,960 8,755 1,007 888 4,285 36 588 3,391 12 0 1,417,433 . 799,991 304,561 70,165 18,706 159,682 53,816 509,507 143,969 2,378 42,613 821 3,342 1,417,433 . 134,253 28,544 38,405 10,810 47,905 21,526 152,852 57,588 951 29,829 246 1,671 3,749,735 1,481,125 0 548,298 1,620,268 51,374 0 0 48,670 227,127 70,313 0 70,854 76,980 6,981 0 0 1,999 96,020 11,523 4,965 103,825 33,207 338,380 82,984 1,377 12,585 560 1,540
1990 Nederland 469 14 48 65 57 119 97 22 9 34 4 0 . . . . . . . . . . . . 23,729 146 1,730 10,219 1,216 1,044 4,894 33 618 3,816 12 0 1,642,646 . 932,832 348,630 81,273 14,357 177,145 38,733 497,455 96,356 2,049 32,675 1,049 4,943 1,642,646 . 131,495 23,645 39,292 6,239 36,492 13,130 140,282 25,149 820 19,474 315 2,471 4,859,804 1,621,964 0 446,575 2,704,575 78,152 0 0 8,538 315,266 81,602 0 63,280 158,107 11,654 0 0 623 127,156 15,900 7,066 140,084 25,553 351,411 70,674 1,213 13,030 691 2,409
1995 Nederland 424 4 27 59 61 102 113 12 10 35 1 0 . . . . . . . . . . . . 24,409 28 1,143 9,842 1,742 1,018 6,222 12 618 3,777 8 0 1,854,023 . 920,541 331,103 83,978 13,756 183,429 37,098 450,635 76,552 1,605 30,951 710 5,673 1,854,023 . 100,486 13,490 36,248 3,529 22,640 5,934 119,868 10,293 380 13,447 172 2,618 2,135,432 0 440,494 471,847 764,592 454,476 0 0 4,023 359,843 0 21,880 80,312 178,820 78,602 0 0 229 160,446 16,455 10,345 140,468 19,299 341,367 63,208 691 10,932 538 2,791
2000 Nederland 391 0 11 52 67 84 125 8 13 31 0 0 . . . . . . . . . . . . 25,242 0 404 8,949 2,847 1,092 7,548 14 1,223 3,165 0 0 1,996,779 . 920,719 353,527 84,726 13,300 156,891 22,707 438,782 59,425 1,030 25,394 511 5,801 1,996,779 . 91,033 11,284 28,952 2,845 17,846 5,035 100,897 8,555 471 12,037 143 2,787 1,426,447 0 287,900 161,739 155,255 778,051 0 0 43,501 336,361 0 14,355 39,452 64,147 180,493 0 0 37,913 128,336 15,962 7,258 130,891 17,322 319,070 51,466 544 11,036 404 3,017
2005 Nederland 368 0 8 58 65 76 123 2 11 24 0 1 . . . . . . . . . . . . 25,539 0 302 9,628 3,044 1,347 7,338 10 1,104 2,743 0 23 1,841,413 . 943,467 351,649 84,825 14,425 159,754 17,128 469,266 43,817 1,317 21,507 419 5,891 1,841,413 . 77,895 8,684 21,742 2,651 12,235 3,474 85,047 6,249 252 9,660 97 2,736 1,494,028 0 0 40,293 60,098 835,453 44,715 137,530 375,940 347,557 0 0 9,697 14,283 232,746 31,097 33,113 26,620 126,997 18,733 7,771 132,360 13,937 372,960 39,312 453 8,967 329 2,952
2010 Nederland 349 0 6 61 61 63 115 2 18 21 1 1 30,365 0 308 10,577 3,867 1,348 9,307 49 1,925 2,865 91 29 24,290 0 279 8,651 2,918 1,092 7,417 41 1,467 2,343 60 23 1,934,310 24,745 953,490 370,007 87,866 13,880 145,405 17,391 460,409 36,893 803 20,905 319 6,295 1,934,310 2,036 75,461 8,012 16,586 2,226 8,842 2,897 85,375 3,901 232 9,367 87 2,848 1,321,586 0 0 0 0 874,505 155,551 265,488 26,042 332,601 0 0 0 0 199,674 64,758 65,717 2,452 110,086 18,736 11,101 132,552 13,715 348,041 39,757 468 11,020 265 3,276
2015 Nederland 334 0 2 61 66 54 116 2 15 16 1 1 . . 30,246 0 108 10,552 4,580 1,254 9,576 49 1,527 2,480 91 29 . . 24,182 0 105 8,618 3,453 1,006 7,692 41 1,139 2,045 60 23 . . 1,957,261 25,686 999,309 405,787 89,122 13,389 144,556 18,345 425,519 35,770 570 19,262 243 7,182 1,957,261 1,916 69,784 6,895 14,641 1,960 9,029 2,234 80,166 2,242 181 7,695 61 3,298 1,302,386 0 0 194 9,178 1,034,423 135,616 119,286 3,689 325,361 0 0 43 2,056 246,663 46,231 29,520 846 102,290 18,318 11,086 128,534 16,163 321,593 32,314 344 9,589 201 3,561
2020 Nederland 315 0 2 58 56 44 118 1 10 14 1 0 9 2 29,713 0 108 10,152 4,615 1,133 9,884 40 956 1,598 91 0 774 363 23,824 0 105 8,386 3,422 906 7,937 32 678 1,415 60 0 629 255 1,938,476 27,031 1,056,480 428,585 93,686 13,297 133,000 14,130 433,742 28,269 435 17,391 194 6,449 1,938,476 1,986 72,302 7,512 14,320 1,644 9,156 1,862 68,981 1,244 82 7,143 26 2,603 1,263,335 0 0 0 5,613 1,063,157 14,514 126,468 53,582 308,360 0 0 0 1,480 250,382 13,614 30,765 12,119 91,789 19,111 11,170 120,715 12,003 325,845 25,755 311 7,939 143 3,247
2021 Nederland 313 0 1 57 56 42 119 2 10 14 1 0 9 2 29,957 0 54 10,225 4,585 1,111 10,058 91 956 1,598 91 0 827 363 23,805 0 60 8,313 3,422 887 8,010 77 678 1,415 60 0 629 255 1,963,884 26,781 1,039,561 438,139 93,852 13,120 . . . . . . . . 1,963,884 1,998 72,524 8,217 14,379 1,681 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2022 Nederland 313 0 1 62 49 44 120 2 11 11 1 0 10 2 29,995 0 54 10,411 4,362 1,182 10,005 91 1,092 1,502 91 0 843 363 23,661 0 60 8,445 3,260 945 7,757 72 794 1,320 60 0 692 255 1,807,838 26,146 1,010,854 409,133 92,433 12,944 115,023 14,284 386,774 23,686 282 16,758 131 6,037 1,807,838 1,827 67,228 7,107 12,960 1,609 8,881 2,198 69,221 1,333 60 7,360 18 2,531 1,299,154 0 0 0 6,521 919,802 16,591 321,536 34,704 300,041 0 0 0 1,494 220,991 15,503 53,936 8,116 89,938 17,755 11,004 109,077 11,795 298,603 23,100 280 7,670 134 3,006
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 22 April 2024:
The figures of 2022 has been added.

When will new figures be published?
New figures on 2023 will be published by March 2025.

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.
Numbers by type
Number of sewage water treatment plants broken down by method of treatment.
Total number
The total number of urban waste water treatment plants in the Netherlands.
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.
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.
Capacity inhabitant 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 capacity expressed in Inhabitant Equivalents is determined on basis of: one inhabitant equivalent = 54 g BOD (Biological Oxygen Demand).
One inhabitant equivalent is the daily quantity of oxygen-demanding, organic substances in the waste water of one person.
Nowadays, the use of the unit inhabitant equivalent is decreasing. The most common unit is the pollution equivalent.
Total capacity inhabitant equivalents
The total capacity of all urban waste water treatment plants.
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
Volume waste water
The annual volume of influent waste water.
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.
Chemical oxygen demand (COD)
Chemical oxygen demand (COD). Measure of the amount of oxygen consumed when a substance is degraded chemically.
Biochemical oxygen demand (BOD)
Biological oxygen demand (BOD). Measure of the amount of oxygen consumed when a substance is biodegraded.
Nitrogen compounds as N (total)
The total amount of nitrogen in organic compounds (e.g. proteins) and inorganic compounds (e.g. nitrate and ammonium)
Phosphorus compounds as P (total)
The total amount of phosphates and other phosphorus compounds in waste water, measured as phosphorus (P).
Copper
Chromium
Zinc
Lead
Cadmium
Nickel
Mercury
Arsenic
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
Volume waste water
The annual volume of effluent waste water.
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.
Chemical oxygen demand (COD)
Chemical oxygen demand (COD). Measure of the amount of oxygen consumed when a substance is degraded chemically.
Biochemical oxygen demand (BOD)
Biological oxygen demand (BOD). Measure of the amount of oxygen consumed when a substance is biodegraded.
Nitrogen compounds as N (total)
The total amount of nitrogen in organic compounds (e.g. proteins) and inorganic compounds (e.g. nitrate and ammonium).
Phosphorus compounds as P (total)
The total amount of phosphates and other phosphorus compounds in waste water, measured as phosphorus (P).
Copper
Chromium
Zinc
Lead
Cadmium
Nickel
Mercury
Arsenic
Sewage sludge
Residue of treated waste water consisting of suspended solids and excess active sludge (biomass). Sewage sludge is measured including water (see Total wet sludge) or as dry solids.
Wet sewage sludge by destination
The volume of wet sewage sludge, i.e. including water by destination (processing method).
Total wet sludge
Total wet sludge discharged.
Agriculture
Application of manure or soil improver in agriculture. Due to rigid legislation impossible since 1995.
Wet oxidation
Wet oxidation of sludge in so-called VerTech installations: the sludge is oxidised under high pressure in a deep shaft.
Composting
Landfill
Dumping of sludge on regional landfill sites or special sludge depots.
Incineration
Incineration of sludge in special sludge incineration plants or in household waste incinerators.
Cement industry
Co-incineration in cement ovens.
Co-incineration at power plants
Sewage sludge used as a secondary fuel at a power plant.
Other destinations
Mainly reuse.
Dry solids by destination
Discharged sewage sludge in kilogrammes of dry solids by destination (processing method). Dry solid is the residue of sewage sludge after evaporation at 105 degrees centigrade.
Total dry solids
Agriculture
Application of manure or soil improver in agriculture. Due to rigid legislation impossible since 1995.
Wet oxidation
Wet oxidation of sludge in so-called VerTech installations: the sludge is oxidised under high pressure in a deep shaft.
Composting
Landfill
Dumping of sludge on regional landfill sites or special sludge depots.
Incineration
Incineration of sludge in special sludge incineration plants or in household waste incinerators.
Cement industry
Co-incineration in cement ovens.
Co-incineration at power plants
Sewage sludge used as a secondary fuel at a power plant.
Other destinations
Mainly reuse.
Nutrients and heavy metals
The total weight of nutrients and heavy metals removed with the sludge. Most heavy metals adsorb strongly to the sludge particles.
Ashes
The residue of non-inflammable, inorganic matter after incineration.
Nitrogen compounds as N
The total amount of nitrogen in organic compounds (e.g. proteins) and inorganic compounds (e.g. nitrate and ammonium).
Phosphorus compounds as P
The total amount of phosphorus in sewage sludge is analysed as P205 (diphosphorus pentoxide) converted to P total.
Copper
Chromium
Zinc
Lead
Cadmium
Nickel
Mercury
Arsenic