Urban waste water treatment per province and river basin district

Urban waste water treatment per province and river basin district

Regions Periods Urban waste water treatment plants Numbers by type Total number (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 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 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 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 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)
Nederland 2020 315 2 58 56 44 118 1 10 14 1 9 2 29,713 108 10,152 4,615 1,133 9,884 40 956 1,598 91 774 363 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
Noord-Nederland (LD) 2020 61 1 9 10 5 29 1 2 2 1 0 1 3,369 54 651 375 81 1,454 40 186 97 91 0 340 222,985 2,812 110,571 44,714 9,589 1,373 15,140 1,667 43,927 2,952 43 1,260 28 604 222,985 255 9,954 906 1,406 170 969 166 5,740 113 10 438 7 256 147,781 0 0 0 990 137,894 0 8,897 0 33,981 0 0 0 278 31,381 0 2,322 0 10,906 2,361 1,233 11,929 1,179 31,138 2,622 25 828 14 328
Oost-Nederland (LD) 2020 83 0 13 13 19 25 0 3 6 0 3 1 6,727 0 1,916 1,684 339 2,270 0 185 211 0 99 23 368,567 6,210 244,548 98,632 21,150 3,027 27,116 3,020 101,902 5,790 84 3,530 36 1,223 368,567 394 13,786 1,221 2,882 379 1,877 369 16,035 241 12 1,205 3 426 294,380 0 0 0 4,623 149,409 0 113,528 26,820 63,700 0 0 0 1,203 29,237 0 27,419 5,841 19,507 4,024 2,198 24,508 2,632 73,493 4,587 63 1,744 29 612
West-Nederland (LD) 2020 121 1 21 28 6 53 0 5 5 0 2 0 13,218 54 4,357 2,113 98 4,617 0 585 927 0 468 0 886,777 11,853 458,913 187,538 42,025 5,664 58,424 5,483 175,465 14,021 167 6,124 90 3,427 886,777 847 30,268 3,086 6,428 681 3,674 721 25,339 581 43 2,801 14 1,449 562,628 0 0 0 0 531,824 0 4,043 26,761 139,549 0 0 0 0 132,248 0 1,023 6,277 37,779 8,631 4,989 54,395 4,565 140,432 12,785 121 2,986 68 1,835
Zuid-Nederland (LD) 2020 50 0 15 5 14 11 0 0 1 0 4 0 6,399 0 3,227 443 615 1,543 0 0 363 0 207 0 460,147 6,155 242,447 97,701 20,922 3,233 32,320 3,960 112,448 5,505 140 6,476 40 1,195 460,147 490 18,294 2,299 3,605 415 2,637 605 21,867 308 17 2,699 2 471 258,545 0 0 0 0 244,031 14,514 0 0 71,130 0 0 0 0 57,515 13,614 0 0 23,597 4,094 2,750 29,884 3,627 80,782 5,761 102 2,380 32 472
Groningen (PV) 2020 22 0 4 4 2 8 1 1 1 0 0 1 1,017 0 180 110 13 260 40 17 56 0 0 340 73,846 840 33,467 12,870 2,773 398 5,718 445 14,064 838 10 395 11 203 73,846 99 3,930 418 622 51 364 42 1,577 35 1 151 3 66 48,346 0 0 0 0 48,346 0 0 0 11,574 0 0 0 0 11,574 0 0 0 4,583 927 416 5,347 405 12,500 1,030 9 338 5 208
Fryslân (PV) 2020 27 1 0 4 1 19 0 0 1 1 0 0 1,336 54 0 170 16 964 0 0 41 91 0 0 91,459 1,101 41,957 17,190 4,051 566 4,876 821 15,675 1,197 17 517 9 273 91,459 86 3,488 243 414 68 338 79 2,545 57 6 177 3 138 71,852 0 0 0 0 71,852 0 0 0 15,285 0 0 0 0 15,285 0 0 0 4,404 1,045 577 4,308 577 11,718 1,117 10 347 5 99
Drenthe (PV) 2020 12 0 5 2 2 2 0 1 0 0 0 0 1,016 0 471 95 51 230 0 169 0 0 0 0 57,680 870 35,148 14,655 2,765 408 4,547 401 14,188 918 16 349 9 128 57,680 69 2,536 245 369 51 267 45 1,618 22 3 110 1 52 27,583 0 0 0 990 17,695 0 8,897 0 7,122 0 0 0 278 4,522 0 2,322 0 1,919 390 240 2,274 197 6,920 476 5 144 3 21
Overijssel (PV) 2020 32 0 9 6 8 2 0 1 5 0 0 1 2,192 0 893 632 219 218 0 21 186 0 0 23 116,450 1,906 74,967 30,880 6,490 949 9,941 803 34,118 2,440 36 1,215 14 261 116,450 128 4,829 407 918 107 676 69 5,448 71 4 439 1 110 97,620 0 0 0 4,623 85,788 0 7,209 0 17,416 0 0 0 1,203 14,442 0 1,771 0 6,218 1,074 704 8,962 954 25,122 1,620 20 694 9 122
Flevoland (PV) 2020 5 0 0 1 0 4 0 0 0 0 0 0 754 0 0 65 0 689 0 0 0 0 0 0 29,602 674 25,766 11,322 2,453 349 2,014 172 5,562 183 6 162 3 406 29,602 33 1,087 91 243 25 170 33 1,468 13 0 75 0 109 38,833 0 0 0 0 35,815 0 0 3,019 8,432 0 0 0 0 7,877 0 0 555 1,870 577 261 1,932 170 4,955 158 4 126 3 229
Gelderland (PV) 2020 46 0 4 6 11 19 0 2 1 0 3 0 3,781 0 1,023 986 121 1,363 0 164 25 0 99 0 222,516 3,631 143,815 56,430 12,206 1,730 15,161 2,045 62,221 3,168 42 2,154 18 556 222,516 233 7,870 723 1,721 247 1,031 268 9,119 157 8 691 2 207 157,927 0 0 0 0 27,806 0 106,318 23,802 37,853 0 0 0 0 6,919 0 25,648 5,286 11,419 2,373 1,232 13,614 1,508 43,416 2,809 39 925 17 260
Utrecht (PV) 2020 22 0 3 4 0 13 0 0 1 0 1 0 2,084 0 185 108 0 1,340 0 0 19 0 432 0 118,175 1,810 70,994 28,645 6,204 823 8,026 792 27,403 1,668 28 795 13 322 118,175 107 3,893 372 864 69 679 106 4,541 71 1 294 1 86 96,947 0 0 0 0 79,419 0 4,043 13,484 21,095 0 0 0 0 16,716 0 1,023 3,356 5,525 1,388 799 6,609 710 20,923 1,544 17 358 9 131
Noord-Holland (PV) 2020 30 1 8 5 3 8 0 3 2 0 0 0 4,582 54 1,940 1,033 82 795 0 433 246 0 0 0 289,642 4,047 153,901 66,440 14,938 1,963 22,881 1,536 58,175 5,318 54 1,821 32 840 289,642 300 10,244 915 2,169 196 1,323 186 8,419 207 18 730 4 350 153,765 0 0 0 0 140,488 0 0 13,277 49,216 0 0 0 0 46,295 0 0 2,921 12,801 2,829 1,724 20,547 1,489 51,003 4,294 40 1,033 24 521
Zuid-Holland (PV) 2020 54 0 4 14 3 30 0 1 2 0 0 0 5,753 0 1,784 786 16 2,439 0 65 662 0 0 0 428,791 5,438 213,200 84,147 18,729 2,612 23,961 2,856 78,047 6,379 73 3,233 41 1,894 428,791 380 13,922 1,479 2,987 368 1,430 385 10,511 280 19 1,657 8 841 287,673 0 0 0 0 287,673 0 0 0 63,216 0 0 0 0 63,216 0 0 0 17,351 4,081 2,261 24,137 2,135 61,158 6,310 57 1,450 32 1,018
Zeeland (PV) 2020 15 0 6 5 0 2 0 1 0 0 1 0 799 0 448 186 0 43 0 86 0 0 36 0 50,169 559 20,819 8,305 2,154 266 3,555 298 11,841 657 12 275 5 371 50,169 60 2,209 321 408 47 242 45 1,868 23 4 120 1 172 24,243 0 0 0 0 24,243 0 0 0 6,021 0 0 0 0 6,021 0 0 0 2,102 333 205 3,103 232 7,348 637 8 145 3 165
Noord-Brabant (PV) 2020 33 0 11 2 14 5 0 0 1 0 0 0 4,358 0 2,744 16 615 620 0 0 363 0 0 0 312,031 4,393 175,023 71,219 14,507 2,482 25,407 2,543 69,720 3,751 90 3,109 29 698 312,031 327 12,437 1,333 2,388 313 2,229 383 14,926 241 17 1,449 1 259 211,980 0 0 0 0 211,980 0 0 0 49,051 0 0 0 0 49,051 0 0 0 15,782 2,933 1,992 23,800 2,547 57,204 4,179 68 1,402 23 354
Limburg (PV) 2020 17 0 4 3 0 6 0 0 0 0 4 0 2,041 0 484 427 0 922 0 0 0 0 207 0 148,116 1,762 67,424 26,482 6,415 750 6,913 1,417 42,728 1,754 50 3,367 12 497 148,116 163 5,857 966 1,217 102 408 223 6,940 67 1 1,250 0 213 46,565 0 0 0 0 32,051 14,514 0 0 22,078 0 0 0 0 8,464 13,614 0 0 7,815 1,162 758 6,084 1,080 23,578 1,582 34 978 9 118
The river Eems 2020 16 0 7 3 0 4 0 0 1 0 0 1 1,134 0 366 102 0 270 0 0 56 0 0 340 78,835 959 38,332 14,910 3,129 440 6,775 482 15,832 914 11 429 12 188 78,835 121 4,683 475 713 62 461 58 1,557 35 2 164 3 64 48,346 0 0 0 0 48,346 0 0 0 11,574 0 0 0 0 11,574 0 0 0 4,583 927 416 5,347 405 12,500 1,030 9 338 5 208
The river Rijn (North Rijn) 2020 38 1 0 5 4 24 1 1 1 1 0 0 1,521 54 0 178 45 1,054 40 17 41 91 0 0 105,753 1,243 47,463 19,412 4,543 639 5,599 888 18,260 1,356 19 580 10 322 105,753 100 4,013 313 494 81 377 83 3,007 64 7 199 3 158 71,852 0 0 0 0 71,852 0 0 0 15,285 0 0 0 0 15,285 0 0 0 4,404 1,045 577 4,308 577 11,718 1,117 10 347 5 99
The river Rijn (East Rijn) 2020 73 0 13 14 13 23 0 2 5 0 2 1 6,849 0 1,509 1,742 314 2,814 0 190 186 0 72 23 365,571 6,114 239,818 97,276 21,032 2,974 26,145 2,790 104,541 6,002 90 3,171 39 1,214 365,571 381 13,503 1,079 2,773 299 1,849 332 16,472 242 9 1,167 2 429 281,660 0 0 0 5,613 162,661 0 84,808 28,579 62,425 0 0 0 1,480 33,037 0 21,077 6,830 19,007 3,867 2,211 23,488 2,468 73,538 4,661 62 1,704 30 563
The river Rijn (Central Rijn) 2020
The river Rijn (West Rijn) 2020 116 1 17 24 11 49 0 6 6 0 2 0 12,860 54 4,602 1,963 153 4,016 0 662 952 0 459 0 868,245 11,879 462,761 189,110 41,499 5,684 57,983 5,674 169,235 13,717 160 6,423 88 3,110 868,245 826 29,325 2,995 6,282 733 3,549 733 23,990 567 42 2,782 14 1,289 573,616 0 0 0 0 506,953 0 41,660 25,003 140,822 0 0 0 0 125,846 0 9,688 5,288 37,845 8,770 4,977 54,156 4,670 139,057 12,467 119 3,008 67 1,720
The river Maas 2020 52 0 14 3 14 16 0 0 1 0 4 0 6,046 0 2,756 427 606 1,686 0 0 363 0 207 0 430,317 5,699 224,044 89,885 19,474 2,976 31,454 3,643 108,624 5,360 129 5,885 37 1,121 430,317 443 16,415 2,151 3,244 342 2,580 563 21,335 302 18 2,500 2 438 232,913 0 0 0 0 218,399 14,514 0 0 66,010 0 0 0 0 52,396 13,614 0 0 21,230 3,862 2,550 27,499 3,132 75,411 5,324 94 2,211 29 423
The river Schelde 2020 20 0 7 7 2 2 0 1 0 0 1 0 1,302 0 919 202 16 43 0 86 0 0 36 0 89,756 1,136 44,064 17,991 4,009 583 5,044 654 17,250 921 26 904 9 493 89,756 115 4,363 499 814 127 340 93 2,620 34 5 332 1 225 54,946 0 0 0 0 54,946 0 0 0 12,243 0 0 0 0 12,243 0 0 0 4,720 640 439 5,918 750 13,621 1,156 16 332 6 234
Source: CBS.
Explanation of symbols

Table description


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 12 May 2022:
The figures of 2020 has been added.
Due to new information on 2019, total influent load of CZV and total Pollution Equivalents of the influent has increased with 4 percent in 2019 compared to the previous version. This results for the two parameters also in small changes in underlying classifications.

When will new figures be published?
New figures on 2021 will be published by March 2023.

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.
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.
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
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.
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