Urban waste water treatment per province and river basin district

Changed on: 22/04/2024 02:00

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