Am Erftverband 6
50126 Bergheim

Contact person
Dr. Ekkehard Christoffels
Phone: +49 2271 88 1109



Institution profile
The catchment of the River Erft
Waste water treatment strategy
Contact person at Erftverband

Institution profile

Erftverband, a non-profit organisation under public law, involves 43 cities and dozens of small towns. It covers a total area of 1,918 km², which is the above-ground catchment area of the Erft, as well as subsurface waters on an area of 2,298 km². The main tasks of the Erftverband are:

1. Groundwater and water supply
• research and observation of the water resources affected by lignite mining;
• measures to secure the private and industrial water supply;
• regulation of the groundwater level;
• compensation of negative ecological effects.

2. Waste water management
• wastewater treatment and sludge removal;
• maintenance of sewer systems.

3. Surface waters
• maintenance of surface water;
• flood prevention and mitigation;
• river restoration.

To perform these tasks, the Erftverband participates in various research projects, especially in the field of water quality enhancement.


The catchment of the River Erft

Figure 1: Erftverband core region and extended region

The catchment area of the Erft River extends over 1,918 km². The operational region of the Erftverband extends beyond the catchment area with a total of ca. 2,298 km². The total observation and research area on watercourses and groundwater extends over 4,216 km² (cf. Figure 1) [1]. The catchment area and the operational region is generally a level plain, with the exception of certain southern areas (the foothills of the Eifel Mountains), and low gradients for water flow.

Figure 2: The middle and lower reaches of the Erft river is steaming in cold seasons

The main watercourse is the Erft river, which flows over a length of 106,6 km [2] from South to North passing to the west of the Cities of Bonn and Cologne. The Erft and it’s numerous tributary streams with a total length of ca. 1,330 km [2] conduct limited volumes of water under normal weather conditions (650 mm average precipitation per year [2]). Near the city of Euskirchen the river, with an average 1% slope of decline, leaves the mountainous region called the Eifel. In the middle and lower reaches the Erft descends at a very gradual slope of 0.1% [3]. At the end of its course the Erft flows into the Rhine river near the city of Düsseldorf.

Wide areas of the river basin are dominated by cultivation of field crops including wheat, rye, barley and sugar beets. In addition, the region is well known for its open pit lignite mines. Large quantities of groundwater must be pumped out to keep these mines dry. About 250 million cubic meters a year [1] of this groundwater is discharged in the Erft river in the middle reach. The water temperature in the middle and lower reaches of the river Erft is considerably influenced by discharge of warm groundwater (cf. Figure 2). The discharged groundwater determines the level of water flow in the middle and lower portions of the river. The mean run off at the mouth is around ten cubic meters per second of which the natural run off amounts to only about 3 cubic meters per second [4]. Besides extensive cultivation of field crops and coal mining, some other significant activities as abstraction of water for aquatic biotopes and intensive fruit and vegetable production, discharge from waste water treatment plants and recreation (e.g. sport fishing, boating) impact the Erft river. The last point is of particular importance, since the population density of 640 inhabitants per km² in parts of the Erft catchment area is 20% above the average for North Rhine-Westphalia [5].


Waste water treatment strategy

The waste water treatment strategy is based on the regional structure with scattered towns and villages as well as limited natural water flow in the Erft river and the contributing stream network. As a result the waste water treatment concept is decentralised with high treatment standards in accordance with the principle “to discharge as close as possible to fresh water removal points to keep the watercourses flowing”. Based on a regional waste water treatment plan, Erftverband receives waste water at various transfer points from the municipalities typically at the boundary limits of the treatment plants or at the border of settled municipal areas, from where it is conducted by a network of collectors, pumping stations and rainwater retention and treatment facilities, to the treatment plants.

Originally many of the waste water treatment plants were initially built and owned by the local municipalities and operated by the Erftverband. The revision of the Erftverband law in 1988 resulted in the transfer of substantially all regional treatment plants into the ownership of the Erftverband during the nineties. The individual regional municipalities continue to be responsible to collect and transfer waste water by their collection channel networks. In general, the facilities have been substantially modernized, upgraded and expanded by the Erftverband.

As of the end of the year 2008 the Erftverband operates [1]:

  • 42 municipal sewage treatment plants and one industrial with a total capacity of more than one million inhabitant equivalents;
  • 351 sewage retention basins;
  • 110 pumping stations;
  • connection channels with a total length of about 238 km;
  • 3 sewerage systems with a total length of about 642 km;
  • 41 controllable weirs;
  • 17 flood control basins.

Most of the operation units belong to the Erft catchment but some belong to the operational region beyond.


[1] Erftverband (2008): Jahresbericht 2008 (Eigenverlag), Bergheim.

[2] Ergebnisbericht Erft (2005): Ergebnisbericht Erft, Wasserrahmenrichtlinie in NRW – Bestandsaufnahme. Ministerium für Umwelt- und Naturschutz, Landwirtschaft und Verbraucherschutz des Landes Nordrhein-Westfalen.

[3] Christoffels (2008): Monitoring und Modellanwendung – Entwicklung eines Immissionsinventars am Beispiel der Erft. Dissertation, Erftverband, Bergheim.

[4] Deutsches Gewässerkundliches Jahrbuch (2000): Rheingebiet, Teil III 1996. [Hrsg.] Landesumweltamt Nordrhein-Westfalen, Essen, ISSN 1432-4628.

[5] Bewirtschaftungsplan Erft (2005): Ergebnisberichte Wasserrahmenrichtlinie in NRW – Bestandsaufnahme – Rheingraben Nord. Ministerium für Umwelt- und Naturschutz, Landwirtschaft und Verbraucherschutz des Landes Nordrhein-Westfalen.


Contact person at Erftverband

Dr. Ekkehard Christoffels

Ekkehard Christoffels has been working at the Erftverband for more than 25 years. The Erftverband is one of the eleven water associations in North Rhine-Westphalia, Germany. Christoffels´ area of responsibility is surface water quality management. During his professional career he was engaged in the advancement of process engineering referring to waste water treatment and questions of water law.

Furthermore, he projected an innovative technology to eliminate heavy metals out of the aqueous phase of mining effluents. Ekkehard Christoffels was significantly involved in the development of the DWA Water Quality Model (DWA, German Water Association) and in this context he supervised the development of the module of heavy metal transport. He established and implemented a concept of online network for monitoring river water quality in the catchment area of the river Erft.