RWW Rheinisch-Westfälische Wasserwerksgesellschaft mbH

About RWW

RWW Rheinisch-Westfälische Wasserwerksgesellschaft mbH, headquartered in Mülheim an der Ruhr, has supplied more than one million people as well as industrial and commercial enterprises in the western Ruhr region, the adjacent Münsterland, municipalities in the Rhein-Erft district and in the districts of Kleve and Steinfurt with drinking water and non-potable water since 1912. In 2025, the water output was 71.5 million cubic meters, of which 34.7 million cubic meters went to special customers from industry and commerce. The waterworks extract groundwater from the Halterner Sanden and Recklinghäuser Sandmergeln formations as well as surface water from the Ruhr; treatment includes, among other methods, the predominantly biological Mülheim process (ozone, activated carbon, soil passage), iron removal, manganese removal and UV disinfection. For large industrial customers, RWW operates the Seewasserwerk Dorsten "Blauer See" for service water. Via the Kahlenberg hydropower plant, the company generates around 15 GWh of green electricity per year. As part of the Westenergie/E.ON group, RWW employs 467 staff with revenue of 140.7 million euros (2025).

Site

Mülheim an der Ruhr

Processes

Drinking water treatment (iron removal, manganese removal), Drinking water and non-potable water supply, Service water supply (large industrial customers), Water dispensers for businesses (rental/purchase options incl. maintenance), Tank cleaning, Valve inspection, Water loss analysis, Leak detection

Materials

Groundwater (Halterner Sanden / Recklinghäuser Sandmergeln), Surface water from the Ruhr, Service water (Seewasserwerk Dorsten 'Blauer See')

Certificates

ISO 14001, EMAS

Founded

1912

Employees

467

Industries

Water supply (private, industrial and commercial customers), Energy generation (hydropower)

1. 01

   Water extraction (groundwater and surface water)

2. 02

   Treatment (iron removal, manganese removal, Mülheim process, UV disinfection)

3. 03

   Control and monitoring via central control room

4. 04

   Distribution via pipeline network

5. 05

   Customer service and metering inspection

Extraction and Treatment

Waterworks and Locations

Mülheim-Styrum/Ost

DE

Ruhr waterworks (drinking water), central control room, testing laboratory, main workshops, headquarters

Materials

Surface water from the Ruhr

• Central control room
• Testing laboratory
• Mülheim process variant 1
• UV system
• Emergency chlorination system
• Aquatorium

Mülheim-Styrum/West

DE

Ruhr waterworks (drinking water)

Materials

Surface water from the Ruhr

• Mülheim process variant 2
• UV system
• Emergency chlorination system

Essen-Kettwig

DE

Ruhr waterworks 'vor der Brücke' (drinking water for the southern supply area)

Materials

Surface water from the Ruhr

• Mülheim process variant 2
• UV system
• Infiltration trench drains
• Cutoff wall

Dorsten-Holsterhausen

DE

Groundwater works (drinking water)

Materials

Groundwater (Halterner Sanden)

• 64 wells
• Iron/manganese removal
• Sludge water treatment

Dorsten 'Blauer See'

DE

Lake waterworks (service water for large industrial customers)

Materials

Surface water from Hammbach/Wienbach

• Reservoir (280,000 m³)
• Gravity-flow pipeline

Reken-Melchenberg

DE

Groundwater works (drinking water) / Service Point Dorsten/Reken

Materials

Groundwater (Halterner Sanden)

• 6 wells
• Phosphate dosing
• Fully automated operation

Velen-Tannenbültenberg

DE

Groundwater works (drinking water)

Materials

Groundwater (Recklinghäuser Sandmergel)

• 3 wells
• Iron removal plant
• Settling tanks

Kahlenberg

DE

Hydropower plant on the lock island in Mülheim (green electricity)

Materials

Ruhr water

• Francis double-chamber turbine
• Two Kaplan turbines
• Kahlenberg weir system

Services

Inside the production

Processes & technical limits

Quality and Certification

An independent testing laboratory regularly examines the drinking water at the waterworks outlet and in the distribution network; all limit values of the Drinking Water Ordinance are undershot. The operating systems for environmental and occupational safety, information security, resilience and energy use are consolidated in an Integrated Management System (IMS).

History

1. 1871

   Foundation stone for today's Styrum/Ost Ruhr waterworks: merger of the Oberhausen waterworks and the Thyssen & Cie waterworks.

2. 1912

   Foundation of RWW; operation of the Styrum/Ost Ruhr waterworks has been its responsibility ever since.

3. 1922-1926

   Construction of the Kahlenberg hydropower plant on the lock island in Mülheim.

4. 1927

   Commissioning of the Dorsten-Holsterhausen groundwater works.

5. 1944

   RWW takes over operation of the Essen-Kettwig 'vor der Brücke' waterworks.

6. 1955

   Commissioning of the Mülheim-Styrum/West Ruhr waterworks and the Dorsten 'Blauer See' lake waterworks.

7. 1958

   Commissioning of the Velen-Tannenbültenberg groundwater works.

8. 1968

   Commissioning of the Reken-Melchenberg groundwater works.

9. 1974

   Capacity increase of the Dorsten-Holsterhausen waterworks to 29 million m³/year through the Üfter Mark well gallery.

10. 1982

    Operation of the Styrum/Ost Ruhr waterworks according to the Mülheim process, variant 1.

11. 2018

    UV system replaces chlorination at the Styrum/Ost waterworks (from March).

12. 2026

    Safety chlorination at the Essen-Kettwig waterworks replaced by a UV system.