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Voigtländer · Cooling water
Control and document Legionella in cooling towers
Voigtländer generates anolyte on site and doses it into the cooling circuit under measurement control; operating data is stored. This supports Legionella control and documentation in cooling towers. The service is for operators of industrial evaporative cooling systems and for facility management and building services. Treatment does not replace the operator's duties under the 42. BImSchV (German ordinance on evaporative cooling systems, cooling towers and wet separators), and which inspections, intervals and values apply depends on the plant type.
Standards & conformity
- DIN EN 901 · § 11 TrinkwV
- DVGW W551
- TrinkwV approval (Umweltbundesamt)
- WHO-compliant
- CE conformity
- No change in taste
Typical entry points
Who the review is for
For facility management, building services and operators of industrial evaporative cooling systems. The review is particularly worthwhile if one of these points applies:
Unstable operating values
Readings fluctuate or fail to hold the target range.
Biofilm in the circuit
Recurring loading despite treatment.
Gap in inspection or documentation
Records are incomplete or scattered.
System context
Why biofilm and operating regime belong together
Evaporative cooling generates aerosols; rising colony counts and Legionella findings usually arise where biofilm, nutrients, temperature and the operating regime come together. A one-off shock treatment addresses the symptoms. Hygiene only becomes durable once water condition, dosing and plant management are run as one system.
When factors combine
Biofilm · nutrients · temperature · operating regime
A one-off shock treatment addresses the symptoms.
Run as one system
Water condition · dosing · plant management
Durably stable hygiene, traceable in operation.
Method
Monitoring water condition, dosing and redox
Voigtländer generates anolyte on site and doses it into the cooling circuit under measurement control, via redox control, for example. Operating data is stored, so the plant's history remains traceable. This method does away with chlorine gas logistics and hazardous-substance storage; the specific risk assessment remains plant-specific.
System overview
Closed control loop of cooling water hygiene
Inlet and water meter, brine tank, the three-chamber generator, anolyte tank, demand-led dosing, measurement and control: seven stages in 34 seconds. Press "Show me the process" to start the animated 3D diagram.
starts when the frame is in view
Modelled from the Voigtländer plant schematic of an anolyte system, in the drawing language of the home page. The cards show documented facts only, no invented figures.
Regulation
Placing the requirements of the 42. BImSchV
The ordinance requires operation according to the state of the art, internal operational inspections, laboratory testing for Legionella, a Betriebstagebuch (operating logbook) and graduated measures when findings occur. Monthly laboratory testing is not the blanket default; it arises, for example, after a confirmed exceedance of a Prüfwert (inspection value). The plant is notified via the KaVKA-Portal.
The "reference value 100" relates to the general colony count, not to Legionella. The binding assignment follows from the classification of the specific plant.
Inspection and action values by plant type, and the duties under the 42. BImSchV
Review sequence
How the operator path runs
- 1
Classify the plant type
Evaporative cooling system, wet separator or cooling tower.
- 2
Internal operational inspection
Check operation against the state of the art.
- 3
Laboratory testing
Testing for Legionella at the defined interval.
- 4
Place the values
Assess the finding against the inspection values for the plant type.
- 5
Measures and records
Graduated measures and keeping the Betriebstagebuch.
A sequence shown for orientation. The binding duties, intervals and deadlines depend on the classification of your specific plant; see Duties under the 42. BImSchV.
Reference
Application in a hospital cooling tower
The Healthcare/HVAC catalogue describes a plant at a German university hospital with continuous redox control and stored operating data. The application is described in Hydreatio's own case study as a cooling tower and HVAC reference; the site is not named until the operator releases it.
Performance figures remain bound to the specific project context and are not a general undertaking.
The objection
The central objection, answered honestly
Treatment does not replace the operator's duties: laboratory testing, the Betriebstagebuch, notification and the graduated measures remain the operator's responsibility. The technology supports plant management; it does not take its place.
Questions before the first call
What operators ask before a plant assessment
01What are the operator duties for evaporative cooling systems under Germany's 42. BImSchV?
Operators must run the plant according to the state of the art, carry out internal operational inspections and laboratory testing for Legionella, keep a Betriebstagebuch (operating logbook) and take graduated measures when findings occur. Notification of the plant is made via the KaVKA-Portal. Which inspections, intervals and values apply depends on how the plant is classified.
02What must be done if the action value for Legionella in a cooling tower is exceeded?
If the action value (Maßnahmenwert) is exceeded, the competent authority must be informed without delay; among other things, Legionella must be differentiated and tested further, and if confirmed, further measures to avert danger follow. Causes are investigated, technical or operational measures taken and steps recorded in the Betriebstagebuch. Details depend on plant category, value level and confirmation result; deadlines and notification routes are in the 42. BImSchV.
03How does the Voigtländer method support Legionella control in cooling towers?
The method supports Legionella control: anolyte is generated on site and dosed into the cooling circuit under measurement control, for example via redox control, and operating data is stored. Design is plant-specific. Hygiene only becomes durable once water condition, dosing and plant management run as one system; a one-off shock treatment addresses the symptoms. Laboratory testing, the Betriebstagebuch, notification and graduated measures stay with the operator.
04What is the difference between inspection values and the action value in the 42. BImSchV?
Inspection values (Prüfwert 1 and 2) are the lower levels: investigate the cause and tighten control. The action value (Maßnahmenwert) is the highest and, among other things, adds differentiation of Legionella, additional laboratory tests and, if confirmed, measures to avert danger. In CFU per 100 ml: 100, 1,000 and 10,000 for evaporative cooling systems and wet separators; 500, 5,000 and 50,000 for legally defined cooling towers.
05Which systems fall under the 42. BImSchV?
The 42. BImSchV covers evaporative cooling systems, cooling towers and wet separators in which water can be trickled, sprayed or otherwise brought into contact with the atmosphere. Many industrial recooling systems fall into the evaporative cooling system category even when called cooling towers in daily operation. The classification follows design, operation and scope of application, not the colloquial name, and determines the relevant inspection and laboratory values.
Last reviewed: October 2026
Voigtländer in other sectors
The same method, proven across sectors
Aviation
Drinking water for aircraft
- Frankfurt Airport, in use since 2003
- Macau Airport
- Saarbrücken Airport
Buildings
Drinking-water hygiene in buildings
- Ten care homes, one programme
- Residential complex with 58 apartments
Cooling systems
Cooling towers and evaporative cooling
- University clinic: anolyte dosing in the cooling circuit, controlled by redox measurement
Food and beverage
CIP and process hygiene
- Soft drinks CIP and bottling plant
- Dairy and brewery
- Salad washing and canned food
Further applications
Agriculture and industry
- Drinking water on a poultry farm
- Tissue production
Every entry is a Voigtländer application. Results are project-specific and are not a forecast for another site.
Next step
Request a cooling tower hygiene review
The entry point runs alongside the building hygiene assessment; the cooling technology is a targeted add-on. It helps to know the plant type, the operating regime, previous laboratory findings and the reason for the review.
- 1You describe the plant, the plant type and the reason.
- 2A specialist assesses your enquiry.
- 3We agree the documents with you.
Request a cooling tower hygiene review
Briefly describe the plant, the plant type and the reason. A few details are enough for a first contact.
Your enquiry will be assessed by a specialist. The applicable duties depend on the classification of your specific plant.
Further pages
Smart Match: cooling water hygiene check
A few questions lead to the right testing route for your plant.
Managing Cooling Tower Hygiene
White paper: operator duties, monitoring and measurement-led water hygiene under the 42. BImSchV.
Duties under the 42. BImSchV
Plant type, inspections, laboratory intervals, the Betriebstagebuch and measures when findings occur.
42. BImSchV System Type: Classify Before Legionella Duties
Many operators call every open evaporative unit on site a cooling tower.
Building and drinking water hygiene
The shared hygiene path for operators with drinking water and cooling water needs.
Vendor-neutral water treatment
For when the cooling circuit, process water and wastewater are to be planned as one overall system.
Describe your water problem
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