MULTI Kühlsysteme

Cooling water hygiene

MULTI Kühlsysteme has been involved in producing cooling water recooling plant of a variety of different designs and types of construction for industrial customers for more than 25 years. Here, the focus is on concepts using evaporative cooling towers. Facility operators of such plant or equipment are faced with special requirements on the hygienic safety of said plant and equipment. The following FAQ will tell you which requirements these are in detail and how we can help you implement and comply with applicable standards of hygiene

What directives and regulations are currently in force and applicable to cooling tower plant and cooling systems?

[Translate to Englisch:] VDI - Vereins Deutscher Ingenieure

The technical guidelines and regulations applicable to the manufacturers and facility operators of evaporative cooling plant or systems have been considerably stepped up. Here, the best available technology is described in VDI 2047 Blatt 2, a recommended practice issued by the Verein Deutscher Ingenieure (VDI). Recooling plant or systems are prone to carry and spread germs or bacteria via the air. The facility operators of said plant or systems are responsible for minimizing this risk. The VDI-Richtlinie standard is designed to assist you in this process. It includes information on “How to guarantee operation of evaporative cooling plant or systems in line with hygiene requirements”.

Beyond that, the legislative has specified a binding legal framework. The “42. Verordnung zur Durchführung des Bundes-Immissionsschutzgesetzes“ (42nd executive order to the German Federal Immission Control Act) entered into force on August 19, 2017. This order titled “Verordnung über Verdunstungskühlanlagen, Kühltürme und Nassabscheider – 42. BImSchV“ (order governing evaporative cooling plant or systems, cooling towers and wet scrubbers – 42nd BImSchV), among others, specifies that the facility operator is obligated to check at regular intervals whether its plant or system emits harmful concentrations of legionella bacteria or germs that may pose a health threat. Legionella are bacteria that may trigger very serious pneumonia. They preferably multiply in water at temperatures of 20 °C to 50 °C. We have summarized the critical content of said regulations at the following FAQ. 

What are the requirements of the legislative in terms of hygienic safety?

[Translate to Englisch:] Untersuchungspflicht

In said 42nd Executive Order to the German Federal Immission Control Act, it reads verbatim: Plant “must be designed, installed and operated  such that contamination of process water by microorganisms, more specifically by legionella bacteria, will be avoided through the use of best available technology” (Section 3 (1) 42. BImSchV). In addition, the facility operator must draft a risk assessment for the respective plant or system prior to the plant or system being commissioned (re-commissioned). A technical expert specialized in the field of hygiene shall be consulted to this end. 

In addition to these more general requirements, the legislator also stipulated more specific requirements such as on the operation of evaporative cooling systems or cooling towers, for example. Here, internal audits and laboratory investigations are required, among others. Thus, the following applies to cooling towers, for example: “The facility operator shall guarantee the good hygienic quality of the process water through regular examination of chemical, physical or microbiological characteristics at intervals of no more than two (2) weeks” (Section 7 (1) 42. BImSchV). In addition, the process water must be tested for legionella bacteria and other microorganisms at a laboratory at intervals of no more than three (3) months.

In addition, said regulations provide for action that must be taken if certain test or trigger values are exceeded or if there is an operational disorder. If the circulation water is heavily contaminated, the competent authorities may even require that the affected evaporation system be shut down. Moreover, the legislative text specifies requirements on monitoring. Here, the facility operator is required to maintain an operation log and to have the plant or system audited for proper operation at intervals of five (5) years each. This audit must be conducted by a sworn technical expert.

Why were hygienic requirements stepped up in the first place?

[Translate to Englisch:] Janice Haney Carr; provided by CDC/ Margaret Williams, PhD; Claressa Lucas, PhD;Tatiana Travis, BS

In Germany, in recent years, we experienced infections with legionella bacteria that were presumable spread via cooling tower exhaust air. Strong media interest was attracted by outbreaks of the disease in Ulm at the turn of the year 2009/2010, in Warstein in 2013 and in Bremen in 2016 respectively.

Ever since that time, an increasing importance was attached to the reliable control of hygienic conditions of operation. Specifically, hygienic safety is of critical importance with open loop evaporative cooling towers. This is due to the fact that contaminated plant or systems may trigger legionella infections within a radius of more than ten (10) kilometers.

The risk of harm to humans through breathing in contaminated exhaust air (for example due to aerosols contaminated with legionella) has been known for some time. Sources have been known to provide information on this for decades already. This potential risk is nothing new to technical experts in the field of cooling tower engineering and water treatment technology or to plant operators respectively. However, it is also known that this risk can be effectively mitigated though specific actions. Thus, regular maintenance and servicing are indispensible with a view to guaranteeing perfect hygiene in cooling systems. 

How does MULTI Kühlsysteme support its customers in implementing hygienic safety?

[Translate to Englisch:] CDC/ Megan Mathias and J. Todd Parker -

We have always paid considerable attention to the conditioning of cooling water. The quality of untreated water is analyzed, and solutions are developed for the effective and environmentally friendly treatment of the circulation water. With us, the use of conductivity controlled blowdown or batching systems or of softening installations respectively has been a generally accepted code of practice for a long time. If required and requested, we also in a position to supply and deliver special systems such as reverse-osmosis systems or deferrization systems respectively.

In the past 15 years, MULTI Kühlsysteme have systematically established after-sales services for the cooling systems supplied and delivered by us. Maintenance and servicing schedules were developed, and a team of trained maintenance staff was put together. Thus, today, we are in a position to offer a comprehensive range of maintenance services for recooling systems. This covers all the customary components such as evaporative cooling towers of different design layouts and types of construction, pump & tank stations, filter systems, heat exchangers, fittings and valves or pipes. Inspection of control systems or installations including sensor systems, switchgear cabinets, electrical wiring or programmable logic controllers (PLCs) is a key component of each maintenance or servicing activity.

Our service engineers are deployed in Germany, Austria, Poland, Luxemburg and Switzerland. Here, we are planning on extending our operating range even more.

Perfect quality of the cooling water is indispensible for the safe operation of the cooling system and thus for smooth flow of the production process. That is what our engineers experience firsthand when they commission recooling systems or when they fill maintenance assignments. High quality of the cooling water is critical in achieving low operating costs and high levels of availability. 

That is why the project engineers of MULTI Kühlsysteme have intensively dealt with the issue of water treatment from a hygiene point of view and have upskilled themselves in this regard. In our operation manuals, for some time now, we recommend our customers to implement the “Hinweise und Empfehlungen zum wirksamen und sicheren Betrieb von Verdunstungskühlanlagen“ (information and recommendations regarding the effective and safe operation of evaporative cooling systems) proposed in the VDMA-Einheitsblatt standard sheet VDMA 24649:2005-05. This recommended code of practice is currently being revised (see the hyperlink).

Moreover, we have referred to the implementation of EUROVENT 9/5 - 2000 „Richtlinien zur Verhinderung unkontrollierten biologischen Wachstums, u. a. Legionellen in Kühltürmen und Verdunstungsverflüssigern“. (terms of reference for the prevention of uncontrolled biological growth such as legionella bacteria in cooling towers or evaporative condensers) for many years. In discussions with our customers, these issues are brought up time and again.

How does MULTI Kühlsysteme respond to the stricter statutory standards of hygiene?

[Translate to Englisch:] Legionellenbekämpfung

To respond to the current development on the market for cooling water recooling plant, we at MULTI Kühlsysteme will expand our range of services with immediate effect. Now, we offer our customers the following services in addition to our proven existing range of services:

  • To prepare the operation log,
  • To conduct a risk assessment,
  • To Sampling for microbiological monitoring and laboratory analysis of the samples ”by our partner laboratory
  • To evaluate and assess the results,
  • To provide assistance in the implementation of action if guidance values are exceeded, and
  • To provide guidance and training regarding relevant technical regulations and terms of reference.

Your contact

Lucas Elsner looks forward to receiving your inquiries.

How to contact him:

By phone:  03771 2467 36

By e-mail: