Tutorial Legionella

At 30 diseased (22 men, 8 women) was 2011 the course of the disease so difficult, that they died of Legionella pneumonia. This corresponds to a mortality of 0,04 per 100.000 population. The lethality, ie the proportion of the deceased among the patients, scam 4,7 % and has thus over the previous year (51 registered deaths, lethality 7,4 %) decreased significantly. Illustration 4 shows the absolute number of registered deaths each year since 2001 and the percentage of dead among sufferers (lethality). The average age of the deceased was 2011 with 64,5 years (Median 69 years; span 0 to 85 years).

In another document, the Robert Koch Institute has the data, including 2017 evaluated. The number of cases has continued to rise significantly. The bright portions show the disease, that could have been related to a trip abroad.

One should not forget, that are counted in these statistics only diseases, whose link has been established for legionellosis. Because the disease of pneumonia is very similar, should the number of unreported cases in Germany to be very high.

Comparing to other nations have to draw even. But it can be assumed, that Germany represents the lower end of the number of diseases and death rate due to the extremely high standard in the sector of water treatment.

Akualisierung Update Update

A major topic is of course the drinking water supply. Here end the rules of DIN, DVGW and VDI regularly in the known drinking water regulation.

The justification of the measures is in paragraph 5 5 witch drinking water regulation anchored. In the (for the purpose of legibility) shortened form states:

So far (…) an agent (…) facts discovered, which to occurrence of a transmissible disease (…) being able to lead, (…) must a preparation, if necessary, including a disinfecting (…) be done. In piping networks (…) where the requirements (…) can be met only by disinfection, have the (…) owner (…) a sufficient disinfection capacity by free chlorine, Chlorine dioxide or other suitable disinfectants or procedures (…) keep ready.

The following quotes apply to Legionella:

f) Legionella: The tests on Legionella spec. is in accordance with ISO 11731 and DIN EN ISO 11731 Part 2 carry out taking into account, if appropriate, present recommendations of the Federal Environmental Agency.

In Part II is for the indicator parameters Legionella spec. a Technical measures value 100 CFU per 100ml set.

b) Analysis of drinking water installations according to § 14 Paragraph 3

Der Parameter Legioonella spec. is at least once a year in accordance with the provisions in § 14 paragraph 3 to investigate. Wasserversorgungsanlagen nach §3 Nummer 2 Letter e, from which part of a commercial, but not public activity is delivered drinking water, are at least every three years relevant provisions of § 14 Paragraph 3 to investigate. The first examination must reach the 31. December 2013 to be finished. For water supply systems according to §3 number 2 Letter d The Health Authority specifies the frequency determined.

Are on the annual tests for Legionella spec. has found no cause for three consecutive years, so the health department can also set longer examination intervals of up to three years, provided that the system and operating mode have not been changed and demonstrably comply with the generally accepted rules of technology. This temporal extension of the examination intervals is not possible in areas, in which patients are at higher risk for hospital infections (as hospitals, Care facilities and rehabilitation centers, Facilities for outpatient surgery, Dialysis facilities, childbirth facilities).

Number and description of representative sampling points according to § 14 paragraph 3 Sentence 1 governed by the generally accepted rules of technology. Sampling is carried out in accordance with DIN EN ISO 19458 as there under ,,purpose b” described. The amount of water drained before filling the sample container is allowed 3 liters not exceed. (compare cooling towers VDI, "not more than 30 seconds ")

Requirements of drinking water regulations 2016

§ 5 Microbiological requirements

(5) As far as the entrepreneur and the other proprietor of a water supply- or water recovery plant or a representative of them in terms of microbial loads of the raw water facts notice, which occurrence of a transmissible disease as defined in § 2 Number 3 of the infection protection law can cause , or accept, that such facts exist, must a preparation, if necessary, including a disinfecting, in accordance with generally accepted engineering standards in compliance with § 6 Paragraph 3 be done. In pipe networks or parts thereof, in which the requirements of paragraph 1 or 2 can be met only by disinfection, the entrepreneur and the other proprietor of a water supply system must according to § 3 Number 2 Letters a and b, or, if the drinking water supply is carried out as part of a commercial or public activity, to letter d or letter f a sufficient disinfection capacity by free chlorine, Chlorine dioxide or other suitable disinfectants or procedures, in accordance with § 11 are included in a list of the Federal Environment Agency, keep ready.

Clarification

The obligation to examine drinking water heating systems applies in accordance with Document drinking water regulations and legionella for drinking water installations. This is an explanation of the drinking water regulations.

• where drinking water is delivered through a public or commercial activity and
• a large plant for heating drinking water and contain
• contains the showers or other facilities, where there is a misting of drinking water.

Under the obligation to inspect fall schools and playschools as well as houses with rented out apartments or hotels, if there is a large plant is operated with hot drinking water. As large plants apply

• Water heaters with more than 400 liters content or
• water installations with one or more pipes with a volume of at least 3 liters.

Owner communities in rise condominiums of the duty to examine only have to comply, if at least one apartment is rented out in the building.

On the subject “Explosiveness of Legionella in drinking water” Many publications have been published in the special press. Here is a link to an exemplary Article in the newspaper “SBZ SANITÄR.HEIZUNG.KLIMA”.

But also on the methods used and its equipment must be paid. At least in one regulation will be rules of (economic) association declared to an act.

For the territory of the Federal Republic of Germany shall apply from the publication of the list of (…) disinfection procedures, Part II, Row 6, UV radiation (240-290 nm), Quote: There are only ultraviolet disinfection equipment permitted, for which in accordance with DVGW worksheet W 294-2 (A) as part of a biodosimetric testing disinfection efficiency of at least 400 Joule / m² (related to 254 nm) was successfully demonstrated. The operating characteristics specified for the respective device in the test report and in the certificate of an accredited industry certifier (max. Flow and associated minimum irradiance) must be observed in operation. The disinfection method (UV) is not applicable for maintaining a disinfection capacity in the distribution network (see. § 5 Paragraph 5 Sentence 2 TrinkwV 2001).

The basis of dimensioning and process selection is DIN 19643 described. The "general requirements" in Part 1 informed about the opinion of the relevant standards committee. In the normative references DIN 19643 with respect to the determination of the concentration of legionella DIN EN ISO 11731-2 and the ISO 11731 listed. About differences between the two standards is not informed.

In DIN 19643-1, Paragraph 5.3, Table 1 The microbiological requirements for the clean water (Note: water after filtering with disinfectant) and the pool water are formulated. By line 5.3.3 Legionella spec. applies the unit cfu/100ml and, split up in several footnotes,

• the upper limit of clean water (by definition filtrate plus disinfectant)
  • Footnote b: In the filtrate at pool water temperature ≥ 23°C,
  • Footnote c: Judgment and measures legionella findings follow 14.4 tables 7 and 8.
• The upper value for pool water
  • Footnote c: Judgment and measures legionella findings follow 14.4 tables 7 and 8.
  • Footnote d: In the pool water of warm spring pools and pools with additional aerosol-forming water circuits and pool water temperatures ≥23°C

The demands on the filling water and thus shifted into another table. Previously, however, pointed to at least one source of infection. DIN 19643-1, Paragraph 10.2.1: Fixed-bed filters (Sandfilters) (Quick filter): In order to avoid filter contamination of the filter ist after 13.4.2 to wash (Operating times depending on the water temperature). If this causes contamination with Legionella spec. or Pseudomonas aeruginosa can not be prevented in the long term, disinfection is required (see the recommendation of the Federal Environment Agency hygiene requirements for pools and monitoring; Anhang II).

Another clue can be found in DIN 19643-1, Paragraph 13.5 Filling water adding: (…) It should be noted, that filling water caused by stagnation and / or heating may be contaminated with Legionella.

To be in the order of the DIN 19643 to stay, the scope of investigation closes again with footnotes. According to DIN 19643-1, Table 5, Row 5.3.3, for Legionella spec. the following areas should be examined

• The filling water without further footnotes
• The filtrate
  • Footnote b (for all parameters): The maximum values ​​are shown in Tables "functional test of the filtration" in the following parts,
  • Footnote c (for all parameters): During microbiological abnormalities: Follow-up of the filtrate and the pool water, Flushing filter. With new microbiological abnormalities review of the treatment, filter flushing, Follow-up of the filtrate and the pool water.
  • Footnote f: In pool water temperature ≥ 23 °C.
• The clean water
  • Footnote d (for all parameters): Investigations carried out only with abnormalities in the pool water and annual maintenance.
  • Footnote e: Investigations must be carried out in microbiological abnormalities in the pool water. Additional examinations provide indications of a possible filter germination.
• The pool water
  • Footnote g: In the pool water of hot whirlpools, and pools with additional aerosol forming water systems and pool water temperatures ≥ 23 °C.

To follow the logic applied here, it is probably not helpful. Because the temperature of the proliferation of legionella >25° C is found, is assumed, that occur throughout the cycle no higher temperatures. All other points are always based their argument on the pool water and to act: "If there something is found". Other points are not to be tested in this standard. But who does not have to look, never finds anything.

The formulations leave room too. Not everyone sees in a connected fan an additional "water cycle". But the "air line" is in the breaks with high probability not connected to the disinfectant and a good stove for Legionella. Possibly the pipeline runs in the technical room, which heat the compressor or pumps to 30 ° C. The Legionella are not temporarily stored in the pool water, but blown directly into the lungs of bathers.

The real measures are in DIN 19643-1, Table 7, Review of the pool water and measures, formulated. Depending on the result of the first investigation on Legionella following formulations are made. Less than 1 CFU/100ml done neither judgement nor measures.

From 1 to 100 CFU/100ml the assessment is "low contamination":

• On the initial examination takes place: a follow-up,
• On the follow-up takes place: follow-up, Control of the filtrate
• The further restructuring is described with: follow-up, Control of the filtrate

This is similar to a circuit. It is advisable, to include the dynamics of reproduction again in the evaluation and with the intervals between the “follow-up” to compare.

From 100 to 1000 CFU/100ml the assessment is "medium contamination":

• On the initial examination takes place: filter flushing, Check disinfectant addition, follow-up, Control of the filtrate
• On the follow-up takes place: filter flushing, Check disinfectant addition, Switch off the aerosol-producing devices, follow-up, Control of the filtrate,
• The further restructuring is described with: further measures with involving of professionals, for example superchlorination, replacement of the filter material, Switch off the aerosol-producing devices, Notification to the relevant health authority, repeated follow-up of pool water and filtrate,

More then 1000 CFU/100ml the assessment is "high contamination":

• Footnote a: In Legionella concentrations > 10 000 CFU/100 ml and legionella detection in the filtrate instant Prohibition of use.
• On the initial examination takes place: filter flushing, Check disinfectant addition, Switch off the aerosol-producing devices, follow-up, Control of the filtrate,
• On the follow-up takes place: prohibition of use, filter flushing, Check disinfectant addition, follow-up, Control of the filtrate, Released after a perfect microbiological findings in the pool water,
• The further restructuring is described with: prohibition of use, further measures with involving of professionals, from. B. Superchlorination, replacement of the filter material. repeated follow-up of pool water and filtrate, Notification to the relevant health authority, Released after a perfect microbiological findings in the pool water,

Even with positive findings 1 to 1000 CFU/100ml in the follow-up is made to the control of the filtrate in DIN 19643-1, Table 8, Judgement of the filtrate (Water after treatment before disinfectant adding) and measures, directed. Here, too, is determined

From 1 to 1000 CFU/100ml (in the filtrate) the assessment "contamination" applies:

• On the initial examination takes place: filter flushing, Follow-up of the filtrate and the pool water
• On the follow-up takes place: filter flushing, Follow-up of the treatment, Follow-up of the filtrate and the pool water
• The further restructuring is described with: further measures with involving of professionals, for example superchlorination, replacement of the filter material, Switch off the aerosol-producing devices, Notification to the relevant health authority, repeated follow-up of pool water and filtrate,

More then 1000 CFU/100ml applies (in the filtrate) the assessment "high contamination":

• On the initial examination takes place: filter flushing, filter flushing, Follow-up of the filtrate and the pool water,
• On the follow-up takes place: filter flushing, Follow-up of the treatment, Follow-up of the filtrate and the pool water, possibly usage restriction (For example, turn off aerosol-producing devices)
• The further restructuring is described with: further measures with involving of professionals, from. B. Superchlorination, replacement of the filter material, Notification to the relevant health authority follow-up of the filtrate and the pool water, possibly usage restriction,

With so frequent mention of the measure "superchlorination" must be here "Hygiene requirements for bathrooms and monitoring the recommendation of the Federal Environment Agency (UBA) after hearing the Swimming- and Pool Water Commission of the Federal Ministry of Health (BMG) at the Federal Environment Agency" and its definition of "Superchlorination" insert. In table 4 of this document are the legionella concentrations of the DIN 19643 listed. In Anhang I: Superchlorination, Paragraph 5.2 pool water, is described:

At the measure in disinfection (of the pool water) to reach disinfection capacity is characterized by a chlorine concentration of at least 10 mg/l (ppm) over a period of at least 2 h. Filter, which are coated with granular activated carbon, should, if possible, be bypassed.

In paragraph 5.3 system components, under which also filters should be considered, the chlorination is defined as follows:

The chlorine concentration should be at least 10 mg/l at a contact time of at least 2 h. When using chlorine dioxide, the minimum concentration of 1,0 mg/l ClO2 is to observe .

It should be noted, that here the infestation by Legionella is thematised. For positive legionella findings the same document says other values:

Is Legionella infestation given, then the chlorine concentration is on 50 mg/l to increase at a contact time of at least 12 h and the concentration of chlorine dioxide to 10 mg/l with a contact time of at least 24 h. (…) Are filters with grain activated carbon occupied, then the rinsing with chlorinated water is often insufficiently effective in the event of microbial contamination due to the decomposition of chlorine on the surface of the material, so that a carbon replacement is required. An attempt to superchlorination can be done, then it must be ensured, that despite the high chlorine demand in the exiting sludge water is still a significant residual chlorine concentration is present.

For the assessment of these measures "superchlorination" is important, to combine the occuring volume flows with the required concentrations.

The view of the Federal Health Ministry of Health

… about swimming- and pool water. Quotes from source:

Legal basis

The legal basis for securing and monitoring the quality of the swimming- and swimming pool water is the "Law for the Prevention and control of infectious diseases in humans (Infection Protection Act – IfSG)”.

The § 37 Paragraph 2 of the IfSG regulates the requirements for the quality of swimming- pool water in public aquaparks, Business entities and are not exclusively privately used in other entities. There it says:

"Swimming- and pool water […] must possess such properties, that by its use harm to human health, in particular by pathogens, is not to be feared".

Treatment of swimming- and pool water

The treatment of swimming- and pool water, including a disinfection, is required, to during operation of swimming- and pools - regardless, whether it is for outdoor- or indoor pools is - to be able to provide a hygienic water available to swimmers and bathers at any time. If treatment and disinfection carried out in accordance with generally accepted engineering regulations, can be assumed, that no pathogens, while bathing and swimming can be transferred. Basis for this is inter alia the DIN 19643.

New findings in the field of swimming- and pool water hygiene and the technical development of appropriate treatment methods have a revision of the standard series DIN 19643 necessitated. As a result, are now by Working Committee NA 119-04-13 AA “Swimming pool water” standards established in the NAW - DIN 19643-1 “Treatment of swimming- and pool water – Part 1: General requirements”; – DIN 19643-2 “Treatment of swimming- and pool water – Part 2: Process combinations with fixed bed- and precoat filters”; – DIN 19643-3 “Treatment of swimming- and pool water – Part 3: Process combinations with ozonation”; – DIN 19643-4 “Treatment of swimming- and pool water – Part 4: Process combinations with ultrafiltration”. The standard applies to the treatment of water, including seawater, Mineral water, healing water, Sole (and man-made) and thermal water, in swimming- and pool equipment. It does not cover the treatment of water in single-family pools and not for water in plants with biological water treatment. The aim of this document is, a good, consistent quality of the pool water in terms of hygiene, safety and aesthetics to ensure, so that damage of the human health, in particular by pathogens, is not to be feared. It is also the well-being of bathers (for example, by minimizing side reaction products of disinfection) to consider. Therefore, requirements for the water quality, the dimensioning, the operation and control will be fixed. For the processing requirements are called, by which this objective can be achieved.

But every bather can contribute, so that the water remains clean. For informations, see here.

Responsibility for the quality of swimming- pool water and monitoring

The responsibility for this lies with the relevant state authorities. The monitoring of swimming- pool water quality, including the necessary treatment plants carried out by the health authorities.

Professional relevance

Accordding to § 40 the IfSG is the Federal Environmental Agency (UBA) the task assigned, Concepts for prevention, to develop detection and prevention of the spread of communicable waterborne diseases.

The relevant work of the department "Drinking- and pooö water" of the UBA is under the supervision of the BMG. (Federal Ministry of Health)

Through the work of this department of the UBA and the relevant authorities of the countries as well as the professionals and associations concerned are supported by appropriate expertise.

Subject commission

The swimming- Pool Water Commission (BWK) is a national commission of the Federal Ministry of Health (BMG) - based at the Federal Environment Agency (UBA). She advises both authorities in the issues of swimming- pool water hygiene.

The BMG appoints together with the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety Building (BMUB) and the responsible supreme state authorities, members of the BWK for a session of three years.

The recommendations of the BWK primarily serve the public health authorities and Badbetreibern as a basis for action. The technical concepts of the UBA and the swimming- Pool Water Commission can also supply an important basis for public health strategies by federal and state governments in this area.

In preparation!

The following description applies currently for the use of non-at-produced chlorine in the standardized DIN delivery.

• Liquid sodium hypochlorite according to DIN EN 901,
• Solid calcium hypochlorite according to DIN EN 900,
• Chlorine gas, liquefied, according to DIN 19607,

The description does not apply:

• Trichlorisocyanuric acid, including as tablets.

The method is suitable for:

• Process water in the pH range less than pH 6.5 and
• Water in swimming- and relaxing pools,

The method is not suitable for:

• Cooling towers, because of pH values >8,2 and
• Drinking water, because of the reaction by-products,
• Disinfection of filters with active carbon layer,

The following restrictions on use must be observed:

• The chlorine can attack the materials used. The compatibility must first be ensured.
• The effectiveness of chlorine decreases with increasing pH. Therefore the use of chlorine or chlorine-containing products in applications such as in an open cooling tower is not optimal.
• When using chlorine for disinfection, disinfection by-products such as trichlorohalomethanes are formed. These products are suspected, to be carcinogenic.
• In the use of chlorine for disinfection strong smelling chloramines are formed. These also affect the taste of water.
• In the provision of chlorine from electrolytic plant are currently the uncertainties from the Biocidal Regulation.

The benefits are:

• Easy availability of industrial production,

Reason:

The chlorine reacts in the dosing with the dissolved metals and organic materials in the water and generates a staining and smells, nothing else. What is left after this first reaction, applies in the next step onto the surface of the biofilm. Chlorine is probably the most widely used disinfectant for water. It kills by its strong oxidative effect on the surface of an organism. The legionella "flying" in the water or located on the surface of the biofilm are killed by the hypochlorous acid.

If amoebae be achieved through the mucus of the biofilm through, so the amoeba is only killed. The legionella inside the amoeba remain untouched. This protects the legionella. It must be used so much chlorine, that the biofilm is total killed. However, this concentration is incompatible with humans and leads to high levels of reaction by-products.

If the legionella should be the goal, then represents the chlorine the following problem: Legionella are a part in amoeba. The amoeba ate Legionella, but those living inside the amoeba more. The amoebae, however, are in the biofilm and are protected by its mucus.

If given chlorine for the purpose of disinfecting the water, should be a high proportion of very effective hypochlorous acid HOCl form. But this depends on the pH. Because it is a (greater) Part of hypochlorous acid in hypochlorite ion ClO^– and hydrogen ion H⁺ split.

The shift from pH8.2 to pH 7.0 is illustrated by the horizontal arrow and results, that the effectiveness of 21,5% to 81,3% improved. The influence of temperature is neglected for this example.

Oxidative disinfectants can kill the amoeba. But the dead Legionella is a protection for the legionella too. Oxidative disinfecting agents such as chlorine, Ozone, H2O2 therefore have an extremely small effect. These disinfectants meet the legionella only at extremely high concentrations. For a comparison, see the Publication on filter germination.

It should also be noted, that the oxidative disinfectants have a strong dependence on the pH. For example, the use of chlorine in the alkaline water of a cooling tower does not make sense.

The only way it is therefore, to change the pH-value or to live with a reduced activity.

Chlorine dioxide is used worldwide as a disinfectant and more important. This success is built:

• by the toxic effects on organisms,
• the high degree of independence from the pH of the water and
• the difference of the reaction by-products of chlorine dioxide to the reaction by-products of chlorine.

A detailed justification for the use of chlorine dioxide is in the newspaper article to Biological contamination of the filters to read about legionella. The topic “Situ production” is already in Tutorial chlorine dioxide generator discussed in detail.

Details for dimensioning, for safety, for consumption and downloadable tables for own calculation are Tutorial chlorine dioxide generator also included.

The following presentation is an example of one of the operating modes. Clicking in the window of the presentation start a production cycle. Other operations are in Tutorial chlorine dioxide generator shown.

The method is suitable for:

• Cooling tower systems,
• Drinking water systems,
• Process water systems,
• Disinfection of filters with active carbon layer,

The method is not suitable for:

• swimming- and relaxing pools, because of the eventual thickening of chlorates

The following restrictions on use must be observed:

• For use in drinking water, the volume flow-proportional dosing is required by the DVGW. This requirement excludes, that errors in the measurement lead to a harmful overdose. Nevertheless, the measurement and archiving of the concentration of chlorine dioxide is recommended.
• A high concentration of chlorine dioxide in water can lead to an explosive gas phase.
• The transportation of chlorine dioxide is not permitted in many states.
• The dosage of chlorine dioxide can lead to the formation of chlorates. This Chlorate can be toxic to humans. In circuits, this Chlorate can focus over time.

The benefits are:

• Efficacy in a wide pH range,
• Toxic effect to microorganism,
• The exclusive transport of sodium NaClO₂ and hydrochloric acid HCl,
• Missing more reaction byproducts,

Reason:

Chlorine dioxide in addition to the oxidative effect also has a toxic effect. The toxic effect is based on the destruction of cell membranes. Therefore, not only the amoebae but also the legionella protected in the amoebae are reached.

With chlorine dioxide, it is possible, reduce the biofilm and to keep permanently removed.

Also chlorine dioxide is partially used also by the dissolved metals. But the rest exerts a toxic effect on the organisms. The cell walls are penetrated. Because the chlorine dioxide ClO₂ but only very small reacts with the organic compounds, there are no organic reaction byproducts, such as THM or AOX. Chlorine dioxide breaks the molecular bonds in the cell and at the same time changed the protein structure, so that the cells can not convert it into resistant forms. A development of resistance of germs is thus effectively prevented.

Chlorine dioxide has been used successfully for the disinfection of drinking water in waterworks since the mid-50s and has already several times the name of related chlorine, but which may form harmful reaction byproducts, replaced.

This tutorial provides a detailed description for chlorine dioxide generators.

For completeness, it should be mentioned, that there are manufacturers, who promote the supply of "stabilized chlorine dioxide". The number of suppliers has decreased in recent years.

Alone the possibility, to transport chlorine dioxide, is already in conflict with the restrictions and safety rules previously described. See tutorial chlorine dioxide generator section Security.

Explained by one manufacturer, Quote:

(The product) is a patented, ready for use and stabilized ClO2 – solution. It eliminates excellent in all areas of water occurring microorganisms (germs, bacteria, algae and legionella). The extra-strong active content of 10% the product is particularly suitable for the continuous degradation of biofilm and its prophylactic treatment. The product in addition to the product features listed below, it still has some significant advantages over, for example. Chlorine dioxide generator plants. In addition to the significantly lower cost of a metering system, our product is neither explosive nor flammable and the application area is not tied to a fixed location. Because the high active share 10% is the product highly effective even in low concentrations.

Product features

• inorganic liquid ClO2 (stabilized chlorine dioxide)
• immediate ready for use at the factory; the preparation of a solution on site is eliminated
• up to 6 Month storable
• extremely high active ingredient content of 109g/l (10 %solution)
• one of the strongest disinfectant products for water worldwide
• safe elimination of microorganisms, such as germs, bacteria, Legionella etc..
• Reduction of biofilm formation and protection against
• Removal of iron, Manganese and other metals
• Reduction of organic compounds (THM)
• Increase of the redox potential by high oxidation potential
• lower AOX compared to other disinfectants- / Oxidation products
• The product is free of chlorite
• Microorganisms can not become resistant to the product develop
• Approved for water treatment in the food- and beverage industry
• easy and safe application – non-flammable / non-explosive

It should again be pointed out at this point, that according to the general rules of chemistry, the gas via a liquid chlorine dioxide with the concentration >8g/l will be explosive. As already written above, see the Security section in the tutorial to chlorine dioxide generators. This manufacturer is reported as active "chlorine dioxide" and in point 4 of the previous list, an active substance content of 109g/l listed.

The data sheet for the same (!) Product can be read, Quote:

The individual reactions of (…) oxygen attaches to the reaction partner. Reducing anions such as sulfite, nitrite, etc.. be converted directly into the maximum value oxidative. Organic compounds can be converted either into oxygen derivatives, or in carboxylic acids, depending on the composition and structure, which further hydrolyze depending on the pH value in carbon dioxide and water. The biocidal effect resulting from the shift of the redox potential of the with (…) treated water and by oxidative disruption of protein structure syntheses, whereby development of resistance of microorganisms are excluded. The algicidal effect results from the oxidation of chlorophyll. The product works against pathogenic and non-pathogenic bacteria, yeasts, algae and viruses.

Some numbers of the manufacturer's information cited here allow the conclusion, that this described product works on chlorine basis. Therefore, the following properties are taken from the properties of disinfection with chlorine in the ex-situ method, and repeated.

The method is suitable for:

• Process water in the pH range less than pH 6.5 and
• Water in swimming- and relaxing pools,

The method is not suitable for:

• Cooling towers, because of pH values >8,2 and
• Drinking water, because of the reaction by-products,
• Disinfection of filters with active carbon layer,

The following restrictions on use must be observed:

• The chlorine can attack the materials used. The compatibility must first be ensured.
• The effectiveness of chlorine decreases with increasing pH. Therefore the use of chlorine or chlorine-containing products in applications such as in an open cooling tower is not optimal.
• When using chlorine for disinfection, disinfection by-products such as trichlorohalomethanes are formed. These products are suspected, to be carcinogenic.
• In the use of chlorine for disinfection strong smelling chloramines are formed. These also affect the taste of water.
• In the supply of a disinfectant without specific mention of the biocidal shares must currently uncertainties from the Biocidal Regulation be assumed.

Reason:

Stated in the introduction.

Sampling for microbiological examination can always provide only a snapshot. Even if the applicable standard DIN EN ISO 19458 is fully respected for sampling, there are systemic uncertainty. In least cases, Legionella are homogeneously distributed in the water, because they are mostly embedded in the biofilm. It is thus an example of a sample of 1 liters in volume of 100m³ exist following theoretical possibilities:

1. The sample contains no single Legionella,
   1. because the sample exactly 0,001% the water volume taken from, that does not contain "free-flying" Legionella or
   2. because the water speed during the trial was so low, that the biofilm nothing could be swept away.
2. The sample contains a few single Legionella,
   1. because the Legionella are common and relatively homogeneously distributed or
   2. because the sample was taken at the right time in the right place.
3. The sample contains a large amount of Legionella,
   1. because the Legionella are very common and present homogeneously or
   2. because you (the) one "pregnant" amoeba up to 800 Legionella has in the sample.

The sample taker has no influence on these factors. The concentration in the sample is thus highly dependent of random. Nevertheless applies: Sampling is the key process for the provision of representative samples.

Against this background, the following definition should be considered. VDI 2047 sheet 29.2 risk assessment: To carry out regular hygienic-microbiological tests during operation, representative sampling points must be defined throughout the entire system.

Using the example of ex situ method for chlorine dioxide can be shown, how important it is, to have been as a sampler of all information about the existing disinfectants. VDI 2047 sheet 29.3.2.1 Regular laboratory tests: The sampling sample containers have to be used, containing a neutralizing medium, at least for oxidative biocides (as example sodium thiosulfate). Since not all biocides used in practice by neutralization media in accordance with DIN EN 13623, Attachment B, can be inactivated (not oxidative biocides), are additional rules to be observed during sampling. The laboratory and the sampler is for selecting the neutralizing medium before sampling the type of biocide (Safety Data Sheet) to announce.

The sampler has generally also responsible for the transport to the laboratory. As shown in section "Dynamics of multiplication", Legionella proliferate at temperatures:

• 5 – 20 °C standstill,
• 20 – 25 °C slow replication

If it comes to samples from a hot-water system or from a cooling system, then these samples also have an optimum temperature for the proliferation of Legionella. It is therefore necessary, the samples to cooled to below 20°C immediately. For this, the sampler must be equipped.

This temperature <20°C must be maintained on the entire transport.

For the laboratory method

Quote Veolia, Challenge Legionella, Basics, risks, Preventing and combating, Dr. Hartmut Lausch, 2016:

Legionella have very specific nutritional requirements and are therefore not be cultivated on conventional culture media. Accordingly, they are not detected also in determining the number of colonies (CFU) after drinking water regulations. For this parameter (Colony forming units) can therefore no statements about a possible Legionella infection derived.

Because of the pathogenicity of Legionella only investigation laboratories are approved for analytical detection, have the permission to §44 IfSG. (because the cultivation in CFU requires a targeted multiplication of the Legionella)

If several of such laboratories with the analysis of the same sample commissioned, will too, if shortcomings in sampling and transport / storage by complying with the DIN EN ISO 194583 may be excluded, obtained sometimes very divergent analysis results.

One reason for this is to be seen in it, that no general standardized procedure for the Legionella analysis exists in Germany. Just as in many other countries has been and will be based on the international standard ISO 11731 and resorted. Since this standard allows many possibilities for variation in the analysis, the distribution of analysis results obtained in this way is correspondingly high for this reason alone.

Therefore, it was in Germany - but only for the indication drinking- and swimming pool water – developed a special protocol, tested in a ring trial and as DIN EN ISO 11731 Part 2 enshrined.

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But even with this – compared to the international standard – quite restrictive procedure, show the ring tests, which according to the recommendations of the Federal Environmental Agency. the DIN the Lower Saxony State Health Department, location Aurich, on behalf of the Lower Saxony Ministry of Social Affairs, women, family, health and integration performs twice a year with Legionella, a very large variation of the laboratories involved in each several hundred received analytical results.

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With this strong fluctuation range up to a factor of 30 and more the uncertainty is connected, that is behind a for the cooling tower operation quite rule-compliant Legionella findings of 500 CFU/100ml with a fluctuation range by a factor 20 with 10.000 CFU/ml limit values ​​are exceeded by 10 times or even a result of only 25 CFU/100ml could conceal, which would not even reached the technical measure value of Drinking Water Regulation.