Disinfection of Water Systems in Accordance with Eu Directives on Health and Safety in Working Environments: Use of A Technologically Advanced ClO2 Generator

One of the main problems in the management of water in
buildings is the risk of legionnaires’ disease for users and workers...


Introduction
One of the main problems in the management of water in buildings is the risk of legionnaires' disease for users and workers.
In fact, legionellosis is currently considered a global problem. The WHO points out those 10-15 cases/1,000,000 inhabitants are reported each year in Europe, Australia and the USA (www.who.int/ en/news-room/fact-sheets/detail/legionellosis December 2016).
The bacterium responsible is Legionella pneumophila. A chlorine dioxide generator is used in the pilot water treatment plant (Figure action is not aggressive against pipes and has a longer lasting effect and at a wider range from the injection point, making it possible to treat entire hydraulic systems even using small quantities of product. There are also no potentially carcinogenic disinfection byproducts, unlike chlorine, and for all these reasons its use is ecological and also suitable for drinking water treatment. As well as to combat legionella in hospitals, retirement homes, hotels, and school buildings. According to data provided by the European  France, Germany, Italy, and Spain together recorded 68% of cases notified in 2017.The majority of cases (69%) are of EU origin, 21% are associated with travel and 8% are of nosocomial origin. 91% of cases are over 45 years of age and the male-to-female ratio is 2.4 to 1. In addition, the lethality rate in 2017 was 8%, a value comparable to that of previous years. Laboratory analysis identified L. pneumophila serogroup 1 as the most frequent aetiological agent (present in 79% of cases confirmed in culture). https://www.epicentro.iss.it/legionellosi/epidemiologia-europa The incidence of legionellosis in Italy in 2017 was 33 The prevention measures to be implemented are those appropriate to prevent the growth and development of the bacterium. In particular, all innovative and technologically advanced procedures and methods for cleaning and disinfecting the water system, any related device, cooling towers, evaporative towers, swimming pools and whirlpools must be carefully considered. In the field of health protection from infectious agents, it is necessary to consider, among the most important collective prevention-protection interventions, the disinfection activity that can be carried out through different methods, for example through manual procedures or using various types of equipment. Disinfection, which is very important for health protection, must be effective against all the biological agents that constitute the source of the infection or infections [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60]. It is necessary to use disinfection methods that carefully consider the necessary contact times of the different substrates and possible interfering means, in which the infectious agents are present, since the microbicidal properties may be insufficient, cancelled out or greatly reduced. At the same time, it is necessary to be careful in the choice of formulations and compounds to be used, also evaluating the characteristics of toxicity for exposed subjects in relation to the concentrations of use.

Results
The tests carried out showed disinfectant efficacy on the various bacterial species already from the samples taken within 5 minutes (T5) of exposition to the disinfectant (T0), with a reduction near 100% (>99.999%) within 30 minutes. In particular: 1) E. faecalis showed a >99% reduction already within the first 5 minutes (Figures 2A & 2B).
2) E. coli showed a >99% reduction already within the first 5   Note: T 0 : situation in the system at zero time; T contact : analysis performed on sample taken immediately after inoculation; T 5 : analysis performed on sample taken after 5 minutes; T 30 : analysis performed on sample taken after 30 minutes. (NB: the data in UG on E. Coli refer to a validity threshold < 33 CT as the tests have been performed using recombinant Taq. In addition, the MPN value at T 5 is overestimated).
3) The total microbial charge, including the biofilm component in the supply water and in the system, is reduced by more than 99% following the activation of the disinfectant equipment able to produce Chlorine Dioxide. This observation is demonstrated both by the cultivation tests ( Figure 4A) and by a molecular test which is able to significantly identify both the indicators used and the complexity of the bacterial microflora present in its different bacterial species ( Figure 4B). In addition, the integration ( Figure 4A   In consideration of the different information acquired, the treatment system based on the action of Chlorine Dioxide and studied through the pilot unit previous described, therefore, shows an effective disinfectant action against Legionella and a particularly valid approach of use, as it is based on the real-time monitoring of various parameters through an integrated and atomized management of the disinfection system. For applications on extended installations of different types, not only in terms of safety but also quality, the proposed water treatment policy is therefore effective and promising. The pilot installation has proved to be a stable and modular system that merits further study and technical-scientific development. The results reported for Legionella are particularly significant not only in the context of the various observations collected, but also in consideration of the controlled conditions in which it was possible to perform tests on the effectiveness of the disinfectant treatment, simulating conditions that could be verified inside a water system.
In conclusion, regarding the efficacy profile of the analyzed ClO 2 generator, an interesting decontamination activity has been observed even in the case of water, which for various reasons does not present suitable characteristics of potability and an important and more than significant possible decontamination activity against different microbial agents, such as yeasts/fungi and bacteria, among the latest we can indicate as frequent contaminants Pseudomanas aeruginosa, E. coli, Legionellaceae.