Aims: An evaluation was made of the prevalence of Legionella species in hot water distribution systems in the city of Bologna (Italy) and their possible association with bacterial contamination ...(total counts and Pseudomonadaceae) and the chemical characteristics of the water (pH, Ca, Mg, Fe, Mn, Cu, Zn and Total Organic Carbon, TOC).
Methods and Results: A total of 137 hot water samples were analysed: 59 from the same number of private apartments, 46 from 11 hotels and 32 from five hospitals, all using the same water supply. Legionella species were detected in 40·0% of the distribution systems, L. pneumophila in 33·3%. The highest colonization was found in the hot water systems of hospitals (93·7% of samples positive for L. pneumophila, geometric mean: 2·4 × 103 CFU l−1), followed by the hotels (60·9%, geometric mean: 127·3 CFU l−1) and the apartments with centralized heating (41·9%, geometric mean: 30·5 CFU l−1). The apartments with independent heating systems showed a lower level of colonization (3·6% for Legionella species), with no evidence of L. pneumophila. Correlation analysis suggests that copper exerts an inhibiting action, while the TOC tends to favour the development of L. pneumophila. No statistically significant association was seen with Pseudomonadaceae, which were found at lower water temperatures than legionellae and in individual distribution points rather than in the whole network.
Conclusions: The water recirculation system used by centralized boilers enhances the spreading of legionellae throughout the whole network, both in terms of the number of colonized sites and in terms of CFU count.
Significance and Impact of the Study: Differences in Legionella colonization between types of buildings are not due to a variation in water supply but to other factors. Besides the importance of water recirculation, the study demonstrates the inhibiting action of copper and the favourable action of TOC on the development of L. pneumophila.
Aims: Evaluation of the efficiency of peracetic acid in the disinfection of wastewater in a large treatment plant.
Methods and Results: Over a period of 18 months 30 sample collections were made, ...each consisting of three samples taken from: raw incoming sewage, secondary effluent (after 10–12 h) and secondary effluent disinfected with 1·5–2 mg l–1 of peracetic acid (contact time: 20 min). Total coliforms and Escherichia coli declined from 107 MPN 100 ml–1 in the raw sewage to 102 in the disinfected effluent and the enterococci fell from 106 MPN 100 ml–1 to 702 MPN 100 ml–1. The reduction of bacteria increased with the rise in temperature and decreased with the rise in BOD5.
Conclusions: Disinfection with peracetic acid reduced levels of faecal contamination by 97%, thus attaining the limit recommended by current Italian law (Escherichia coli≤ 5000 MPN 100 ml–1) for discharge into surface waters.
Significance and Impact of the Study: The process of disinfection with peracetic acid is easier to manage than other more common methods and the tests performed confirm that from the bacteriological point of view good results can be obtained for urban effluents.
The aim of the study was to assess the efficiency of low doses of peracetic acid against viral and bacterial indicators in wastewater and to evaluate if the treatment allows regulatory requirements ...to be satisfied. A total of 31 samplings were carried out, each involving the collection of secondary effluent and of effluent disinfected with 1.2 or 1.5 mg 1
−1
of peracetic acid (contact time 20 minutes). In each sample were measured: somatic coliphages, F-specific RNA bacteriophages, Escherichia coli, total and faecal coliforms, enterococci. Peracetic acid disinfection showed significant differences between the reductions of the microorganisms tested: E. coli showed the highest reduction (1.78 and 2.43 Log respectively with 1.2 and 1.5 mg 1
−1
of peracetic acid) and phages the lowest (ranging between 0.52 and 0.60 Log). Only a concentration of 1.5 mg 1
−1
of peracetic acid would enable the effluent to be discharged into surface waters in compliance with Italian regulations. The variability of microbial resistance against the peracetic acid disinfection treatment, underlines the importance of assessing disinfection efficiency by using more than one indicator microorganism. The detection of E. coli could be usefully accompanied by tests for more resistant microorganisms such as enterococci or coliphages. In conclusion, peracetic acid can be used for the disinfection of effluents even at low doses, with the advantage of reducing costs and preventing the formation of significant amounts of genotoxic by-products.
Aims: The aim of this study was to compare the efficiency of peracetic acid with that of chlorine dioxide in the disinfection of wastewater from a sewage treatment plant (serving about 650 000 ...inhabitants) that has been using peracetic acid as a disinfectant since 1998.
Methods and Results: A total of 23 samplings were made, each consisting of three samples: from secondary effluent, effluent disinfected with 2 mg l−1 of peracetic acid and effluent disinfected with 2·2 mg l−1 of chlorine dioxide (contact time 20 min). For each sample, measurements were made of the heterotrophic plate count at 36°C, total and faecal coliforms, Escherichia coli, enterococci, pH, suspended solids and chemical oxygen demand (COD). During the first phase of the experiment the peracetic acid was seen to be less efficient than chlorine dioxide. To improve the disinfectant action a system of mechanical agitation was added which led to a greater efficiency in the inactivation of bacteria of faecal origin.
Conclusions: Both products were found to be influenced by the level of microbial contamination, the amount of suspended solids and COD but not by the pH of the effluent before disinfection. The immediate mixing of the wastewater and disinfectant caused a greater reduction in enterococci.
Significance and Impact of the Study: Since peracetic acid was seen to produce a high abatement of micro‐organisms, it can be considered as a valid alternative to chlorine dioxide in the disinfection of wastewaters.
Aims: Transmission of microbial pathogens to patients from water in dental units is a concern. To reduce this risk, the decontaminating efficiency of hydrogen peroxide was evaluated.
Methods and ...Results: Three percent hydrogen peroxide diluted 1 : 4 in distilled water (contact time 15 min) was used daily to disinfect the waterlines of a pilot unit previously contaminated with Pseudomonas aeruginosa or Staphylococcus aureus. The behaviour of the test bacteria was seen to differ over time. Staph. aureus numbers slowly decreased until only low numbers were recovered, after which the levels remained stable. Ps. aeruginosa abatement was more rapid and the density of the bacteria reached a peak when the circuit was empty.
Conclusions: Staph. aureus and Ps. aeruginosa treated with hydrogen peroxide fell from 6 to 4 log.
Significance and Impact of the Study: Treatment of dental unit waterlines with hydrogen peroxide was seen to be able to keep the number of the bacteria under control, as long as the treatment was repeated daily.
We investigated Legionella and Pseudomonas contamination of hot water in a cross-sectional multicentric survey in Italy. Chemical parameters (hardness, free chlorine, and trace elements) were ...determined. Legionella spp. were detected in 33 (22.6%) and Pseudomonas spp. in 56 (38.4%) of 146 samples. Some factors associated with Legionella contamination were heater type, tank distance and capacity, water plant age, and mineral content. Pseudomonas presence was influenced by water source, hardness, free chlorine, and temperature. Legionella contamination was associated with a centralized heater, distance from the heater point >10 m, and a water plant >10 years old. Furthermore, zinc levels of <100 microg/L and copper levels of >50 microg/L appeared to be protective against Legionella colonization corrected. Legionella species and serogroups were differently distributed according to heater type, water temperature, and free chlorine, suggesting that Legionella strains may have a different sensibility and resistance to environmental factors and different ecologic niches.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A study was carried out to evaluate the extent of the colonization of dental water systems by Comamonas acidovorans and to investigate how the occurrence of these bacteria is related to certain water ...characteristics. The 152 water samples were collected from the oral rinsing cup, air‐water syringe, turbine and supply lines to dental units. Comamonas acidovorans was found most frequently and in greatest quantities in samples taken from water entering the units and in samples with a lower total bacterial count at 22 °C, higher temperature, lower content of organic matter and, in general, higher concentrations of residual chlorine.
Social-demographic information of a total of 1249 students attending the University of Bologna was analyzed by means of an anonymous questionnaire containing 33 questions with particular reference to ...tobacco smoking and sports activity. Results revealed that 31.6% of the students practise some form of sports regularly (6 hours a week or more), 40.5% occasionally (at least an hour a week for 8 months in a year) and 27.9% do not take part in any kind of sport. Significant differences were seen between those that practise sports (60.4% are non-smokers and 33.5% are habitual smokers) and those that do not (52.9% are non-smokers and 40.1% smoke habitually). The smokers who are active in sports smoke a lower mean number of cigarettes a day than the inactive group and thus belong to the category of light smokers. They also smoke fewer cigarettes on days when they take part in sports activity. As far as knowledge of health risks is concerned, 21.1% of those who practise sports obtained a score between good and excellent compared to 15.9% of those who do not. Although on the whole the results appear to show a certain influence of sports on smoking habits, the kind of study we led and the differences in the number of smokers are not sufficient to consider sports practitioners as a group not at risk for behaviour harmful to the health. Further studies are necessary to verify the cause-effect relationship between sports activity and smoking habits.
A survey was carried out into the smoking habits and exposure to passive smoking among health staff in the hospitals of Faenza, Forli and Rimini (Emilia-Romagna, Northern Italy), 2453 subjects ...answered anonymously a 41 question questionnaire. 53% of the subjects were professionals nurses, 16% doctors, 15% maintenance staff, 10% ancillary staff, 1% non-medical graduates, 2% were administrators and 3% were assigned to the category ¿other'. Of the subjects answering the questionnaire 39% were smokers, 19% ex-smokers and 42% non smokers. The highest number of smokers was found among women (41%) compared to men (37%) and among ancillary staff (48%) compared to nurses (41%) and doctors (31%). The males were mostly heavy smokers (> or = 20 cigarettes/d) and smoked strong cigarettes (> or = 12 mg/cig condensate content). The females were mostly light smokers (< 10 cigarettes/d) and smoked light cigarettes (1-6 mg/cig condensate content). A high percentage of subjects (87%) smoked at work especially in areas reserved for staff. 43% and 26% of shift workers and non-shift workers tended not to modify their habit when on morning or afternoon shifts. During night shifts the majority of them increased their tobacco consumption. Around 87% of hospital employees stated they were exposed to passive smoking inside the hospital especially in cooking areas, at information desks and corridors. Nurses, ancillaries and maintenance staff were those most exposed and for a greater number of hours per day compared to doctors. Almost all subjects were aware of the harm caused by passive smoking. 56% of smokers, 65% of ex-smokers and 72% of non smokers said they were willing to participate in future campaigns to limit smoking in their hospitals.
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