Search

A study was carried out to assess the efficiency of filtration in reducing microbial contamination in municipal secondary effluent. After primary and secondary treatments, the wastewater underwent filtration through sand/hydroanthracite filters. A total of 20 samplings were made, each consisting of two instant samples (secondary effluent and filtered effluent). Each of the 40 samples was tested for: total and faecal coliforms, Escherichia coli, enterococci and somatic coliphages. The mean concentrations detected in the secondary effluent were in the order of 5 log for the total and faecal coliforms, 4 log for enterococci and Escherichia coli, and approx. 3 log for the coliphages. The filtration showed a higher efficacy in the reduction of faecal coliforms, Escherichia coli and in particular total coliforms. The results obtained for enterococci and coliphages were significantly lower. Filtration alone was not enough to reduce the bacterial indicators to within Italian legal limits, and showed a poor capacity to abate coliphages. However, by performing the filtration before disinfection, secondary effluents require a lower dose of disinfectant. This results in less pollution of surface waters from by-products and a consequent reduction in the chemical risk for the general population. Copyright © Source Interlink Media.

The quantity of Aeromonas spp. and Aeromonas hydrophila was determined in samples of fresh surface water, brackish, and seawater with different degrees of pollution, and their presence was compared with the classical indicators of water fecal pollution. Aeromonas spp. were isolated from all the water samples examined and their number, like that of Aeromonas hydrophila, was always higher than, and in some cases correlated with, that of fecal coliforms. The results obtained seem to confirm the opinion already expressed by other researchers regarding the importance of monitoring the presence of these bacteria to obtain more complete information on the degree of contamination of surface water.

The abilities of peracetic acid and hydrogen peroxide to remove or reduce Pseudomonas aeruginosa and Stenotrophomonas maltophilia in output water from microfiltered water dispensers (MWDs) were investigated. Two MWDs were inoculated with strains of P. aeruginosa and S. maltophilia isolated from water. Dispensers A and B were disinfected with 10% (v/v) peracetic acid (PAA) and 3% (v/v) hydrogen peroxide (HP) respectively. Each dispenser was disinfected three times at monthly intervals with contact times of 10, 30 and 40 min. Water dispensed by the MWDs was collected immediately before and after each treatment and then twice weekly for the remaining period. Once a week a sample of the tap water entering the dispensers was tested. P. aeruginosa and S. maltophilia were enumerated in the 90 samples collected during 6 months. In the output water from the dispensers before the first treatment, the number of the bacteria was 3 to 4 log cfu/100 mL. Treatment with PAA greatly reduced the numbers of P. aeruginosa and S. maltophilia in the dispensed water initially. However, by 2 days after treatment, the numbers increased and remained high. In the case of disinfection with HP for 40 min, P. aeruginosa was not detected in most of the samples (73.7%). Numbers of S. maltophilia decreased with increasing time after treatment.

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 l(-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 l(-1) of peracetic acid) and phages the lowest (ranging between 0.52 and 0.60 Log). Only a concentration of 1.5 mg l(-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.

A prospective surveillance study of legionnaires disease and an environmental survey of Legionella species were performed simultaneously in a general hospital. During a period of 3 years, 705 patients with pneumonia were screened with a Legionella urinary antigen test, and pneumonia was confirmed by culture and serological tests. Twelve cases of legionnaires disease were identified, none of which were hospital acquired, despite the fact that 60% of hospital water samples were contaminated with Legionella pneumophila at a concentration of more than 103 colony-forming units/L. The probable source of infection was identified for only 2 community-acquired cases. The results show that environmental contamination alone is not able to predict the risk of legionnaires disease. If no cases are present, monitoring of hospital water systems is of little significance; clinical surveillance is much more important.

Objective.To evaluate the effectiveness of different disinfection treatments in a spa water system contaminated byLegionella pneumophilaand associated with a case ofLegionellapneumonia.Design.During an 18-month period, the spa water was analyzed by taking samples from the well, the recirculation line, and the final distribution devices (nebulizers and nasal irrigators). Various attempts were made to eradicateLegionellaorganisms by chemical and thermal shock. The final protocol consisted of heat shock treatment at 70°C-75°C for 3 hours, 2 nights per week, followed by a lowering of the water temperature to 30°C ± 1°C for use in the plant. In addition, 3 times a week superheated steam (at a pressure of 1 atmosphere) was introduced for 1 hour into the nebulization machines.Setting.A spa at which sulfurous water was used for hydrotherapy by means of aerosol and nasal irrigation.Patient.A 74-year-old woman with legionnaires disease.Results.After the case of infection occurred,L. pneumophilawas isolated from the recirculation line at a concentration of 400,000 cfu/L and from the nebulizers and nasal irrigators at levels ranging from 3,300 to 1,800,000 cfu/L. The colonizing organisms consisted of a mixture ofL. pneumophilaserogroup 1 (12%) and serogroup 5 (88%). The shock treatment with chlorine dioxide and peracetic acid resulted in the eradication ofLegionellaorganisms from the recirculation line but not from the water generated from the final distribution devices. After the restructuring of the plant and the application of thermal shock protocol, an evaluation after 12 months revealed no evidence ofLegionellacontamination.Conclusion.To preventLegionellacolonization, disinfection treatment is effective if associated with carefully selected materials, good circuit design, and good maintenance practices.

Tests for Escherichia coli and E. coli O157 were carried out on meat samples collected from randomly chosen stores throughout the city of Bologna and suburban areas. The samples consisted of 25 g of loose minced beef, sometimes already shaped into meatballs or hamburgers, some of which were mixed with vegetables. The meat was purchased from retail outlets, open market stalls, and supermarket chains during 25 sampling visits from October 2000 to December 2001. For E. coli detection, Tryptone soya broth (TSB) supplemented with novobiocin and C-EC agar were used. Immunomagnetic separation with SMAC-BCIG-CT agar and chromogenic E. coli O 157 agar, API 20E system and agglutination latex test were used to detect E. coli O157; Vero cell assay and polymerase chain reaction (PCR) were used to assess toxin production and the presence of virulence genes. E. coli were detected in 45 (30.2%) of the 149 samples examined, mainly in the hamburger samples mixed with vegetables and in the loose minced beef. E. coli O157 was found in one sample of hamburger and two samples of hamburger mixed with vegetables (2%) collected from three different butcher's stores between July and October. All the strains of E. coli O157 and most cases of E. coli were found in meat from small retailers. The three strains of E. coli O157 were positive for verocytotoxin production. PCR analysis revealed genes coding for vt2 and one strain possessed the gene for eae A. Chromogenic E. coli O157 agar was found to be more selective and differential, allowing easier identification of suspected colonies with mixed flora and producing less false-positive colonies.