Evaluation of the microbiological quality of reclaimed water produced from a lagooning system

The use of lagooning as a complementary natural method of treating secondary effluents of wastewater treatment plants has been employed as an affordable and easy means of producing reclaimed water. However, using reclaimed water for some purposes, for example, for food irrigation, presents some risks if the effluents contain microbial pathogens. Classical bacterial indicators that are used to assess faecal contamination in water do not always properly indicate the presence of bacterial or viral pathogens. In the current study, the presence of faecal indicator bacteria (FIB), heterotrophic bacterial counts (HBC), pathogens and opportunistic pathogens, such as Legionella spp., Aeromonas spp., Arcobacter spp., free-living amoeba (FLA), several viral indicators (human adenovirus and polyomavirus JC) and viral pathogens (noroviruses and hepatitis E virus) were analysed for 1 year in inlet and outlet water to assess the removal efficiency of a lagooning system. We observed 2.58 (1.17-4.59) and 1.65 (0.15-3.14) log reductions in Escherichia coli (EC) and intestinal enterococci (IE), respectively, between the inlet and outlet samples. Genomic copies of the viruses were log reduced by 1.18 (0.24-2.93), 0.64 (0.12-1.97), 0.45 (0.04-2.54) and 0.72 (0.22-2.50) for human adenovirus (HAdV), JC polyomavirus (JCPyV) and human noroviruses (NoV GI and GII), respectively. No regrowth of opportunistic pathogens was observed within the system. FLA, detected in all samples, did not show a clear trend. The reduction of faecal pathogens was irregular with 6 out of 12 samples and 4 out of 12 samples exceeding the EC and IE values, specified in the Spanish legislation for reclaimed water (RD 1620/2007). This data evidences that there is a need for more studies to evaluate the removal mechanisms of lagooning systems in order to optimize pathogen reduction. Moreover, surveillance of water used to irrigate raw edible vegetables should be conducted to ensure the fulfilment of the microbial requirements for the production of safe reclaimed water.

Effect of thermal treatment on free-living amoeba inactivation

AIMS

To evaluate the effect of temperature on two amoeba strains of the genera Acanthamoeba and two amoeba strains of the genera Hartmannella separately treated depending on their life stage, trophozoite or cyst, when cells are directly exposed under controlled conditions.

METHODS AND RESULTS

For thermal treatments, three temperatures were selected 50, 60 and 70°C, and a microcosm was designed using dialysis bags. The inactivation of each strain was determined using a method based on the most probable number quantification on agar plates. The results showed that for all amoeba strains, thermal treatment was more effective against trophozoites compared with cyst stages. The inactivation patterns showed statistical differences between the two genera analysed at temperatures above 50°C. The effectiveness of the thermal treatments at 60 and 70°C was higher for both life stages of Hartmannella vermiformis strains compared with Acanthamoeba strains, being the most resistant Acanthamoeba cysts.

CONCLUSIONS

Free-living amoebae have been isolated in a wide range of environments worldwide due to their capacity to survive under harsh conditions. This capacity is mainly based on the formation of resistant forms, such as double-walled cysts, which confers a high level of resistance as shown here for thermal treatments.

SIGNIFICANCE AND IMPACT OF STUDY

Free-living amoebae survival can promote a rapid recolonization of drinking water systems and is a likely source of emerging opportunistic pathogens such as Legionella. Because of that a better understanding of the factors that affect micro-organism inactivation in water systems would allow more efficient application of disinfection treatments.

Multilocus sequence typing of Campylobacter jejuni and Campylobacter coli strains isolated from environmental waters in the Mediterranean area

Campylobacter jejuni and Campylobacter coli are important animal-related waterborne pathogens that are distributed worldwide. To further understand Campylobacter populations in water from the Mediterranean area, the genetic diversity of environmental strains was analyzed using multilocus sequence typing (MLST). MLST was also used to determine the potential geographical differences between these bacterial strains and other campylobacters isolated worldwide. The typing study was conducted using 58 strains isolated from the Llobregat river and other water sources, such as urban sewage, animal wastewater and clinical samples. Thirty-nine different sequence types were obtained; eight of these sequences were described for the first time in this study, suggesting the presence of local strains. The identified C. jejuni strains were the most diverse population, whereas the identified C. coli strains showed a high clonal structure, which clustered most of the sequence types into a few clonal complexes. The strains were not exclusively related to specific water sources. However, comparing the identified strains with an international database showed that most of the Mediterranean strains that were exclusively isolated from environmental waters have previously been isolated from similar sources, particularly those obtained from river water. Additional studies, including those in different geographical areas using a wide range of Campylobacter sources, are required to improve the global knowledge concerning Campylobacter dissemination in the environment.