Abstract
In order to verify the microbial quality of the influents and effluents of one STP from southern Brazil, an eight-month survey was conducted to examine the presence of total and fecal coliforms and of adenovirus (HAdV), enterovirus (EV), genogroup A rotaviruses (GARV) and Torque teno virus (TTV), in treated effluent samples from São João/Navegantes STP, Porto Alegre (Brazil). A total of 16 samples were collected, eight of influent (raw sewage, prior to treatment), and the other eight of the effluent (post-treatment sewage). Total and fecal coliform levels ranging from 3.6 × 10(4) to 4.4 × 10(7) MPN/100 mL and 2.9 × 10(3) to 1.7 × 10(7) MPN/100 mL, were detected in all samples. In raw sewage, HAdV (25%) and GARV (28.6%) viral genomes were detected. The analysis of effluent samples revealed the presence of HAdV (50%), EV (37.5%), and TTV (12.5%) genomic fragments. All samples, regardless of the month analysed, presented detection of a least one virus genus, except for in April. Higher virus detection rates were observed in treated sewage samples (62.5%), and in 80% of them (effluent positive samples) HAdV was detected. Results showed that improvements in sewage monitoring and treatment processes are necessary to reduce the viral and bacterial load on the environment in southern Brazil. To the knowledge of the authors, this is the first study showing the monitoring of viral genomes in influent and effluent samples from a STP located in Porto Alegre (Rio Grande do Sul, Brazil), southern Brazil.
Highlights
Most treated wastewater, as well as untreated sewage, flow into the environmental water bodies and harbors the potential to impact agricultural, recreational and drinking related water uses
EV was not detected in influent samples and it was detected in three out of eight (37.5%) effluent samples
genogroup A rotaviruses (GARV) was detected in two out of seven (28.6%) influent samples analysed and it was not detected in effluent samples
Summary
As well as untreated sewage, flow into the environmental water bodies and harbors the potential to impact agricultural, recreational and drinking related water uses Bacterial indicators, such as total and fecal coliforms (Escherichia coli), are still commonly employed as the only bioindicator to verify the microbial quality of water (WHO, 2008), specially in South America. Human enteric viruses are causative agents of many non-bacterial gastrointestinal and respiratory tract infections, as well as other clinical syndromes, including conjunctivitis, hepatitis and other diseases with high morbidity and mortality in immunocompromised individuals such as aseptic meningitis, encephalitis, myocardits and acute flaccid paralysis (Kapikian et al, 2001; Pallansch and Roos, 2001; Carter, 2005; Lenaerts et al, 2008; Okoh et al, 2010) These agents infect and replicate in the gastrointestinal tract of their hosts and are released in large quantities in the stools of infected individuals, about 105 to 1011 virus particles per gramme of stool (Bosch, 1998). Many studies have found that, despite the treatment applied, enteric viruses may persist in high levels in wastewaters (He and Jiang, 2005; Villar et al, 2007; Carducci et al, 2008; Fong et al, 2010; Kokkinos et al, 2010; La Rosa et al, 2010a, b; Prado et al, 2011), proposing the use of a viral indicator of treated sewage contamination
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