A somatic coliphage threshold approach to improve the management of activated sludge wastewater treatment plant effluents in resource-limited regions
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Fecha
2020-06
Tipo
artículo original
Autores
Chacón Jiménez, Luz María
Barrantes Jiménez, Kenia
Santamaría Ulloa, Carolina
Solano Barquero, Melissa
Reyes Lizano, Liliana
Taylor Castillo, Lizeth
Valiente Álvarez, Carmen Isabel
Symonds, Erin Michelle
Achí Araya, María Rosario
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Resumen
Effective wastewater management is crucial to ensure the safety of water reuse projects and
29 effluent discharge into surface waters. Multiple studies have demonstrated that municipal
30 wastewater treatment with conventional activated sludge processes is inefficient for the removal
31 of the wide spectrum of viruses in sewage. In this study, a well-accepted statistical approach was
32 used to investigate the relationship between viral indicators and human enteric viruses during
33 wastewater treatment in a resource-limited region. Influent and effluent samples from five urban
34 wastewater treatment plants (WWTP) in Costa Rica were analyzed for somatic coliphage and
35 human enterovirus, hepatitis A virus, norovirus genotype I and II, and rotavirus. All WWTP
36 provide primary treatment followed by conventional activated sludge treatment prior to
37 discharge into surface waters that are indirectly used for agricultural irrigation. The results
38 revealed a statistically significant relationship between the detection of at least one of the five
39 human enteric viruses and somatic coliphage. Multiple logistic regression and Receiver
Operating Characteristic curve analysis identified a threshold of 3.0 ×103 40 (3.5-log10) somatic
41 coliphage plaque forming unit per 100 mL, which corresponded to an increased likelihood of
encountering enteric viruses above the limit of detection (>1.83×102 42 virus target/100 mL).
43 Additionally, quantitative microbial risk assessment was executed for famers indirectly reusing
44 WWTP effluent that met the proposed threshold. The resulting estimated median cumulative
45 annual disease burden complied with World Health Organization recommendations. Future
46 studies are needed to validate the proposed threshold for use in Costa Rica and other regions.
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Palabras clave
Wastewater treatment, Enteric viruses, Somatic coliphage, Fecal indicator bacteria, Activated sludge, Threshold values