A Somatic Coliphage Threshold Approach To Improve the Management of Activated Sludge Wastewater Treatment Plant Effluents in Resource-Limited Regions

Abstract

Effective wastewater management is crucial to ensure the safety of water reuse projects and effluent discharge into surface waters. Multiple studies have demonstrated that municipal wastewater treatment with conventional activated sludge processes is inefficient for the removal of the wide spectrum of viruses in sewage. In this study, a well-accepted statistical approach was used to investigate the relationship between viral indicators and human enteric viruses during wastewater treatment in a resource-limited region. Influent and effluent samples from five urban wastewater treatment plants (WWTP) in Costa Rica were analyzed for somatic coliphage and human enterovirus, hepatitis A virus, norovirus genotype I and II, and rotavirus. All WWTP provide primary treatment followed by conventional activated sludge treatment prior to discharge into surface waters that are indirectly used for agricultural irrigation. The results revealed a statistically significant relationship between the detection of at least one of the five human enteric viruses and somatic coliphage. Multiple logistic regression and Receiver Operating Characteristic curve analysis identified a threshold of 3.0 ×103 (3.5-log10) somatic 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 virus target/100 mL). Additionally, quantitative microbial risk assessment was executed for famers indirectly reusing WWTP effluent that met the proposed threshold. The resulting estimated median cumulative annual disease burden complied with World Health Organization recommendations. Future studies are needed to validate the proposed threshold for use in Costa Rica and other regions. Importance Effective wastewater management is crucial to ensure safe direct and indirect water reuse; nevertheless, few countries have adopted the virus log reduction value management approach established by the World Health Organization. In this study, we investigated an alternative and/or complementary approach to the virus log reduction value framework for the indirect reuse of activated sludge treated wastewater effluent. Specifically, we employed a well-accepted statistical approach to identify a statistically sound somatic coliphage threshold value, which corresponded to an increased likelihood of human enteric virus detection. This study demonstrates an alternative approach to the virus log reduction value framework, which can be applied to improve wastewater reuse practices and effluent management.

Evaluación temporal y espacial en la calidad microbiológica del agua superficial: caso en un sistema de abastecimiento de agua para consumo humano en Costa Rica

“…de los indicadores de contaminación fecal viral más reconocidos son los colifagos somáticos. Estos bacteriófagos son virus que infectan E. coli intestinal y su detección en aguas se asocia a la presencia de virus entéricos capaces de provocar enfermedad diarreica en seres humanos (Chacón et al, 2020;McMinn et al, 2017). La movilidad de contaminantes microbiológicos, como los ya mencionados, hacia ambientes acuáticos es favorecida por condiciones ambientales como la altitud y pendiente, el uso de suelo y fluctuaciones temporales en la precipitación, entre otras (Bergion et al, 2017).…”

Wastewater-Based Epidemiology of Enteric Viruses and Surveillance of Acute Gastrointestinal Illness Outbreaks in a Resource-Limited Region

“…Detection of pathogenic viruses. The virus presence/ absence analyses were performed by end-point PCR and real-time PCR according to our previously published protocol; 13 results are summarized in Table 2. Out of a total of 60 collected samples, viral tests were run as follows: 59 samples were tested for enterovirus (EV) and hepatitis A virus (HAV), and 38 samples were tested for norovirus GI (NV GI), for norovirus GII (NV GII), and rotavirus group A (RV).…”

“…Because the limit of detection of each assay was not tested in this study, the theoretical process limit of enteric virus detection for any given assay was estimated to range from 183 to 18,300 virus copies/100 mL. 13 Analysis of cases of acute diarrheal disease in 2013 using endemic ranges. Bortman's method to estimate endemic ranges and outbreak events 22 was used to analyze the cases of acute diarrheal disease in 2013.…”

“…10,11 Viral detection in wastewater has some methodological limitations because pathogen detection by molecular methods is difficult due to the presence of polymerase chain reaction (PCR) inhibitors, no single effective concentration method, and no universal quality controls for determining the efficiency of virus detection that is accepted for all enteric viruses types. 12,13 Wastewater-based epidemiology has been poorly applied in Latin America. Haiti, Mexico, Colombia, and Brazil are examples of countries that used WBE for polio environmental surveillance.…”

Human Fecal Pollution Monitoring and Microbial Risk Assessment for Water Reuse Potential in a Coastal Industrial–Residential Mixed-Use Watershed

“…Therefore, water reuse is an effective solution to resolving water scarcity for industries and residential communities (Piadeh et al, 2014). Indirect wastewater reuse, a practice referring to the utilization of surface water contaminated by either treated or untreated wastewater, has been reported for agricultural irrigation (Jeong et al, 2016;Chacón et al, 2020;Jampani et al, 2020) and recreational activities (Crank et al, 2019). However, the protection of public health is an essential aspect when evaluating water reuse and reclamation.…”