Evaluation of recreational surface water quality according to water quality index and quantitative microbial risk assessment of noroviruses and SARS-COV-2

Abstract

Outbreak of waterborne virus are the major concern worldwide. The Water Quality Index (WQI) is a tool used to assess water quality for related activities. However, its suitability for assessing risks associated with waterborne pathogens remains questionable. This study aims to identify potential limitations and gaps in the WQI, especially in the context of risks from waterborne pathogens. The WQI of Maha Sawat Canal (MSC), Thailand was evaluated during both wet and dry seasons. The results were then integrated with the quantitative microbial risk assessment (QMRA) methodology for norovirus GI (NoV GI) and SARS-CoV-2. The results have shown that NoV GI (34%) and SARS-CoV-2 (9.9%) were detected in 81 water samples. The WQI analysis categorized MSC’s water quality as a ‘fair’ level of overall nine-month event to study including wet and dry seasons, suggesting its suitability for agricultural and transportation. While considering each month, water quality was at a “good” level in May, which might relate to the first month of the wet season. However, the probability of contracting an illness from NoV GI during swimming (0.148), boat transportation (0.126) also consumed vegetables (Lettuce) from the MSC agriculture irrigation (0.225,0.229, 0.022) exceeded the acceptable benchmark of gastroenteritis illness (GI) for NoV (0.036). The risk of SARS-CoV-2 remains relatively lower in boat activity and consumed vegetables (Lettuce) from the MSC agriculture irrigation (≥0.001) while the illness from SARS-CoV-2 during swimming (0.01, 02, 0.01) exceeds the set of benchmarks for SARS-CoV-2 (0.001). These findings suggest that the WQI alone may not provide a comprehensive assessment of the suitability of water for specific activities. Thus, incorporating QMRA into the water quality evaluation can provide a more in-depth analysis, particularly when considering risks from specific pathogen contamination.