Evaluation of the physical and chemical characteristics of water on the removal efficiency of rotavirus in drinking water treatment plants and change in induced health risk

Rotavirus is one of the main waterborne causes of diarrhoea. Rotavirus type A is responsible for diarrhoea in infants and causes thousands of deaths annually around the world, especially in developing countries. Rotavirus is very small and is highly resistant to common disinfectants, so the World Health Organization (WHO) has chosen this virus as a reference pathogen in drinking water and has recommended a its 6-log removal by the conventional water treatment process to supply safe drinking water. We measured some physical and chemical characteristics of raw water at a water treatment plant in Tehran, Iran, including temperature, pH, total organic compound (TOC) concentration and initial turbidity, to determine their effect on rotavirus removal efficiency in various processes. We then measured rotavirus removal efficiency in clarified water and filtrate to determine their removal efficiency. Finally, we applied the WHO guideline and an empirical quantitative microbial risk assessment (QMRA) model to estimate probable health risk based on a residual number of rotavirus in finished water. We found that TOC concentration and water temperature are both effective on residual rotavirus in clarified water but they have no significant effect on the efficacy of filtration in rotavirus removal. Maximum rotavirus removal efficiency by clarification and filtration was 97.2% and 4.5% in April and January respectively. TOC and water temperature were shown to have a significant effect on clarification virus efficiency, so filtration performance was independent of these variables. The results showed that induced risk by residual rotavirus is in an acceptable range (99.99945% removal annually), and also showed that the critical process in virus removal is clarification that can be affected by raw water quality.