What is the log removal efficiency for Reverse Osmosis concerning viruses?

Reverse osmosis (RO) is a highly effective process for removing a wide range of contaminants from water, including viruses. The log removal efficiency of a treatment process indicates how many times the concentration of a contaminant is reduced. For viruses, reverse osmosis typically achieves a log removal efficiency of about 4 to 5 log, meaning it can effectively reduce the concentration of viruses by 99.99% to 99.999%.

This high level of removal is attributed to the size of the virus particles and the characteristics of the RO membrane, which has very small pores. The membranes are designed to block particles that are larger than the water molecules, effectively filtering out viruses, which are substantially larger than water molecules.

The choice indicated as correct reflects a solid understanding of the capabilities of reverse osmosis in virus removal, which aligns with empirical data and standard treatment expectations in advanced water treatment practices.