Conventional sedimentation has a _____ removal of Cryptosporidium oocysts.

• A. More than 1 log
• B. Less than 0.5 log
• C. About 0.5 log
• D. Complete removal

Answer: (B)

Conventional sedimentation processes are designed to remove suspended solids, primarily through the settling of larger particles due to gravity. When it comes to microbial pathogens like Cryptosporidium oocysts, these are relatively small and can remain suspended in water despite sedimentation processes.

The removal efficiency of Cryptosporidium oocysts by conventional sedimentation is generally low, often quantified as less than 0.5 log. This indicates that there is only a modest reduction in the number of oocysts present in the water after sedimentation. Removal efficiencies of this magnitude indicate that sedimentation alone is insufficient to adequately reduce the concentration of these pathogens, necessitating additional treatment processes (like filtration or disinfection) to ensure safe drinking water.

In contrast, complete removal or substantial removal (more than 1 log) is unrealistic for conventional sedimentation due to the size and buoyancy characteristics of oocysts. Thus, stating that conventional sedimentation has a removal of less than 0.5 log accurately reflects the limitations of this method in targeting Cryptosporidium oocysts.