Which of these treatments does NOT remove leptospires effectively?

Primary sedimentation does not effectively remove leptospires from wastewater. This treatment process involves allowing solids to settle at the bottom of a tank, which primarily addresses the removal of larger particulate matter and some floating materials. However, leptospires, being microscopic spirochete bacteria, remain suspended in the water column and are not substantially removed during this phase.

In contrast, biological treatment, trickling filters, and filtration methods are designed to either break down organic material or physically remove smaller particles, including bacteria, from wastewater. These methods utilize various mechanisms that can significantly reduce the presence of leptospires, thus making them more effective for their removal compared to primary sedimentation.