1507. The amount of residual chlorine left in public water supply for safety against pathogenic bacteria is about______________? September 7, 2025 by Admin A. 0.01 to 0.05 ppm B. 0.05 to 0.5 ppm C. 0.5 to 1.0 ppm D. 1.0 to 5.0 ppm ✅ The correct answer is option B.
