Table 3.

Average density of protozoa and bacteria in the water and biofilm of the distribution system fed for 4 months with GAC water (network A)a

Sampling pointAvg density (SD [n = 3]), liter−1 or cm−2
CiliateThecamoebaeAmoebaeFlagellateBacterial cells
GAC water entering the network695 (61)1,170 (34)548 (37)3 × 104 (1.5 × 108)2.6 × 108 (1.9 × 107)
Loop 1
 Water3,300 (360)2,870 (38)2,100 (72)1.67 × 105 (8 × 104)3.6 × 108 (4.7 × 107)
 Biofilm765 (10)673 (73)0a04.3 × 107 (3.5 × 105)
Loop 2
 Water936 (180)1,380 (180)110 (6)1 × 105 (6 × 104)3.9 × 108 (5.2 × 107)
 Biofilm817 (53)584 (22)001.4 × 107 (7.3 × 105)
Loop 3
 Water727 (180)1,090 (290)02.5 × 104 (4 × 103)2.9 × 108 (1.8 × 107)
 Biofilm322 (52)568 (30)001.1 × 107 (0)
  • a Hydraulic residence time, 12 h loop−1; temperature, 25 ± 1.5°C. Detection limits: flagellate, 1,480 liter−1 or 15 cm−2; ciliate, thecamoebae, and naked amoebae, 100 liter−1 or 15 cm−2. 0, not detectable.