Table 3.
Summary statistics for arsenic in first-draw water samples and categorization of systems based on the pattern of arsenic release.
| System |
Arsenic Before Treatment AVG ± STDEV, μg/L |
Arsenic After Treatment AVG ± STDEV, μg/L |
Arsenic Pattern | |||||
|---|---|---|---|---|---|---|---|---|
| # samples over 10.0 μg/L, % | # samples over 10.0 μg/L, % | |||||||
| DS1 | DS2 | DS3 | Treatment Effluent | DS1 | DS2 | DS3 | ||
| Adsorptive Media | ||||||||
| AL | 47±31 | 31±2 | 36±10 | 1±1 | 3±4 (2±1)* | 2±1 | 2±1 | A |
| 100% | 100% | 100% | 0% | 8% (0%)* | 0% | 0% | ||
| BW | 46±7 | 44±4 | 45±5 | 14±12 | 14±10 | 13±9 | 15±9 | A |
| 100% | 100% | 100% | 54% | 53% | 61% | 56% | ||
| BC | 12±1 | 9±1 | 11±1 | 4±3 | 6±2 | 6±2 | 6±3 | A |
| 100% | 0% | 75% | 4% | 6% | 6% | 11% | . | |
| GF | 30±4 | 30±4 | 31±4 | 3±3 | 3±2 | 3±2 | 3±2 | A |
| 100% | 100% | 100% | 0% | 0% | 0% | 0% | ||
| LD | 25±3 | 21±8 | 21±7 | 0.2±0.1 | 1±1 | 1±1 | 1±1 | A |
| 100% | 100% | 100% | 0% | 0% | 0% | 0% | ||
| DM | 29±2 | 34±5 | 39±8 | 1±0.5 | 9±10* | 3±2 | 5±3 | B |
| 100% | 100% | 100% | 0% | 33% | 0% | 11% | ||
| FC | 14±16 (6±1)* | 22±NA | 24±NA | 4±1 | 5±3 | 5±2 | 5±2 | C |
| 25% (0)* | NA | NA | 0% | 8% | 0% | 0% | ||
| Coagulation/Filtration | ||||||||
| CM | 33±8 | 37±11 | 41±12 | 10±4 | 51±136 (12±3)* | 13±2 | 11±3 | B |
| 100 | 100 | 100 | 39% | 75% (73%)* | 83% | 67% | ||
| LW | 39±7 | 39±6 | 40±14 | 8±1 | 16±2 | 12±2 | 9±2 | B |
| 100% | 100% | 100% | 0% | 100% | 86% | 14% | ||
| PW | 16±1 | 17±5 | 17±1 | 8±4 | 7±1 | 8±3 | 8±2 | C |
| 100% | 100% | 100% | 18% | 0% | 33% | 25% | ||
| Iron Removal & Adsorptive Media | ||||||||
| SF | 43±19 | 17±8 | 12±2 | 0.2±0.1 | 2±1 | 0.5±0.3 | 2±0.5 | B |
| 100% | 100% | 75% | 0% | 0% | 0% | 0% | ||
| ST | 29±2 | 35±3 | 29±1 | 2±2 | 6±2 | 5±2 | 8±4 | B |
| 100% | 100% | 100% | 0% | 0% | 0% | 8% | ||
| Oxidizing media & Adsorptive Media | ||||||||
| SV | 34±17 | 31±11 | 26±13 | 0.1±0.0 | 1±0.4 | 1±0.6 | 2±2 | B |
| 100% | 100% | 100% | 0% | 0% | 0% | 0% | ||
| WA | 35±4 | 36±4 | 36±3 | 10±15 | 11±16 | 11±17 | 12±17 | A |
| 100% | 100% | 100% | 36% | 36% | 36% | 36% | ||
| WL | 12±2 | 12±1 | 11±1 | 0.5±0.2 | 4±2 | 2±2 | 4±1 | B |
| 100% | 100% | 100% | 0% | 0% | 0% | 0% | ||
| Iron Removal | ||||||||
| WV | 13±2 | 20±7 | 40±20 | 3±1 | 12±4 | 7±4 | 8±3 | B |
| 100% | 100% | 100% | 0% | 60% | 20% | 20% | ||
| CL | 11±7 | 8±5 | 13±6 | 4±5 | 3±2 | 5±5 | 7±6 | C |
| 25% | 25% | 75% | 17% | 0% | 9% | 10% | ||
| DV | 13±3 | 16±2 | 16±1 | 8±5 | 10±6 | 8±6 | 10±6 | C |
| 67% | 100% | 100% | 28% | 39% | 23% | 23% | ||
| SA | 16±10 | 55±52 | 12±2 | 7±2 | 9±3 | 17±19 | 7±3 | C |
| 75% | 100% | 50% | 7% | 29% | 50% | 14% | ||
| SC | 24±2 | 21±5 | 25±2 | 6±4 | 8±6 | 8±4 | 9±7 | C |
| 100% | 100% | 100% | 21% | 23% | 23% | 23% | ||
AVG Average; STDEV Standard Deviation; NA: Not Applicable; DS1, DS2, DS3: Three distribution system sites sampled (i.e., homes or occasionally other buildings like schools);
*
single irregular spike that skews distribution removed from calculation in parenthesis