Table 1.
Background Information on the Phase I (DWTP 1–9) and Phase II (DWTP 1–5; 10–29) locations.
| Location | Pop serveda (1000s) | Production at samplinga (MGD) | Residence time of treatmentb (h) | Sampling intervalb (h) | Primary disinfectantc | GAC depth (feet) | GAC recharge rate (years) | Simplified treatment traine |
|---|---|---|---|---|---|---|---|---|
| DWTP 1 | >500 | >100 | PI4 | PI 4.5 | O3 + NH2Cl | nad | na | O3, coag/floc, NH2Cl, C, floc, C, F |
| PII 10 | PII 8 | |||||||
| DWTP 2 | >500 | >100 | PI 69 | PI 75 | Cl2 | 11.4 | 0.6 | Coag/floc, S, SF, GAC, Cl2 |
| PII 72 | PII 73 | |||||||
| DWTP 3 | 50–500 | 10–100 | 6 | PI 7 | Cl2 + UV | 2.5 | 3 | Coag/floc, C/S, F, GAC, Cl2, UV |
| PII 7 | ||||||||
| DWTP 4 | >500 | 10–100 | PI 38 | PI 45 | Cl2 + NH2Cl | na | na | Pre-Cl2, coag/floc, S, secondary Cl2, SF, NH3 |
| PII 46 | PII 48 | |||||||
| DWTP 5 | <50 | <10 | 0.13 | PI 0 | Cl2 | na | na | Cl2 |
| PII 0 | ||||||||
| DWTP 6 | 50–500 | 10–100 | 24 | 24 | ClO2 + Cl2 | na | na | ClO2, coag, S,pre-Cl2, F, Cl2 |
| DWTP 7 | 50–500 | 10–100 | 8 | 8 | Cl2 | na | na | Coag, pre-Cl2, PAC, floc, S, F, Cl2 |
| DWTP 8 | <50 | <10 | 6 | 6 | ClO2 + Cl2 | 3 | 2 | ClO2, Cl2, coag/floc, S, GAC and SF, Cl2 |
| DWTP 9 | <50 | <10 | 10 | 6 | Cl2 | na | na | S, coag/floc, SF, Cl2 |
| DWTP 10 | 50–500 | >100 | 7 | 9.25 | NH2Cl | na | na | Coag/floc, S, NH2Cl, F |
| DWTP 11 | <50 | <10 | 7 | 2.25 | O3 + Cl2 | 6 | 4 | Coag/floc, S, C, O3, GAC and SF, Cl2 |
| DWTP 12 | <50 | <10 | 30.72 | 23.75 | Cl2 | 1.25 | as needed | Coag/floc, pre-Cl2, C, GAC and SF, post-Cl2 |
| DWTP 13 | >500 | >100 | 1 | 0.75 | Cl2 | na | na | Cl2 |
| DWTP 14 | 50–500 | 10–100 | 10 | 3.25 | ClO2 + Cl2 | 0.75 | 8 | Coag/floc, pre-ClO2, GAC and SF, Cl2 |
| DWTP 15 | <50 | <10 | 1 | 4 | Cl2 | na | na | Coag/floc, S, F, Cl2 |
| DWTP 16 | 50–500 | 10–100 | 6 | 9 | NH2Cl | 2.5 | 3 | Coag/floc, S, GAC and SF, NH2Cl |
| DWTP 17 | <50 | <10 | 2 | 4 | Cl2 | na | na | C, coag/floc, pre-Cl2, F, Cl2 |
| DWTP 18 | <50 | <10 | 7.3 | 7.25 | O3 + NH2Cl | 4 | 2 | O3, floc, S, pre-Cl2, GAC and SF, NH2cl |
| DWTP 19 | 50–500 | 10–100 | 26 | 57.25 | NH2Cl | na | na | Coag/floc, PAC, S, ultrafiltration, NH2Cl |
| DWTP 20 | >500 | 10–100 | 30 | 46.75 | O3 + CI2 | 5 | >4 | Floc, S, O3, GAC and SF, Cl2 |
| DWTP 21 | 50–500 | 10–100 | 90 | 14.5 | Cl2 | na | na | PAC pre-Cl2, coag, S, Cl2 F |
| DWTP 22 | 50–500 | 10–100 | 10 | 1.5 | O3 + Cl2 + UV | 4 | as needed | Pre-O3, coag, S, O3, GAC and SF, UV, Cl2 |
| DWTP 23 | 50–500 | 10–100 | 7 | 6.5 | ClO2 +UV + Cl | na | na | Pre-ClO2, coag/floc, S, dual media F, UV, Cl2 |
| DWTP 24 | 50–500 | 10–100 | 8 | 6.25 | NH2Cl | 1.7 | 3 | PAC, GAC and SF, NH2Cl |
| DWTP 25 | 50–500 | 10–100 | 13.6 | 12 | O3 + NH2CI | 3 | 5–10 | Pre-O3, coag, NH2Cl |
| DWTP 26 | 50–500 | 10–100 | 24–36 | 3.25 | Cl2 | na | na | Pre-Cl2, PAC, coag, S, Cl2, F, Cl2 |
| DWTP 27 | 50–500 | <10 | 4 | 13.75 | NH2Cl + UV | na | na | PAC, coag/floc, S, F, UV, NH2Cl |
| DWTP 28 | >500 | >100 | 1 | 1.5 | O3 + NH2Cl | na | na | NH2cl, O3, F |
| DWTP 29 | <50 | <10 | 8 | 8.75 | Cl2 | na | na | PAC, pre-Cl2, coag/floc, S, Cl2, F |
a
Population sizes binned to give indication of DWTP size variation while maintaining plant anonymity.
b
DWTPs were asked to match the residence time of treatment. Some locations achieved this better than others. PI = Phase I of study; PII = Phase II of study.
c
O3 = ozone; NH2Cl = chloramine; Cl2 = chlorine; UV = ultraviolet radiation; ClO2 = chlorine dioxide.
d
na = not applicable.
e
Major steps in treatment in each plant. Coag = coagulation; floc = flocculation; C = clarification; F = filtration; S = sedimentation; SF = sand filter; NH3 = ammonia; PAC = powdered activated carbon; GAC = granular activated carbon.