Table 1 Tested filter types, operating time and test intervals (trial 1–4)
Filter type/trial | sample sets (n samples) | Operating time of filter (weeks) | Additional test intervals during operating time (weeks) |
|---|---|---|---|
1/1 | 3 × 6 (18)* | 1 | 0 |
1/2 | 13 × 6 (78)* | 1 | 0 |
2/3 | 12 × 18 (216) | 4 | 1 |
3/4 | 3 × 18 (54) | 8 | 1, 4 |