Table 2. The counts of water quality indicator bacteria (range of MPN or CFU/100 mL), occurrence of faecal pathogens and chlorine concentrations in the water samples taken in July and August, 2012 in Vuorela, Finland.
| Date (number of samples) | E. coli | Coliform bacteria | Entero-coccus | Faecal pathogens | Chlorine (mg/l) |
| Drinking water distribution system samples from the clean area | |||||
| 5–19 Jul (12) | 0 | 0–1 | 0 | Not detected/3–6 samples1 | ND, 0.4–1.82 |
| Drinking water distribution system samples from the boil water notice area | |||||
| 5 Jul (1) | 0 | 0 | ND | ND | ND |
| 16 Jul (4) | 0–150 | 0–150 | 0–17 | Arcobacter spp./1–4 samples3 | ND |
| 17 Jul (4) | 0–21 | 0–34 | 0–2 | EHEC, EPEC and EAEC virulence genes4 | ND |
| 18–20 Jul (10) | 05 | 0 | 0 | Not detected/2–4 samples1 | <0.1–1.6 |
| 23–30 Jul (13) | ND6 | ND | ND | Not detected/3 samples7 | <0.1–2.0 |
| 1–29 Aug (9) | ND6 | ND | ND | ND | 0.4–1.9 |
| Water storage reservoir | |||||
| 17 July (1) | 110 | 190 | 15 | Norovirus and adenovirus8 | ND |
| 21 July (1) | 0 | 0 | ND | Not detected9 | ND |
| Biofilms from the water meters removed from the boil water notice area | |||||
| 1 Aug (2) | ND | ND | ND | Arcobacter spp.10 | ND |
| Raw water at the groundwater abstraction plant | |||||
| 9 August (1) | 0 | 0 | ND | Not detected11 | ND |
| Surface water samples (contaminant source) | |||||
| 23 Jul (1) | 86 | 450 | 44 | Campylobacter jejuni 10–100 cfu/l, EPEC virulence genes12 | ND |
| 29 Aug (5) | 0–94 | ND | 5–80 | ND | ND |
| Community wastewater | |||||
| 25 Jul (1) | ND | ND | ND | Sapovirus | ND |
ND; not determined.
A portion of the samples were selected for Salmonella, Campylobacter, enterohaemorragic E. coli (EHEC) culture analyses and for norovirus analysis.
Measured from three locations at 19 July.
Samples were tested for noro-, adeno-, rota- and sapoviruses, Campylobacter and E. coli virulence genes. Arcobacter was tested from DNA extracts and genus specific PCR was positive in one sample (point 9 in Figure 1).
E. coli virulence genes were detected after ultrafiltration from one sampling location (point 5 in Figure 1). Salmonella, Campylobacter, EHEC (culture method), noro-, rota- and sapovirus, Giardia and Cryptosporidium were not detected (1–4 samples tested/method).
One colony of Clostridium perfringens was found from 1 000 mL of tap water sample taken from the most contaminated area.
Clostridium perfringens was analyzed and not detected from 5 000 mL samples.
Samples were tested for sapovirus.
Sample was tested for noro-, adeno-, rota- and sapoviruses, Salmonella, Campylobacter and E. coli virulence genes. Clostridium perfringens was detected (10 CFU/L).
Sample was tested for Campylobacter and noroviruses. Clostridium perfringens was detected (2 CFU/L).
Sample tested for Campylobacter, Arcobacter, Giardia and Cryptosporidium.
Sample tested for Campylobacter.
Sample tested for Campylobacter, E. coli virulence genes, noro- and adenoviruses, Giardia and Cryptosporidium. Clostridium perfringens was detected (40 CFU/L).