Drinking Water Scheme - Gov.uk
Summary of Results External Quality Assessment of Water Microbiology
Drinking Water Scheme Distribution Number: W178
Sample Numbers: W178A, W178B, W178C
Distribution Date: Results Due: Report Date:
November 2017 08 December 2017 18 December 2017
Samples prepared and quality control tested by:
Angela Appea Richard Borrill Thomas Harper Zak Prior Judith Spellar Aneta Stranc Lili Tsegaye
Data analysed by:
Nita Patel Manchari Rajkumar
Report compiled by:
Nita Patel Manchari Rajkumar
Authorised by:
Nita Patel
This report must not be reproduced without permission of the organisers. Public Health England Food and Environmental Proficiency Testing Unit (FEPTU) 61 Colindale Avenue London NW9 5EQ Tel: +44 (0)20 8327 7119 Fax: +44 (0)20 8200 8264 Email: [email protected] The data in FEPTU reports is confidential
Page 1 of 29
Printed at 14:04 on Monday, 18 December, 2017
For further information on the scheme please refer to: Scheme Guide: https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scheme-guide Guide to Scoring and Statistics: https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scoring-systems-and-statistics
General guidance for z-scores: Participants' enumeration results are converted into z-scores using the following formula:
Z = (xi-Xpt) σpt
xi Xpt
= participants' result expressed (expressed as a log 10 value) = assigned value (participants' consensus median (expressed as a log 10 value))
σpt
= the fixed standard deviation for the examination (calculated by FEPTU)
The σpt-value expresses the acceptable difference between the individual participant 's result and the participants' consensus median. The σpt-value used for calculating z-scores for all parameters in the Drinking Water Scheme is 0.35. A guide to interpreting z-scores follows, although laboratories must interpret their scores in the context of their own laboratory situation. z = -1.99 to +1.99 z = -2 to -2.99 or +2 to +2.99 z= < -3.00 or > + 3.00
satisfactory questionable unsatisfactory
It is usually recommended that z-scores exceeding +/-2 are investigated to establish the possible cause. rule, PHE recommends that all questionable and unsatisfactory results are investigated.
As a general
FEPTU Quality Control: To demonstrate homogeneity of the sample, a minimum of 10 LENTICULE® discs, selected randomly from a batch, are tested in duplicate for parameters requiring enumeration.
To demonstrate stability of the sample, a minimum of nine LENTICULE discs, selected randomly from a batch, are examined throughout the distribution period for enumeration parameters. PHE uses methods stipulated in the DWI 's series of documents: The Microbiology of Drinking Water (2002) - Methods for the Examination of Waters and Associated Materials. The FEPTU results are used for guidance in the preliminary intended results notification, letters are posted on the website immediately after every distribution; electronic notification of their availability is sent to all participants. Refer to section 17.0 of the Scheme Guide if you have experienced difficulties with any of the examinations . https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scheme-guide
Participants are reminded that reporting an incorrect or false negative results could have serious public health implications. Participants who report unexpectedly high or low results for enumerations on single occasions only should not be unduly alarmed, although they should still assess the reason(s) for the outlying result. The results, as summarised in the performance assessment sheet included in this report, provide a more effective indication of on-going problems with the enumeration of low levels of indicator organisms in drinking water samples. Performance assessment cannot be undertaken as effectively if laboratories do not participate in all distributions for the Drinking Water Scheme.
Please contact FEPTU staff for advice and information: Repeat samples
Carmen Gomes or Kermin Daruwalla
Data Analysis
Manchari Rajkumar or Nita Patel
Microbiological advice
Nita Patel or Zak Prior
General comments and complaints
Nita Patel or Zak Prior
Scheme consultants
Julie E. Russell
Scheme Co-ordinator
Nita Patel
Tel: Fax: Email:
+44 (0)20 8327 7119 +44 (0)20 8200 8264 [email protected]
FEPTU's website
Accreditation: PHE Water EQA Scheme for Drinking Water is accredited by the United Kingdom Accreditation Service (UKAS) to ISO/IEC 17043:2010.
0006 The data in FEPTU reports is confidential
Page 2 of 29
Printed at 14:04 on Monday, 18 December, 2017
Sample: W178A Contents:
Escherichia coli (wild strain), Enterococcus faecium (NCIMB 12672), Clostridium perfringens (wild strain), Kocuria kristinae (NCTC 11038), Pseudomonas fluorescens (wild strain)
Expected Results: All counts are expressed as colony forming units (cfu) per 100mL except the colony counts at 37ºC/48h and 22ºC/72h which are cfu per mL.
Colony count 22ºC/72h
Colony count 37ºC/48h
C.perfringens
P.aeruginosa
Enterococci
E.coli
Parameter
Coliform bacteria
The fixed standard deviation value (σpt value) used for calculation of the z-scores is 0.35 for all parameters.
FEPTU median
17
17
146
0
36
49
48
No. results returned
134
140
126
114
106
127
123
Assigned value
31
30
130
0
42
45
44
Uncertainty of assigned value*
0.03
0.02
0.01
N/A
0.02
0.01
0.01
Participants mean (all results)
29
28
128
0
41
45
44
7 - 98
6 - 95
41 - 411
N/A
13 - 133
14 - 142
14 - 139
0.25
0.23
0.08
N/A
0.16
0.08
0.1
No of outlying counts
20
16
6
N/A
8
9
14
False positives
N/A
N/A
N/A
1
N/A
N/A
N/A
False negatives
5
7
0
N/A
3
1
1
(Participants median all results)
Expected Range
Standard deviation** ( log₁₀)
Your result
Score for performance assessment
Z-score
Analyst 2 Result
Analyst 2 Z-score
Analyst 3 Result
Analyst 3 Z-score
*
U(Xpt) is based on results transformed to a log₁₀ scale
**
Robust S* based on median absolute deviation about the participants' median (MADe) and is based on logged data
Total sent samples
152
Not examined
8
Non returns
3
Late returns
0
The data in FEPTU reports is confidential
Page 3 of 29
Printed at 14:04 on Monday, 18 December, 2017
Sample: W178B Contents:
Escherichia coli (wild strain), Enterobacter cloacae (wild strain), Pseudomonas aeruginosa (wild strain), Clostridium paraputrificum (wild strain), Microbacterium sp. (wild strain)
Expected Results: All counts are expressed as colony forming units (cfu) per 100mL except the colony counts at 37ºC/48h and 22ºC/72h which are cfu per mL.
0
64
0
2
72
No. results returned
135
140
125
114
106
126
122
Assigned value
106
74
0
38
0
2
76
Uncertainty of assigned value*
0.04
0.04
N/A
0.03
N/A
0.05
0.01
Participants mean (all results)
109
73
0
35
0
3
75
34 - 335
13 - 234
N/A
12 - 119
N/A
0-9
24 - 240
0.3
0.36
N/A
0.23
N/A
0.37
0.1
No of outlying counts
11
18
N/A
12
N/A
12
13
False positives
N/A
N/A
9
N/A
2
N/A
N/A
False negatives
3
5
N/A
2
N/A
0
2
E.coli
Parameter
Colony count 22ºC/72h
Colony count 37ºC/48h
39
P.aeruginosa
65
Enterococci
FEPTU median
Coliform bacteria
C.perfringens
The fixed standard deviation value (σpt value) used for calculation of the z-scores is 0.35 for all parameters.
(Participants median all results)
Expected Range
Standard deviation** ( log₁₀)
Your result
Score for performance assessment
Z-score
Analyst 2 Result
Analyst 2 Z-score
Analyst 3 Result
Analyst 3 Z-score
*
U(Xpt) is based on results transformed to a log₁₀ scale
**
Robust S* based on median absolute deviation about the participants' median (MADe) and is based on logged data
Total sent samples
152
Not examined
7
Non returns
3
Late returns
0
The data in FEPTU reports is confidential
Page 4 of 29
Printed at 14:04 on Monday, 18 December, 2017
Sample: W178C Contents:
Enterococcus faecalis (wild strain), Pseudomonas aeruginosa (wild strain), Clostridium perfringens (wild strain), Lactococcus lactis (wild strain), Providencia rettgeri (NCTC 7475), Staphylococcus epidermidis (wild strain)
Expected Results: All counts are expressed as colony forming units (cfu) per 100mL except the colony counts at 37ºC/48h and 22ºC/72h which are cfu per mL.
Colony count 22ºC/72h
41
48
16
13
134
140
126
114
106
127
122
0
0
44
28
58
14
11
Uncertainty of assigned value*
N/A
N/A
0.01
0.02
0.01
0.03
0.02
Participants mean (all results)
0
0
44
27
57
13
12
Expected Range
N/A
N/A
14 - 139
9 - 89
18 - 183
4 - 44
3 - 35
Standard deviation**
N/A
N/A
0.1
0.18
0.13
0.24
0.16
N/A
N/A
3
13
7
12
12
False positives
6
1
N/A
N/A
N/A
N/A
N/A
False negatives
N/A
N/A
0
3
2
0
4
No. results returned
Assigned value
C.perfringens
44
P.aeruginosa
0
FEPTU median
Enterococci
E.coli
0
Parameter
Coliform bacteria
Colony count 37ºC/48h
The fixed standard deviation value (σpt value) used for calculation of the z-scores is 0.35 for all parameters.
(Participants median all results)
( log₁₀) No of outlying counts
Your result
Score for performance assessment
Z-score
Analyst 2 Result
Analyst 2 Z-score
Analyst 3 Result
Analyst 3 Z-score
*
U(Xpt) is based on results transformed to a log₁₀ scale
**
Robust S* based on median absolute deviation about the participants' median (MADe) and is based on logged data
Total sent samples
152
Not examined
7
Non returns
3
Late returns
0
The data in FEPTU reports is confidential
Page 5 of 29
Printed at 14:04 on Monday, 18 December, 2017
1
Outlying results
Outlying results
5-6
PHE score 30
25
0
2
Outlying results
0
98
88-98
83-87
78-82
73-77
68-72
63-67
58-62
53-57
48-52
43-47
38-42
33-37
28-32
23-27
18-22
7-12
13-17
0
Count per 100mL
Method based presentation W178A : Coliform bacteria
FEPTU Method: Chromogenic coliform agar
Method
Robust S*
Number of Results
Excluded Results
Percentage of the total
Median
Range Reported
Colilert (18/250)
39
0
29
36
0.17
0
-
165
Colisure
0
0
0
Tube combinations
3
1
2
Other (MPN)
3
0
2
MLSB
18
0
13
24
0.22
4
-
68
MLSA
4
0
3 20
0.29
0
-
50
(Log₁₀)
MLGA
13
0
9
Tergitol 7 (TTC)
3
0
2
Chromogenic coliform agar
39
0
29
32
0.29
0
-
190
Other (Membrane filtration)
11
0
8
23
0.39
1
-
44
31 Participant Median 17 FEPTU Median
Outlying results
Outlying results
5-6
20
15
10
5
>98
88-98
83-87
78-82
73-77
68-72
63-67
58-62
53-57
48-52
43-47
38-42
33-37
28-32
23-27
18-22
13-17
0
7-12
No. of Results
25
Outlying results
30
95
86-95
81-85
76-80
71-75
66-70
61-65
56-60
51-55
46-50
41-45
36-40
31-35
26-30
21-25
16-20
12-15
0
6-11
No. of Results
45
Outlying results
50
1-5
55
Outlying results
60
411
372-411
352-371
332-351
312-331
292-311
272-291
252-271
232-251
213-231
194-212
175-193
156-174
137-155
118-136
99-117
80-98
61-79
411
372-411
352-371
332-351
312-331
292-311
272-291
Count per 100mL
252-271
232-251
213-231
194-212
175-193
156-174
137-155
118-136
99-117
80-98
61-79
41-60
0
133
120-133
113-119
106-112
99-105
92-98
85-91
79-84
73-78
67-72
61-66
55-60
49-54
43-48
37-42
31-36
25-30
19-24
133
120-133
113-119
99-105
92-98
106-112
Count per 100mL TSC (Membrane Filtration)
85-91
79-84
73-78
67-72
61-66
55-60
49-54
43-48
37-42
31-36
25-30
19-24
13-18
0
142
129-142
122-128
115-121
108-114
101-107
94-100
87-93
80-86
73-79
66-72
59-65
52-58
45-51
39-44
33-38
27-32
21-26
14-20
142
129-142
122-128
115-121
108-114
94-100
101-107
Count per mL
87-93
80-86
73-79
66-72
59-65
52-58
45-51
39-44
33-38
27-32
21-26
14-20
0
335
302-335
285-301
268-284
251-267
234-250
217-233
Count per 100mL
200-216
183-199
166-182
149-165
132-148
115-131
99-114
83-98
67-82
51-66
0
34-50
No. of Results
25
Outlying results
30
234
209-234
196-208
183-195
171-182
159-170
147-158
Count per 100mL
135-146
123-134
111-122
99-110
87-98
75-86
63-74
51-62
39-50
27-38
0
13-26
No. of Results
25
Outlying results
30
119
108-119
96-101
90-95
84-89
78-83
102-107
Count per 100mL Pseudalert (MPN)
72-77
66-71
60-65
54-59
48-53
42-47
36-41
30-35
24-29
18-23
0
12-17
No. of Results
25
Outlying results
30
139
126-139
119-125
112-118
105-111
98-104
91-97
84-90
77-83
70-76
63-69
56-62
50-55
44-49
38-43
32-37
26-31
20-25
139
126-139
119-125
112-118
98-104
105-111
Count per 100mL
91-97
84-90
77-83
70-76
63-69
56-62
50-55
44-49
38-43
32-37
26-31
20-25
14-19
0
89
80-89
75-79
70-74
65-69
60-64
55-59
50-54
45-49
41-44
37-40
33-36
29-32
25-28
21-24
17-20
13-16
0
9-12
No. of Results
25
Outlying results
30
183
166-183
157-165
148-156
139-147
130-138
121-129
112-120
103-111
94-102
85-93
76-84
67-75
59-66
51-58
43-50
35-42
27-34
183
166-183
157-165
148-156
139-147
130-138
121-129
Count per 100mL TSC (Membrane Filtration)
112-120
103-111
94-102
85-93
76-84
67-75
59-66
51-58
43-50
35-42
27-34
18-26
0
44
39-44
36-38
33-35
31-32
29-30
27-28
25-26
23-24
21-22
19-20
17-18
15-16
13-14
11-12
9-10
7-8
0
4-6
No. of Results
25
Outlying results
30
41
No. of Results
30
11 Participant Median 13 FEPTU Median
35-41
35
Outlying results
40
25
20
15
10
5
32-35
30-31
28-29
26-27
24-25
22-23
20-21
18-19
16-17
14-15
12-13
10-11
8-9
6-7
5-5
4-4
3-3
41
35-41
32-35
30-31
28-29
26-27
24-25
22-23
20-21
18-19
16-17
14-15
12-13
10-11
8-9
6-7
5-5
4-4
3-3
0
Drinking Water Scheme Distribution Number: W178
Sample Numbers: W178A, W178B, W178C
Distribution Date: Results Due: Report Date:
November 2017 08 December 2017 18 December 2017
Samples prepared and quality control tested by:
Angela Appea Richard Borrill Thomas Harper Zak Prior Judith Spellar Aneta Stranc Lili Tsegaye
Data analysed by:
Nita Patel Manchari Rajkumar
Report compiled by:
Nita Patel Manchari Rajkumar
Authorised by:
Nita Patel
This report must not be reproduced without permission of the organisers. Public Health England Food and Environmental Proficiency Testing Unit (FEPTU) 61 Colindale Avenue London NW9 5EQ Tel: +44 (0)20 8327 7119 Fax: +44 (0)20 8200 8264 Email: [email protected] The data in FEPTU reports is confidential
Page 1 of 29
Printed at 14:04 on Monday, 18 December, 2017
For further information on the scheme please refer to: Scheme Guide: https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scheme-guide Guide to Scoring and Statistics: https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scoring-systems-and-statistics
General guidance for z-scores: Participants' enumeration results are converted into z-scores using the following formula:
Z = (xi-Xpt) σpt
xi Xpt
= participants' result expressed (expressed as a log 10 value) = assigned value (participants' consensus median (expressed as a log 10 value))
σpt
= the fixed standard deviation for the examination (calculated by FEPTU)
The σpt-value expresses the acceptable difference between the individual participant 's result and the participants' consensus median. The σpt-value used for calculating z-scores for all parameters in the Drinking Water Scheme is 0.35. A guide to interpreting z-scores follows, although laboratories must interpret their scores in the context of their own laboratory situation. z = -1.99 to +1.99 z = -2 to -2.99 or +2 to +2.99 z= < -3.00 or > + 3.00
satisfactory questionable unsatisfactory
It is usually recommended that z-scores exceeding +/-2 are investigated to establish the possible cause. rule, PHE recommends that all questionable and unsatisfactory results are investigated.
As a general
FEPTU Quality Control: To demonstrate homogeneity of the sample, a minimum of 10 LENTICULE® discs, selected randomly from a batch, are tested in duplicate for parameters requiring enumeration.
To demonstrate stability of the sample, a minimum of nine LENTICULE discs, selected randomly from a batch, are examined throughout the distribution period for enumeration parameters. PHE uses methods stipulated in the DWI 's series of documents: The Microbiology of Drinking Water (2002) - Methods for the Examination of Waters and Associated Materials. The FEPTU results are used for guidance in the preliminary intended results notification, letters are posted on the website immediately after every distribution; electronic notification of their availability is sent to all participants. Refer to section 17.0 of the Scheme Guide if you have experienced difficulties with any of the examinations . https://www.gov.uk/government/publications/food-and-water-proficiency-testing-schemes-scheme-guide
Participants are reminded that reporting an incorrect or false negative results could have serious public health implications. Participants who report unexpectedly high or low results for enumerations on single occasions only should not be unduly alarmed, although they should still assess the reason(s) for the outlying result. The results, as summarised in the performance assessment sheet included in this report, provide a more effective indication of on-going problems with the enumeration of low levels of indicator organisms in drinking water samples. Performance assessment cannot be undertaken as effectively if laboratories do not participate in all distributions for the Drinking Water Scheme.
Please contact FEPTU staff for advice and information: Repeat samples
Carmen Gomes or Kermin Daruwalla
Data Analysis
Manchari Rajkumar or Nita Patel
Microbiological advice
Nita Patel or Zak Prior
General comments and complaints
Nita Patel or Zak Prior
Scheme consultants
Julie E. Russell
Scheme Co-ordinator
Nita Patel
Tel: Fax: Email:
+44 (0)20 8327 7119 +44 (0)20 8200 8264 [email protected]
FEPTU's website
Accreditation: PHE Water EQA Scheme for Drinking Water is accredited by the United Kingdom Accreditation Service (UKAS) to ISO/IEC 17043:2010.
0006 The data in FEPTU reports is confidential
Page 2 of 29
Printed at 14:04 on Monday, 18 December, 2017
Sample: W178A Contents:
Escherichia coli (wild strain), Enterococcus faecium (NCIMB 12672), Clostridium perfringens (wild strain), Kocuria kristinae (NCTC 11038), Pseudomonas fluorescens (wild strain)
Expected Results: All counts are expressed as colony forming units (cfu) per 100mL except the colony counts at 37ºC/48h and 22ºC/72h which are cfu per mL.
Colony count 22ºC/72h
Colony count 37ºC/48h
C.perfringens
P.aeruginosa
Enterococci
E.coli
Parameter
Coliform bacteria
The fixed standard deviation value (σpt value) used for calculation of the z-scores is 0.35 for all parameters.
FEPTU median
17
17
146
0
36
49
48
No. results returned
134
140
126
114
106
127
123
Assigned value
31
30
130
0
42
45
44
Uncertainty of assigned value*
0.03
0.02
0.01
N/A
0.02
0.01
0.01
Participants mean (all results)
29
28
128
0
41
45
44
7 - 98
6 - 95
41 - 411
N/A
13 - 133
14 - 142
14 - 139
0.25
0.23
0.08
N/A
0.16
0.08
0.1
No of outlying counts
20
16
6
N/A
8
9
14
False positives
N/A
N/A
N/A
1
N/A
N/A
N/A
False negatives
5
7
0
N/A
3
1
1
(Participants median all results)
Expected Range
Standard deviation** ( log₁₀)
Your result
Score for performance assessment
Z-score
Analyst 2 Result
Analyst 2 Z-score
Analyst 3 Result
Analyst 3 Z-score
*
U(Xpt) is based on results transformed to a log₁₀ scale
**
Robust S* based on median absolute deviation about the participants' median (MADe) and is based on logged data
Total sent samples
152
Not examined
8
Non returns
3
Late returns
0
The data in FEPTU reports is confidential
Page 3 of 29
Printed at 14:04 on Monday, 18 December, 2017
Sample: W178B Contents:
Escherichia coli (wild strain), Enterobacter cloacae (wild strain), Pseudomonas aeruginosa (wild strain), Clostridium paraputrificum (wild strain), Microbacterium sp. (wild strain)
Expected Results: All counts are expressed as colony forming units (cfu) per 100mL except the colony counts at 37ºC/48h and 22ºC/72h which are cfu per mL.
0
64
0
2
72
No. results returned
135
140
125
114
106
126
122
Assigned value
106
74
0
38
0
2
76
Uncertainty of assigned value*
0.04
0.04
N/A
0.03
N/A
0.05
0.01
Participants mean (all results)
109
73
0
35
0
3
75
34 - 335
13 - 234
N/A
12 - 119
N/A
0-9
24 - 240
0.3
0.36
N/A
0.23
N/A
0.37
0.1
No of outlying counts
11
18
N/A
12
N/A
12
13
False positives
N/A
N/A
9
N/A
2
N/A
N/A
False negatives
3
5
N/A
2
N/A
0
2
E.coli
Parameter
Colony count 22ºC/72h
Colony count 37ºC/48h
39
P.aeruginosa
65
Enterococci
FEPTU median
Coliform bacteria
C.perfringens
The fixed standard deviation value (σpt value) used for calculation of the z-scores is 0.35 for all parameters.
(Participants median all results)
Expected Range
Standard deviation** ( log₁₀)
Your result
Score for performance assessment
Z-score
Analyst 2 Result
Analyst 2 Z-score
Analyst 3 Result
Analyst 3 Z-score
*
U(Xpt) is based on results transformed to a log₁₀ scale
**
Robust S* based on median absolute deviation about the participants' median (MADe) and is based on logged data
Total sent samples
152
Not examined
7
Non returns
3
Late returns
0
The data in FEPTU reports is confidential
Page 4 of 29
Printed at 14:04 on Monday, 18 December, 2017
Sample: W178C Contents:
Enterococcus faecalis (wild strain), Pseudomonas aeruginosa (wild strain), Clostridium perfringens (wild strain), Lactococcus lactis (wild strain), Providencia rettgeri (NCTC 7475), Staphylococcus epidermidis (wild strain)
Expected Results: All counts are expressed as colony forming units (cfu) per 100mL except the colony counts at 37ºC/48h and 22ºC/72h which are cfu per mL.
Colony count 22ºC/72h
41
48
16
13
134
140
126
114
106
127
122
0
0
44
28
58
14
11
Uncertainty of assigned value*
N/A
N/A
0.01
0.02
0.01
0.03
0.02
Participants mean (all results)
0
0
44
27
57
13
12
Expected Range
N/A
N/A
14 - 139
9 - 89
18 - 183
4 - 44
3 - 35
Standard deviation**
N/A
N/A
0.1
0.18
0.13
0.24
0.16
N/A
N/A
3
13
7
12
12
False positives
6
1
N/A
N/A
N/A
N/A
N/A
False negatives
N/A
N/A
0
3
2
0
4
No. results returned
Assigned value
C.perfringens
44
P.aeruginosa
0
FEPTU median
Enterococci
E.coli
0
Parameter
Coliform bacteria
Colony count 37ºC/48h
The fixed standard deviation value (σpt value) used for calculation of the z-scores is 0.35 for all parameters.
(Participants median all results)
( log₁₀) No of outlying counts
Your result
Score for performance assessment
Z-score
Analyst 2 Result
Analyst 2 Z-score
Analyst 3 Result
Analyst 3 Z-score
*
U(Xpt) is based on results transformed to a log₁₀ scale
**
Robust S* based on median absolute deviation about the participants' median (MADe) and is based on logged data
Total sent samples
152
Not examined
7
Non returns
3
Late returns
0
The data in FEPTU reports is confidential
Page 5 of 29
Printed at 14:04 on Monday, 18 December, 2017
1
Outlying results
Outlying results
5-6
PHE score 30
25
0
2
Outlying results
0
98
88-98
83-87
78-82
73-77
68-72
63-67
58-62
53-57
48-52
43-47
38-42
33-37
28-32
23-27
18-22
7-12
13-17
0
Count per 100mL
Method based presentation W178A : Coliform bacteria
FEPTU Method: Chromogenic coliform agar
Method
Robust S*
Number of Results
Excluded Results
Percentage of the total
Median
Range Reported
Colilert (18/250)
39
0
29
36
0.17
0
-
165
Colisure
0
0
0
Tube combinations
3
1
2
Other (MPN)
3
0
2
MLSB
18
0
13
24
0.22
4
-
68
MLSA
4
0
3 20
0.29
0
-
50
(Log₁₀)
MLGA
13
0
9
Tergitol 7 (TTC)
3
0
2
Chromogenic coliform agar
39
0
29
32
0.29
0
-
190
Other (Membrane filtration)
11
0
8
23
0.39
1
-
44
31 Participant Median 17 FEPTU Median
Outlying results
Outlying results
5-6
20
15
10
5
>98
88-98
83-87
78-82
73-77
68-72
63-67
58-62
53-57
48-52
43-47
38-42
33-37
28-32
23-27
18-22
13-17
0
7-12
No. of Results
25
Outlying results
30
95
86-95
81-85
76-80
71-75
66-70
61-65
56-60
51-55
46-50
41-45
36-40
31-35
26-30
21-25
16-20
12-15
0
6-11
No. of Results
45
Outlying results
50
1-5
55
Outlying results
60
411
372-411
352-371
332-351
312-331
292-311
272-291
252-271
232-251
213-231
194-212
175-193
156-174
137-155
118-136
99-117
80-98
61-79
411
372-411
352-371
332-351
312-331
292-311
272-291
Count per 100mL
252-271
232-251
213-231
194-212
175-193
156-174
137-155
118-136
99-117
80-98
61-79
41-60
0
133
120-133
113-119
106-112
99-105
92-98
85-91
79-84
73-78
67-72
61-66
55-60
49-54
43-48
37-42
31-36
25-30
19-24
133
120-133
113-119
99-105
92-98
106-112
Count per 100mL TSC (Membrane Filtration)
85-91
79-84
73-78
67-72
61-66
55-60
49-54
43-48
37-42
31-36
25-30
19-24
13-18
0
142
129-142
122-128
115-121
108-114
101-107
94-100
87-93
80-86
73-79
66-72
59-65
52-58
45-51
39-44
33-38
27-32
21-26
14-20
142
129-142
122-128
115-121
108-114
94-100
101-107
Count per mL
87-93
80-86
73-79
66-72
59-65
52-58
45-51
39-44
33-38
27-32
21-26
14-20
0
335
302-335
285-301
268-284
251-267
234-250
217-233
Count per 100mL
200-216
183-199
166-182
149-165
132-148
115-131
99-114
83-98
67-82
51-66
0
34-50
No. of Results
25
Outlying results
30
234
209-234
196-208
183-195
171-182
159-170
147-158
Count per 100mL
135-146
123-134
111-122
99-110
87-98
75-86
63-74
51-62
39-50
27-38
0
13-26
No. of Results
25
Outlying results
30
119
108-119
96-101
90-95
84-89
78-83
102-107
Count per 100mL Pseudalert (MPN)
72-77
66-71
60-65
54-59
48-53
42-47
36-41
30-35
24-29
18-23
0
12-17
No. of Results
25
Outlying results
30
139
126-139
119-125
112-118
105-111
98-104
91-97
84-90
77-83
70-76
63-69
56-62
50-55
44-49
38-43
32-37
26-31
20-25
139
126-139
119-125
112-118
98-104
105-111
Count per 100mL
91-97
84-90
77-83
70-76
63-69
56-62
50-55
44-49
38-43
32-37
26-31
20-25
14-19
0
89
80-89
75-79
70-74
65-69
60-64
55-59
50-54
45-49
41-44
37-40
33-36
29-32
25-28
21-24
17-20
13-16
0
9-12
No. of Results
25
Outlying results
30
183
166-183
157-165
148-156
139-147
130-138
121-129
112-120
103-111
94-102
85-93
76-84
67-75
59-66
51-58
43-50
35-42
27-34
183
166-183
157-165
148-156
139-147
130-138
121-129
Count per 100mL TSC (Membrane Filtration)
112-120
103-111
94-102
85-93
76-84
67-75
59-66
51-58
43-50
35-42
27-34
18-26
0
44
39-44
36-38
33-35
31-32
29-30
27-28
25-26
23-24
21-22
19-20
17-18
15-16
13-14
11-12
9-10
7-8
0
4-6
No. of Results
25
Outlying results
30
41
No. of Results
30
11 Participant Median 13 FEPTU Median
35-41
35
Outlying results
40
25
20
15
10
5
32-35
30-31
28-29
26-27
24-25
22-23
20-21
18-19
16-17
14-15
12-13
10-11
8-9
6-7
5-5
4-4
3-3
41
35-41
32-35
30-31
28-29
26-27
24-25
22-23
20-21
18-19
16-17
14-15
12-13
10-11
8-9
6-7
5-5
4-4
3-3
0
