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Examination of the Effectiveness of "BelKraft" Filter Candles (Ceramic shells with whole house filters)
Report Prepared for:
BelKraft
Materials:
1) Food grade Polyprepoline:
2) Six bacteriological "BelKraft" Filter candles.
Test Organisms:
Salmonella typhi NCTC 786.
Shigella dysenteriae Type 2. NCTC 2966.
Vibrio cholerae Inaba NCTC 10732.
Methods:
1. Preliminary
Two complete assemblies were tested for efficiency of filtration using Escherichia coli. During the course of these tests we found that two of the filter candles provided had hair-line cracks which allowed organisms through the filter. These were discarded and the two assemblies finally used gave complete retention of E. coli. There were no leaks thorough the seals.
2. Test
Between test runs the the Raw Water we added 1% formalin which was allowed to run through the filter. This was followed by two lots of tap water. This treatment effectively killed off pathogenic test organisms and the washing effectively removed inhibitory traces of formalin. The following test sequence was followed:
a) Inoculum of test organisms (in broth culture) was added to give approximate contamination level of 100,000 per ml. This was mixed and a sample taken to confirm inoculum level.
b) When the whole volume had passed through the filter samples were taken for detection of contaminating organisms and the absence of inhibitory levels of formaldehyde.
Two filtrations were run for each test organism.
Results:
| Organism |
Test organisms per ml
Before Filtration |
Test organism per 10ml
After Filtration |
| Shigella dysenteriae |
390,000
180,00 |
0
0 |
| Salmonella typhi |
71,000
150,000 |
0
0 |
| Vibrio cholerae |
340,000
330,000 |
0
0 |
Comments:
1. Providing the physical integrity of the filter candles is intact these can be used to filter sterilise water.
2. Success of the treatment is dependent on the apparatus being assembled correctly with no leaks and on the absence of cross contamination.
Signed: N.J. Butler
M.Sc., F.I.Biol., A.I.F.S.T
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