Practical bacteriology for chemical students / by David Ellis.

  • David Ellis
Date:
1923
Catalogue details

Licence: In copyright

Credit: Practical bacteriology for chemical students / by David Ellis. Source: Wellcome Collection.

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    CHAPTER X. Methods of Examination of Sewage. Dilution of Sewage: Total-count: Number of Bac. coli in Sewage: Indol-tests: Examination for Bac. enteritidis. Sewage and Sewage-Effluents. Before examining a sewage or an effluent consideration must be given to the fact that it is possible that all life in the sewage may have been destroyed owing to admixture with trade effluents containing ingredients inimical to life. There will therefore be little use in making a bacteriological examination until some information has been obtained on this point. Exercise 77. To ascertain whether a fluid contains living bacteria. 1. Take up a loopful of fluid with a ster. platinum loop. 2. Transfer to Agar-slope. 3. Incubate for 24 hours at room-temperature or at 30 0 C. If growth is perceptible after this interval, the exercises set below may be taken in hand. The next procedure, if the bacteria in Sewage have not been killed, is to secure a dilution such that it will be possible to deal adequately with the fluid. Domestic Sewage may contain as many as 100 million bacteria per cub.cm. The method of dilution is the same as for drinking water only the dilution must be carried further. Exercise 78. Dilution of Sewage. 1. Place 6 small flasks on table each containing 9 c.c. of sterile water.