ANNUAL REPORT, 1943-44 17 



Bacteriological Study of Septic Tank Efficiency. (James E. Fuller.) This 

 project was intended to be a cooperative study with the Division of Engineering 

 of the Massachusetts State Department of Health, with whom it originated. 

 The purpose of the study was, and still is, to study the effect of different sewage 

 retention periods on the bacterial and chemical quality of the effluent from septic 

 tanks. A tank was constructed having three compartments. Sewage from one 

 of the college dormatories was fed from a common receiving chamber into these 

 compartments through orifices of such size as to provide three different retention 

 periods for the sewage. 



State Department of Health representatives designed and supervised construc- 

 tion of the installation, and its operation was originally the responsibility of 

 Western Massachusetts District Engineering Office in Amherst. The design of 

 the tank proved to be faulty, and the state engineer in charge entered the Army. 

 The project then was taken over by the Experiment Station and assigned to the 

 Bacteriology Department. Attempts to operate the tank satisfactorily proved 

 futile, and the Army Air Corps cadets were removed from the college dormitory 

 which supplied the sewage. As a result, the project was suspended until the 

 dormitory is once more occupied to provide sewage. Meanwhile, plans are under- 

 way to redesign and reconstruct the tank in the effort to improve its operation. 

 The future of the project depends on the effectiveness of the reconstruction, 

 which is being supervised by the Engineering Department of the College, and 

 upon the dormitory being occupied to provide an adequate supply of sewage. 



Recovery of Agar from Used Laboratory Media. (James E. Fuller and John 

 M. Woodward.) The purpose of this study was to develop a rapid and efficient 

 method for recovery of agar that would be practical for small laboratory use. 

 The method developed follows: 



Preparation. Melt the used media and filter through a layer of cheesecloth. 

 Put into beakers to solidify, in a refrigerator if haste is necessary, or otherwise 

 at room temperature. Cut the solid agar into small bits and then force it through 

 a wire screen J^ or 3/8 inch mesh. Put into a cheesecloth bag for washing. 



Washing. (1) If running water can be used, the time required for washing the 

 agar may be substantially reduced. Suspend the cheesecloth bag in a container 

 deep enough to permit complete immersion of the agar. Run water gently and 

 continuously through the container for about 6 hours. By that time the agar 

 will be clarified, and the Fehling's and biuret tests will be negative. (2) If it is 

 not practicable to use running water, the bag of agar may be suspended in 3 liters 

 of water for each liter of agar. Start the washing in the morning and change the 

 water in the evening, the next morning, and the next evening. A half day of 

 washing the third day should complete the process satisfactorily. Either method 

 of washing should recover about 90 percent of the theoretical yield of agar. 



Drying. After the agar has been washed, suspend the bag to permit drainage 

 of surplus water, then spread the agar in a thin layer in a shallow pan and dry 

 at 45° C. The dried agar may be used in the same way as commercial agar. 



The recovery of agar from media containing d^es is not recommended because 

 the bleaching process is tedious and is apt to impair the gelling property of the agar. 



The Effect of Physical and Chemical Agents on Plate Counts. (James E, 

 Fuller and Thomas Sparkes.) One of the limitations of bacteriological plating 

 technique is the difficulty of breaking up clumps of bacteria. In this study both 

 market milk and sterile milk artificially inoculated were employed. Rates of 

 shaking were 200, 400, and 900 per minute, with and without broken glass. 

 Two and five minute periods were employed with each rate. Counts were not 



