1100 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1957 



AGED 

 SEA WATER 



OCEAN BOTTOM 

 SEDIMENT 



RAW 

 SEA WATER 



TEST MATERIAL 



(a) SATURATE WITH 

 FREE OXYGEN 



OR 



(b) REMOVE ALL 

 FREE OXYGEN 



^ 



ENRICHMENT 



CULTURE 

 (INOCULUM) 



^ 





TEST BOTTLE 



Fig. 2 — Flow chart of biochemical oxygen demand (BOD) ty-pe test. 



The materials which have been tested thus far by the BOD type pro- 

 cedure include polyethylene, polyvinyl chloride plastics, casting resins, 

 elastomers and jute. The individual materials are listed in Table I. Other 

 plastics and elastomers are still to be tested. 



The general features of both the aerobic and anaerobic parts of the 

 test procedure are shown in the flow chart in Fig. 2. Certain features of 

 the test are common to both parts. These features will be described first. 

 The four primary constituents of the test are aged sea water, test ma- 

 terial, ocean bottom sediment, and raw (unaltered) sea water. Aged sea 

 water is raw sea water which has been filtered through Millipore filters 

 of 0.5 micron pore size, and then aged in the dark until the biochemical 

 oxygen demand (BOD) is quite low; i.e., until the water contains about 

 1 ppm of organic matter. This usually requires about eight weeks of 

 aging. In the first tests which were run, materials were finely ground so 

 as to expose a large surface area, and so accelerate attack. However, it 

 soon became apparent in efforts to relate the rate of oxidation to surface 

 area exposed that only crude estimates could be made of the irregular 

 surface areas. Consequently, after the first few tests, thin sheets of ma- 

 terial were employed whei'ever possible so that a measured amount of 

 surface area could be exposed in each case. 



The inoculum for the test comes from specially prepared enrichment 

 cultures. Approximately 90 cc of marine sediment is placed in a 250 ml 



