Unclassified 



CLASSIFICATION OF THIS PAGEflfhon DelB En 



20. Continued 



bags were suspended near the surface of the ocean, some at depths of 200 and some at 

 depths of 1,000 feet. Some of the bags were suspended in opaque containers to protect 

 them from sunUght; others were suspended in translucent containers. All of the E. coli 

 cultures exposed near the surface of the ocean in translucent containers died in approx- 

 imately 4 hours. Those suspended near the surface in opaque containers survived for 

 periods of an estimated 2 weeks. Cultures of E. coli suspended in either translucent or 

 opaque containers at depths of 200 and 1,000 feet (where little or no light penetrates) 

 also survived for periods of an estimated 2 weeks, with only slight differences in the 

 mortality rates at these two depths. If the sewage were discharged at a depth of 1,000 

 feet, there would be no danger of contaminating surface waters because the cold deep 

 water does not mix with the warmer surface waters. If the sewage were discharged at 

 a depth of 200 feet, there would probably also be no danger of contaminating surface 

 waters unless the thermocline was deeper than that. If the sewage were discharged at 

 shallow depths, there would be contamination of surface waters; but at least one species 

 of the contaminating microorganisms would probably survive for only a few hours in 

 sunlight. 



Library Card 

 I 



Civil Engineering Laboratory 



THE SURVIVAL OF SEWAGE BACTERIA AT VARIOUS 



OCEAN DEPTHS (Final), by H. P. Vind, J. S. Muraoka, and 



C. W. Mathews 



TN-1396 20p. illus July 1975 Unclassified 



1. Sewage bacteria— survival 2. Escherichia coli I. Z-ROOO-01-140 



Sewage outfalls in the ocean are usually relatively close to shore at depths of 200 feet or 

 less. An investigation was undertaken to ascertain if Escherichia coli, the principal species of 

 bacteria in sewage, would survive for shorter or longer periods if the sewage were discharged at 

 depths of 1,000 feet or so, where there is no light, and where the pressure is greater and the 

 temperature is lower. Cultures of the Seattle strain of E^ coli in autoclaved seawater were 

 placed in 25-ml bags made of dialyzing tubing. Some of the bags were suspended near the 

 surface of the ocean, some at depths of 200 and some at depths of 1,000 feet. It was found 

 that if the sewage were discharged at a depth of 1,000 feet, there would be no danger of con- 

 taminating surface waters because the cold deep water does not mix with the warmer surface 

 waters; if the sewage were discharged at a depth of 200 feet, there would probably also be no 

 danger of contaminating surface waters unless the thermocline was deeper than that; if the 

 sewage were discharged at shallow depths, there would be contamination of surface waters, 

 but at least one species of the contaminating microorganisms would probably survive for only 

 a few hours in sunlight. 



Unclassified 



.ASSiriCATION OF 



