and booms are beyond the scope of this paper, but suffice it to indicate that 

 in a sea condition with waves of possibly 3 to 4 ft (0.9 to 1.2 m) , oil recovery 

 is limited. In those situations where recovery of the oil is not feasible, the 

 following benefits can be realized as a result of chemically dispersing the oil 

 into the water column as fine droplets: 



1. The rate of biodegradation of the oil is increased . This is the historical 

 basis for the dispersion of oil. It is perhaps the most significant contribution 

 of dispersants. The order of magnitude of increase in the interfacial area 

 that are affected by the dispersant greatly increases the rate of biodegradation 

 of the oil. Zobell (1964) has reported biodegradation rates that are one 

 or two orders of magnitude higher in laboratory experiments in which the oil 

 is emulsified. Not only is the physical state of the oil (i.e., small droplets) 

 more conducive to bacterial action, but the oil is also made available to 

 a much larger population of microbial organisms. Because of the importance of 

 this aspect, some pertinent excerpts from Zobell (1964) are presented: 



"The growth of oil-oxidizing bacteria is believed to be beneficial 

 to the food-chain in the sea, because such bacteria are eaten by 

 numerous animal species. In discussing the sequence of events in 

 oil-polluted water, Voroshilova and Dianova (1950) relate that the 

 water becomes progressively enriched with bacteria. The protozoa 

 in turn are devoured by higher animals. Rodina (1949) has reviewed 

 some of the extensive literature on the contribution of bacteria to 

 the nutrition of aquatic animals. 



In controlled laboratory experiments, we find that oil-oxidizing 

 bacteria convert an average of 30 to 40 percent of the carbon content 

 of hydrocarbons into bacterial cell substance or protoplasm. Thus 

 for each gram of oil oxidized, from 300 to 400 mg of animal food 

 might be manufactured by bacteria. 



The rate at which microorganisms oxidize HCs is influenced largely 

 by the dispersion or solubility of the HCs and by the water temperature. 

 In fact, HCs will not be attacked at all by microorganisms unless 

 there is contact of the HC molecules with water. Since most liquid 

 and solid HCs are only poorly soluble in water, their utilization 

 by microorganisms is dependent upon emulsification, adsorption on 

 solids, or other means of dispersion in water" as reported by Zobell 

 (1964). 



"Virtually all kinds of oils are susceptible to microbial oxidation. 

 The rate of such oxidation is influenced by the kinds and abundance 

 of microorganisms present, the availability of oxygen, temperature, and 

 the dispersion of the oil in water. Microbial oxidation is most rapid 

 when the hydrocarbon molecule is in intimate contact with water and 

 at temperatures ranging from 15 to 35 C; some oxidation occurs 

 at temperatures as low as C. An average of one-third of the 

 hydrocarbon may be converted into bacterial cells, which provide 

 food for many animals. The remaining two-thirds of the hydrocarbon 

 are oxidized largely to C0o and Ho0. In the marine environment, 

 oil persists only when protected from bacterial action." 



88 



