found to be 10:1 and 100:1 respectively (Atlas, 1981).

Since carbon is utilized for both energy (non-growth) and

synthesis requirements (growth) while nitrogen and

phosphorus are used essentially for synthesis of new cells,

the optimal N:P ratio is somewhat less variable than the C:N

and C:P ratios, and 10:1 seems to be a reasonable value to

choose when supplying nutrients to microorganisms.

 The optimal C:N or C:P ratio will need to be determined

experimentally for each specific case, because they are

largely dependant on the carbon-energy conversion efficiency

of the tested microorganisms. Dibble and Bartha (1979)

indicated that a C:N:P ratio of 800:13:1 was found to be

optimum and cost-effective for oil sludge biodegradation in

a "landfarming" process, but this ratio is far removed from

the theoretical values. They also reported that addition of

micronutrients and organic supplements (such as yeast

extract) were not beneficial to biodegradation.

 The form of phosphorus or nitrogen is not critical for

the growth of microorganisms. However, it has been

recommended that an ammonia-nitrogen source is preferable to

a nitrate-nitrogen source because ammonia-nitrogen is more

easily assimilated by microorganisms (USEPA, 1985).

 Kaufman (1978), on the other hand, stated that yeast

extracts accelerated PCP degradation, whereas glucose at 100

ppm suppressed degradation, and the substitution of ammonium

sulfate for sodium nitrate as a nitrogen source also

suppressed degradation. Because Kaufman studied the