the rate of biodegradation. Within the ambient temperature

range, rates of biodegradation are faster at higher

temperatures than at lower temperatures. ZoBell (1969)

found that hydrocarbon degradation was over an order of

magnitude faster at 250 C than at 5 C. Larger

microorganism populations as well as higher assimilation

rates at higher ambient temperatures both contribute to this

increase. Vela and Ralston (1978) found that at higher

temperatures more phenol was metabolized per cell than was

required to support growth. A modified Arrhenius

mathematical model is available to estimate the effects of

temperature on biodegradation rate constants:
 (T2-T1)
 K2 = K1 (T2-TI) (3-11)

where K1 and K2 are the rate constants at temperature T1 and

T2 respectively, and g is a coefficient. Typical values for

g are from 1.01 to 1.04 in wastewater treatment systems

(Benefield and Randall, 1980).


 Genus of microorganisms. Many microorganisms in the

natural environment are capable of degrading organic

compounds. Although the microorganisms may prefer some

particular compounds, they can rapidly adapt in order to

utilize available substrates (Hollibaugh, 1979; Haller,

1978; Hutchins et al., 1984).

 Spain et al. (1984) found the microorganisms in a pond

were successfully acclimated to degrade p-nitrophenol after

a 6-day lag period. Healy and Young (1979) indicated that

microbial populations acclimated to a particular compound