then became 4.56 mg as sludge was added to each system, or

0.0114% (4.56 mg organic carbon in 40 g of soil) in the soil

matrix.

 In the batch isotherm study of aquifer material with

added sludge, the addition of sodium azide at different

concentration levels, 2 ppm and 6 ppm, did not cause

Freundlich sorption coefficients to significantly change

based on a paired difference t-test at alpha= 0.05

significance level (McClave and Dietrich, 1985), which

indicated that the presence of sodium azide did not

interfere with the sorption behaviors of the phenolic

compounds. Thus the average of those two sets of parameters

was taken and used to calculate the sorption parameters on

organic carbon, with the exception of the phenol data.

Phenol adsorption on aquifer material with sludge and with 2

mg/l sodium azide showed an unusually high KFA value, and

later in the consequent desorption study all the phenol

concentrations were biodegraded to trace amounts, which

indicates that the sodium azide at 2 mg/l was not effective

enough to inhibit all the microorganisms (also, it indicates

that phenol degrades rather quickly). Therefore the data

obtained from this experiments, although presented, were not

used for the calculation of the sorption coefficients.

 The Freundlich sorption coefficients for the isotherms

with sludge are quite different from those without sludge

addition. Because both sets of isotherms were performed

under the same conditions (other than the addition of