Hydraulic conductivity values were evaluated before and

after a set of column biodegradation experiments. This test

was designed to determine the effect of bacterial population

increases on hydraulic conductivity.


4.2.3 Sludge Characterization


 Total volatile solids measurement. The following

procedure provided the total volatile solids (TVS)

measurements. Dry sludge weight and ash weight from 100 ml

of wet sludge were measured after drying in an oven at 103 C

overnight and combusting in a muffle furnace at 5500C,

respectively (Sawyer and McCarty, 1967).

 TVS = ([wt. of dry solid] [wt. of ash]) x 10 (4-3)


 Organic carbon determination. In the sorption isotherm

studies the organic carbon content of the sludge was

determined in order to calculate K values. In sludges
 oc
from municipal wastewater plants the volatile solids are

mainly biomass. Accordingly, it was assumed that organic

matter was the same as volatile solids, and corresponds to

the biomass formula C60H 87023N12P (Benefield and Randall,

1980). Therefore, organic carbon, OC, is

 OC (mg/l) = TVS x (720/1374) = 0.52 x TVS (4-4)

 This factor, 0.52, agrees with the values 0.40-0.53 as

suggested in Methods of Soil Analysis (Nelson and Sommers,

1982).