The Effect of Chemical Composition of
Substrate and Loading on the
Performance and Bulking of
Activated Sludge*
E. J. GENETELLI
and
H. HEUKELEKIAN
There is some evidence (1X2) to indicate that the performance and
physical characteristics of activated sludge varies with the chemical composition of the waste being neated. Certain industrial wastes (cannery, paper
mill) can be treated efficiently at loadings at high as three lbs BOD per lb of
mixed liquor volatile suspended solids (3). Domestic sewage on the other
hand, cannot be treated at loadings higher than 0. 3 without bulking of the
sludge(6). Both the quantity of BOD and the composition of the waste making
up the BOD influence the loading at which a waste can be efficiently treated.
METHODS
Three continuous-flow laboratory units were set up(Figure 1) in a constant-temperature room at 20 C. Lucite tubes, six in. in diameter and four Is
in capacity, were used as aeration tanks. Sixteen Is of substrate were fed to
each unit daily providing a detention time in the aeration tank of six hrs.
Mixed liquor was discarded daily in amounts necessary to maintain the mixed
liquor suspended solids content at 2, 000 mg/l. The volume in the aeration
tank was controlled by discharging the clear liquor into a constant head chamber, the overflow of which was discharged into an effluent container.
Glucose, egg albumin, and casein hydrolysate, the substrates used, were
prepared by diluting with standard BOD dilution water. The substrates were
chosen as representative of a carbohydrate, protein, and amino-acid respectively. Ammonia nitrogen was added to the glucose substrate to give a BOD/N
ratio of 20/1.
Sludge loadings, based on the volatile solids content of the sludge at the
start of each experiment, varied from 0.3 to 1.5 lb BOD per lb of mixed
liquor volatile suspended solids.
Two series of experiments were performed. Series A consisted of feeding
three different substrates at the same loading to a seed-activated sludge.
Series B consisted of feeding the same substrate at three different loadings.
EFFECT OF LOADING AND SUBSTRATE COMPOSITION
ON BOD REMOVAL
The BODremoval obtained when egg albumin was fed to activated sludge
'Paperof the Journal Series, New Jersey Agricultural Experiment Station, Ruggers, the State University of New Jersey, Department of Sanitation, New
Brunswick, N.J.
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