The Operation of Plants Treating Mixed Industrial Wastes
555
[11, 12]. The value η is between 0.6 - 0.9 for soluble COD, depending on influent
composition.
In the case of low biological loadings, the concentration of all components in the
mixed liquor is low. Consequently, they exert very little or no toxic effect, even if they
are toxic in higher concentration. Again, the enzyme systems of sludge bacteria are not
saturated as they certainly would be in the case of excess substrate. Thus, as Eckhoff and
Jenkins postulate, for systems described above, first-order removal kinetics will hold for
each component, and all components will be removed independently from each other
[11,13].
Substrate concentrations and removal rates (measured in COD) will be additive. Thus,
it can be written:
n
S e = Σ 0-*?i) S 0 i
(19)
i=l
where S 0 i and r\\ are the influent concentration and best removal effect, respectively, for
the i-th component of the waste. The resulting S e overall effluent concentration can be
calculated according to the dilution formula:
n
Σ
qi (1 - r ? i ) S 0 i
S e = i ^ i —
(20)
Σ ^
i=l
Experimental results
Determination oftoxicity and treatability of formaldehyde
On Fig. 2 biological treatability of formaldehyde was found; activated sludge grown on
municipal waste was employed. For each point on Fig. 2, the basic respiration r 0 was
measured with an oxygen probe, formaldehyde added, and respiration r measured again. S
was calculated from the amount of formaldehyde added and the sludge volume.
Anticipating Krn
= 4 mg/1, from St = 20 mg/1 a value of I = 100 mg/1 was calculated. The
Rt = 21 value indicates that formaldehyde, in spite of its toxicity, is still efficiently
treatable.
According to our observations, if S t > 100 mg/1, (this means, accepting an average K m
= 5 mg/1 for dissolved substrates,) I > 2000 mg/1, the waste cannot be practically regarded
as toxic. The above method can be used with advantage for quickly controlling and
characterizing industrial effluents.
Effect of blood discharge on the treatment of slaughterhouse effluents
Fig. 3 shows the respiration enhancing effects of slaughterhouse process effluents. The
R(S) functions have no maximum, indicating that effluents are not toxic. However, blood
is more quickly oxidizable than the rendering waste, this latter containing mostly colloid
droplets of fat, which can be metabolized but slowly. Excess blood, again, may cause
septicity, lack of oxygen in the aeration tank, especially in case of shock loadings.
Fig. 4 gives the C(Hi) functions of S = 3000 mg/1 waste mixtures. The ratio of the
blood component ranged from zero (pure rendering waste) to 1 (pure blood). In the range
of 0 < Hi < 0,1, dC/dHi = 1 was measured; between 0,3 < Hj < 1, dC/dHj = 6,5 was
found. A practical interpretation of this result is that blood is a critical effluent; it should
555
[11, 12]. The value η is between 0.6 - 0.9 for soluble COD, depending on influent
composition.
In the case of low biological loadings, the concentration of all components in the
mixed liquor is low. Consequently, they exert very little or no toxic effect, even if they
are toxic in higher concentration. Again, the enzyme systems of sludge bacteria are not
saturated as they certainly would be in the case of excess substrate. Thus, as Eckhoff and
Jenkins postulate, for systems described above, first-order removal kinetics will hold for
each component, and all components will be removed independently from each other
[11,13].
Substrate concentrations and removal rates (measured in COD) will be additive. Thus,
it can be written:
n
S e = Σ 0-*?i) S 0 i
(19)
i=l
where S 0 i and r\\ are the influent concentration and best removal effect, respectively, for
the i-th component of the waste. The resulting S e overall effluent concentration can be
calculated according to the dilution formula:
n
Σ
qi (1 - r ? i ) S 0 i
S e = i ^ i —
(20)
Σ ^
i=l
Experimental results
Determination oftoxicity and treatability of formaldehyde
On Fig. 2 biological treatability of formaldehyde was found; activated sludge grown on
municipal waste was employed. For each point on Fig. 2, the basic respiration r 0 was
measured with an oxygen probe, formaldehyde added, and respiration r measured again. S
was calculated from the amount of formaldehyde added and the sludge volume.
Anticipating Krn
= 4 mg/1, from St = 20 mg/1 a value of I = 100 mg/1 was calculated. The
Rt = 21 value indicates that formaldehyde, in spite of its toxicity, is still efficiently
treatable.
According to our observations, if S t > 100 mg/1, (this means, accepting an average K m
= 5 mg/1 for dissolved substrates,) I > 2000 mg/1, the waste cannot be practically regarded
as toxic. The above method can be used with advantage for quickly controlling and
characterizing industrial effluents.
Effect of blood discharge on the treatment of slaughterhouse effluents
Fig. 3 shows the respiration enhancing effects of slaughterhouse process effluents. The
R(S) functions have no maximum, indicating that effluents are not toxic. However, blood
is more quickly oxidizable than the rendering waste, this latter containing mostly colloid
droplets of fat, which can be metabolized but slowly. Excess blood, again, may cause
septicity, lack of oxygen in the aeration tank, especially in case of shock loadings.
Fig. 4 gives the C(Hi) functions of S = 3000 mg/1 waste mixtures. The ratio of the
blood component ranged from zero (pure rendering waste) to 1 (pure blood). In the range
of 0 < Hi < 0,1, dC/dHi = 1 was measured; between 0,3 < Hj < 1, dC/dHj = 6,5 was
found. A practical interpretation of this result is that blood is a critical effluent; it should