552
P. Farkas
I
4
/T)
I
^24
Km
*20 mg/l
'4 mg/l
*ψ= *oo mg/l
Formatld&hyde concentnottionj 3 [mg/
—i
1
r
1
1 — - i — i — i — i —
y
V
1
1
1 1 1 — τ — ι — ι —
5
1
1
1
1 r ~
Z
J
^ 5 6 7 6 9 €
2
3
* S 6 7 6 9 JO*
2
3
ί £ 6 7
Fig. 2.
The effect of formaldehyde on sludge respiration
Effluent substrate concentration will get still higher, when its high concentration causes
poisoning (it will impede its own removal):
where
S t < S ° o
(8)
In the instances described in Equs. 7 and 8, a phenomenon called "soluble substrate
leak-through" (SSLT) occurs. High amounts of dissolved, organic BOD appear in the
effluent.
The trouble can easily be detected if a mixed liquor sample is loaded with a sample of
waste to be treated. The extent and direction of change in respiration informs us about
the prevailing degree of sludge loading. To detect effluent BOD, some kind of short-term
biological oxygen demand test (STOD) should be employed [9].
Effect of the change in substrate composition
For mixed wastes, the substrate concentration: