dry anaerobic digestion of municipal solid waste and digestate ...

the VFA concentration increased to 7500 mg/L because of increased organic loading rate.
This trend shows the destabilization of the reactor caused by increase in OLR.
pH
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
51 71 91 111 131 151
Time (days)
Figure 4.9 Evolution of pH in ITDAR during continuous loading
It is important to note that at the start of each OLR, the VFA started to accumulate, which
is related with imbalance of activity of microbial groups and initial temporary
destabilization of reactor as a result of increase in OLR as discussed above in the case of
pH. Similarly, at the end of each of first two OLRs, the concentration of VFA declined,
which is a sign of stability of the system. However, this drop in VFA concentration for
OLR of 8.50 kg VS/m 3 /d was not observed probably because the reactor at this stage was
operated for duration equal to only one cycle of SRT.
VFA 100 X (mg/L)
80
70
60
50
40
30
20
OLR 4.55 OLR 6.4 OLR 8.5
OLR 4.55 OLR 6.4 OLR 8.5
51 71 91 111 131 151
Time (days)
Figure 4.10 Concentration of VFA in ITDAR during continuous loading
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