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

digestate TS was kept constant at 12-13%.Thus adjustment of TS in the reactor helped in
its smooth operation.
TS (%FM)
Run
Figure 4.15 Comparison of feed and digestate regarding total solids in phase I
experiment
TKN in digestate dropped at the beginning and was low during day 20-90. After day 90, it
started to increase and became almost constant for rest of the study period in the range of
1.8-2.0%. The significant decrease in TKN at the start of the experiment compared to TKN
in feed suggests that the TKN might have been utilized in the build-up of big size of
microbial biomass sufficient to sustain the reactor. Once sufficient microbial biomass was
developed, consumption of TKN might have been decreased, and thus its concentration
increased in reactor. Conversely, C/N ratio of the digestate was higher in the beginning.
After day 95, C/N ratio was low in the range of 15-20 (Figure 4.16, Appendix C, Table C-
3) and remained in the same range for the rest of study period. This finding is in agreement
with increase in TKN concentration.
C/N ratio of digestate
35
30
25
20
15
10
5
50
45
40
35
30
25
20
15
10
5
0
Feed TS Digestate TS Digestate VS/TS
Start-up 1 2 3 4 5 6 7 8
C/N ratio of digestate Digestate TKN
1 31 61 91 121 151 181 211 241 271
Run Time (days)
Figure 4.16 TKN and C/N ratio of the digestate in phase I experiment
80
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
3.0
2.5
2.0
1.5
1.0
0.5
0.0
VS/TS of digestate
TKN in digestate (%TS)