Table 3.
The average numbers of microorganisms indicators—sulphite-reducing Clostridia (SRC) and Escherichia coli—before and after mesophilic/thermophilic fermentation process (mean values ± standard deviation)
| Sample (% volume in the reactor) | SRC (cfu/g dry weight) | E. coli (cfu/g dry weight) | ||||
|---|---|---|---|---|---|---|
| Start of the process | End of the mesophilic process | End of the thermophilic process | Start of the process | End of the mesophilic process | End of the thermophilic process | |
| 70 %WAS + 30 %DS (only MAD) | (4.25 ± 0.23)∙105 | (3.38 ± 0.17)∙105 | – | (5.23 ± 0.27)∙105 | (5.68 ± 0.25)∙103 | – |
| 40 %WAS + 30 %DS + 30 %WASD (only MAD) | (3.43 ± 0.18)∙105 | (9.75 ± 0.15)∙104 | – | (9.68 ± 0.29)∙104 | (3.18 ± 0.21)∙103 | – |
| 40 %WAS + 30 %DS + 30 %WASD (5 days MAD + 19 days TAD) | (2.83 ± 0.19)∙105 | (2.46 ± 0.24)∙102 | (3.54 ± 0.23)∙104 | 0 | ||
| 40 %WAS + 30 %DS + 30 %WASD (7 days MAD + 17 days TAD) | (2.75 ± 0.21)∙105 | (3.25 ± 0.15)∙102 | (2.78 ± 0.22)∙104 | 0 | ||
| 40 %WAS + 30 %DS + 30 %WASD (9 days MAD + 15 days TAD) | (1.43 ± 0.14)∙105 | (4.46 ± 0.18)∙102 | (1.82 ± 0.26)∙104 | 0 | ||
“%” volume of sludge, WAS waste-activated sludge, DS digested sludge, WASD WAS after hybrid disintegration, MAD mesophilic anaerobic digestion, TAD thermophilic anaerobic digestion, cfu colony-forming unit