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Table 2 Operating parameters and performance variables (mean ± standard deviation) for the 8 anaerobic digesters during steady state

From: The effect of temperature and retention time on methane production and microbial community composition in staged anaerobic digesters fed with food waste

Parameter Unit Digesters
DS1 DS2 DS3 DS4
TDS1 MDS1 TDS2 MDS2 TDS3 MDS3 TDS4 MDS4
HRT Days 3 17 3 17 3 10 3 10
Temperature  °C 55 37 65 37 55 37 65 37
Methane flow (3-day mean) mL/day 49 ± 5 3991 ± 307 32 ± 6 3665 ± 158 135 ± 49 7289 ± 1001 446 ± 134 6890 ± 921
Methane flow mL/day 93 ± 22 3889 ± 583 39 ± 17 3523 ± 284 191 ± 96 8019 ± 517 478 ± 150 7761 ± 579
CH4 % 4 ± 4 70 ± 2 2 ± 1 69 ± 2 9 ± 3 70 ± 1 28 ± 5 71 ± 1
pH   5.69 ± 0.06 8.03 ± 0.06 5.55 ± 0.06 7.98 ± 0.09 5.74 ± 0.08 8.09 ± 0.11 6.22 ± 0.08 8.07 ± 0.09
Total ammonia nitrogen mg/L 121 ± 18 966 ± 84 101 ± 12 915 ± 88 170 ± 16 534 ± 27 256 ± 19 579 ± 25
Free NH3 mg/L 0.2 90.2 0.2 76.3 0.3 55.8 2.2 59.0
TCOD g/L 57.9 ± 30 15.7 ± 12.8 54.1 ± 33.4 16.3 ± 13.5 39.1 ± 1.4 10.5 ± 1.6 44.1 ± 3.9 13.4 ± 1.1
PCOD g/L 41.6 ± 30.1 14.2 ± 12.9 37.3 ± 33.5 14.8 ± 13.5 24.9 ± 3.1 8.8 ± 1.5 29.1 ± 5.3 11.7 ± 1
SCOD g/L 16.4 ± 0.6 1.5 ± 0.3 16.8 ± 1.5 1.5 ± 0.3 14.2 ± 2.8 1.7 ± 0.3 15 ± 2.7 1.7 ± 0.2
COD Conc. g/L 44.3 ± 16.2 10.5 ± 1.3 41.8 ± 16.7 10.7 ± 0.7 39.4 ± 1.1 10.9 ± 1.2 43.0 ± 1.9 13.1 ± 0.7
COD removal % 78.4 ± 3.8 77.6 ± 4.7 77.0 ± 3.3 71.0 ± 2.0
Alkalinity g/L as CaCO3 1.5 ± 0.4 6.1 ± 0.7 1.3 ± 0.2 6.2 ± 0.2 1.2 ± 0.4 4.7 ± 0.2 1.7 ± 0.2 5 ± 0.2
FOS/TAC   3.25 ± 1.25 0.06 ± 0.07 3.8 ± 0.46 0.03 ± 0.05 4.65 ± 3.08 ND 2.08 ± 0.28 ND
Acetate  mg/L 2607.4 ± 177.9 19 ± 2.4 3744.1 ± 390 3.8 ± 1.7 2336.5 ± 95.2 ND 2724.7 ± 678.9 ND
Propionate  mg/L 143.4 ± 23.4 1.2 ± 3 32.3 ± 7.6 0.4 ± 0.9 244.4 ± 22.2 ND 237.7 ± 134.3 ND
Butyrate  mg/L 6161.2 ± 339.3 ND 6946.7 ± 641.1 ND 3351.1 ± 178.6 ND 1878.3 ± 1093.9 ND
Valerate mg/L 296.3 ± 56.9 8.9 ± 8.5 279.5 ± 197.6 13.1 ± 6.1 ND ND ND ND
Volatile solids (VS) g/L 16.7 ± 1.5 6.3 ± 0.5 17.5 ± 1.6 6.8 ± 0.7 21.6 ± 4.2 7.2 ± 0.7 21.1 ± 2.2 8.3 ± 0.4
VS removal % 75.2 ± 1.7 74.1 ± 1.0 73.9 ± 2.4 70.1 ± 1.1