Table 2 Main process parameters measured during the steady-state period in the AF of maize silage under stepwise HRT decrease (mean ± standard deviation)
Chemical parameters | 15-day HRT | 12.5-day HRT | 10-day HRT | 7.5-day HRT |
|---|---|---|---|---|
pH | 5.5 ± 0.1 | 5.5 ± 0.1 | 5.5 ± 0.1 | 5.5 ± 0.1 |
tCODout (g/L) | 44.7 ± 1.6 | 53.9 ± 5.6 | 54.9 ± 3.1 | 43.8 ± 6.8 |
sCODout/tCODout (%) | 44.3 ± 3.1 | 36.4 ± 2.6 | 30.1 ± 1.2 | 22.0 ± 1.9 |
TS (g/L) | 34.1 ± 5.7 | 31.1 ± 3.8 | 27.2 ± 1.3 | 26.5 ± 1.3 |
VS (g/L) | 25.9 ± 3.8 | 24.3 ± 3.1 | 20.2 ± 1.5 | 19.9 ± 1.7 |
N-NH4+ (g N/L) | 675.8 ± 63.4 | 439.2 ± 11.2 | 312.7 ± 15.6 | 291.6 ± 7.9 |
tSCFAs (g/L) | 14.3 ± 0.6 | 10.6 ± 0.4 | 9.6 ± 0.6 | 5.9 ± 0.1 |
% acidification (CODSCFAs,out/sCODout) | 95.2 ± 12.2 | 87.2 ± 10.0 | 90.5 ± 3.3 | 82.4 ± 5.9 |
COD removal (%) | 27.9 ± 2.2 | 13.06 ± 4.3 | 7.9 ± 3.4 | 3.4 ± 0.8 |