Table 4 Seasonal characteristics of VFAs in acidogenic phase
Volatile fatty acids (mg/L) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Acetic acid | Propionic acid | Isobutyric acid | Butyric acid | Isovaleric acid | Valeric acid | Isocaproic acid | Hexanoic acid | Heptanoic acid | Total | |
Spring | 6146 ± 141 (98.4%) | 49 ± 1.67 (0.8%) | N/D (–) | 48 ± 1.34 (0.8%) | N/D (–) | N/D (–) | N/D (–) | – (–) | N/D (–) | 6244 ± 144 |
Summer | 2691 ± 172 (29.1%) | 4041 ± 287 (43.6%) | 958 ± 54 (10.3%) | 120 ± 8.28 (1.3%) | 1192 ± 70 (12.9%) | 165 ± 9.08 (1.8%) | 40 ± 1.84 (0.4%) | 47 ± 2.54 (0.5%) | 11 ± 0.61 (0.1%) | 9263 ± 605 |
Autumn | 1472 ± 49 (24.1%) | 3231 ± 116 (52.8%) | 702 ± 19 (11.5%) | 86 ± 3.61 (1.4%) | 453 ± 15 (7.4%) | 105 ± 2.10 (1.7%) | 37 ± 0.78 (0.6%) | 33 ± 0.56 (0.5%) | N/D (–) | 6120 ± 206 |
Average | 3436 (47.7%) | 2440 (33.9%) | 553 (7.7%) | 85 (1.2%) | 548 (7.6%) | 90 (1.2%) | 26 (0.4%) | 40 (0.6%) | 4 (0.1%) | 7209 |