Table 2.
Summary of physicochemical parameters characterizing bioreactors operation in Experiments 1 and 2. M1—domination of lactate, M2—domination of butyrate, M3—domination of propionate, M4—domination of acetate
| Parameter | COD [g/L] | Substrate utilization [%] | pH | Methane content in biogas [%] | Methane [dm3/day] | Methane [dm3/g C OD reduced] | S2- [mg/L] | Fe2+/3+ [mg/L] | Total nitrogen [mg/L] | Redox potential [mV] | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Bioreactor | Medium | Effluent | Medium | Effluent | Medium | Effluent | Medium | Effluent | Medium | Effluent | |||||
| Experiment 1 | |||||||||||||||
| M1 | 14.1 | 3.7±0.7 (3.5) | 73.8±5.0 (75.2) | 5.00 | 7.1±0.1 (7.1) | 74.6±3.0 (77.8) | 2.3±0.7 (2.6) | 0.4±0.1 (0.5) | <0.05* | 0.08±0.02 (0.1) | <10* | 0.6±0.01 (0.6) | 115.0 | 96.0 | − 280 |
| M2 | 16.3 | 5.4±0.5 (5.1) | 66.9±3.0 (68.7) | 5.40 | 7.0±0.7 (6.9) | 81.5±1.4 (83.4) | 3.3±0.3 (3.5) | 0.6±0.1 (0.6) | <0.05* | 0.14±0.05 (0.1) | <10* | 1.2±0.2 (1.4) | 115.0 | 108.0 | − 255 |
| M3 | 16.6 | 5.0±0.5 (5.3) | 69.7±2.9 (68.1) | 5.50 | 7.2±0.1 (7.1) | 81.3±3.9 (82.8) | 2.3±0.5 (2.4) | 0.4±0.1 (0.4) | <0.05* | 0.14±0.01 (0.1) | <10* | 0.9±0.1 (0.9) | 115.0 | 112.0 | − 280 |
| M4 | 11.0 | 2.7±0.5 (3.1) | 75.6±4.2 (71.8) | 5.60 | 7.2±0.1 (7.2) | 76.2±4.4 (84.1) | 1.9±0.1 (2.1) | 0.5±0.0 (0.5) | <0.05* | 0.19±0.06 (0.2) | <10* | 0.4±0.1 (0.5) | 115.0 | 120.0 | − 305 |
| Experiment 2 | |||||||||||||||
| M1 | 12.2 | 2.2±0.8 (1.3) | 82.2±6.7 (89.0) | 7.00 | 7.5±0.2 (7.2) | 73.9±3.7 (74.0) | 2.5±0.6 (2.9) | 0.5±0.1 (0.4) | <0.05* | 0.08±0.03 (0.1) | <10* | 0.8±0.06 (0.8) | 115.0 | 110.0 | − 400 |
| M2 | 16.7 | 6.1±2.1 (7.5) | 63.7±12.6 (55.1) | 7.00 | 7.2±0.4 (6.9) | 79.1±2.3 (78.0) | 2.4±0.5 (2.0) | 0.4±0.1 (0.4) | <0.05* | 0.12±0.06 (0.1) | <10* | 1.5±0.6 (1.7) | 115.0 | 110.0 | − 363 |
| M3 | 14.9 | 4.4±1.1 (4.7) | 70.3±7.5 (68.5) | 7.00 | 7.6±0.1 (7.5) | 84.2±2.4 (89.0) | 2.2±0.4 (2.4) | 0.4±0.1 (0.5) | <0.05* | 0.12±0.06 (0.2) | <10* | 0.6±0.1 (0.6) | 115.0 | 90.0 | − 333 |
| M4 | 9.5 | 1.9±0.7 (2.5) | 80.5±7.4 (73.7) | 7.20 | 7.9±0.2 (7.9) | 87.8±2.9 (90.0) | 1.5±0.4 (2.5) | 0.4±0.1 (0.7) | <0.05 | 0.22±0.21 (0.1) | <10* | 0.4±0.1 (0.5) | 115.0 | 115.0 | − 343 |
*The limit of quantification
In parenthesis, there are data from the time of sample collection for DNA isolation (day 751, /week 108/ for Experiment 1 and day 884 /week 127/ for Experiment 2). COD utilization and methane production are shown as arithmetic means ± SD