Table 2.
MFC voltage (mV), current density (A/m2) and power density (mW/m2) after adding humic acids as additional electron carriers with a MFC with a small cathode (surface area is 50 × 10−6 m2)
| MFC reactor | Voltage (mV) | Current density (A/m2) | Fold change | Power density (mW/m2) | Fold change |
|---|---|---|---|---|---|
| Base case #1 | 670 ± 60 | 0.10 ± 0.01 | 1 | 68 ± 6 | 1 |
| Base case #2 | 721.5 ± 0.7 | 0.6 ± 0.1 | 6 | 450 ± 90 | 7 |
| Base case #2 + humic acids (total 0.5%) | 712 ± 4 | 2.1 ± 0.4 | 21 | 1400 ± 200 | 21 |
| Base case #2 + humic acids (total 3.3%) | 750 ± 60 | 6 ± 1 | 60 | 4700 ± 800 | 69 |
| Base case #2 + cytochrome C from S. cerevisiae (20 µM) | 732 ± 2 | 0.97 ± 0.07 | 10 | 710 ± 40 | 10 |
The base case #1 is M. acetivorans AA/pES1MAT mcr3 (“M. acetivorans”) and G. sulfurreducens was added first followed by sludge once the voltage was below 150 mV and using 38-mm-diameter cathode electrode (surface area is 0.00227 m2). The base case #2 consists of G. sulfurreducens added at the start followed by the addition of sludge + M. acetivorans AA/pES1MAT mcr3 once the voltage was reduced below 150 mV and using a small cathode electrode (surface area is 50 × 10−6 m2). The additional electron carriers (humic acids) were added after obtaining the first maximum voltage; 0.5% humic acids were added after 7–8 days and 3.3% humic acids were added after 13–14 days of adding sludge and M. acetivorans. Cytochrome C from S. cerevisiae (20 µM) was added as an additional electron carrier after obtaining the first maximum in voltage after adding sludge and M. acetivorans AA/pES1MAT mcr3. The external resistance was 1000 Ohm