Nutrient-limited wastewater (COD:N:P = 100:2.35:0.01) from a petrochemical company was used, with different batches (collected at the company at different timepoints) being fed to the reactor during the operational period of 150 days. The average concentration of the wastewater is shown in Table 2, showing the variation of the influent. Concentrations of Cl−, 
and Na+ were also determined, being 18, 5 and 10 g·L−1, respectively. Combined with high electrical conductivity (EC) values, the wastewater can therefore be classified in the category of seawater (30–35 g salts·L−1). Nutrients were dosed (as NH4Cl and K2HPO4 solutions) in the wastewater when nutrient requirements for optimal growth were not met (to a COD:N:P ratio of 100:3.5:0.4) based on Hamza et al. (2019) and preliminary research.
Average influent wastewater characteristics
| Parameter | Value (±standard deviation) |
|---|---|
| COD (mg COD L−1) | 2,010 ( ± 426) |
| sCOD (mg sCOD L−1) | 1,800 ( ± 535) |
| DOC (mg C L−1) | 547.9 ( ± 72.6) |
| NH4-N (mg NH4-N L−1) | 15.38 ( ± 8.12) |
| Total N (mg total N L−1) | 48 ( ± 21) |
| PO4-P (mg PO4-P L−1) | 0.28 ( ± 0.25) |
| Volatile fatty acids (mg VFA L−1) | 609 ( ± 127) |
| pH (–) | 8.00 ( ± 0.39) |
| Electrical conductivity (EC, mS cm−1) | 53.13 ( ± 3.91) |
| Parameter | Value (±standard deviation) |
|---|---|
| COD (mg COD L−1) | 2,010 ( ± 426) |
| sCOD (mg sCOD L−1) | 1,800 ( ± 535) |
| DOC (mg C L−1) | 547.9 ( ± 72.6) |
| NH4-N (mg NH4-N L−1) | 15.38 ( ± 8.12) |
| Total N (mg total N L−1) | 48 ( ± 21) |
| PO4-P (mg PO4-P L−1) | 0.28 ( ± 0.25) |
| Volatile fatty acids (mg VFA L−1) | 609 ( ± 127) |
| pH (–) | 8.00 ( ± 0.39) |
| Electrical conductivity (EC, mS cm−1) | 53.13 ( ± 3.91) |