Quality of the wastewater entering the CWs at the Formosa Steel plant, Vietnam, and concentration limits in the Vietnamese standards for industrial wastewater discharges to different recipients (class A and B; QCVN 40:2011/BTNMT)
| Variable measured . | Unit . | Mean value ± SD (min-max) . | Standard for industrial wastewater, class A . | Standard for industrial wastewater, class B . |
|---|---|---|---|---|
| pH | – | 7.3 ± 0.18 (6.8–7.8) | 6–9 | 5.5–9 |
| Color | Pt/Co | 27.8 ± 4.9 (20–39) | 50 | 150 |
| COD | mg/l | 23.1 ± 2.6 (14–30) | 75 | 150 |
| BOD5 | mg/l | 9.4 ± 2.3 (5 –15.8) | 30 | 50 |
| TSS | mg/l | 17.4 ± 2.1 (14–26) | 50 | 100 |
| Mn | mg/l | 0.43 ± 0.12 (0.08 –0.75) | 0.5 | 1 |
| Fe | mg/l | 0.33 ± 0.18 (0.01 –0.86) | 1 | 5 |
| TN | mg/l | 10.5 ± 2.8 (6.1 –19.2) | 20 | 40 |
| NH4+-N | mg/l | 0.57 ± 0.19 (0.04 –2.1) | 5 | 10 |
| Cr (VI) | mg/l | <0.003 | 0.05 | 0.1 |
| Cd | mg/l | <0.0007 | 0.05 | 0.1 |
| Hg | mg/l | <0.0003 | 0.005 | 0.01 |
| Phenol | mg/l | <0.01 | 0.1 | 0.5 |
| CN− | mg/l | <0.004 | 0.07 | 0.1 |
| Grease and fats | mg/l | <0.3 | 5 | 10 |
| Variable measured . | Unit . | Mean value ± SD (min-max) . | Standard for industrial wastewater, class A . | Standard for industrial wastewater, class B . |
|---|---|---|---|---|
| pH | – | 7.3 ± 0.18 (6.8–7.8) | 6–9 | 5.5–9 |
| Color | Pt/Co | 27.8 ± 4.9 (20–39) | 50 | 150 |
| COD | mg/l | 23.1 ± 2.6 (14–30) | 75 | 150 |
| BOD5 | mg/l | 9.4 ± 2.3 (5 –15.8) | 30 | 50 |
| TSS | mg/l | 17.4 ± 2.1 (14–26) | 50 | 100 |
| Mn | mg/l | 0.43 ± 0.12 (0.08 –0.75) | 0.5 | 1 |
| Fe | mg/l | 0.33 ± 0.18 (0.01 –0.86) | 1 | 5 |
| TN | mg/l | 10.5 ± 2.8 (6.1 –19.2) | 20 | 40 |
| NH4+-N | mg/l | 0.57 ± 0.19 (0.04 –2.1) | 5 | 10 |
| Cr (VI) | mg/l | <0.003 | 0.05 | 0.1 |
| Cd | mg/l | <0.0007 | 0.05 | 0.1 |
| Hg | mg/l | <0.0003 | 0.005 | 0.01 |
| Phenol | mg/l | <0.01 | 0.1 | 0.5 |
| CN− | mg/l | <0.004 | 0.07 | 0.1 |
| Grease and fats | mg/l | <0.3 | 5 | 10 |
Arithmetic means ± SD for the period September 2017–July 2018.