Effluent water quality standards are not applied to factories discharging wastewater into the sewage system, however the municipal treatment plants themselves are designated by the water pollution control law. Effluent water quality standards, or regulation of the total discharge load, are applied to municipal treatment plants.
Note that most wastewater treatment plants use the activated sludge process. This process will not remove heavy metals such as cadmium and refractory organic chemicals from wastewater. Therefore, heavy metals and refractory organic compounds should be removed from wastewater before discharge into the sewage system. A cabinet order identifies effluent water quality standards that must be met for substances that affect human health and the environment, but that cannot be removed effectively by municipal treatment plants. More stringent standards for those substances and effluent standards for BOD and SS are identified by local laws.
Effluent water quality standards are shown in the following Table. Sewage treatment plants use fees applied to wastewater usually are proportional to the concentration of BOD or COD if these demands are higher than a given value. Therefore, surcharges are applied to wastewater having more than 200 mg/L or 300 mg/L of BOD or COD, respectively.
Table: Effluent water quality standards applied to wastewater discharged into sewage systems
| Category |
Parameters |
Regulations |
| Large scale factories |
Temperature |
< 45°C |
| pH |
ph = 5.7~8.7 |
| BOD |
< 300mg/l |
| SS |
< 300mg/l |
| n-hexane extract |
< 50mg/l |
| lodine consumption |
< 220mg/l |
| Phenol concentration |
< 50mg/l |
| Cyanide |
< 2mg/l |
| total Cr |
< 3mg/l |
| Regular |
Temperature |
< 40°C |
| pH |
pH = 5~8 |
| BOD |
< 600mg/l |
| SS |
< 600mg/l |
| n-hexane extract |
< 300mg/l |
| lodine consumption |
< 220mg/l |
| Phenol concentration |
< 100mg/l |
|
