Water quality standards of water discharged from plants and factories are referred to as "effluent standards" in legal terms. The effluent standards define the maximum allowable values of restricted substances in units of the concentration level (mg/L). [Table 1] is an example of items related to surface treatment processes that are regulated by the effluent standards.

[Table 1] Example of effluent standards 1)

Restricted substances Water Pollution Control Act Sewerage Act Sewerage Ordinance of Tokyo Metropolitan Government Tokyo Metropolitan Ordinance on Environmental Preservation Cyanogen mg/L 1 1 1 1 Hexavalent chromium mg/L 0.5 0.5 0.5 0.5 Cadmium mg/L 0.1 0.1 0.1 0.1 Lead mg/L 0.1 0.1 0.1 0.1 Arsenic mg/L 0.1 0.5 0.5 0.1 Total mercury mg/L 0.005 0.005 0.005 0.005 Alkyl mercury mg/L Not Detected 2) Not Detected Not Detected Not Detected Organic phosphorus mg/L 1 1 1 1 Trichloro- ethylene mg/L 0.3 0.3 0.3 0.3 Tetrachloro- ethylene mg/L 0.1 0.1 0.1 0.1 Boron and its compounds mg/L 10 10 10 10 Fluorine and its compounds mg/L 8 8 8 8 pH - 5.8〜8.6 5〜9 5〜9 5.8〜8.6 Temp ℃ 45 45 45 40 Total chromium mg/L 2 2 2 2 Copper mg/L 3 3 3 3 Zinc mg/L 5 5 5 5 Soluble iron mg/L 10 10 10 10 Soluble Mn mg/L 10 10 10 10 Phenol mg/L 5 5 5 5 Mineral oil mg/L 5 5 5 5 Nitrogen mg/L 120 240 120 120 Phosphorus mg/L 16 32 16 16 BOD mg/L 300 600 600 25 SS mg/L 300 600 300 50 Restricted substances Water Pollution Control Act Sewerage Act Sewerage Ordinance of Tokyo Metropolitan Government Tokyo Metropolitan Ordinance on Environmental Preservation

As we have seen here, the surface treatment plants must fully comply with various regulations for discharging water from the plants. In order to do so, they must implement measures, such as adopting a process of converting toxic substances into non-toxic substances, etc.