King County local discharge limits: heavy metals and cyanide
The limits: King County local limits are set for heavy metals and cyanide, listed below. The metal limits are for total metals, not dissolved metals. If a company discharges less than 5,000 gallons of wastewater per day, the company must comply only with the instantaneous limits.
Parameter |
Daily Average Maximum |
Instantaneous Maximum |
|
mg/l (ppm) |
mg/l (ppm) |
Arsenic |
1.0 |
4.0 |
Cadmium |
0.5 |
0.6 |
Chromium |
2.75 |
5.0 |
Copper |
3.0 |
8.0 |
Lead |
2.0 |
4.0 |
Mercury |
0.1 |
0.2 |
Nickel |
2.5 |
5.0 |
Silver |
1.0 |
3.0 |
Zinc |
5.0 |
10.0 |
Cyanide |
2.0 |
3.0 |
About heavy metals: Heavy metals greater than permitted limits can upset or disable treatment plant operations. Also, heavy metals either pass through the sewage treatment plant into the effluent discharged to Puget Sound, or accumulate in biosolids used to improve soils.
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