MIL-HDBK-1005/9A
Table 3
Threshold Concentrations for Heavy Metal Inhibition of
Biological Treatment Processes1
Concentration2 (mg/L)
Metal
Continuous Loading
Shock Loading
Cadmium
1
10
Chromium (hexavalent) 2
2
Copper
1
1.5
Iron
35
100
Lead
1
1
Mercury
0.002
0.5
Nickel
1
2.5
Silver
0.03
0.25
Zinc
1 to 5
10
Cobalt
<1
Cyanide
1
1 to 5
0.7
1
Satisfy local pretreatment requirements for indirect discharge
to most POTW.
2
The specific level can be variable depending on biological
acclimation, pH, sludge age, and degree of metal complexation.
2.4.6.4
Nutrients. Certain minimum amounts of nutrients are
required for efficient biological treatment. Normal proportions
needed for active microbiological growth are typically about 1
pound (0.45 kg) of phosphorous (as P) and 5 pounds (2.25 kg) of
nitrogen (as N) for each 100 pounds (45 kg) of BOD removed
(requirements are somewhat lower for lightly loaded systems).
Mixing industrial wastes with domestic sewage often avoids the
need for supplemental nutrients since sewage contains excess
amounts. However, nutrient levels must be evaluated for both
separate and combined industrial waste treatment systems.
2.4.6.5
Other. Other wastewater characteristics (such as pH,
dissolved solids, and nontoxic industrial organic chemicals) can
inhibit biological treatment performance. The identification
and allowable concentration of these characteristics can best be
determined from treatment of similar wastes and from review of
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