MIL-HDBK-1005/9A
g) Process Control. Process pH control is absolutely
essential for favorable performance. Use self-cleaning pH
probes and oxidation-reduction potential (ORP) probes. Metal
hydroxide precipitates will resolubilize if operating pH varies
from optimum. Metal sulfide precipitates are less sensitive to
loss of pH control and are less affected by metal chelates and
metal complexes.
h) Process Performance. Hydroxide and sulfide
precipitations are highly reliable if proper monitoring and
control are maintained. Estimated achievable maximum 30-day
average concentrations of several heavy metals under different
chemical precipitation processes are shown in Table 8.
2.6.5.3
Chemical Oxidation. The primary purpose of chemical
oxidation is to enhance the treatability of industrial wastes
and to detoxify (if possible) hazardous wastes. Oxidation is
accomplished by addition of oxidizing agents, such as chlorine,
permanganate and ozone. Examples of chemical oxidation of
industrial wastes from Navy facilities are destruction of
hydrogen sulfide, cyanide, and phenol, conversion of cuprous ion
(Cu+) or ferrous ion (Fe+2) to the more treatable cupric ion
(Cu+2) and ferric ion (Fe+3), respectively.
a) Oxidizing Agents. Use chlorine gas or liquid, or
solutions of hypochlorite salts, ozone, potassium permanganate,
oxygen (by aeration), or hydrogen peroxide. See Table 7 for
selection of oxidizing agent and for application guide. In
absence of treatability data on similar waste, conduct bench or
pilot scale tests to determine treatability, reaction rates,
dosage, and catalyst requirements, and the formation of noxious
or toxic reaction byproducts.
b) Process Design Consideration. Use batch treatment
whenever possible. Provide for sufficient excess feed capacity
of oxidizing agent to satisfy full expected range of contaminant
and extraneous reducing agents. This should be determined by
bench or pilot testing of wastewater spiked with appropriate
reducing agents.
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