MIL-HDBK-1005/9A
(1) Chemical Oxidation. Treatment with agents
such as hydrogen peroxide and chlorine or hypochlorite is
effective in removing sulfides. The amount of chemical needed
should be determined from laboratory investigation as the amount
can vary significantly from stoichiometric requirements.
one gram of hydrogen sulfide, but under actual operation the
amount may vary by up to two to three times. Hydrogen peroxide
is commercially available as either a 30, 50 or 70 percent
solution by weight and the equipment required is relatively
simple. For most oily wastewater plants, a package system in
which peroxide is withdrawn directly from the container and
applied with a metering pump will be adequate and is available
from various suppliers. Peroxide is a strong oxidizing chemical
and therefore tanks, pumps, and piping should be made with
peroxide resistant materials. These include PVC, polyethylene,
aluminum, or stainless steel.
Hypochlorite and chlorine can also be used for
sulfide control. For smaller plants, hypochlorite is
recommended due to safety reasons and the simple hardware
requirements. The actual amount of these chemicals needed to
oxidize sulfides should be determined from laboratory
experiments as the actual amount can vary significantly from the
stoichiometric amount.
(2) Chemical Precipitation. The removal of
sulfides by precipitation should be used at plants where removal
of emulsified oils from wastewater is desired (see paragraph
3.9.5) due to common hardware and treatment requirements.
Accurate pH control is required for this process to control
sulfide equilibrium. Under alkaline conditions (pH about 8.5),
sulfides will be removed by precipitation with dissolved metals
in wastewater; whereas, at lower pH, the sulfides will escape
into plant atmospheres as odorous hydrogen sulfide gas.
Sodium hydroxide solution may be used to raise
wastewater pH. This solution should be added in-line, prior to
wastewater mixing to avoid sulfide release to the atmosphere.
An in-line addition system, shown in Figure 13, consists of a
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