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monitored for chemical constituents, and treated as appropriate prior to release to
the lower troposphere. At the end of each burn period the system must be cooled
so that the ash can be removed prior to monitoring for chemical constituents and
subsequent treatment prior to ultimate disposal.
CALCULATING DESTRUCTION REMOVAL
Federal hazardous waste incineration standards require that hazardous organic
compounds meet certain destruction efficiencies. These standards require that
any hazardous waste undergo 99.99% destruction of all hazardous wastes and
99.9999% destruction of extremely hazardous wastes such as dioxins. The de-
struction removal efficiency (DRE) is calculated as
W
in
−
W
out
W
in
=
×
DRE
100
(3.4)
where
W
in
is the rate of mass of waste flowing into the incinerator and
W
out
is the
rate of mass of waste flowing out of the incinerator. For example, let us calculate
the DRE if during a stack test, the mass of pentachlorodioxin is loaded into
incinerator at the rate of 10 mg min
−
1
, and the mass flow rate of the compound
measured downstream in the stack is 200 picograms (pg) min
−
1
. Is the incinerator
up to code for the thermal destruction of this dioxin?
10 mg min
−
1
200 pg min
−
1
10 mg min
−
1
W
in
−
W
out
W
in
−
=
×
=
×
DRE
100
100
10
−
12
gand1mg
10
−
3
, then 1 pg
10
−
9
mg. So
Since 1 pg
=
=
=
10
−
9
mg min
−
1
10mg min
−
1
10mg min
−
1
−
×
200
×
100
=
999999
.
98% removal
Even if pentachlorodioxin is considered to be “extremely hazardous,” this is better
than the “rule of six nines” so the incinerator is operating up to code.
If we were to calculate the DRE value during the same stack test for the mass
of tetrachloromethane (CCl
4
) loaded into incinerator at the rate of 100 L min
−
1
and the mass flow rate of the compound measured downstream is 1 mL min
−
1
.
Is the incinerator up to code for CCl
4
? This is a lower removal rate since 100 L
is in and 0.001 is leaving, so the DRE
99.999. This is acceptable (i.e., better
removal efficiency than 99.99% by an order of magnitude), as long as CCl
4
is not
considered an extremely hazardous compound. If it were, it would have to meet
the rule of six nines (it has only five).
=
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