The Science of the Total Environment, 9 (1978) 117—124
© Elsevier Scientific Publishing Company, Amsterdam
—
Printed in The Netherlands
THE COMBUSTION OF WASTE CONTAINING DDT AND UNDAN
BENGT AHLING
Swedish Water and Air Pollution, Research Laboratory, Box 21060, 5-100 31 Stockholm (Sweden)
(Received June lOth, 1977)
ABSTRACT
Both DDT and Lindan have been used as inseeticides in Sweden for many years.
After DDT was prohibited at the tum of the year 1969/70, there were large quantities
of DDT and Lindan left in stock. This report deseribes experiments carried out to
examine the possibility of disposing of these stocks through incineration.
Experiments show that a temperature of 800 0C and a transit time of 1.7 see are
sufficient for the destruction of Lindan.
DDT requires a temperature of 8000C and a transit time of at least 1.5 see. In the
case of lower temperatures or shorter transit times, there is a marked inerease in
emissions from the combustion. At 8000C and with a transit time of 0.7 see, the
emission is 500 mg/kg DDT. The cause of this inerease is primarily the formation of
DDE which occurs in connection with the combustion of DDT. At 7000C and with
a transit time of 0.7 see, the emission is 6000 mg DDT + DDE/kg DDT.
INTRODUCTION
After a decision was made in 1969 to prohibit the use of DDT and Lindan in
certain areas of application in Sweden, a considerable proportion of the preparations
at consumers and retailers was colleeted together. These preparations have then been
stored while waiting for disposal.
In order to ensure the destruction of DDT and Lindan, combustion under controlled conditions would appear to be the method providing the greatest possibility
of ensuring dependable destruction.
Combustion tests on a pilot scale with DDT and Lindan have been carried out
by the Swedish Water and Air Pollution Research Laboratory within its experimental
activities in order to obtain information for appraisal of the combustion conditions
to determine dependable destruction.
A SURVEY OF THE LITERATURE
i) Kennedy et al. 1 ~ have deseribed several experiments aimed at determining
the thermal stability of DDT. Different forms of thermal analysis show an exothermic
peak at 825 0C which indicates the temperature where complete combustion should
—
118
occur. Combustion efficiency has also been examined by burning DDT in a muffie
furnace and determining the loss of weight. No analysis of flue gases has been carried
out in this case. In order to determine the composition of the flue gases, a test was
carried out at 9000C by using a pyrolysis unit of a gas chromatograph to which air
was fed to simulate combustion. The combustion products identified, however,
consisted merely of CO, CO
2, HCl and C12. A number of peaks are specified as being
unidentified.
4 have carried out attempts to subject DDT to combustion by
ii) Whatley
mixing
it with et
ou al.
and feeding it into an oil burner. Analysis of the flue gases was
carried out but only, however, with respect to inorganic chiorine compounds such as
HCI, C1
2, HC1O2, HCIO3, etc. The conclusion drawn from these tests is stated to be
that DDT can be destroyed in a dependable way by subjecting it to combustion in
this manner.
5 carried out combustion tests whereby 1 g of DDT was subjected
Putman ettogether
al.
to iii)
combustion
with paper in an aluminium container. Samples of the flue
gases were allowed to pass through a wash-bottle containing ethanol which was later
analysed with respect to DDT. Experiments show that less than 0.500 of the DDT
could be recovered. No break-down products were found.
iv) Ottinger et al.6 state, with reference to Kennedy et al.1’ 2 that the combustion
of DDT and Lindan at 1500 0F (800 0C) with a transit time of 0.5 sec together with an
afterburner, which has a minimum temperature of 22000F (1200 0C) and a transit
time of 1 sec, would ensure acceptable destruction. It should be mentioned, however,
that neither transit times nor an afterburner are mentioned in the article written by
Kennedy et al. No attempts were made to combust at 2200 0F. It is by no means
clear whether the authors of the articie have access to references or experiments which
they do not mention.
v) Copra et al.7’ 8 have reported combustion tests where gas chromatography
analysis has been carried out for various organic break-down products of DDT.
Two types of experiments have been carried out, partial pyrolysis of p,p-DDT
without air access at 9000C and also combustion ofp,p-DDT together with tobacco.
The flue gases were allowed to pass a cooling trap with pentane after which qualitative
analysis was carried out. In the pyrolysis experiment, identification was made of
CH
2C12, CHC13, CCl4, CHC1
CCI2, CCI2
CCI2, chlorobenzene, CC13—CCI3,
p-dichlorotoluene, p,p-dichlorobiphenyl, bis (p-chlorophenyl) methane, cis-p, pdichiorostilbene, bis (p-chlorophenyl) chioromethane, p,p-DDM, p,p-DDE, p,pdichiorostilbene, p,p-TDE and p,p-DDT.
In relation to combustion tests, methyl chioride, bis-(p-chlorophenyl), methane,
p,p-dichlorobenzophenone, p,p-D DM”, p,p-dichlorostilbene, p,p-DDE, p,p-TDE, and
p,p-DDT were identified.
A DESCRIPTION OF THE TEST
In order to be able to carry out combustion tests on a pilot scale a combustion
9, and
facility has been built up. This facility has been described in detail earlier
119
TABLE 1
THE RE5ULT OF DE5TRUCTION EXPERIMENT5 CONCERNED WITH LINDAN
Experiment number
Introduced amount
Lindan (g/h) 0C)
Temperature (
Transit time (sec)
CO
2 following
the furnace (on)
Total unburned Lindan
mg/kg Lindan
a
Expt. 13
—
10
J3a
15
16
32.6
800
4.6
308.7
820
1.7
48.3
890
3.6
70.0
965
4.6
5.4
5.0
10.0
9.0
8.7
62.3
25.9
18.3
combustion of solid preparation; remaining expts. combustion of liquid preparation.
therefore, only certain supplements concerned with the experiments with DDT and
Lindan are to be described.
A test series consisting of 13 experiments has been carried out at different temperatures and transit times. Tables 1 and 2 show the test conditions. The preparations used
have been dissolved in isopropanol and fed continuously for 10 min into the furnace
with LP-gas as support fuel. In one experiment (No. 13) with a solid preparation, when
the experiment was started, momentary addition was made of 2 kg of preparation
containing about 1 kg of DDT and 300 g of Lindan mixed with sawdust. The intention
of this experiment was partly to confirm the tests with small amounts and also to
simulate destruction on a larger scale.
SAMPLING AND ANALYSIS
Sampling during the DDT and Lindan
experiment
was carried out
in
9’ ~ with
a glass-wool-filled
dustcompletely
precipitator
accordance
with by
earlier
descriptions
column
followed
an absorption
column containing Apiezon M. The samples were
further treated as previously described1 0; a summary is given below.
The collected dust was extracted with chioroform in a Soxhlet apparatus for 24h.
After addition of a few drops of Apiezon M the chioroform was evaporated off at
room temperature under a stream of air. The extract was cleaned up by transferring
it in hexane solution to a Florisil column which was then eluted with hexane. The elute
was, after concentration, further cleaned by treatment with fuming sulphuric acid.
The Apiezon-containing absorption column was eluted with absolute ethanol. The
volume of the ethanol solution was reduced by evaporation under a stream of air at
room temperature and transferred to a measuring flask. Hexane was added to the
flask, followed by distilled water. The hexane phase was then transferred to a Florisil
column for dean-up.
The samples were then analysed by gas chromatography using a Hewlett-Packard
5713A gas chromatograph with a 63Ni electron capture detector. The columns used
120
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121
were one 800 QFl +
described earlier’0
40
SF96 and one
300
SP2300. Operating conditions have been
THE RESULTS
The destruction of Lindan
Only four experiments have been carried out with Lindan (Table 1). The table
indicates that there is a relationship between the transit time and the residual content.
The margin of dependability in the residual content measured, however, is probably
relatively large. This depends on the fact that only gas chromatography has been
used for identification and determination of Lindan which can cause other substances
to have overlapped the Lindan peak which on the chromatogram is located in a
section where many other substances also occur. The residuat contents measured are,
however, relatively low in all the experiments and vary between 0 and 62 mg per kg
of initial Lindan feed.
The highest value provides the basis for an appraisal as to whether Lindan can
possibly be destroyed by combustion under normal combustion conditions. This value
is furthermore measured in experiment 13 when a larger quantity of Lindan was
mixed with sawdust and wood chips in order to simulate a realistic full-scale destruction process. The temperature during this experiment was 8000C and the transit time
was 1.7 sec, which can be considered to be realistic values for a conventional combustion installation. The residual content was then 62 mg/kg, thus 99.9940~ was
destroyed as a result of combustion.
The destruction of o,p-DDT and p,p-DDT
Figure 1 shows a summary based on the result of the DDT and indicates that very
low residual contents are obtained at a temperature of 8000C for both p,p-DDT
and o,p-DDT which implies residual contents of less than 10 mg/kg DDT initial feed
in all the experiments with the exception of experiment 13.
In experiment 13, the “destruction experiment”, as mentioned earlier, a larger
quantity of DDT preparation in fixed form was added mixed with sawdust. The
unburned amount of p,p-DDT + o,p-DDT in the experiment was 30 mg/kg DDT
initial feed, this being larger than what could have been expected at the prevailing
temperature conditions. One explanation of this could be that a certain extinguishing
effect resulted at the actual moment of feed-in and this may have caused a small
amount of unburned DDT to pass through. In this case, it would be a phenomenon
which cannot occur if continuous feed-in were used. The fact that this was not carried
out in this case depended exclusively on the hygiene risk of the work when using a
process of this type in a test furnace.
Transit times, which at 8000C varied between 0.7 and 3.2 sec, do not appear to
to have had any decisive influence on the residual content of DDT at this temperature.
At 700 0C, the transit time has a considerably greater influence on the result of the
combustion and the residual contents vary between 200 mg/kg at 0.7 sec and 1.3
mg/kg with a transit time of 3.6 sec. It is obvious from the result that transit times of
122
Emission
mg ODTI kg DDT
100~
5000
X
0
————o
PP
PP
DOT 700~C
DDT+ PP DDE
pp
PP
DOT 800~C
0DT~PP DDE 800%
700
1000
500
100
50
x
10
5
Transit
05
1
1.
Fig. 1. Relation between transit time and residue of DDT and DDE.
less than one second produce a marked increase in residual content. The individual
tests carried out at 600 0C show that even with relatively long transit times, residual
contents of 100—350 mg/kg are obtained.
The /brmation of DDE
In the previous description, only residual contents of the DDT preparation added
have been described. In an appraisal of destructibility with respect to DDT, possible
break-down products must also be taken into account.
Large quantities of DDE have been measured in the samples from the combustion
experiments. In some cases, there were small quantities of DDE in the final substance
but in many cases it was absent. The occurrence of DDE must therefore depend on the
formation of DDE as a result of the combustion of DDT which has been considered
earlier by Chopra et al.7’ 8 who however only carried out a qualitative determination.
In Fig. 1 it can be seen that the total emissions ofp,p-DDT + p,p-DDE are very high
123
even at 8000C if combustion is carried out with transit times which are about one
second or shorter. In comparison with the emission of DDT alone, the emission of
DDT + DDE becomes several thousand times greater. At 700 0C, changes in the
transit time have a very marked effect on the formation of DDE also, as mentioned
earlier, for DDT alone. When the transit time is decreased from 2 sec to 1.0 and 0.7
sec, respectively, the emission increases 30 and 220 times, respectively. The total
emission at 7000C and a transit time of 0.7 sec is then 6O~ of the amount of DDT
initial feed which should be compared with 200 mg/kg for DDT alone. This formation
of DDE implies that, even if DDT in itseif is relatively easy to destroy, then higher
temperatures and/or longer transit times must be used for destruction in order to
dispose of the DDE formed as weil. There is no possibility of calculating the extent
of DDE formation since only the net effect can be studied, that is to say the difference
between DDE formed and destroyed.
CONCLUSIONS
The examination carried out shows that it is possible to destroy insecticides
containing DDT and Lindan by combustion in the pilot installation used for the tests.
The temperature needed for destruction, on condition that the transit time is
sufficiently long, is approx. 700 0C, this being a temperature which is attained in
many full-scale plants. Due attention, however, should be paid to the fact that the
temperature is not the flame temperature inside the furnace but the temperature
measured in the uncooled flue gases immediately followingthe furnace with a thermoelement protected from radiation heat.
Destruction at 7000C requires, however, a transit time of at least 1.5 sec. This
means that many installations are within a very critical transit time range where a few
tenths of a second can have vital importance to the result of the combustion. A very
insignificant overload can therefore give rise to a marked increase in emission. This
is a fact which should be used to a greater extent in connection with combustion
where temperature has often been given far too much importance particularly with
respect to the fact that often only the flame temperature is mentioned. In order to
be on the safe side, with respect to the transit time, a temperature of 8000C must be
maintained for at least one second and this would appear to be easy to accomplish.
Even if the emission from an existing full-scale installation were not greater than
that from the pilot installation, appraisal must be carried out as to whether this
emission can be considered permissible. In this connection, it is only possible to
carry out calculations which show the possible total emission if the existing DDT
stocks in Sweden were to be incinerated under the conditions described. Then, it is
the task of the authorities concerned to appraise the material.
Let us assume that the DDT preparations in stock today correspond to the amount
consumed during one year before the prohibition this being about 70 tons counted
as active substance.
With a maximum emission of 100 mg DDT/kg DDT which would correspond to a
—
124
combustion which is better than 99~990
of the entire batch would be 7 kg DDT.
the total emission during the combustion
ACKNOWLEDGEMENTS
1 should like to express my great appreciation for the work carried out by Leif
Johansson and Anders Lindström who have assisted me in the experiments and also
Anne Lindskog and Anne-Christine Rosen who have carried out the analysis work.
This work has been carried out in co-operation with the Swedish Product Control
Bureau at the Swedish Environment Protection Board.
REFERENCES
1
2
3
4
M. F. Kennedy, B. J. Stojanovic and F. L. Shuman, Jr., Residue Rev., 29 (1969) 29.
M. F. Kennedy, B. J. Stojanovic and F. L. Shuman, Jr., J. Environ. Quai., 1 (1972) 63.
M. F. Kennedy, B. J. Stojanovic and F. L. Shuman, Jr., J. Agr. Food Chem., 20 (1972) 341.
14. Whatley, G. K. Lee, R. K. Jeifrey and E. R. Mitchell, The thermal destruction of DDTin an ou
carrier, Canadian Mines Braach Research Report R 225.
5 R. C. Putnam, F. Ellison, R. Protzmann and J. Hulovsky, Organic Pesticides and Pesticide
containers — A study of their Decontamination and Combustion, EPA Report SW-210-71, 1971.
6 R. 5. Ottinger, J. L. Blumenthal, D. F. Dal Porto, G. 1. Gruber, M. J. Santy and C. C. Shih,
Recommended methods of reduction, neutralization, recovery or disposal of harzadous waste,
Vol. V, EPA Report EPA-670/2-73-053-e, 1973.
7 N. M. Chopra and N. B. Osborne, Anal. Chem., 43 (1971) 849.
8 N. M. Chopra and 1. 1. Domanski, Beitr. Tabakforsch., 6 (1972) 139.
9 B. Ahling, Chemosphere, 7 (1977) 437.
10 A. Laveskog and A. Lindskog, Chem. Ing. Tech., 48 (1976) 65.