Task Force on Antifreeze Biodegradability · biochemical oxygen demand (BOD), and it can be...
Transcript of Task Force on Antifreeze Biodegradability · biochemical oxygen demand (BOD), and it can be...
.' First Brands Report 1
LETTER ON "FIE SUBJECT OF DISPOSAL OF USED ETHYLENE GLYCOL ANTIFREEZE S O L U T I O F
In response to your inquiry regarding the biodegradability of ethylene glycol base antifreeze, we offer the following comments.
As you may know, biodegradability expresses the degree to which a com- pound is broken down by microorganisms. are oxidized and oxygen is consumed. The amount of oxygen used is called the biochemical oxygen demand (BOD), and it can be measured in the laboratory by incubating a sample of the material with domestic sewage. then calculated by comparing the amount of oxygen consumed in the BOD test with the theoretical amount required to completely oxidize the material to carbon dioxide and water.
During this process, organic materials
Biodegradability is
BOD tests conducted by a major producer and at an outside laboratory with uninhibited ethylene glycol and inhibited antifreeze have established that the materials are completely biodegradable. down cannot be predicted from BOD test data because it depends upon the efficiency of the sewage treatment plant and the type of bacteria present. col received no treatment, it would be degraded in the existing surface waters which contain a variety of indigenous microorganisms and a supply of oxygen. discharged to the ground, the microbial and filtering action of the soil and rock strata will purify the waste material.
The time required for complete break
Even if the gly-
If
Some time ago a study was made of how much ethylene glycol originating from drained coolants might be found in waste waters. metropolitan areas and calculations were made under hypotlietical conditions in which all of the discarded antifreeze was drained in a one-week period. The cal- culations showed that the level of ethylene glycol in the metropolitan waste waters would be in the approximate range of 370 to 530 parts per million; levels well below the published aquatic toxicity threshold values of 1,000 to 10,000 ppm for ethylene glycol. 8
Data were obtained for four
In real life, where drainings are made over a considerably longer period of time, levels are much lower. Moreover, when taking into account the established biodegradability of ethylene glycol, the concentrations in metropolitan discharges into receiving waters will be very low o r nonexistent.
In summary, the used coolant drained every year presents no threat to the environment whether it be drained into sanitary sewers, storm sewers, surface waters, o r directly into the ground. In all cases the ethylene glycol is broken down into harmless carbon dioxide and water.
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Ecolosical Aspects of PRESTONE Antifreeze and Ethylene Glycol
summary: In its simplest terms, biodegradability expresses the degree-to which a compound is reduced in structural complexity by the action of microorganisms in a natural, or natural-simulated, environment.
PRESTONE Antifreeze and its base liquid ethylene glycol, have been subjected to many biodegradation procedures including those described in the Standard Methods For The Examination of water and Wastewater, 15th Edition, American Public Health Association (1980) . The testing results indicate rapid biodegradation of both antifreeze and ethylene glycol, and their amenability to standard septic tank or municipal waste disposal and treatment.
Toxicity studies carried out on selected indicator species of aquatic life suggest a l o w order of toxicity in aqueous concentrations up to 2 grams per litre.
No studies have been reported on the effect of PRESTONE Antifreeze and ethylene glycol on plant life. I.t is recognized, however, that high concentrations of any water-soluble liquid may cause some injury to many varieties of plant life. The natural dilution that occurs when antifreeze is disposed of into septic or municipal treatment pipelines should minimize, or eliminate, irreverisble plant toxicologial effects.
b
In conclusion, PRESTONE Antifreeze may be discharged into septic tank and municipal waste treatment facilities, wherein natural
biodegradation processes readily destroy the chemical composition. Of course, local water officials should be contacted to ensure that any contemplated disposal scheme is in concert with all applicable area regulations.
DAMcKenzie/dn
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TECHNICAL SERVICE REPORT
ECOLOGICAL ASPECTS OF PRESTONE ANTIFREEZE AND ETHYLENE GLYCOL
UNION CARBIDE CORPORATION ' I
HOME AND AUTOMOTIVE PRODUCTS DIVISION
DECEMBER 1, 1985
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ECOLOGICAL ASPECTS OF PRESTONE ANTIFREEZE AND ETHYLENE GLYCOL
SUMMARY
The information contained in this report shows that
PRESTONE Antifreeze and ethylene glycol are readily biodegradable
and relatively nontoxic to aquatic life. Disposal of used product,
or wastewater containing these materials, may be accomplished by
discharging them to septic tank or municipal waste treatment
facilities (biological or physical/chemical treatment). The
compatibility of these disposal procedures with Federal, State, and
the environmental regulations existant in your local area first
should be verified with local authorities. .
Please refer to our current Material Safety Data Sheets for
additional information. b
Biodesradabilitv +,
In its simplest terms, biodegradability expresses the
degree by
the action of microorganisms. A committee of the Water Pollution
Control Federation(’) has suggested three different terms to
to which a compound is reduced in structural complexity
describe biodegradation.
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Primary Biodesradation: Biodegradation to the minimum
extent necessary to change the identity of the compound.
Environmentallv Acceptable Biodesradation: Biodegrada-
tion to the minimum extent necessary to remove under-
sirable properties of the compound such as foaminess
and/or toxicity.
Ultimate Biodesradation: Biodegradation to inorganic
end products.
Several quantitative expressions are commonly used to describe
the biosusceptibility of organic matter:
Biochemical Oxysen Demand .
When aerobic bacteria oxidize organic matter, oxygen is consumed during the process and the amount required is
proportional to the amount of organic material present. As long
as oxygen is available, aerobic microbial decomposition of the
organics will continue until the oxygen demand is satisfied; that
is, until the aerobic microorganisms have oxidized all of the
organic material they are capable of oxidizing. The amount of
oxygen used during this process is the biochemical oxygen demand
-,
(BOD).
Chemical Oxvsen Demand
The amount of oxygen required to completely oxidize an
organic material to carbon dioxide and water is known as the
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chemical oxygen demand (COD). This value may be calculated on a
theoretical basis, knowing the composition of the organic
material. If the chemical structure is not known, COD can be
determined by a standard dichromate oxidation procedure ( 3 ) . BOD Test Procedure
For measurement purposes, BOD is considered to be the
quantity of oxygen required for biological stabilization of
water-bourne substances under a specific set of test conditions.
The most common test is the 5-day BOD(*), A sample of the
material to be tested is incubated at 20°C for 5 days in the
presence of a selected biota consisting principally of bacteria.
comparison of the dissolved oxygen content of the sample at the
beginning and end of the incubation period provides a measure of
the BOD. Because the solubility of oxygen in water is very low,
about 9.2 ppm at 2OoC, the material to be tes-ted has to be
diluted to the low ppm range in order to avoid completely L
depleting the dissolved oxygen during the 5-day test.
Few, if any, materials are cgmpletely degraded during
the 5-day test. When the test is continued beyond 5 days, until
the material is oxidized as completely as possble, the result is
termed an ultimate BOD. Determination of ultimate BOD has been * ,
observed to require approximately 20 days for most materials at
the dilutions normally employed in the test.
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The oxygen consumed during the test is used by the
microorgansms to oxidize carbonaceous matter to carbon dioxide
and water and to oxidize nitrogenous matter to nitrite ions
and/or nitrate ions. The oxidation of nitrogen can become
particularly important in the longer-term BOD tests but generally
does not occur during the 5-day test.
The most commonly employed source of microorganisms for
use in the BOD test is domestic sewage. When an organic material
is not commonly found in nature, as is the case with many
petrochemicals, sewage microorganisms can be slow to attack the
material, and the BOD test results may be lower than experienced
in nature. Adaptation (termed nacclimationti) of microorganisms
to the organic material can often result in an increased rate and
extent of oxidation of the materials. Acclimation refers to the
process of contacting a microbial culture with a material in such
a way as to permit an increase in the number of those organisms
in the culture which have the ability to oxidize and utilize the
material, as well as permitting the organisms to tlgear-uptt
enzymatically for the oxidation and utilization of the material.
b
In general, it can be assumed that a biological waste
treatment facility, which has been receiving a material for a
long period of time, is acclimated to that material. Acclimation
can be lost if the material only intermittently enters the
biological waste treatment facility.
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The concentrations of organic material and microorganisms are
much higher in a biological waste treatment system than in the
BOD tests. These higher concentrations result in an entirely
different set of reaction kinetics and generally a much more
rapid rate of BOD exertion. For example, a conventional
activated sludge biological waste treatment system can remove as
much as 90 percent of the 5-day BOD in 6 to 12 hours.
Measurement of Biodeqradabilitv P
Biodegradability can be measured through several
different means, for example, through the disappearance of foam-
producing properties as in detergents, or a change in some other
physical property. One quantitative method of expressing
biodegradability is to compare the amount of oxygen consumed in
the standard BOD test with the amount of oxygen required to
completely oxidize the material to carbon dioxide and water on a
theoretical basis. For example, the theoretical oxygen demand of
ethylene glycol is calculated as indicated below:
r
b
indicated below:
2HOCH2 CH OH + 5 0 2 7 4 C O i + H20 Ethylene zlycol Oxygen MW = 62 Mw = 32
mq EG 2 x 62
X mg 0, 5 X 32
Theoretical Oxygen Demand = 5 x 32 = 1.29 mg 02/mg EG 2 x 62
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,
The measured 5-day BOD of ethylene glycol is 0 .465 mg
02/mg EG, or 36 percent of the theoretical oxygen demand(5)
Simlarly, the measured 20-day BOD is 1.39 mg 02/mg EG which is
100 percent of the theoretical oxygen demand. In a biological
system, some of the organic material is incorporated into new
microbial cells rather than being completely oxidized to carbon
dioxide and water, and thus oxygen consumption equal to 100
percent of the theoretical oxygen demand is onlf approached in
the 20-day period. Therefore, in making a judgement concerning
whether or not a material is biodegradable, some arbitrary
percentage of the theoretical oxygen demand must be selected as
the break point between biodegradable and non-biodegradable
materials. A minimum of 50 percent oxidation in the 20-day BOD
test would seem to be an acceptable rate of oxidation for a
material to be classed as biodegradable in most instances where
this type of data need to be employed. However, in special
cases, either higher or lower percent oxidations could be
reasonable for the break point between biodegradability and non-
biodegradability.
.
+,
It should be noted that the extent of removal of a
material in a biological waste treatment system cannot be easily
predicted from BOD test data. In general, however, the higher
the percent oxidation in 5- and 20-day BOD tests, the greater
would be the removal in a biological waste treatment plant. The
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h
importance of acclimating a biological waste treatment system to
a given waste or waste constituent cannot be overemphasized.
Acclimation can increase the rate and extent of bio-oxidation as
well
organic material.
as aiding in overcoming inhibitory or toxic effects of an
Biodesradabilitv of PRESTONE Antifreeze and Ethylene Glycol
A comparative set of Data on the biodegradability
PRESTONE Antifreeze and ethylene glycol as a percent of
chemical oxygen demand are presented below:
Measured Bio-oxidation
Product Tested Theoretical Measured Day 5 Day 10 Dav 20
Chemical Oxygen as Percent of Demand (COD) , m s / m Chemical Oxvqen Demand(b1
. PRESTONE Antifreeze 1.24 1.25 21 69 04
b
Ethylene Glycol 1.30 1.39 14 62 75
Measured chemical oxygen demand value was determined by
catalyzed chromic acid procedure outlined in Standard
Methods for the Examination of Water and Wastewater(3).
-, (a)
(b) Bio-oxidation data are calculataed from chemical oxygen
data obtained by procedures outlined in Standard demand
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Methods(*). Calculation is:
BOD XlOO chemical oxygen demand
Reported value is the percentage ratio of BOD to the
total COD.
(c) The difference between 21 and 14 percent at Day 5 is
caused by variation in biological seed activity
(domestic waste is employed as a source of
microorganisms). The difference in seed activity
can result in significant variation in percent oxidation
in the early stages of the test.
The above results indicate rapid biodegradation of
PRESTONE Antifreeze and straight ethylene glycol. The BOD
test simulates river conditions and consequently is a very dilute
biological system. A biodegradation period of 5 to 10 days in
this test environment may correspond to only a few hours in a
conventional biological waste treatment facility. Thus, it is
anticipated that the PRESTONE Antifreeze and ethylene glycol are
readily amenable to biological waste treatment.
..
- ,
However, because these materials are biodegradable, large
quantities could represent a significant oxygen demand in
receiving streams ( 5 ) Oxygen depletion of the stream is
proportional to the biodegradability of the material added; i.e.,
materials with high biodegradability cause high oxygen depletion.
In a natural stream, the oxygen is provided from the dissolved
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oxygen in the water or waste. Because dissolved oxygen cannot
exceed about 14 ppm and is usually less than half that
concentration, it is apparent that the oxygen demand of a strong
waste can be satisfied or destroyed only by dilution with a large
amount of oxygen-bearing water or by abundant replenishment of
dissolved oxygen either by photosynthesis or by absorption from
the atmosphere. If the dissolved oxygen is depleted,
microorganisms will use conbined oxygen from nitrate, nitrite,
and sulphate ions from organic compounds in the waste or from the
water molecule itself, resulting in the formation of gaseous
compounds such as methane and hydrogen, instead of the carbon
dioxide and water formed under aerobic conditions.
Aquatic Toxicity of Ethylene Glvcol and Related Products
Aquatic toxicity tests on PRESTONE Antifreeze and
ethylene glycol have shown both to be non-toxic to an indicator
organism (the brine shrimp Artemia Salina) at concentrations in
excess of 20,000 mg/liter. Measured aquatic toxicity values for
ethylene glycol and PRESTONE Antifreeze with fathead minnows
b
were greater than 10,000 mg/liter. Substances having LC50 values
(concentraton lethal for 5 0 percent of the minnows exposed) in
this concentration range are generally considered relatively non-
toxic.
-,
E f f e c t on Plant Life
No study appears to have been made on the effect of
ethylene glycol on plant life. However, many people are aware of
the herbicidal properties of organic liquids. It is reasonable
to state that higher concentrations of any water-soluble liquid
would probably cause injury to many representative plants. -The - -
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would probably cause injury to many representative plants. The
natural dilution occurring when ethylene glycol based products
are disposed of would minimize this problem. The greatest risk
would occur when undiluted runoff may flow into the planted
areas.
REFERENCES
1.
2.
3.
4 .
5 .
Standard Methods Committee - Subcommittee on Biodegradability, J. Water Pollution Control Federation, 39, p. 1232 (1967).
llAerobic Biological Treatment of Waste Waters, Principles and Practice,I1 A. W. Busch, Oligodynamics Press, Houston, Texas, 1971, p. 152.
Chemical Oxygen Demand procedure published in Standard Methods for the Examination of Water and Wast'ewater, 15th Ed, Am Public Health Association, (1980).
Biochemical Oxygen Demand procedure publised in Standard Medhods for the Examination of Wate and Wastewater, 15th Ed, Am Public Health Association, (1980).
ttAqueous Wastes from Petroleum and Petrochemical Plantsv1, M. R. Beychok, Wiley, 1967, p. 38.
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