ASTM D-15 Committee on Engine Coolants

FIRST REPORT

Task Force on Antifreeze Biodegradability

.' 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

4

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.

5

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.

7

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.

8

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

9

,

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

10

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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