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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Reference
Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Type of information:
experimental study
Adequacy of study:
key study
Study period:
28 days
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
OECD Guideline 306 (Biodegradability in Seawater)
Deviations:
no
GLP compliance:
yes
Radiolabelling:
no
Oxygen conditions:
aerobic
Inoculum or test system:
other: The test solution contains an indigenous population of heterogeneous microorganisms and is not inoculated with any further test seed.
Details on source and properties of surface water:
- Details on collection (e.g. location, sampling depth, contamination history, procedure): Test water used is natural seawater collected by the Marine Biological Laboratory, Aquatic Resources Division, Woods Hole, Massachusetts.
- Storage conditions: Cool environmental chamber until use
- pH at time of collection: 8.2
- Hardness (CaCO3): 2.75 %
- Dissolved organic carbon (mg/L): 3.26 (TOC)
- Water filtered: yes
- Type and size of filter used, if any: 5 micron
Details on source and properties of sediment:
Not applicable
Details on inoculum:
The natural seawater used for testing had an initial population 10-100 organisms per mL as determined by the sterile Marine Broth extinction bottle test.
Duration of test (contact time):
28 d
Initial conc.:
2 other: ppm
Parameter followed for biodegradation estimation:
other: Percent biodegradability is calculated as the ratio of the BOD to the chemical oxygen demand (COD) multiplied by a factor of 100.
Reference substance:
other: Sodium acetate
Key result
% Degr.:
ca. 13
Parameter:
O2 consumption
Sampling time:
28 d
Transformation products:
not measured

Mean oxygen depletion values for the controls and the samples are presented below:

 

Mean Oxygen Depletion (mg/L)

Incubation Period

Blank Unseeded Control

Sodium Acetate Standard 2 ppm

Sample 2 ppm

5 Day mg/L

0.5

1.5

0.8

13 Day mg/L

0.7

1.9

1.1

20 Day mg/L

0.9

2.1

1.4

28 Day mg/L

0.9

2.1

1.4

 

The COD value for MK-92 is 1.94 mg oxygen per mg substance. Biochemical oxygen demand values expressed in mg BOD/L and percent biodegradation are presented below:

 

Biochemical Oxygen Demand (mg BOD/L)

Incubation Period

Sodium Acetate Standard 2 ppm

Sample 2 ppm

BOD5

0.50

0.15

BOD13

0.60

0.20

BOD20

0.60

0.25

BOD28

0.60

0.25

 

Percent Biodegradability (BOD as % COD)

Incubation Period

Sodium Acetate Standard 2 ppm

Sample 2 ppm

BOD5

71%

8%

BOD13

86%

10%

BOD20

86%

13%

BOD28

86%

13%

Validity criteria fulfilled:
yes
Conclusions:
The COD value for MK-92 is 1.94 mg oxygen per mg substance.
Percentage biodegradation is estimated as ca 13%
Executive summary:

The ready biodegradability in seawater of MK-92 was determined by measuring dissolved oxygen consumption of a dilute solution of the designate organic material in natural seawater. The test solution contained an indigenous population of heterogeneous microorganisms and was not inoculated with any further test seed. Test bottles were incubated in the dark at a temperature of 20 ± 1°C. Biological oxygen demand (BOD) of the test system was monitored over a specified incubation period. Percent biodegradability was calculated as the ratio of the BOD to the chemical oxygen demand (COD) multiplied by 100.

The COD value of MK-92 is 1.94 mg oxygen per mg substance.

Percentage biodegradation is estimated as ca 13%

Description of key information

The ready biodegradability in seawater of MK-92 was determined by measuring dissolved oxygen consuption of a dilute solution of the designate organic material in natural seawater. The test solution contained an indigenous poulation of heterogeneous microorganisms and was not inoxulated with any further test seed. Test bottles were incubated in the dark at a temperature of 20 ± 1°C. Biological oxygen demand (BOD) of the test system was moitored over a specified incubation period. Percent biodegradability was calculated as the ratio of the BOD to the chemical oxygen demand (COD) multiplied by 100.
The COD value of MK92 is 1.94 mg oxygen per mg substance.

Key value for chemical safety assessment

Additional information

The ready biodegradation of MK92K in seawater was determined according to OCED guideline 306 (Biodegradability in Seawater).