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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2002-03-20 - 2002-04-28
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The test was performed according to relevant guidelines and compliant with GLP. However, the study is insufficiently documented and details important for calculating the theoretical oxygen demand are lacking. However, the results are plausible as degradation proceeded steadily in a essentially linear manner and from day 17 to day 23 approaching a platoe.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2002
Report Date:
2002

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
yes
Remarks:
duplicate measurements for inoculum blanks and test items had not been performed.
Qualifier:
according to
Guideline:
other: Dissolved oxygen, DIN EN 25814 (G 22)
Qualifier:
according to
Guideline:
other: ThOD (theoretical (chemical) oxygen depletion) DIN 38409-H 41
Qualifier:
according to
Guideline:
other: Nitrate DIN EN ISO 10304-1 (D 19); Nitrite DIN EN 26777 (D 10);
Qualifier:
according to
Guideline:
other: dissolved organic carbon (DOC), DIN EN 1484 (H 3)
Principles of method if other than guideline:
not applicable
GLP compliance:
yes
Remarks:
according to GLP-part II 2;7

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Name: Licowax OP Powder
chemical name: ester of montanacids
active content: 100 %;
solubility: practically not soluble in water
appearance: Iight yellow solid
Solubility as determined in this study: DOC = 29 mg/L (dissolved organic carbon)

Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not applicable

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
local sewage work, secondary effluent; no further specification on type of sewage treatment plant or handling and amount of sludge used.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
4 mg/L
Based on:
other: test material, nominal concentration
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
A mixture containing the test substance, mineral medium and a relative small number of micro¬organism were kept in completely full and closed bottles in dark at constant temperature.
There was a weekly (daily) analysis of dissolved oxygen for the expression of biodegradation as percentage of ThOD.
Dilution water: deionized (distillate) water.
Mineral medium: As described in the guideline (OECD 301 D).

Procedure:
a) Preparation of bottles
The preparation of the stock solution was set up by a weighted portion of about 40 mg from the test substance which was made up to 100 ml with distillate water (stock solution).
The mineral medium was strongiy aerated for at least 30 minutes and was allowed to stand for 20 h at the test temperature (O2-concentration was about 9 mg/L at 20 °C).
Then there was added about 1.5 I fully-aerated mineral medium to a large bottle (4 I) so that it was about one-third full. Afterwards there was added an appropriate amount (about 40 ml) of the stock solution of the test substance to reach the final concentration of 4 mg/L (between 2 and 5). Then the solution was inoculated with secondary effluent. Finally, the solution was made up to volume with aerated mineral medium.
The same procedure was repeated to prepare the reference compound.
Each test series consisted of:
- about 10 bottles containing test suspension (test substance and inoculum)
- about 10 bottles containing inoculum alone (blank inoculum)
- about 10 bottles containing reference compound and inoculum (procedure control)

b) Test procedure
Afterwards the prepared solution was dispensed immediately into the BOD bottles by hose from the lower quarter of the appropriate large bottles, so that all BOD bottles were completely filled. After analysing the zero-time bottles for dissolved oxygen there was a incubating of the other ones in dark and at constant temperature (about 20 °C).
To allow the assessment of percentage removal in a 14 d (10 d) window there was a observation of dissolved oxygen weekly (3 - 4 daily).
All test series were running in parallel.
The reference substance was Propylenalkylbenzolsulfonate with a known biologicat degradation rate (about 30 %).

Reference substance
Reference substance:
other: Propylenealkylbenzolsulfonate

Results and discussion

Preliminary study:
not applicable
Test performance:
For the flasks with the inoculated test substance Nitrate had been determined and the respective amount of oxygen used for nitrification subtracted from the absolute oxygen depletion.

Some validity criteria are not fulfilled:
1) O2-consumption of the inoculum control from day 0 to day 28 was 1.68 mg/L, i.e. > 1.5 mg/L which should not have been exeeded.
2) No replicates in the study; therefore the difference of extremes of replicate values of the removal of the test subst. at day 28 had not been determined (should have been below 20%).
3) The percentage degradation of the reference compound should have reached the pass levels at day 14 (i.e. minimal 60% degradation within 10 days). As the reference substance used does not belong to the ones cited in the guideline, this point can not be checked. The study report states a 30% degradation for the used reference substance within the test, which had been reached, indeed.
% Degradation
Parameter:
% degradation (O2 consumption)
Value:
22
Sampling time:
28 d
Remarks on result:
other: In a 10 day window, about 10% had been degraded
Details on results:
The ThOD for the test item is given in the study without explanation of the deduction: 3.69 mg O2/mg.
The O2-concentration for all bottles at t=0 is given as about 9 mg/L.
The O2-consumption of the inoculum control from day 0 to day 28 was 1.68 mg/L. A validity criterium of the guideline is therefore not fulfilled (1.5 mg/L should not be exeeded).
A plateau is reached at day 23 at a degradation level of 22%.

BOD5 / COD results

Results with reference substance:
The ThOD for the reference substance propylenalkylbenzolsulfonate is given in the study without explanation of the deduction: 2.84 mg O2/mg.
The known degradation level for the reference substance is stated to be about 30%.
The O2-concentration for all bottles at t=0 is given as about 9 mg/L.
The O2-consumption of the inoculum control from day 0 to day 28 was 1.68 mg/L. A validity criterium of the guideline is therefore not fulfilled (1.5 mg/L should not be exeeded).
A plateau is reached at day 28 at a degradation level of about 32%.

Any other information on results incl. tables

biological degradation (BOD/ThOD*100%)

days

BOD test subst.
[mg/mg]

BOD reference subst.
[mg/mg]

Biol. degrad. test subst. [%]

Biol. degrad. reference subst. [%]

1

0.020

0.047

0.5

1.6

2

0.083

0.157

2.3

5.5

5

0.152

0.384

4.1

13.5

12

0.367

0.717

9.9

25.3

17

0.694

0.857

18.8

30.2

23

0.806

0.892

21.8

31.4

28

0.814

0.917

22.0

32.3

Applicant's summary and conclusion

Validity criteria fulfilled:
not applicable
Remarks:
See section "Test performance", as in this field the text is truncated.
Interpretation of results:
other: inherent (primary) biodegradable
Conclusions:
In a test for ready biodegradability according to OECD 301 D (closed bottle), the test item proved to be not readiliy biodegradable. Neither the pass level of 60% ThOD (theoretical oxiygen demand), nor the 10-day window had been fulfilled. At the end of the test at day 28 a biodegradation of 22 % ThOD had been reached. The result is plausible as degradation proceeded steadily in a essentially linear manner and approached a platoe at day 23 with a degradation of 22% . According to criteria set by the OECD (2006) the observed biodegradation may be interpreted as sign for inherent primary biodegradation.
Executive summary:

In a test for ready biodegradability according to OECD 301 D (closed bottle), the test item proved to be not readiliy biodegradable. Neither the pass level of 60% ThOD (theoretical oxiygen demand), nor the 10-day window had been fulfilled. At the end of the test at day 28 a biodegradation of 22 % ThOD had been reached. The result is plausible as degradation proceeded steadily in a essentially linear manner and approached a platoe at day 23 with a degradation of 22% . According to criteria set by the OECD (2006, OECD GUIDELINES FOR THE TESTING OF CHEMICALS, SECTION 3. PART 1: PRINCIPLES AND STRATEGIES RELATED TO THE TESTING OF DEGRADATION OF ORGANIC CHEMICALS) a biodegradation rate above 20% may be interpreted as sign for inherent primary biodegradation.