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Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
15 April-13 May 2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Criteria of validity: - the difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20% and the percentage degradation of the reference substance has reached the pass levels by day 14 (at least 60% of ThOD) - oxygen depletion in the inoculum blank should not exceed 1.5 mg dissolved oxygen/L after 28 days - residual concentration of oxygen in the test bottles did not fall below 0.5 mg/L at any time. The results are considered valid, because all criteria of validity were satisfied.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, adapted
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Key result
Parameter:
% degradation (test mat. analysis)
Value:
17.52
Sampling time:
28 d
Details on results:
The ready biodegradability, closed bottle test of 2,4,6-trinitrotoluene (TNT) was conducted by 28 days. Filtrate obtained from
activated sludge from a biological sewage refinery in Pszczyna was used in the test as microbial inoculum. Filtrate, in amount 1.0 mL
per litre, was added for preparation tested solutions.
The test system was made BOD bottles containing mixture of given volume of water, mineral medium, filtrate obtained from activated
sludge and solutions of reference substance or test material. Reference substance was applied in concentration 5 mg/L, and test
material – 2 mg/L. Measurement of dissolved oxygen was made by oxygen electrode which was placed directly in BOD bottles. Two
bottles of each series of samples for dissolved oxygen analysis at weekly time intervals over the 28 days of incubation were
withdrawn.
BOD values after each sampling time were evaluated by diminution the oxygen depletion (mgO2/L) of the inoculum blank from the
exhibited by the test substance. This depletion was divided by the concentration (mg/L) of the tested substance, to obtain the specific
BOD as mg oxygen per mg test substance. The percentage biodegradation of tested material and reference substance was
calculated by dividing the specific BOD by the specific ThOD.

During the evaluation of ready biodegradability, closed bottle test of 2,4,6-trinitrotoluene (TNT) the following results were obtained:
percent of degradation of test item after 28 days of experiment was equal 17.52 %, whereas biodegradation value of reference
substance (acetate sodium) after 7 days of experiment was equal 90,5 % and after 28 days of experiment 100.0%.

Basic on results obtained in this study for 2,4,6-trinitrotoluene (TNT) it is poorly biodegradable in water environment in this study
conditions and in compared with reference substance.

Table 1.Results obtained during 2,4,6-trinitrotoluene (TNT) test.

Day

Rate of sample

Measure oxygen content [mgO2/L]

Average oxygen content

[mgO2/L]

O2

Recruitment [mgO2/dm3]

Rate of sample

Measure oxygen content [mgO2/L]

O2

Recruitment [mg/O2/dm3]

BOD

[mgO2/mg of test material]

ThOD

[mgO2/mg of test material ]

% of test material degradation

[%]

 Average of % of test material degradation

[%]

0

ŚP1/0

ŚP2/0

8.88

8.86

8.87

-

BM1/0

BM2/0

8.69

8.70

-

-

-

-

-

7

ŚP1/7

ŚP2/7

8.38

8.42

8.40

0.47

BM1/7

BM2/7

7.80

7.85

0.89*

0.85*

0.21

0.19

1.27

16.54

14.96

15.75

14

ŚP1/14

ŚP2/14

8.21

8.19

8.20

0.67

BM1/14

BM2/14

7.58

7.59

1.10*

1.10*

0.215

0.215

1.27

16.93

16.93

16.93

21

ŚP1/21

ŚP2/21

8.08

8.05

8.065

0.805

BM1/21

BM2/21

7.38

7.40

1.236*

1.223*

0.215

0.209

1.27

16.95

16.46

16.71

28

ŚP1/28

ŚP2/28

7.46

7.44

7.45

1.42

BM1/28

BM2/28

6.64

6.66

1.87*

1.86*

0.225

0.220

1.27

17.72

17.32

17.52

* Correction for nitrification is involved.

Validity criteria fulfilled:
yes
Interpretation of results:
other: poorly biodegradable
Conclusions:
Basic on results obtained in this study for 2,4,6-trinitrotoluene (TNT) it is poorly biodegradable in water environment in this study
conditions and in compared with reference substance.

Description of key information

After 28 days, level of biodegradation of TNT was equal 17,52%. Based on results obtained in this study for 2,4,6-trinitrotoluene (TNT) it is poorly biodegradable in water environment in this study conditions and in compared with reference substance.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

IUCLID does not prescribe how detailed the study summaries should be recorded. Test Facility does not have the data or access to relevant guidance for the respective chemical regulatory programme thereof. According to OECD Guideline No 301 D, closed bottle test was performed for 28 days. The test item 2,4,6-trinitrotoluene (TNT) was applied in one concentration: 2 mg/L. Correction for nitrification was applied. After 28 days, level of biodegradation of TNT was equal 17,52%.