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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
Remarks:
test on C12 naphthalene
Adequacy of study:
key study
Study period:
Start : 05 December 2012 Completion : 03 January 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP OECD guideline study without deficiencies that affected study validity

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2013
Report date:
2013

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid: viscous
Details on test material:
Description: Clear amber slightly viscous liquid
Batch: 18515
Purity/Composition: UVCB (tested as 100% pure)

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', Heeswijk-Dinther, The Netherlands, receiving predominantly domestic sewage.
The freshly obtained sludge was used immediately. The concentration of suspended solids, determined on sludge taken 2 days later from the same sewage treatment plant was 4 g/l in the concentrated sludge. The amount of suspended solids is representative for the sludge used in this study. Before use, the sludge was allowed to settle (78 minutes) and the supernatant liquid was used as inoculum at the amount of 10 ml/l of mineral medium.
Duration of test (contact time):
>= 28 d
Initial test substance concentration
Initial conc.:
>= 12 mg/L
Based on:
ThIC
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
The study consisted of six bottles:
- 2 inoculum blanks (no test substance),
- 2 test bottles (alkylated naphthalene),
- 1 positive control (sodium acetate) and
- 1 toxicity control (alkylated naphthalene) plus sodium acetate).

Results and discussion

Preliminary study:
No preliminary test was conducted.
Test performance:
1. The positive control substance was biodegraded by at least 60% (68%) within 14 days.
2. The difference of duplicate values for %-degradation of the test substance was always less than 20.
3. The total CO2 release in the blank at the end of the test did not exceed 40 mg/l (56 mg CO2 per 2 litres of medium, corresponding to 28 mg CO2/l).
4. The Inorganic Carbon content (IC) of the test substance (suspension) in the mineral medium at the beginning of the test was less than 5% of the Total Carbon content (TC). Since the test medium was prepared in tap-water purified by reverse osmosis (Milli-RO water (Millipore Corp., Bedford, Mass., USA, carbon levels < 500 ppb)), IC was less than 5% of TC (mainly coming from the test substance, 12 mg TOC/l).
Since all criteria for acceptability of the test were met, this study was considered to be valid.
4. The Inorganic Carbon content (IC) of the test substance (suspension) in the mineral medium at the beginning of the test was less than 5% of the Total Carbon content (TC). Since the test medium was prepared in tap-water purified by reverse osmosis (Milli-RO water (Millipore Corp., Bedford, Mass., USA, carbon levels < 500 ppb)), IC was less than 5% of TC (mainly coming from the test substance, 13 mg TOC/l).

Since all criteria for acceptability of the test were met, this study was considered to be valid.

% Degradation
Parameter:
% degradation (CO2 evolution)
Value:
>= 1 - <= 2
Sampling time:
29 d
Details on results:
See results table

BOD5 / COD results

Results with reference substance:
The reference substance biodegraded by 68% within 14 days.


Any other information on results incl. tables

Table  1  CO2production and percentage biodegradation of the test substance (bottle A).

 

 

Day

HCl (0.05 N) titrated (ml)

Produced CO2

(ml HCl)

Produced CO2

(mg)

Cumulative CO2

(mg)

Biodegradation1)

(%)

 

Blank (mean)

bottle A

 

2

46.27

45.45

0.82

0.9

0.9

1

 

5

44.69

44.70

0.00

0.0

0.9

1

 

7

44.92

46.30

0.00

0.0

0.9

1

 

9

45.85

46.38

0.00

0.0

0.9

1

 

14

45.04

45.59

0.00

0.0

0.9

1

 

19

43.74

44.76

0.00

0.0

0.9

1

 

23

44.08

44.91

0.00

0.0

0.9

1

 

26

44.98

44.67

0.31

0.3

1.2

1

 

29

43.36

43.41

0.00

0.0

1.2

1

 

29

46.23

46.64

0.00

0.0

1.2

1

 

29

47.85

47.55

0.30

0.3

1.6

2

 

1): Calculated as the ratio between CO2produced (cumulative) and the ThCO2of the test substance: 84.2 mg CO2/2l

 

Table 2    CO2production and percentage biodegradation of the test substance (bottle B).

 

 

Day

HCl (0.05 N) titrated (ml)

Produced CO2

(ml HCl)

Produced CO2

(mg)

Cumulative CO2

(mg)

Biodegradation1)

(%)

 

Blank (mean)

bottle B

 

2

46.27

45.49

0.78

0.9

0.9

1

 

5

44.69

44.89

0.00

0.0

0.9

1

 

7

44.92

45.11

0.00

0.0

0.9

1

 

9

45.85

46.85

0.00

0.0

0.9

1

 

14

45.04

46.28

0.00

0.0

0.9

1

 

19

43.74

45.19

0.00

0.0

0.9

1

 

23

44.08

45.48

0.00

0.0

0.9

1

 

26

44.98

45.66

0.00

0.0

0.9

1

 

29

43.36

43.66

0.00

0.0

0.9

1

 

29

46.23

46.69

0.00

0.0

0.9

1

 

29

47.85

47.66

0.19

0.2

1.1

1

 

1): Calculated as the ratio between CO2produced (cumulative) and the ThCO2of the test substance: 87.9 mg CO2/2l

 

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
other: not readily biodegradable
Conclusions:
Alkylated naphthalene was not readily biodegradable under the conditions of the modified Sturm test presently performed.
Executive summary:

A Ready Biodegradation Test was conducted with alkyalted naphthalene. The study procedures described in this report were based on the OECD guideline No. 301 B, 1992. In addition, the procedures were designed to meet the test methods of the Commission Regulation (EC) No. 440/2008 of 30 May 2008, Publication No. L142, Part C.4-C, ISO International Standard 9439, 1999 and ISO Standard 10634, 1995.

Alkylated naphthalene, a UVCB, was a clear amber slightly viscous liquid and was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 1 g/l.

The Total Organic Carbon (TOC) content of alkyalted naphthalene was determined to be 91%. The test substance was tested in duplicate at approximately 13 mg/l, corresponding to 12 mg TOC/l. The Theoretical CO2 production (ThCO2) was calculated to be 3.33 mg CO2/mg.

The study consisted of six bottles:

- 2 inoculum blanks (no test substance),

- 2 test bottles (Alkylated naphthalene),

- 1 positive control (sodium acetate) and

- 1 toxicity control (Alkylated naphthalene plus sodium acetate).

Weighed amounts were added to the 2-litres test bottles containing medium with microbial organisms and mineral components. To this end, approximately 20 ml of Milli-RO water was added to each weighing bottle containing the test substance. After vigorous mixing (vortex) the resulting suspension was added quantitatively to the test medium. The test solutions were continuously stirred during the test, to ensure optimal contact between the test substance and the test organisms. Test duration was 28 days (last CO2-measurement on the 29th day).

The relative biodegradation values calculated from the measurements performed during the test period revealed no significant biodegradation of Alkylated naphthalene..In the toxicity control, Alkyalted naphthalene was found not to inhibit microbial activity. Since all criteria for acceptability of the test were met, this study was considered to be valid.

In conclusion, Alkylated naphthalene was designated as not readily biodegradable.