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Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Principles of method if other than guideline:

Directive 79/831 EWG Appendix V (revised edition, 1990)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

TEST ORGANISM:
- mixed population of aquatic microorganisms of a laboratory sewage treatment plant, treating  predominantly domestic sewage (Wupper area water  authority, STP Odenthal, Germany)  
- pretreatment: none
- concentration: 30 mg/L (dry weight)

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Reference substance:

aniline

Remarks:

purity: not specified

Parameter:

% degradation (O2 consumption)

Value:

25

Sampling time:

8 d

Parameter:

% degradation (O2 consumption)

Value:

31

Sampling time:

12 d

Parameter:

% degradation (O2 consumption)

Value:

39

Sampling time:

18 d

Parameter:

% degradation (O2 consumption)

Value:

43

Sampling time:

22 d

Parameter:

% degradation (O2 consumption)

Value:

50

Sampling time:

28 d

Details on results:

Degradation products: no
Chemcal oxygen demand (COD) of test substance: 2120 mg O2/g

Results with reference substance:

Kinetic of control substance (in %):
2 after 8 day(s)
67 after 12 day(s)
76 after 28 day(s)

Validity criteria fulfilled:

yes

Remarks:

toxicity control: negative

Interpretation of results:

not readily biodegradable

Conclusions:

The test item is not readily biodegradable. Within 28 days only 50 % of the test substance was degraded in a test conducted according to the EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)(Bayer AG, 1994).

Executive summary:

The test item is not readily biodegradable. Within 28 days only 50 % of the test substance was degraded in a test conducted according to the EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)(Bayer AG, 1994).

Reference 2

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))

Version / remarks:

(based on standard operating procedures for OECD Guideline 301F (1992) and the Council Regulation (EC) No 440/2008, method C.4-D “Manometric Respirometry Test” (2008))

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Type : mixed population of aquatic microorganisms (activated sludge)
- Origin : 2 x 40 % activated sludge of an aeration tank of two different wastewater plants treating predominantly domestic sewage (Wupper area water authority, STP Odenthal and STP Cologne-Stammheim) 20 % activated sludge of aeration tanks of a sewage treatment plant treating predominantly sewage of industrial origin (STP Leverkusen Bürrig)
- Date of collections : 2009-07-21
- Concentration of inoculum (dry weight) : 100 mg/L suspended solids (ss) for all treatments with test item and toxicity control and 30 mg/L (ss) in the reference compound, respectively

CHEMICAL ANALYSIS
- COD
- Method : Determination of Chemical Oxygen Demand of solids and substances which are not water-soluble (COD).
- Calibration Standard : Potassium hydrogen phthalate
- Test apparatus : Titrator / Methrohm 730/759

Duration of test (contact time):

28 d

Details on study design:

PRETREATMENT of the inoculum
- the three slugdes were mixed proportionally as described before
- the sludge was washed twice by adding mineral medium and centrifuging for 10 min at 2000 rpm and 20 °C and decanting off the supernatant
- 0.820 g of the wet sludge were dried in order to calculate the amount of wet sludge to achieve a concentration of activated sludge of 5 g/L (ss)
- the calculated amount of sludge was first dissolved in mineral medium and then filled up to a defined end volume
- the inoculum was stored at room temperature under continuous shaking with aeration until use for one day

PRETREATMENTof the test item
-7.5 mg of the test item were weighed out on aluminium foil. Both were added into the test flasks, which had already been filled with 200 mL of mineral medium. Afterwards the flask content was made up to 250 mL with mineral medium containing inoculum to give a test concentration of 30 mg test item/L.
- For the toxicity control 7.5 mg were weighed out to give a test concentration of 30 mg test item/L.

PRETREATMENT of the reference compound
- Reference compound name : sodium benzoate (Fluka-BioChemika)
- 25 mg of the reference compound were weighed out on aluminium foil. Both were added into the test flasks, which had already been filled with 200 mL of mineral medium. Afterwards the flasks were made up to 250 mL with mineral medium containing inoculum to give a test concentration of 100 mg reference compound/L. For the toxicity control 7.5 mg were weighed out to give a test concentration of 30 mg reference compound/L.

EXPOSURE CONDITIONS
- Test volume : 250 mL
- Test apparatus : OxiTop System (WTW)
- Mixing : 1 magnetic stirrer per test vessel
- Incubation time : 28 days
- Incubation temperature : 25 ± 1 °C

Reference substance:

benzoic acid, sodium salt

Remarks:

- Purity : 100.1 % - Batch-no. : 1373379

Parameter:

% degradation (O2 consumption)

Value:

73

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

53

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

68

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

72

Sampling time:

21 d

Results with reference substance:

The reference compound sodium benzoate showed 78 % degradation after 7 days and 80 % degradation after 14 days.

Validity criteria fulfilled:

yes

Remarks:

The percent degradation of reference compound sodium benzoate reached the level of ≥ 40 % after 7 days and ≥ 65 % after 14 days. No toxicity of the test item was observed in the toxicity control.

Interpretation of results:

inherently biodegradable

Conclusions:

Within 28 days a degradation of 73 % was determined for the test item according to the OECD Guideline 302 C. Therefore the test item is considered to be "Inherently Biodegradable" (Currenta, 2009).

Executive summary:

Within 28 days a degradation of 73 % was determined for the test item according to the OECD Guideline 302 C. Therefore the test item is considered to be "Inherently Biodegradable" (Currenta, 2009).

Description of key information

A test on ready biodegradability showed that 50 % of the substance is degraded within 28 days. These results show that the substance is not readily biodegradable, but additionally provided evidence from an inherent test show that the substance can be degraded in sewage treatment plants. The substance is not readily biodegradable but inherent biodegradable (Bayer AG, 1994; Currenta, 2009). 

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, fulfilling specific criteria

Type of water:

freshwater

Additional information

The ready biodegradability of the substance was determined according to the EU method C.4 -D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test) with the following result (Bayer AG, 1994): 50 % degradation after 28 days.

The inherent biodegradability was determined according to the OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II)) and results in 73 % degradation within 28 days (Currenta, 2009).

Based on these results, the substance is considered to be "Not Readily Biodegradable", but "Inherently Biodegradable" .