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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:
2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP - Guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2009

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
(2008)
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
(1992)
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Benzothiazol (BT Crude Quality)
- Analytical purity: 97.0 %
- Lot/batch No.: tank B 134

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum: aeration tank of a wastewater plant treating predominantly domestic sewage (Wupper area water authority, STP Odenthal)

- Preparation of inoculum for exposure:
=> 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
=> 1.348 g of the wet sludge was dried in order to calculate the amount of wet sludge to achieve a concentration of activated sludge of 3 g/L (dry weight) suspended solids
=> the calculated amount of sludge was first dissolved in mineral medium and then filled up to a defined end volume

- Storage conditions: room temperature, continuous shaking with aeration

- Storage length: max. 3 days

- Concentration of sludge: 30 mg/l
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Remarks:
(reported as BOD)
Details on study design:
TEST CONDITIONS
- Composition of medium: mineral medium was prepared from stock solutions of 1) Mineral salt solution, 2) Magnesium sulphate solution, 3) Calcium chloride solution and 4) Iron (III) chloride solution
- preparation of medium: 10 mL of the mineral salt solution were mixed with 800 mL deionised water. Then 1 mL each of the magnesium sulphate-, calcium chloride- and the iron (III) chloride solution were added and filled up to 1 litre with deionised water.
- Test temperature: 22 ± 1 °C
- pH: 7.2 - 7.9 (at the end of the test)
- pH adjusted: no
- Continuous darkness: yes


TEST SYSTEM
- Culturing apparatus: OxiTop System (WTW) => closed respirometer flasks
- Mixing: 1 magnetic stirrer per test vessel
- Testvolume: 250 ml
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: consumed oxygen was replaced by electrolysis (maintaining a constant gas volume in the respirometer flasks)
- Details of trap for CO2: solution of potassium hydroxide


SAMPLING
- Sampling frequency: daily measurements of oxygen consumption


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 2x (inocolum without test substance)
- Abiotic sterile control: no
- Toxicity control: yes, 1x (test substance and reference compound mixed)
Reference substance
Reference substance:
other: sodium benzoate (Fluka-BioChemika), Purity: 100 %, test concentration: 100 mg/l

Results and discussion

% Degradationopen allclose all
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
7 d
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
14 d
Parameter:
% degradation (O2 consumption)
Value:
58.4
Sampling time:
21 d
Parameter:
% degradation (O2 consumption)
Value:
74.3
Sampling time:
28 d
Details on results:
Toxicity control: The used concentrations of the test item did not show toxic effects to bacteria.
Oxygen uptake by nitrification: No nitrification was observed in the flasks with test item.
Degradation of reference compound: The reference compound reached the level for ready biodegradability within 14 days (BOD = 85%).

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Executive summary:

Lanxess, 2009:

A study was performed to assess the ready biodegradability of Benzothiazol (BT Crude Qualität).

The study was conducted in accordance with the Council Regulation (EC) No 440/2008, Method C.4-D "Manometric Respirometry Test" (2008). This test method is in all essential parts identical with OECD Guideline 301 F (adopted July 1992).

A solution of Benzothiazol (BT Crude Qualität) in a mineral medium was inoculated and incubated for 28 d under aerobic conditions. During this period, degradation was followed by BOD determinations.

Benzothiazol (BT Crude Qualität) showed:

0 % degradation after 7 days

0 % degradation after 14 days

58 % degradation after 21 days

74 % degradation after 28 days

Therefore, Benzothiazol (BT Crude Qualität) is considered to be "Readily Biodegradable".

The reference compound sodium benzoate showed 85 % degradation after 14 days.