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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
30 September 2009-29 October 2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study has been performed according to OECD and/or EC guidelines and according to GLP principles

Data source

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

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
no
Qualifier:
according to
Guideline:
ISO DIS 9439 (Ultimate Aerobic Biodegradability - Method by Analysis of Released Carbon Dioxide)
Deviations:
no
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): Terate® 091 Residue
- Substance type: Dark brown solid with soft lumps (determined at NOTOX)
- Physical state: Solid
- Analytical purity: 100%
- Lot/batch No.: NB8322-091
- Expiration date of the lot/batch: 14 July 2010
- Stability under storage conditions: Stable
- Storage condition of test material: At room temperature in the dark
- Stability in water: Not indicated
- Solubility in water: Not indicated

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Source:
The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap de Maaskant', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.

Treatment:
The freshly obtained sludge was kept under continuous aeration until further treatment. The concentration of suspended solids was 3.5 g/l in the concentrated sludge (information obtained from the municipal sewage treatment plant). Before use, the sludge was allowed to settle (50 minutes) and the liquid was decanted for use as inoculum at the amount of 10 ml/l of mineral medium.
Duration of test (contact time):
28 d
Initial test substance concentrationopen allclose all
Initial conc.:
17.5 mg/L
Based on:
test mat.
Initial conc.:
12 mg/L
Based on:
other: Total Organic Carbon (TOC)
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: 1 litre mineral medium contains: 10 ml of solution (A), 1 ml of solutions (B) to (D) and Milli-RO water
Stock solutions of mineral components
A) 8.50 g KH2PO4; 21.75 g K2HPO4; 67.20 g Na2HPO4.12H2O; 0.50 g NH4Cl; dissolved in Milli-Q water and made up to 1 litre, pH 7.4 ± 0.2
B) 22.50 g MgSO4.7H2O dissolved in Milli-Q water and made up to 1 litre.
C) 36.40 g CaCl2.2H2O dissolved in Milli-Q water and made up to 1 litre.
D) 0.25 g FeCl3.6H2O dissolved in Milli-Q water and made up to 1 litre.

- Test temperature: between 21.7 and 22.2°C.
- pH:
At t=0 d: 7.4-7.5
At t=28 d: 7.6-7.8
- pH adjusted:no
- Aeration of dilution water: Not before the test, the test is aerated continously
- Suspended solids concentration: The concentration of suspended solids was 3.5 g/l in the concentrated sludge (information obtained from the municipal sewage treatment plant).
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 2 litre all-glass brown coloured bottles
- Number of culture flasks/concentration:
Test suspension: containing test substance and inoculum (2 bottles).
Inoculum blank: containing only inoculum (2 bottles)
Positive control: containing reference substance and inoculum (1 bottle).
Toxicity control: containing test substance, reference substance and inoculum (1 bottle).
- Method used to create aerobic conditions:
Synthetic air (a mixture of oxygen (ca. 20%) and nitrogen (ca. 80%)) was sparged through the solutions at a rate of approximately 1-2 bubbles per second (ca. 30-100 ml/min).
- Test performed in open system: yes
- Details of trap for CO2 and volatile organics if used:
CO2 was trapped in barium hydroxide solution. The amount of CO2 produced was determined by titrating the remaining Ba(OH)2 with 0.05 M standardized HCl (1:20 dilution from 1 M HCl (Titrisol® ampul). Titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until the 28th day, for the inoculum blank and test suspension. Titrations for the positive and toxicity control were made at least 14 days.


SAMPLING
- Sampling frequency: Titration were made on day: 2, 5, 7, 9, 14, 19, 23, 27 and 29
- Sampling method: Titration of the whole volume of CO2-absorber

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes
- Other:
Reference substance
Reference substance:
acetic acid, sodium salt

Results and discussion

% Degradationopen allclose all
Parameter:
% degradation (CO2 evolution)
Value:
24
Sampling time:
29 d
Remarks on result:
other: HCL added on the 28th day (last CO2-measurement on the 29th day)
Parameter:
% degradation (CO2 evolution)
Value:
29
Sampling time:
29 d
Remarks on result:
other: HCL added on the 28th day (last CO2-measurement on the 29th day)
Details on results:
In the toxicity control more than 25% biodegradation occurred within 14 days (41%, based on ThCO2). Therefore, the test substance was assumed not to inhibit microbial activity

BOD5 / COD results

Results with reference substance:
The positive control substance was biodegraded by at least 60% (75%) within 14 days

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
other: The relative biodegradation values calculated revealed 29 and 24% biodegradation of Terate® 091 Residue, for the duplicate bottles tested. Thus, the criterion for ready biodegradability (at least 60% biodegradation within a 10-day window) was not met.
Conclusions:
Terate® 091 Residue was not readily biodegradable under the conditions of the modified Sturm test presently performed.
Executive summary:

According to OECD 301B and EU-method C.4-C (CO2 -evolution), ready biodegradability of the submission substance had been assessed compliant to GLP. The positive control sample was degraded by 75% within 14 days, proving the functionality of the test system. No inhibition of microbial toxicity by the submission substance could be observed with the toxicity control. The calculated relative biodegradation of the duplicate samples of the submission substance were 29% and 24% within 28 days. Concluding from these experimental results, despite some biodegradation was observed the submisson substance fails the criteria for ready biodegradability (at least 60% biodegradation within a 10-day window).