Registration Dossier

Administrative data

Endpoint:
hydrolysis
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance is readily biodegradable
Cross-reference
Reason / purpose:
data waiving: supporting information
Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From October 28, 2015 to November 27, 2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge : municipal wastewater treatment plant Breisgauer Bucht
- Sampling date: October 27, 2015
- Concentration of sludge: 30 mg dry solids/L
- Pretreatment: The activated sludge was washed twice with tap water and one time with mineral medium by settling the sludge, decanting the supernatant and resuspending the sludge.
Dry solid of the activated sludge was determined as 4.9 g/L by weight measurements after drying at 105°C (mean of triplicate measurements).
Duration of test (contact time):
29 d
Initial conc.:
10 mg/L
Based on:
other: Organic carbon
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Temperature: 21.1 – 23.1°C
- Aeration rate: 30 - 100 mL/min (1.6 - 5.5 bubbles/s); the determination by counting the gas bubbles over a defined period using a stop watch was made at Day 14 and 28.

SOLUTIONS
- Test substance: A stock solution with a concentration of 500 mg/L in mineral medium was prepared. This corresponds to a test concentration of 10.0 mg/L organic carbon.
- Reference substance: A stock solution of 10 g/L sodium benzoate in water was prepared. This corresponds to a concentration of 20 mg/L organic carbon.
- Toxicity control: 99.4 ml of the test substance stock solution and 5.15 mL of the reference stock solution were added to the toxicity control vessel corresponding to a concentration of 30 mg/L organic carbon.

EXPERIMENTAL SET UP
- Inoculum blank: 9.2 mL activated sludge was filled up to 1,500 mL with 1,490.2 mL mineral medium corresponding to 30 mg/L dry solids.
- Test substance: 3 reactors; 99.4 mL of the test substance stock solution was added and filled up to 1,500 mL with mineral medium in each reactor.
- Reference substance: 3 reactors; 5.15 mL of a reference stock solution was added and filled up to 1,500 mL with mineral medium in each reactor.
- Toxicity control: 1 reactor; 99.4 mL of the test substance stock solution and 5.15 mL of the reference stock solution was added and filled up to 1,500 mL with mineral medium.

IC determination: Day 4, 7, 11, 14, 21, 28 and 29. At the beginning of the study, IC concentration of the 0.2 M NaOH used for the CO2-absorption flasks was determined as 2.3 ppm.

The CO2-free air production system, the air-tightness of the whole experimental set-up, the aeration of the absorber flasks and the magnetic stirrers were controlled daily on working days.

PROCEDURE
9.2 mL activated sludge was filled up to 1,500 mL with 1,490.2 mL mineral medium corresponding to 30 mg/L dry solids. The system was sealed and aerated with CO2-free air overnight. The reactors were kept mixed with magnetic stirrers. On the next day, after filling the absorber wash bottles with 0.2 M NaOH, the test substance and reference compound were introduced and the test started.

Reference substance:
benzoic acid, sodium salt
Remarks:
10 g/L
Key result
Parameter:
% degradation (CO2 evolution)
Value:
83.9
Sampling time:
29 d
Details on results:
The degradation extent of the test substance at the end of the test was 83.9% (28 d after acidification mean of three replicates). The mean degradation extent on Day 11 was higher than 60% (65%). Therefore the criteria for ready biodegradation i.e. 10-d-window was met. The degradation extent in the toxicity control was 77.6% within 14 d, the test substance has no inhibitory effect on the inoculum.
Results with reference substance:
The reference substance sodium benzoate reached the pass levels for ready biodegradability within 4 d.

Before adding the test substance, the IC in the reactor was determined, but only insignificant amounts of IC (0.1 mg/L) were found. The IC-concentration of the NaOH in the second CO2 absorber flasks in line used as protective flasks showed that there was no CO2 absorption from room air in the test flasks.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test substance was considered to be ‘readily biodegradable’.
Executive summary:

A study was conducted to assess the ready biodegradability of the test substance according to OECD Guideline 301B, in compliance with GLP. Domestic activated sludge was used as inoculum (concentration in the test: 30 mg/L dry solids). The test substance was tested at 10 mg/L organic carbon (corresponding to 500 mg/L of test substance) for 29 d. Sodium benzoate was chosen as positive control. The degradation was assessed by IC-measurements in the CO2 absorber flasks on Day 4, 7, 11, 14, 21, 28 and 29. The degradation extent of the test substance at the end of the test was 83.9%. The degradation of toxicity control was 77.6% within 14 d, this indicate that the test substance has no inhibitory effect on the inoculum. The reference compound sodium benzoate reached the pass levels for ready biodegradability within 4 d. All validity criteria for the acceptability of the test was met. Hence under the study conditions, the test substance was considered as readily biodegradable in a CO2 evolution test (Brunswik-Titze A, 2015).

Data source

Materials and methods

Results and discussion

Applicant's summary and conclusion