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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:
Jan 16th to Feb 16th 2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study, performed in conformity with GLP-principles

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2006
Report Date:
2006

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Identity: LZ 1780
Chemical name: L-Carnitine L-tartrate
Lot number: 21205
Expiry date: 09 December 2007
Appearance: White crystalline powder
Storage conditions: Room temperature
Date received: 4 January 2006

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
A sample of activated sludge was collected from a sewage treatment works, which treats predominantly domestic waste. Aliquots (25 ml) of a homogenised sample were filtered through dried (approximately 105OC) and pre-weighed Whatman GFIC filter papers. The filters were dried for at least one hour, allowed to cool and re-weighed. The solids level in the sludge was determined and then an appropriate volume used to inoculate control and
test vessels to give a fmal suspended solids concentration of 30 mg/l.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
10 mg/L
Based on:
other: carbon
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
The test item was added to two, five-litre vessels containing three litres of mineral salts medium inoculated with activated sludge (30 mg solids/l) to give a nominal test concentration of 10 mg Carbon [C]/l. Two control vessels contained inoculated mineral salts medium alone and one contained inoculated mineral salts medium plus the reference substance, sodium benzoate (10 mg C/l). An additional mixture containing sodium benzoate (10 mg C/l) and LZ 1780 (10 mg C/l) was established in order to assess the potential inhibitory effects of the test substance on the activity of the microbial inoculum.
Test, control and reference mixtures were aerated for 29 days with air that had been treated to remove carbon dioxide (C02). The COz produced by each culture was trapped in a series of Dreschel bottles containing barium hydroxide, which were connected to the outlet fiom each test vessel. The residual barium hydroxide was determined at intervals by titration.
The pH of control, reference and test mixtures was measured at the start of the test and after 28 days. The pH of the test plus reference mixture was measured at the start of the test and on the day of its termination (Day 5).
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Preliminary study:
None.
Test performance:
See details on study design.
% Degradationopen allclose all
Parameter:
% degradation (CO2 evolution)
Value:
12
Sampling time:
2 d
Parameter:
% degradation (CO2 evolution)
Value:
69
Sampling time:
6 d
Parameter:
% degradation (CO2 evolution)
Value:
82
Sampling time:
14 d
Parameter:
% degradation (CO2 evolution)
Value:
86
Sampling time:
21 d
Parameter:
% degradation (CO2 evolution)
Value:
90
Sampling time:
28 d

BOD5 / COD results

Results with reference substance:
22 % degradation after 2 d
43 % degradation after 3 d
57 % degradation after 4 d
65 % degradation after 5 d
70 % degradation after 6 d
73 % degradation after 7 d
75 % degradation after 9 d
78 % degradation after 14 d
81 % degradation after 21 d
84 % degradation after 28 d
85 % degradation after 29 d

Any other information on results incl. tables

Sodium benzoate had been biodegraded by 65% after 5 days and 85% after 29 days in the absence of the test item, and by 60% after 5 days in its presence, which confirmed that the test item was not inhibitory to the activity of the microbial inoculum. Cumulative levels of CO2 production in the controls after 29 days (65.5 and 70.4 mg C02) were within the acceptable range for this assay system (recommended maximum = 120 mg C02 for a three-litre culture). These results confirm that the inoculum was viable and that the test was valid. Mean cumulative C02 production by mixtures containing the test item was rapid and equivalent to 10% of the theoretical value (TC02, 110.1 mg CO2) after approximately 2 days of incubation, 61% after 5 days and 79% by Day 9. The rate of CO2 evolution then slowed and had achieved 91% of the TCOz by the end of the test on Day 29.

Substances are considered to be readily biodegradable in this test if CO2 production is equal to or greater than 60% of the theoretical value within ten days of the level achieving 10%. The test item can, therefore, be considered to be readily biodegradable.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test item showed a biodegradation rate of 90% after 28 days. Based upon the results of this test, the test substance can be considered to be readily biodegradable.
Executive summary:

The test item was tested for ist ready biodegradability according to OECD-Guideline No. 301B, EU-Testing Method C.4 -C and in conformity with GLP-principles. The study was performed from January - February 2006.

Based on the mean biodegradation rate of 90% after 28 days, the test item was found to be readily biodegradable in this test system.