Registration Dossier

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:
20 May 2003 - 9 December 2003
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2004
Report Date:
2004

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
EPA OPPTS 835.3120 (Sealed Vessel Carbon Dioxide Production Test)
Deviations:
yes
Remarks:
No expiry date for the substance was supplied / Temperature range during study exceeded specification of 0.2C
Principles of method if other than guideline:
Method was based on ISO Standard 14593:1999, which is essentially equivalent to US EPA OPPTS 835.3120
GLP compliance:
yes
Remarks:
QA statement included in the study report

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Remarks:
White powder
Specific details on test material used for the study:
Based on the empirical formula of the test substance, its carbon content expressed as a percentage by weight is 61.1%. This value was used in setting the concentration of test substance to be applied in the study.

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 one of the return lines at Burley Menston sewage treatment works (Yorkshire water), a treatment works with a wastewater catchment that is predominantly domestic. On arrival at the laboratory, the sample was aerated by means of a CO2-free compressed air supply delivered through a diffuser block.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
ca. 10 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
inorg. C analysis
Details on study design:
Three treatment groups were established. Control: Inoculated mineral salts medium alone. Reference: Inoculated mineral salts medium plus sodium benzoate at 15 mgC/L. Test: Inoculated mineral salts medium plus Thio Acid (GR46580X) at 10mgC/L.
Incubation and test measurements were conducted in a facility where the temperature was maintained at a nominal 21C. Temperatures recorded during the study fell between 19.8 and 20.8C and were essentially compliant with the Test Guideline requirement that the temperature be maintained in the range 20 to 25C, with the overall variation not exceeding +/- 2C.
Reference substance
Reference substance:
benzoic acid, sodium salt
Remarks:
at 15 mgC/L

Results and discussion

Test performance:
The ISO standard states that degradation of the reference substance should be at least 60% on the 14th day of incubation. Degradation of sodium benzoate was 91% on day 14, thus satisfying this requirement. The ISO standard states that the control IC value at day 28 should be no more than 15% of the organic carbon added as test compound. Although the mean reached 25.6% at this time, this was considered to be due to absorption of atmospheric carbon dioxide by the sodium hydroxide solution. There was no adverse effect on this study.
% Degradation
Parameter:
% degradation (inorg. C analysis)
Value:
< 1
Sampling time:
28 d
Details on results:
The mean inorganic carbon yield attributable to Thio Acid (GR46580X) was less than 1% of the initial organic carbon loading throughout the time course of this study. Although Thio Acid (GR46580X) did not undergo significant mineralisation under the conditions employed in this study, this is not necessarily an indication that Thio Acid (GR46580X) would persist or accumulate in the environment.

Any other information on results incl. tables

See attached "Biodegradation"

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The mean inorganic carbon yield attributable to Thio Acid (GR46580X) was less than 1% of the initial organic carbon loading throughout the time course of this study. Although Thio Acid (GR46580X) did not undergo significant mineralisation under the conditions employed in this study, this is not necessarily an indication that Thio Acid (GR46580X) would persist or accumulate in the environment.
Executive summary:

The ultimate biodegradability of Thio Acid (GR46580X) was assessed by measuring the yield of inorganic carbon recovered under standard test conditions. The methods used were as described in ISO standard 14593: Water quality - Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium - Method by analysis of inorganic carbon in sealed vessels (CO2 headspace test), and is essentially the same as that described in US EPA Guideline OPPTS 835.3210.

The mean inorganic carbon yield attributable to Thio Acid (GR46580X) was less than 1% of the initial organic carbon loading throughout the time course of this study. Although Thio Acid (GR46580X) did not undergo significant mineralisation under the conditions employed in this study, this is not necessarily an indication that Thio Acid (GR46580X) would persist or accumulate in the environment.

The mean inorganic carbon yield attributable to the reference substance, sodium benzoate, was 90% of the initial organic loading on days 14 and 28. These data satisfy the validity criteria stated in the ISO standard, and show that the microbial inoculum employed was exerting normal degrative activity.