Thermal cracking oil from blends of rubber, fuel oils and paraffin waxes, steam distillation concentrate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

May 13 2019 - September 10 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Method C.29 of Commission Regulation (EU) No 260/2014

Deviations:

no

Principles of method if other than guideline:

Aliquots of inoculated medium were dispensed into replicate bottles to give a headspace to liquid ratio of approximately 1:5 (i.e. 133 ml liquid into the 160 ml-capacity bottles). This ratio was deviating from the recommended ratio of 1:2, since according to the guidelines, a smaller headspace volume may be used when testing substances which are more volatile (Henry’s law constant > 50 Pa·m3/mol).

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Domestic sewage treatment plant, ARA Birs (Birsfelden / Switzerland)
- Pretreatment: The aerobic activated sewage sludge was washed three times by centrifugation, decantation of the supernatant liquid phase and resuspension of the solid material in mineral medium. Aliquots of the homogenized final sludge suspension were weighed, thereafter dried and the dry weight of the suspended solids was determined.
- Concentration of sludge: Calculated amounts of wet sludge were suspended in mineral medium to obtain a concentration equivalent to 4 g dry material per liter. Prior to use, the dry weight of the sludge was again determined and the sludge was diluted with mineral medium to a concentration of 1 g dry material per liter. Defined volumes of the diluted activated sludge were added to the mineral medium in the test vessels to obtain a final concentration of 4 mg dry material per liter.
- Water filtered: yes (purified water)
- Type and size of filter used, if any: ELGA PURELAB Option-Q water purification system

Duration of test (contact time):

28 d

Initial conc.:

17.3 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Parameter followed for biodegradation estimation:

inorg. C analysis

Details on study design:

TEST CONDITIONS
- Composition of medium: according to the testing guidelines
- Test temperature: 20°C
- pH: 7.6
- pH adjusted: no
- CEC (meq/100 g): Not applicable
- Suspended solids concentration: 4 mg/L
- Continuous darkness: yes


TEST SYSTEM
- Culturing apparatus: 125 mL Wheaton glass serum bottles,with a total volume of around 160 mL, sealed with aluminium crimp caps with Teflon lined chlorobutyl septa.
- Number of culture flasks/concentration: 5
- Method used to create aerobic conditions: The test was performed in sealed bottles with a headspace of air, which provided a reservoir of oxygen for aerobic biodegradation
- Measuring equipment: TOC infrared gas analyzer vario TOC cube from Elementar Analysensysteme GmbH, Langenselbold, Germany
- Test performed in closed vessels due to significant volatility of test substance: Yes
- Details of trap for CO2 and volatile organics if used: Aliquots of inoculated medium were dispensed into replicate bottles to give a headspace to liquid ratio of approximately 1:5 (i.e. 133 ml liquid into the 160 ml-capacity bottles). All bottles were sealed with Teflon-lined chlorobutyl septa and aluminum caps.

SAMPLING
- Sampling frequency:Bottles were sacrificed for analysis on the following sampling days: Test item and inoculum control: Exposure day 0, 2, 5, 7, 9, 14, 21 and 28,Procedure control: Exposure day 0, 2, 7, 14 and 28, Toxicity control: Exposure day 0, 7, 14 and 28.Triplicate bottles were measured on each sampling occasion throughout the test. Five bottles from each series (except the toxicity control) were analyzed at the end of the test, on day 28, to enable 95 % confidence intervals to be calculated for the mean percentage biodegradation value.
- Sampling method: CO2 production in the bottles was determined by measuring the increase in the concentration of inorganic carbon (IC) during incubation. By the addition of alkali and shaking, complete CO2 was converted to carbonate and the concentration of IC in the headspace was negligible. Samples for analysis were withdrawn from the liquid phase.This was done as follows: an aliquot (1 mL) of a 7M NaOH solution was injected through the septum of each bottle sampled and the bottles were shaken for 1 hour at the test temperature. The same NaOH solution was used for all bottles sacrificed on a particular day and its IC content was determined. The test bottles were removed from the shaker and allowed to settle. Suitable
volumes of the liquid phase were withdrawn and subjected to IC analyses.
- Sample storage before analysis: Triplicate bottles were measured on each sampling occasion throughout the test. The test was conducted at 20°C, in a temperature-controlled environment. The bottles were incubated in the dark.


CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes
- Abiotic sterile control: Not addressed
- Toxicity control: Yes


STATISTICAL METHODS: Not addressed

Reference substance:

other: 1-Octanol

Key result

Parameter:

% degradation (CO2 evolution)

Value:

31

Sampling time:

28 d

Details on results:

At the end of the test, on exposure day 28, the mean percentage biodegradation of the five test item bottles sampled was calculated to be 31 % with a 95 % confidence interval of ± 1.3 %. Therefore, the pass level for ready biodegradability, i.e. an IC formation of at least 60 % of the theoretical maximum IC production (ThIC) in a 10-day window within the 28-day period of the test, was not reached.

Results with reference substance:

The reference item 1-octanol was degraded by an average of 69 % and 76 % by exposure day 7 and 14, respectively, thus confirming suitability of the activated sludge (> 60 % degradation by exposure day 14). At the end of the 28-day exposure period, the mean percentage biodegradation of the five procedure control bottles sampled was 84 % with a 95 % confidence interval of ± 1.2 %.

In the toxicity control, containing both the test item and the reference item, no inhibitory effect on the biodegradation of the reference item was determined. Thus, Thermal cracking oil from blends of rubber, fuel oils and paraffin waxes, steam distillation condensate had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 17.3 mg/L (corresponding to 15.1 mg C/L). The validity criteria of the test were met.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

In conclusion, Thermal cracking oil from blends of rubber, fuel oils and paraffin waxes, steam distillation condensate was found to be not readily biodegradable under the test conditions within 28 days.

Executive summary:

In accordance with GLP, the test item Thermal cracking oil from blends of rubber, fuel oils and paraffin waxes, steam distillation condensate was investigated for its ready biodegradability in a Headspace Test (CO2 in sealed vessels) over 28 days according to the OECD Guideline for Testing of Chemicals, No. 310 (2014) and the Method C.29 of Commission Regulation (EU) No 260/2014. The inorganic carbon (IC) production in the test vessels containing the test item Thermal cracking oil from blends of rubber, fuel oils and paraffin waxes, steam distillation condensate increased from the start until the end of the test, on exposure day 28. No plateau was reached. At the end of the test, on exposure day 28, the mean percentage biodegradation of the five test item bottles sampled was calculated to be 31 % with a 95 % confidence interval of ± 1.3 %. Therefore, the pass level for ready biodegradability, i.e. an IC formation of at least 60 % of the theoretical maximum IC production (ThIC) in a 10-day window within the 28-day period of the test, was not reached. In conclusion, Thermal cracking oil from blends of rubber, fuel oils and paraffin waxes, steam distillation condensate was found to be not readily biodegradable under the test conditions within 28 days. The obtained biodegradation value of 31 % may be used to indicate inherent, primary biodegradability, based on paragraph 36 of the “Revised Introduction to the OECD Guidelines for Testing of Chemicals, Section 3” (2006). In the procedure control, the reference item 1-octanol was degraded by an average of 69 % and 76 % by exposure day 7 and 14, respectively, thus confirming suitability of the activated sludge (> 60 % degradation by exposure day 14). At the end of the 28-day exposure period, the mean percentage biodegradation of the five procedure control bottles sampled was 84 % with a 95 % confidence interval of ± 1.2 %. In the toxicity control, containing both the test item and the reference item, no inhibitory effect on the biodegradation of the reference item was determined. Thus, Thermal cracking oil from blends of rubber, fuel oils and paraffin waxes, steam distillation condensate had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 17.3 mg/L (corresponding to 15.1 mg C/L). The validity criteria of the test were met.

Description of key information

In accordance with GLP, the test item Thermal cracking oil from blends of rubber, fuel oils and paraffin waxes, steam distillation condensate was investigated for its ready biodegradability in a Headspace Test (CO2 in sealed vessels) over 28 days according to the OECD Guideline for Testing of Chemicals, No. 310 (2014) and the Method C.29 of Commission Regulation (EU) No 260/2014. The inorganic carbon (IC) production in the test vessels containing the test item Thermal cracking oil from blends of rubber, fuel oils and paraffin waxes, steam distillation condensate increased from the start until the end of the test, on exposure day 28. No plateau was reached. At the end of the test, on exposure day 28, the mean percentage biodegradation of the five test item bottles sampled was calculated to be 31 % with a 95 % confidence interval of ± 1.3 %. Therefore, the pass level for ready biodegradability, i.e. an IC formation of at least 60 % of the theoretical maximum IC production (ThIC) in a 10-day window within the 28-day period of the test, was not reached. In conclusion, Thermal cracking oil from blends of rubber, fuel oils and paraffin waxes, steam distillation condensate was found to be not readily biodegradable under the test conditions within 28 days. The obtained biodegradation value of 31 % may be used to indicate inherent, primary biodegradability, based on paragraph 36 of the “Revised Introduction to the OECD Guidelines for Testing of Chemicals, Section 3” (2006). In the procedure control, the reference item 1-octanol was degraded by an average of 69 % and 76 % by exposure day 7 and 14, respectively, thus confirming suitability of the activated sludge (> 60 % degradation by exposure day 14). At the end of the 28-day exposure period, the mean percentage biodegradation of the five procedure control bottles sampled was 84 % with a 95 % confidence interval of ± 1.2 %. In the toxicity control, containing both the test item and the reference item, no inhibitory effect on the biodegradation of the reference item was determined. Thus, Thermal cracking oil from blends of rubber, fuel oils and paraffin waxes, steam distillation condensate had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 17.3 mg/L (corresponding to 15.1 mg C/L). The validity criteria of the test were met.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater