Octadecanedioic acid, 1,18-dimethyl ester

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:

2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3100 (Aerobic Aquatic Biodegradation)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

The activated sludge was collected at the Columbia Wastewater Treatment Plant in Columbia, Missouri, which predominantly treats domestic sewage. Approximately 1.0 L of activated sludge was collected from Aeration Basin #1.

The activated sludge was homogenized in a blender at a medium speed for two minutes. The homogenized sludge was allowed to settle for 30 to 60 minutes then filtered through glass wool. A volume of 30 mL of the filtrate was used as the inoculum for each reaction flask. The suspended solids concentration in each filtered solution was determined by filtering three 10 mL aliquots of sludge through pre-weighed Whatman glass-fiber filter pads, followed by drying on a Mettler HR73P halogen moisture analyzer. The increase in weight of the filter pads was used to determine the suspended solids level. The suspended solids concentration of the prepared activated sludge was determined in the triplicate aliquots to be 1.3, 0.7, and 1.2 g/L, which correspond to a mean of 1.1 g/L. Therefore, the total concentration of suspended solids in each reaction flask (30 mL of inoculum to 3,000 mL of test medium) was 11 mg/L.

Duration of test (contact time):

21 d

Initial conc.:

10 mg/L

Based on:

other: Carbon from test substance per liter

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

Test Procedures
Pre-Initiation Procedures
One day prior to dosing, six test systems were assembled. Each 5-L carboy received 2,400 mL of mineral salts medium and 30 mL of the prepared activated sludge. Stirring and aeration with CO2-free air at approximately 90 mL/minute were started for each flask. The flasks were allowed to aerate overnight to purge the systems of CO2 before initiation of the test (dosing on Day 0).

Initiation (Day-0) Procedures
Duplicate control systems were prepared by adding 570 mL of reagent water to the 5-L carboys. The final volume was 3,000 mL. Duplicate test substance systems were prepared by adding 570 mL of reagent water and approximately 43 mg (dosed gravimetrically) of test substance to two of the 5-L carboys. The nominal concentration of carbon from the test substance in the final volume of 3,000 mL of solution was 10 mg C/L.

The reference substance system was prepared by adding 467 mL of reagent water and 103 mL of 1.00-mg/mL reference substance stock solution to a 5-L carboy. The nominal concentration of carbon from the reference substance in the final volume of 3,000 mL of solution was 20 mg C/L. The toxicity control system was prepared by adding 467 mL of reagent water, 103 mL of the 1.00-mg/mL reference substance stock solution, and approximately 43 mg (dosed gravimetrically) of test substance to a 5-L carboy. The nominal concentration of carbon from the toxicity system in the final volume of 3,000 mL of solution was 30 mg C/L.

After all additions, each of the reaction flasks was connected to a series of three traps containing 100 mL of 0.2 N KOH. Aeration and stirring of the flasks were continued. Flow meters connected to the test systems were adjusted to facilitate airflow at 50-100 mL/min. The bubbling of air and stirring in each flask, as well as the bubbling in each trap, confirmed the constant aeration.

Approximately one hour after dosing, approximately 80 mL of each test solution was removed, and the pH of each of the test solution was measured. One sample was filtered with a 0.45-μm nylon filter (sample for DOC analysis) and both samples were deposited into autosampler bottles, which were stored refrigerated until analysis for dissolved organic carbon (DOC) and inorganic carbon (IC) concentrations.

Sampling of 0.2 N KOH Trapping Solution
The CO2 produced in the test systems was trapped in the 0.2 N KOH solutions, which were then analyzed for inorganic carbon (IC) content. Samples of the KOH solutions were collected for CO2 analysis on Days 0, 2, 5, 7, 9, 12, 15, 19, 21, and 22.

Reference substance:

benzoic acid, sodium salt

Remarks:

20 mg Carbon/L

Test performance:

The toxicity control, sodium benzoate plus ODDAME, exhibited a % ThCO2 value of 41.5% on Day 5 of the study. The value through Day 22 of the study was 86.7% ThCO2. Since the biodegradation value was greater than 25% ThCO2 by day 22, the test substance can be assumed to not be inhibitory.

Microbial evaluation showed the test substance had no significant effects on the population of microbes, and the microbial populations in the inoculum were viable.

Parameter:

% degradation (CO2 evolution)

Value:

62

Sampling time:

9 d

Remarks on result:

other: Replicate A

Parameter:

% degradation (CO2 evolution)

Value:

67.9

Sampling time:

9 d

Remarks on result:

other: Replicate B

Key result

Parameter:

% degradation (CO2 evolution)

Value:

110.4

Sampling time:

22 d

Details on results:

The test substance, ODDAME, exhibited % ThCO2 values (after correction for background CO2
from the controls) of 62.0% for replicate A and 67.9 for replicate B at Day 9 of the study, and were within 20% of each other at the end of the 10-day window. The mean % ThCO2 value through Day 22 of the study was 110.4%. Since biodegradation values exceeded 60% ThCO2 within a 10 day window, these results indicate that the test substance may be classified as readily biodegradable

The final % ThCO2 levels exhibited by the test substance treatments were higher than desired, i.e. greater than 100%. However, if the biodegradation values were corrected by 10%, the test substance would still have biodegradation values exceeding 60% within a 10-day window. For example, the mean at Day 2 and Day 12 was 5.5 and 79.3% ThCO2, respectively. Corrected for a 10% reduction, the mean at Day 2 and Day 12 would by 0 and 69.3% ThCO2, respectively.

Results with reference substance:

The reference substance, sodium benzoate, exhibited a % ThCO2 value of 61.7% on Day 5 of the study. The value through Day 22 of the study was 100.2% ThCO2. The results from Day 5 (61.7% ThCO2 evolved) indicated greater than 60% ThCO2 evolved in the first 5 days of the test. These results indicate that the inoculum was viable according to the criteria outlined in the applicable testing guideline.

pH and temperature:

The pH of the control solutions were 7.11 and 7.16 at study initiation and 7.59 and 7.52 at termination for replicates A and B. The pH of the test solutions were 7.52 and 7.57 at study initiation and 7.57 and 7.61 at termination for replicates A and B. The pH of the reference system increased from 7.07 at study initiation to 7.92 at study termination. The pH of the toxicity control system was 7.50 at study initiation and 7.85 at study termination. All pH values were suitable for biological systems.

The average temperature of the environmental chamber ranged from 21.67 to 22.15 °C during the test duration.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The mean percent theoretical CO2 produced by the test substance, ODDAME, was 64.9% by Day 9 of the study and 110.4% by Day 22 of the study. Since the biodegradation value exceeded 60% ThCO2 within a 10-day window, the test substance may be classified as readily biodegradable from the results of this study.

Executive summary:

A study was performed to assess the ready biodegradability of the test item in an aerobic aqueous medium. The method followed was designed to be compatible with the OECD Guideline 301 B  and U.S. EPA OPPTS 835.3100 The test item, at a concentration of 10 mg carbon/L was exposed to inoculum consisting of sewage treatment microorganisms with mineral medium in sealed culture vessels for 21 days. The degradation of the test item was assessed by measurement of evolved CO2 values. Control solutions with inoculum and the reference item, sodium benzoate, together with a toxicity control were used for validation purposes. The test item attained a mean degradation value of 64.9% degradation by Day 9 and 110.4% by Day 22 and satisfied the 10-day window validation criterion. Octadecanedioic acid dimethyl ester (ODDAME) is therefore considered to be readily biodegradable from the results of this study. The reference item attained 61.7% degradation by Day 5, confirming the inoculum was viable. The toxicity control attained 41.5% by Day 5, confirming the test substance is not inhibitory (ABC Lab, 2013).

Description of key information

A reliable study was performed in accordance with GLP and OECD Guideline 301B to assess the ready biodegradability of octadecanedioic acid dimethyl ester (ODDAME) in an aerobic aqueous media. The test item, at a concentration of 10 mg carbon/L was exposed to inoculum consisting of sewage treatment microorganisms with mineral medium in sealed culture vessels for 21 days. The degradation of the test item was assessed by measurement of evolved CO2 values. Control solutions with inoculum and the reference item, sodium benzoate, together with a toxicity control were used for validation purposes.

The test item attained a mean degradation value of 64.9% degradation by Day 9 and 110.4% by Day 22 and satisfied the 10 day window validation criterion. Octadecanedioic acid dimethyl ester (ODDAME) is therefore considered to be readily biodegradable from the results of this study.

The reference item attained 61.7% degradation by Day 5, confirming the inoculum was viable. The toxicity control attained 41.5% by Day 5, confirming the test substance is not inhibitory.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

A study was performed to assess the ready biodegradability of the test item in an aerobic aqueous medium. The method followed was designed to be compatible with the OECD Guideline 301 B  and U.S. EPA OPPTS 835.3100 The test item, at a concentration of 10 mg carbon/L was exposed to inoculum consisting of sewage treatment microorganisms with mineral medium in sealed culture vessels for 21 days. The degradation of the test item was assessed by measurement of evolved CO2 values. Control solutions with inoculum and the reference item, sodium benzoate, together with a toxicity control were used for validation purposes. The test item attained a mean degradation value of 64.9% degradation by Day 9 and 110.4% by Day 22 and satisfied the 10-day window validation criterion. Octadecanedioic acid dimethyl ester (ODDAME) is therefore considered to be readily biodegradable from the results of this study. The reference item attained 61.7% degradation by Day 5, confirming the inoculum was viable. The toxicity control attained 41.5% by Day 5, confirming the test substance is not inhibitory (ABC Lab, 2013).