Benzoic acid, C12-15-alkyl esters

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:

24. Feb. 2010 - 13. Apr. 2010

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:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Activated sludge from the municipal wastewater treatment plant Breisgauer Bucht was used as inoculum with a concentration corresponding to 30 mg dry solids per litre. The treatment plant clarifies predominantly domestic wastewater and has a capacity of 600.000 inhabitant equivalents. Sampling date of activated sludge was on march 2nd, 2010. Dry solid of the activated sludge was 5.72 g/l by weight measurements after 2 h drying at 105°C (mean of triplicate measurements). The activated sludge was washed twice by settling the sludge, decanting the supernatant and re-suspending the sludge in tap water.

Duration of test (contact time):

28 d

Initial conc.:

15.67 mg/L

Based on:

test mat.

Initial conc.:

20 mg/L

Based on:

other: TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral medium according to relevant OECD TG
- Test temperature: 20 - 21.5 °C
- pH adjusted: no
- Aeration of dilution water: aerated with CO2-free air at a rate of 30-100 ml/min overnight
- Suspended solids concentration: 30 mg dry solids/L


TEST SYSTEM
- Culturing apparatus: glas containers (2000 mL gas wash bottles)
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: aeration
- Measuring equipment: total carbon analyser (TOC-5000A Shimadzu with an autosampler ASI-5000A)
- Test performed in open system: yes
- Details of trap for CO2 and volatile organics if used: two CO2-absorber flasks connected in line with 0.2 M NaOH
- Other:

SAMPLING
- Sampling frequency: 8 samling dates
- Sampling method: 4 ml NaOH from the first of two CO2-absorber flasks connected in line was sampled and the IC's were determined
- Other:

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3
- Reference substance: 3
- Other:

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

102.8

Sampling time:

28 d

Remarks on result:

other: 10 day window criterion satisfied

Details on results:

The degradation extent of the test item was 102.8% within 28 days after acidification (mean of three replicates). For finding the exact position of the 10-d-window the degradation extents of the days without measurement were calculated by interpolation.

On day 1 the calculated mean degradation extent of the test item was for the first time higher than 10% (mean value: 12.1%). According, the end of the 10-d window is on day 11. On day 7 the mean degradation extent of the test item already reached 81.9%. Therefore the test item reached the pass level for ready biodegradability (60% ThCO2 and 10 d-window).

The highest mean CO2-evolution of the blank flasks was 29.6 mg/l within 28 days after acidification.

Results with reference substance:

The reference compound sodium benzoate reached the pass levels for ready
biodegradability within 4 days

Ultimate Biodegradation after x days (% of ThCO2)

Reactor	Day	0	4	7	11	14	21	28	29
7	Test flasks	0	58.6	88.6	101.8	104.7	105.3	108.0	108.2
8		0	43.1	79.7	92.3	95.1	96.9	100.2	100.9
9		0	45.3	77.4	89.6	92.6	95.0	99.6	99.3
4	Reference flasks	0	82.1	93.7	100.5	101.2	101.1	105.1	103.2
5		0	81.1	92.9	95.8	99.8	101.2	102.0	100.6
6		0	81.2	94.5	98.9	102.0	102.2	102.6	104.5

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The degradation of the test item was 102.8% within 28 days (after acidification). The test item reached the criterion for ready biodegradability.

Executive summary:

Benzoic acid, C12 -15 -alkyl esters was tested in a Modified Sturm Test according to the OECD Guideline for the Testing of Chemicals, No.: 301 B, July 17^th, 1992: Ready Biodegradability, CO2Evolution Test (Modified SturmTest) for 28 days (and 29 days after acidification) to determine whether the test substance is readily biodegradable. In the Modified Sturm Test the evolution of carbon dioxide shows the degree of mineralisation of the test substance. Degradation was followed over 28 days by determining the carbon dioxide (CO2) produced. The CO2was trapped in sodium hydroxide solution which was measured for its inorganic carbon content on 8 sampling dates. The amount of carbon dioxide produced from the test substance (corrected for that derived from the blank inoculum) was expressed as a percentage of the theoretical carbon dioxide production (ThCO2).The test was carried out with one concentrations of the test substance corresponding to 20 mg carbon per litre. At the end of the exposure period a degradation rate of 102.8 % of the Theoretical CO2(ThCO2) of the test substance was measured. The pass level (= 60 % ThOD for respirometric methods according to the OECD-Guideline 301) was reached within the 10-day time window. The test substance can be considered to be readily biodegradable within a test period of 28 days.

Description of key information

The degradation of the test item was 102.8% within 28 days (after acidification). The test item reached the criterion for ready biodegradability.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

Benzoic acid, C12 -15 -alkyl esters was tested in a Modified Sturm Test according to the OECD Guideline for the Testing of Chemicals, No.: 301 B, July 17^th, 1992: Ready Biodegradability, CO2Evolution Test (Modified SturmTest) for 28 days (and 29 days after acidification) to determine whether the test substance is readily biodegradable. In the Modified Sturm Test the evolution of carbon dioxide shows the degree of mineralisation of the test substance.Degradation was followed over 28 days by determining the carbon dioxide (CO2) produced. The CO2was trapped in sodium hydroxide solution which was measured for its inorganic carbon content on 8 sampling dates. The amount of carbon dioxide produced from the test substance (corrected for that derived from the blank inoculum) was expressed as a percentage of the theoretical carbon dioxide production (ThCO2).The test was carried out with one concentrations of the test substance corresponding to 20 mg carbon per litre. At the end of the exposure period a degradation rate of 102.8 % of the Theoretical CO2(ThCO2) of the test substance was measured. The pass level (= 60 % ThOD for respirometric methods according to the OECD-Guideline 301) was reached within the 10-day time window. The test substance can be considered to be readily biodegradable within a test period of 28 days.