Nonanoic acid

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:

experimental phase: 04 Dec 1998 - 06 Jan 1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Cited as Directive 92/69/EEC, C.4-C

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

other: activated sludge, predominantly domestic, non-adapted

Details on inoculum:

A sample of activated sludge was collected on the day before the test from Oakley sewage treatment works, which treats predominantly domestic waste. Aliquots (25 ml) of a homogenised sample were filtered through dried (approximately 105°C) and pre-weighed Whatman GFC 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 final suspended solids concentration of 30 mg/l.

Duration of test (contact time):

29 d

Initial conc.:

10 mg/L

Based on:

test mat.

Initial conc.:

30 mg/L

Based on:

COD

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral salts medium according to guideline
- Additional substrate: none
- Solubilising agent (type and concentration if used): none
- Test temperature: 20-24 °C
- pH: day 0: 7.3-7.5; day 29: 7.5-7.7
- pH adjusted: no
- CEC (meq/100 g): no data
- Aeration of dilution water: yes
- Suspended solids concentration: 30 mg/L
- Continuous darkness: not explicitly stated - however, study performed according to OECD 301; as such, incubation either in darkness or diffuse light.


TEST SYSTEM
- Culturing apparatus: 5-L glass culture bottles
- Number of culture flasks/concentration: 2/test substance
- Method used to create aerobic conditions: aerated continuously with CO2-free air
- Measuring equipment: titration of 20 mL samples (in duplicate) from traps with 0.05 N HCl using phenolphthalein indicator
- Test performed in closed vessels due to significant volatility of test substance: no
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: CO2 traps containing 0.0125 M barium hydroxide solution (3 Drechsel bottles connected in series)


SAMPLING
- Sampling frequency: day 2, 3, 4, 6, 8, 10, 15, 22, 28 and 29
- Sampling method: 20 mL samples (in duplicate) from CO2 traps
- Sterility check if applicable: no
- Sample storage before analysis: no


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes (2 flasks)
- Abiotic sterile control: no
- Toxicity control: yes (1 flask)
- Other: reference (1 flask)

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

>= 12 - <= 17

Sampling time:

2 d

Parameter:

% degradation (CO2 evolution)

Value:

>= 45 - <= 49

Sampling time:

6 d

Key result

Parameter:

% degradation (CO2 evolution)

Value:

>= 60 - <= 62

Sampling time:

10 d

Parameter:

% degradation (CO2 evolution)

Value:

>= 65 - <= 69

Sampling time:

15 d

Key result

Parameter:

% degradation (CO2 evolution)

Value:

>= 68 - <= 75

Sampling time:

28 d

Results with reference substance:

The reference substance sodium benzoate was degraded to 70% within 10 days and to 76 % within 22-29 days.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The test substance is readily biodegradable according to OECD criteria in the modified Sturm test (OECD 301 B).

Executive summary:

The ready biodegradability of nonanoic acid was tested in the Modified Sturm test according to OECD TG 301 B. Non-adapted activated sludge from a wastewater treatment plant treating predominantly domestic sewage served as the inoculum. The test mixtures (in duplicate) were incubated over 28 d at 20-24 °C. The evolving CO2 was trapped in barium hydroxide solution and analysed after 2, 3, 4, 6, 8, 10, 15, 22, 28 and 29 days (after acidification on day 28). After 28 days the degradation reached 68 -75 % ThCO2 (n=2). The 10-d window was met.

Based on the results of a toxicity control (sodium benzoate plus test item), at a test item concentration of 10 mg carbon /L no inhibition (inoculum toxicity) was observed.

Description of key information

The test substance is readily biodegradable according to OECD criteria in the modified Sturm test (OECD 301 B; Celanese, 1999).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

The ready biodegradability of nonanoic acid was tested in the Modified Sturm test according to OECD TG 301 B (Celanese, 1999). Non-adapted activated sludge from a wastewater treatment plant treating predominantly domestic sewage served as the inoculum. The test mixtures (in duplicate) were incubated over 28 d at 20-24 °C. The evolving CO2 was trapped in barium hydroxide solution and analysed after 2, 3, 4, 6, 8, 10, 15, 22, 28 and 29 days (after acidification on day 28). After 28 days the degradation reached 68 -75 % ThCO2 (n=2). The 10-d window was met.

Based on the results of a toxicity control (sodium benzoate plus test item), at a test item concentration of 10 mg carbon /L no inhibition (inoculum toxicity) was observed.