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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:

22 Sept 2011 - 20 Oct 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Purity of a.i.: Approx. 82 %
- Purity of the dispersion: 5.038 %

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Fresh samples of activated sludge are withdrawn on September 22nd, 2011 from the sewage treatment plant Ruhrverband Klaranlage, Sunthelle 6, 57392 Schmallenberg, Germany, which is mainly fed with municipal wastewater. Since it was not necessary, the samples were not washed with mineral medium after the arrival at the laboratory but kept aerobic until use.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Remarks:

corresponding to 56 mg ThOD

Initial conc.:

20.6 mg/L

Based on:

test mat.

Remarks:

corresponding to 270 mg ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Test temperature: 22±1°C
- pH adjusted: yes (7.4 ±0.2)
- Aeration of dilution water: yes
- Continuous darkness: yes
- 29.6 mg dry mass inoculum/L

TEST SYSTEM
- Culturing apparatus: 500 mL glass vessels, fill volumr 250 mL
- Number of culture flasks/concentration: 2
- Measuring equipment: SAPROMAT respirometer

SAMPLING
- Sampling frequency: continuous measrurement

CONTROL AND BLANK SYSTEM
Test suspension A: 2 vessels containing test item (20.6 mg/L) and inoculum
Test suspension B: 2 vessels containing test item (100 mg/L) and inoculum
Inoculum blank: 2 vessels containing only inoculum
Abiotic control: 2 vessels containing test item (100 mg/L) and a sterilising agent
Procedural control: 2 vessels containing reference item (100 mg/L) and inoculum
Toxicity control: 2 vessels containing test item (100 mg/L), reference item (100 mg/L) and inoculum

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

69

Sampling time:

10 d

Remarks on result:

other: 100 mg/L

Parameter:

% degradation (O2 consumption)

Value:

82

Sampling time:

10 d

Remarks on result:

other: 20.6 mg/L

Parameter:

% degradation (O2 consumption)

Value:

80.7

St. dev.:

1.3

Sampling time:

28 d

Remarks on result:

other: 100 mg/L

Parameter:

% degradation (O2 consumption)

Value:

92.6

St. dev.:

3.8

Sampling time:

28 d

Remarks on result:

other: 20.6 mg/L

Details on results:

The biodegradation of the test item after 28 days of incubation in the static test was 93% (SD = 3.8%) and 81% (SD = 1.3%) in the assays with 20.6 mg/L and 100 mg/L, respectively.
The biodegradation within the 10-day-window was 82% and 69% in the assays with 20.6 mg/L and 100 mg/L, respectively. The 10-day-window starts at day 1 (20.6 mg/L) and day 2 (100 mg/L), respectively.
No significant abiotic degradation of the test item was noticeable after 28 days of incubation. The biodegradation of the item mixture in the toxicity control was 38% after 14 days of incubation. Thus, the demanded threshold value of 25% is exceeded and the test item can be identified as non-toxic in a ready biodegradability test.

Results with reference substance:

The reference item sodium benzoate was degraded to 85% within the first 14 days.

The test is considered valid, as

- the difference of extremes of replicate values of the removal of the test item at the end of the test was less than 20 %,

- the percentage degradation of the reference item has exceeded the pass level of 60 % by day 14,

- the oxygen uptake of the inoculum blank is < 60 mg/L in 28 days and the pH value was inside the range of 6.0 - 8.5.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

In conclusion, the test item can be identified as readily biodegradable under the chosen test conditions.

Executive summary:

The biodegradation of MDEA-Esterquat C18 unsatd. was investigated over a 28-day period in a Manometric Respirometry Test according to EC method C.4-D (440/2008/EEC) and OECD guideline 301 F (1992). The test medium was inoculated with microorganisms from a digester of a sewage treatment plant mainly fed with municipal wastewater.

The test solutions were stirred in closed flasks at 22 °C ± 1°C for 28 days. The rate of degradation was monitored by measuring the quantity of oxygen required to maintain a constant gas volume in the respirometer flasks over a 28-d period. The amount of oxygen taken up by the microbial population during biodegradation of the test item at a concentration of 20.6 mg/L (ThOD = 56 mg) and 100 mg/L (ThOD = 270 mg), respectively, corrected for uptake by the blank inoculum run in parallel, was expressed as a percentage of the ThOD (theoretical oxygen demand). In order to check the procedure, sodium benzoate was used as a degradable reference item at a concentration of 100 mg/L, along with a toxicity control at 100 mg/L test item and 100 mg/L sodium benzoate.

The biodegradation of the test item in the static test was found to be 93 % with a standard deviation of 3.8% for a concentration of 20.6 mg test item per liter and 81 % with a standard deviation of 1.3% for a concentration of 100 mg test item per liter after 28 days. For a concentration of 20.6 mg test item per liter biodegradation within the 10-day-window — which started at day 1 — was found to be 82%. For a concentration of 100 mg test item per liter biodegradation within the 10-day-window — which started at day 2 — was found to be 69 %. Here to mention is that the test item suspension with a concentration of 20.6 mg/L already meets the criteria of 50 - 100 mg ThOD or COD/L, as demanded in the guideline.

The degradation of the reference substance sodium benzoate had reached 85 % within the first 14 days. The difference of extremes of replicate values of the removal of the test item at the end of the test is less than 20%. Therefore, the test can be considered as valid.

No inhibitory effects of the test item were observed (more than 25 % degradation occurred within 14 days) in the toxicity control.

MDEA-Esterquat C18 unsatd. can be considered to be readily biodegradable under the chosen test conditions.

 

Description of key information

readily biodegradable (OECD TG 301F, RL1, GLP)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

The biodegradation of MDEA-Esterquat C18 unsatd. was investigated over a 28-day period in a Manometric Respirometry Test according to EC method C.4-D (440/2008/EEC) and OECD guideline 301 F (1992). The test medium was inoculated with microorganisms from a digester of a sewage treatment plant mainly fed with municipal wastewater.

The test solutions were stirred in closed flasks at 22 °C ± 1°C for 28 days. The rate of degradation was monitored by measuring the quantity of oxygen required to maintain a constant gas volume in the respirometer flasks over a 28-d period. The amount of oxygen taken up by the microbial population during biodegradation of the test item at a concentration of 20.6 mg/L (ThOD = 56 mg) and 100 mg/L (ThOD = 270 mg), respectively, corrected for uptake by the blank inoculum run in parallel, was expressed as a percentage of the ThOD (theoretical oxygen demand). In order to check the procedure, sodium benzoate was used as a degradable reference item at a concentration of 100 mg/L, along with a toxicity control at 100 mg/L test item and 100 mg/L sodium benzoate.

The biodegradation of the test item in the static test was found to be 93 % with a standard deviation of 3.8% for a concentration of 20.6 mg test item per liter and 81 % with a standard deviation of 1.3% for a concentration of 100 mg test item per liter after 28 days. For a concentration of 20.6 mg test item per liter biodegradation within the 10-day-window — which started at day 1 — was found to be 82%. For a concentration of 100 mg test item per liter biodegradation within the 10-day-window — which started at day 2 — was found to be 69 %. Here to mention is that the test item suspension with a concentration of 20.6 mg/L already meets the criteria of 50 - 100 mg ThOD or COD/L, as demanded in the guideline.

The degradation of the reference substance sodium benzoate had reached 85 % within the first 14 days. The difference of extremes of replicate values of the removal of the test item at the end of the test is less than 20%. Therefore, the test can be considered as valid.

No inhibitory effects of the test item were observed (more than 25 % degradation occurred within 14 days) in the toxicity control.

MDEA-Esterquat C18 unsatd. can be considered to be readily biodegradable under the chosen test conditions.