A mixture of: propan-2-one-O,O'-(methoxymethylsilandiyl)dioxime; propan-2-one-O-(dimethoxymethylsilyl)oxime; propan-2-one-O,O',O''-(methylsilantriyl)trioxime

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:

From October 4, 2004 to November 3, 2004

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

According to OECD Guideline 301 B, with GLP.

Qualifier:

according to guideline

Guideline:

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

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:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Activated sludge was collected from a sewage treatment works A-2500 Baden, which waste-water catchment is predominantly domestic.
- Preparation of inoculum for exposure: On arrival in the laboratory, the sample was aerated by means of a filtered compressed air before being used for the study. The suspended solids concentration was determined by filtering a 5 mL sample through a pre-dried and pre-weighed glass filter (Whatman GF/C). The filter with solids were dried at 105 °C and re-weighed and the sludge solids determined by difference.
- Pre-treatment: The inoculum was not acclimatised or adapted before exposure to the test substance.
- Concentration of sludge: The concentration of the final suspended solids of the sludge in all vessels was nominally about 20 mg/L.

Duration of test (contact time):

28 d

Initial conc.:

15 other: mg/L (of organic carbon)

Based on:

DOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium:
a) KH2PO4 8.51 g
K2HPO4 21.75 g
Na2HPO4x 2H2O 33.40 g
NH4CI 0.50 g
pH 7.4, dissolved in deionised water and filled up to 1000 mL.
b) MgSO4 X 7H2O 22.50 g
dissolved in deionised water and filled up to 1000 mL.
c) CaCb x 2H2O 36.40 g
dissolved in deionised water and filled up to 1000 mL.
d) FeCb x 6H2O 0.25 g
dissolved in deionised water and filled up to 1000 mL.
30 mL of solution a) was added to 2400 mL deionised water, 3 mL each of the solutions b) to d) and 11 mL activated sludge were added and then made up to a total volume of 3000 mL deionised water.
- Test temperature: 21.6 ± 0.5 ºC
- pH: 7.35 – 7.62
- pH adjusted: no
- Aeration of dilution water: yes
- Suspended solids concentration: the concentration of suspended solids was not more than 30 mg/L.
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5 L flasks.
- Number of culture flasks/concentration: 2 flasks, each with 15 mg/L of nominal carbon concentration at the beginning.
- Method used to create aerobic conditions: Apparatus for carbon dioxide scrubbing and a mixture of CO2-freeoxygen and CO2-free
nitrogen, from gas cylinders (Linde Gase, A-2492 Eggendorf), in the correct proportions (20% O2: 80 % N2) were used. The air flow was regulated for each vessel individually. Air flow was determinated volumetrically in intervals. Adjustments were made as necessary to maintain a flow rate in the range of 30 to 100 mL per minute (1 - 3 bubbles per sec). As an added precaution, a 0.0125 M barium hydroxide solution was used as CO2absorber.
- Measurement equipment, details of trap for CO2: Barium hydroxide was used to trap the CO2 formed by the degradation of the test substance. Absorption bottles each containing 100 mL of 0.0125 M barium hydroxide solution, were connected in series to each 5-litre flask.
- Measurement of CO2 evolution: The amount of CO2 produced was determined by titrating the remaining Barium hydroxide with 0.05 M HCI (1.0997.3 Titrisol@,Merck KGaA, 64271 Darmstadt, Germany). Phenolphtalein (ACS Merck, 64271 Darmstadt, Germany) was used as a pH indicator. A factor of 5 was used to convert titres for 20 mL samples to values for the entire 100 mL wash-bottle contents and a second factor of 1.1 to convert volume-corrected titres to milligrams CO2.

SAMPLING
- Sampling frequency: The CO2 evolution was determined on Days 1, 2, 4, 6, 8, 10, 15, 20, 25 and 28/29
- Sample storage before analysis: The samples were analysed on the same day, except for Day 28, at which the incubation media were acidified with 1 mL 32 % HCl (Merck KGaA, 64271 Darmstadt, Germany) to release any residual CO2. CO2 was removed by continuous air flow overnight and absorber solutions were titrated on Day 29.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, the medium plus inoculum was used as negative control (2 replicates)
- Toxicity control: yes, this contained sodium benzoate and the test substance (1 replicate)
- Other: sodium benzoate was used as positive control substance (1 replicate)

Reference substance:

benzoic acid, sodium salt

Remarks:

(15 mg organic carbon per litre, theoretical yield of CO2 was 165 mg in 2 L medium)

Key result

Parameter:

% degradation (CO2 evolution)

Value:

32.1

Sampling time:

28 d

Details on results:

The final biodegradation for Wasox-MMAC2 was 32.1 %.
Toxicity control: Degradation in the toxicity control, which contained sodium benzoate and the test substance, was not indicative of an inhibition of the microbial activity by the test substance. The final biodegradation was 50.8 %.

Results with reference substance:

Positive control: The plateau of biodegradation was reached on about Day 10 and the degradation of the positive control substance sodium benzoate exceeded the pass level of 60 % on about Day 6.

Biodegradation as percentage of the theoretical CO2 yield.

Elapsed time	Test substance			Positive control	Toxicity control
Days	A3	A4	Mean	PK5	TK6
1	1.7	1.3	1.5	6.5	4.0
2	3.9	3.7	3.8	25.3	14.9
4	6.5	6.5	6.5	47.6	27.6
6	10.5	11.0	10.8	63.9	36.9
8	14.2	15.2	14.7	75.3	42.1
10	16.0	18.6	17.3	81.5	45.1
15	18.5	22.4	20.5	87.1	46.8
20	20.4	24.4	22.4	92.2	48.0
25	23.8	29.0	26.4	95.8	49.1
28	30.4	33.9	32.1	103.5	50.8

Validity criteria fulfilled:

yes

Remarks:

(The percentage degradation of the positive control exceeded 60 % within ten days of first reaching 10 %. The total mean blank CO2 production in this study was 96.3 mg per 3 liters).

Interpretation of results:

not readily biodegradable

Conclusions:

The carbon dioxide evolution from the test substance with a nominal concentration of 15 mg Carbon/L reached a maximum of 23.6 % after 28 days of incubation at 21.6 ± 0.5 °C. According to the results of this study he test substance is not readily biodegradable.

Executive summary:

The biodegradability of the test substance Wasox-MMAC2 was analysed by the determination of carbon dioxide evolution at frequent intervals over a 28 days period ( intervals: 1, 2, 4, 6, 8, 10, 15, 20, 25 and 28/29 days). The method used was according to OECD Guidelines 301B. The test substance was suspended in buffered mineral salts medium at a nominal concentration of 15 mg organic carbon per liter. The medium was inoculated with microorganisms derived from a sample of activated sludge not previously exposed to the test substance (30 mg/L of suspended solids). The mixtures were incubated in the darkness at 21.6 ºC ± 0.5 ºC for 28 days under constant stirring.

The reference substance sodium benzoate was degraded by 81.5 % within 10 days.

Degradation in the toxicity control, which contained sodium benzoate and the test substance, was not indicative of a significant inhibition of the microbial activity by the test substance.

The carbon dioxide evolution from the test material reached a maximum of 32.1 % after 28 days of incubation at 21.6 ± 0.5 °C. According to the results of this study the test substance Wasox-MMAC2 is determinet to be not readily biodegradable.

Description of key information

Key study: OECD 301B and GLP. The test item Wasox-MMAC2 was determined to be not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

Key study: A biodegradability test on Wasox-MMAC2 was performed according to OECD Guideline 301B and GLP. The carbon dioxide evolution from the test material reached a maximum of 32.1 % after 28 days of incubation with 30 mg/L of activated sludge inoculum at 21.6 ± 0.5 °C. Therefore, the test substance Wasox-MMAC2 was determined to be not readily biodegradable at a concentration of 15 mg organic carbon per liter.