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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Version / remarks:
1981-05-12
GLP compliance:
not specified
Specific details on test material used for the study:
Purity: not specified
Meltiung point: -48 °C
oiling point: 100.3 °C0
Solubility water: 59 % @ 20 °C
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): In March, June, September, and December, sludge was sampled at the following 10 places in Japan: 1. Fukogawa city sewage plant, 2. Fukashiba industry sewage plant, 3. Nakahama city sewage plant, 4. Ochiai city sewage plant, 5. Kitakami river, 6. Shinano river, 7. Yoshino river, 8. Lake Biwa, 9. Hiroshima bay, 10. Dookai bay; sampling: 1. City sewage: Returned sludge from sewage plants was taken. 2. Rivers, lake and sea: Surface water and surface soil which were in contact with atmosphere were collected.
- Method of cultivation: About 30 minutes after ceasing aeration to the sludge mixture, supernatant corresponding to about 1/3 of the whole volume was removed. Then the equal volume of dechlorinated water was added to the remaining portion and aerated again, followed by addition of synthetic sewage at a concentration of 0.1% (w/v). This procedure was repeated once every day. The culturing was carried out at 25 ± 2 °C. 5 L of the filtrate of the supernatant of old activated sludge was mixed with 500 mL of the filtrate of the supernatant of new sludge and cultured at pH 7.0 ± 1.0 under sufficient aeration using prefiltered open air. During the cultivation, appearance of the supernatant, precipitability, formation of flock, pH, dissolved oxygen concentration in the solution and temperature were checked and necessary adjustments were made, Microflora in the activated sludge was microscopically observed and sludge with no abnormal symptom was used for the test.
- Concentration of sludge: 30 mg/L
Duration of test (contact time):
14 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: 3 mL each of four stock solutions, as described in JIS K 0102-1986-21, are diluted to 1000 mL with purified water
- pH: 7.0
- pH adjusted: yes
- Suspended solids concentration: determined according to Method Japanese Industrial Standards (JIS) K 0102-1986-14.1
- Cultivation temperature: 25 °C

TEST SYSTEM
- Culturing apparatus: Closed system oxygen consumption measuring apparatus (Coulometer: Ohkura Electric Co., Ltd.); 300 mL vessel, absorbent for evolving carbon dioxide Soda lime No .l (extra pure reagent, Wako Pure Chemical Industries, Ltd.).
- Number of culture flasks/concentration: 1
- Measuring equipment: Coulometer, Okhura Electric Co., Ltd.
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: soda lime, extra pure, Wako Pure Chemical Industries, Ltd.)

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: yes
- Toxicity control: no
Reference substance:
aniline
Key result
Parameter:
% degradation (O2 consumption)
Value:
94
Sampling time:
14 d
Details on results:
Percentage biodegradation(%) average
BOD = 94.3
TOC = 99
GC = 99
UV = 99
Validity criteria fulfilled:
no
Interpretation of results:
readily biodegradable
Conclusions:
In a modiefied MITI test (OECD 301C) the biodegradation of methyl methacrylate was 94.3% after 14 days.
Executive summary:

In a modiefied MITI test (OECD 301C) the biodegradation of methyl methacrylate was 94.3% after 14 days.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2003-09-08 to 2003-10-05
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Qualifier:
according to guideline
Guideline:
ISO 10707 Water quality - Evaluation in an aqueous medium of the "ultimate" aerobic biodegradability of organic compounds - Method by analysis of biochemical oxygen demand (closed bottle test)
GLP compliance:
no
Specific details on test material used for the study:
Sample No. 2647/03W
Supplier: Röhm GmbH, Darmstadt
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Municipal Sewage plant Kirrweiler, Germany
Duration of test (contact time):
28 d
Initial conc.:
2.92 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Closed bottle test
Test substance: Molecular formula: C5H8O2
Theoretical oxygen demand: 1.92 mg/mg
Stock solution: 730 mg/l


Reference substance:
acetic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
96
Sampling time:
28 d
Details on results:
Kinetic of test substance (in %):
= 62 after 7 days
= 77 after 14 days
= 85 after 21 days
= 96 after 28 days
Results with reference substance:
= 72 % after 7 days
= 76 % after 14 days
= 84 % after 21 days
= 84 % after 28 days
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Executive summary:

In a biodegradation test acc. ISO 10707 in closed bottels methyl methacrylate

Description of key information

Methyl methacrylate is readily biodegradable in OECD 301 screening test, fulfilling 10 -day window.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

For the evaluation of the biodegradability of methyl methacrylate the following test result is considered:

MITI-I-Test (OECD 301C): 94% degradation after 14 days. (CITI, 1992).

Although in the key-study the criterion of the 10-day window was not assessed, the high degradation rate of 94% within 14 days in the MITI-I-Test indicates that the criterion of the 10 d-window is likely fulfilled.

This result is confirmed by a test according ISO 10707 where methyl methacrylate degraded 62 % after 7 days (10-day window fulfilled) and achieved 98 % after 28 days (LGU, 2003).

Two additional tests are available where methyl methacrylate did not achieve the criteria of readily biodegradability: In an OECD 301 D Closed bottle test methyl methacrylate achieved 88 % degradation after 28 days but failed the 10-day window. The trend of the biodegradation curve of MMA is however implausible in this test due to the simple structure of the substance. Measurements were conducted only on 3 days on day 5, 15 and 28 (Huntingdon, 1992).

A second OECD 301 C modified MITI test is available with methyl methacrylate. After day 5 and ca. 30 % biodegradation the degradation curve remained static and no further degradation occurred. This result is implausible in contrast to other biodegradation tests with methyl methacrylate. It seems that after 5 days no test substance has been left due to technical reasons (Fraunhofer, 1988).

In summary methyl methacrylate fulfills the criteria readily biodegradability according CLP.