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Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2002-09-16 to 2002-12-03
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)
Version / remarks:
July 1992
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
Specific details on test material used for the study:
Name: "o-Phthaldialdehyde"
Chemical name: 1,2-Benzene dicarboxaldehyde
Trade name: OPA
CAS No.: 643-79-8
Molecular formula: C8H6O2
Supplier: DSM Fine Chemicals
Batch No.: OSHO 201
Appearance: Pale yellow scales or powder
Boiling point: 83°C/1 mbar
Melting range: 54-56 °C
Solubility: in water: 53 g/L at 20 °C; in other solvents: organic solvents
Conditions of storage: Refrigerator, in the dark, may be used under light
Stability at conditions of storage: Stable
Expiration date: January 2004
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): sewage treatment work A-2500 Baden, which waste-water catchment is predominantly domestic.
- Preparation of inoculum for exposure: It was not acclimatised or adapted to "o-Phthaldialdehyde" before exposure to the test substance
- Pretreatment: 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.
- Concentration of sludge: 30 mg suspended solids/ L (nominal)
- Water filtered: deionised water
- Type and size of filter used, if any: The suspended solids concentration was determined by filtering a 5 mL sample through a pre-dried and pre-weighed glass filter (Whatman GF/C)
Duration of test (contact time):
28 d
Initial conc.:
15 mg/L
Based on:
TOC
Initial conc.:
165 other: mg/3L
Based on:
ThCO2
Parameter followed for biodegradation estimation:
inorg. C analysis
Remarks:
Determine carbon dioxide produced an dabsorbed to barium hydroxide
Details on study design:
TEST CONDITIONS
- Composition of medium:
- a) KH2P04 8.50 g; K2HPQ4 21.75 g; Na2HP04 x 2H20 33.40 g; NH4CI 0.50 g; pH 7.4, dissolved in deionised water and filled up to 1000 mL.
- b) MgS04 x 7H20 22.50 g; dissolved in deionised water and filled up to 1000 mL.
- c) CaCl2 27.50 g; dissolved in deionised water and filled up to 1000 mL.
- d) FeC'3 x 6H20 0.25 g; dissolved in deionised water and filled up to 1000 mL.
Chemicals for solutions "a - d" were analytical grade supplied by E. Merck, D-64273, Darmstadt.
-30 mL of solution a) was added to 2400 mL deionised water, 3 mL each of the solutions b) to d) and 34. 7 mL activated sludge were added and then made up to a total volume of 3000 mL deionised water. The concentration of the final suspended solids of the sludge in all vessels was nominally 30 mg/L.
- Test temperature: 22 ± 2 °C.
- pH: 7.45-7.63
- pH adjusted: no
- CEC (meq/100 g): not reported
- Aeration of dilution water: yes
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes
- Air flow: 50 to 100 mL/min; air used was a CO2-free "control air" (Linde Gase, A-2492 Eggendorf)

TEST SYSTEM
- Culturing apparatus: 5 L flasks containing 2400 mL mineral medium
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: the medium continually supplied with CO2-air
- Measuring equipment: titration
- Details of trap for CO2 and volatile organics if used: Three absorption bottles were connected in line each containin g100 mL of 0.0125 M barium hydroxide solution, in series to each 5 L flask.

SAMPLING
- Sampling frequency: Days 1, 2, 4, 6, 8, 10, 15, 20, 25, 28
- Sampling method: On the days of CO2 measurement, the barium hydroxide absorbers closest to the test vessels were disconnected and the barium-hydroxide solution was titrated with 0.05 M HCl using phenolphthalein as the indicator. The remaining absorbers were connected to the incubation vessels and a new absorber containing 100 mL fresh 0.0125 M barium hydroxide was placed at the far end of the series. In case a substantial precipitation was seen in the first trap, the second bottle was analysed.

CONTROL AND BLANK SYSTEM
- Inoculum blank: medium plus inoculum
- Abiotic sterile control: no
- Toxicity control: sodium benzoate

STATISTICAL METHODS: none reported
Reference substance:
benzoic acid, sodium salt
Remarks:
C6H5COONa (Merck)
Key result
Parameter:
% degradation (CO2 evolution)
Value:
7
Sampling time:
28 d
Details on results:
The test is valid if the difference of extremes of replicate values of the removal of the test substance at the plateau, at the end of the test or at the 10-day window, is less than 20 % and if the percentage degradation of the reference compound has reached the pass levels by day 14. The percentage degradation of the positive control exceeded 60% within ten days of first reaching 10%. The guidelines require that the final cumulative CO2 yield from the blanks should not exceed 120 mg per 3 L of medium and that values greater than 240 mg CO2/3L should trigger the critical checking of the experimental techniques. The total mean blank CO2 production in this experiment was 80.64 mg per 3 L. Because the reference substance yielded satisfactory results, the test method and the inoculum were adequate.

Degradation of positive control

The plateau of biodegradation was reached on about day 10, and the degradation of the positive control sodium benzoate exceeded the pass level of 60 % on day 6.

Degradation of toxicity control

Degradation in the toxicity control (containing sodium benzoate and the test substance) started on day 5 and was indicative of an initially complete inhibition of the microorganisms. The final biodegradation was approx. 49 %.

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test substance ortho-phthaladehyde is not readily biodegradable as the biodegradation reached only 7 % after 28 days.
Executive summary:

The biodegradation of ortho-phthaladehyde was studied in a suspension in mineral medium inoculated with activated sludge, in accordance with OECD test guideline 301B "CO2 Evolution Test/Modified Sturm Test" and in compliance with OECD-GLP standards. The test substance providing the sole source of carbon and energy suspended at a nominal concentration of 15 mg organic carbon per litre. For 28 days, the mixtures were incubated, stirring, in the dark at temperature 22 ± 2°C. CO2 was trapped in barium hydroxide and measured by titration of the residual hydroxide in intervals. The amount of CO2 produced from the test item minus the amount derived from the blank inoculum is expressed as a percentage of theoretical amount of CO2. The test was valid according to the guideline.

The test substance ortho-phthaladehyde is not readily biodegradable in this test as carbon dioxide evolution reached only 7 % after 28 days.

Description of key information

In a CO2 Evolution (Modified Sturm Test) Test according to OECD guideline 301B the biodegradation of ortho-phthalaldehyde was studied. The test substance is not readily biodegradable under the employed test conditions as the carbon dioxide evolution reached only 7 % after 28 days.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information