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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1998-08-04 to 1998-09-02
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))
GLP compliance:
yes
Remarks:
No certificate
Specific details on test material used for the study:
- Names of test material (as cited in study report): Aldehyde C10 decyclic; decanal
- Substance type: Colourless to pale yellow liquid
- Physical state: Liquid
- Purity test date: No data
- Lot No: 286750
- Expiration date of the lot: No data
- Stability under test conditions: No data
- Storage condition of test material: No data
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of activated sludge: Domestic sewage works, Aïre, Geneva, Switzerland.
- Procedure: Sludge was obtained on day 0 of study, washed 3 times with mineral medium (centrifuging at 1000 g for 10 mins), supernatant discarded, resuspended in mineral medium, and kept aerobic until being used on the same day.
- Mineral medium: 50 mL of solution A, and 2000 mL water, added 5 mL each of Solutions B, C and D and made up to 5 L with water. pH adjusted to 7.4 ± 0.2 with phosphoric acid or potassium hydroxide.
- Water used was deionised with < 10 mg/L dissolved organic carbon.
- Solutions:
-- Solution A: KH₂PO₄ (8.5 g), K₂HPO₄ (21.75 g), Na₂HPO₄.2H₂O (33.4 g) NH₄Cl (0.5 g), dissolved in water and made up to 1 L.
-- Solution B: CaCl₂ (27.5 g), dissolved in water and made up to 1 L.
-- Solution C: MgSO₄.7H₂O (22.5 g), dissolved in water and made up to 1 L.
-- Solution D: FeCl₃.6H₂O (0.25 g), concentrated HCl (1 drop), dissolved in water and made up to 1 L.
- Dry weight of suspended solids was determined by taking 2 × 50 mL samples of homogenised sludge, evaporating water in steam bath, drying in an oven at 105 °C to 110 °C and weighing the residue.
Duration of test (contact time):
28 d
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
APPROACH
- 3 different concentrations of test/reference substance were used:
-- Reference substance only
-- Test substance only
-- Sludge only

TEST CONDITIONS
- Closed flasks used
- Composition of medium:
Solution A:
KH2PO4 8.5 g
K2HPO4 21.75 g
Na2HPO4.2H2O 33.5 g
NH4Cl 0.5 g
dissolved in water and made up to 1L.

Solution B:
CaCl2 27.5 g
dissolved in water and made up to 1L.

Solution C:
MgSO4.7H2O 22.5 g
dissolved in water and made up to 1L.

Solution D:
FeCl3.6H2O 0.25 g
HCl Conc. One drop
dissolved in water and made up to 1L.

Mineral medium was prepared by mixing 50 mL solution A and 2000 mL deionised water , adding 5 mL of each of solutions B, C and D and making up to 5 L with deionised water. The p H is measured and if necessary adjusted to 7.4 ± 0.2 with phosphoric acid or potassium hydroxide.

-- Samples of test substance, reference substance added as required.
--- Test substance samples (30 mg, corresponding to 30 mg/L in 1000 mL flask) weighed in small aluminium boats, added directly.
--- Reference substance added as 1.0 mL of a 100 mg/L solution in mineral medium
-- Dry weight of suspended solids in sludge was determined to be 5.148 g/L. Therefore, to obtain a concentration of 100 mg/L (dry weight) suspended sludge in 1000 mL, 19.43 mL of sludge was added (inoculum)
- Test temperature: 25 °C ± 1 °C (temperature maintained by water bath)
- Initial pH: 7.38 (assumed, based on mineral medium)
- Final pH: 7.10 to 7.14 (measured)
- pH adjusted: No
- Stirring: Yes

CONCENTRATIONS
- Test substance:
-- Nominal concentration: 30.0 mg/L
-- Measured concentrations: 30.07 mg/L; 29.91 mg/L
- Reference substance nominal concentration: 100 mg/L

TEST SYSTEM
- Apparatus: BI-1000, manufactured by Bioscience Inc., Bethlehem, Pennsylvania, United States
- Number of culture flasks/concentration: 2
- Details of trap for CO2 and volatile organics if used: Soda lime pellets

SAMPLING
- Sampling frequency: Oxygen consumption recorded daily
- Oxygen consumption measured by quantity of oxygen produced electrolytically required to maintain a constant pressure within the test system.
- Volume of of oxygen is expressed as a % of theoretical oxygen demand (ThOD), calculated from the elemental composition, assuming that water is oxidised to H₂O and carbon to CO₂.
- Oxygen uptakes as recorded by the apparatus were corrected for the differences between actual and nominal concentrations of the test and reference substances
- Oxygen uptake of sludge only control was used to correct for the basic oxygen uptake of sludge by the test material runs.
Reference substance:
benzoic acid, sodium salt
Remarks:
Flucha, Buchs, Switzerland, purity >99.0 %
Test performance:
Biodegradation of reference substance sodium benzoate was 80 % (day 7) and 89 % (day 14), in excess of the validity criterion. This verifies the activity of the inoculum and the test is considered valid.
Parameter:
% degradation (O2 consumption)
Value:
78
St. dev.:
4.24
Sampling time:
28 d
Remarks on result:
other: Mean value
Details on results:
Mean biodegradation was 42 % (day 5),56 % (day 7), 60 % (day 10), 66 % (day 14), 71 % (day 21), 78 % (day 28). For full details see Appendices 1-3.
Results with reference substance:
Biodegradation of reference substance sodium benzoate was 80 % (day 7) and 89 % (day 14). For details see Appendix 1.
Validity criteria fulfilled:
yes
Remarks:
Biodegradation of reference substance sodium benzoate was 80 % after 7 d and 89 % after 14 d, in excess of the validity criterion. This verifies the activity of the inoculum and the test is considered valid.
Interpretation of results:
inherently biodegradable, not fulfilling specific criteria
Conclusions:
Aldehyde C10 decylic undergoes 78 % biodegradation after 10 days in the test conditions. Biodegradation starts immediately and already exceeds 40 % after two days. The test substance was therefore shown to be inherently biodegradable.
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010-07-23 to 2010-08-25
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 835.3110 (Ready Biodegradability)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
- Name of test material (as cited in study report): Aldehyde C10 decyclic food grade; decanal
- Substance type: Colourless liquid
- Physical state: Liquid
- Purity test date: No data
- Lot No: VE00097618
- Expiration date of the lot: 2011-06-01
- Stability under test conditions: No data
- Storage condition of test material: No data
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum: Biological waste water treatment plant, Bois-de-Bay, Satigny, Switzerland
- Procedure: Sludge was obtained on day 0 of study, washed 3 times with mineral medium (centrifuging at 1000 g for 10 mins), supernatant discarded, resuspended in mineral medium, and kept aerobic until being used on the same day.
- Mineral medium: 50 mL of solution A, and 2000 mL water, added 5 mL each of Solutions B, C and D and made up to 5 L with water. pH adjusted to 7.4 ± 0.2 with phosphoric acid or potassium hydroxide.
- Water used was deionised with < 10 mg/L dissolved organic carbon.
- Solutions:
-- Solution A: KH₂PO₄ (8.5 g), K₂HPO₄ (21.75 g), Na₂HPO₄.2H₂O (33.4 g) NH₄Cl (0.5 g), dissolved in water and made up to 1 L.
-- Solution B: CaCl₂ (27.5 g), dissolved in water and made up to 1 L.
-- Solution C: MgSO₄.7H₂O (22.5 g), dissolved in water and made up to 1 L.
-- Solution D: FeCl₃.6H₂O (0.25 g), concentrated HCl (1 drop), dissolved in water and made up to 1 L.
Duration of test (contact time):
33 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
APPROACH
- 3 different concentrations of test/reference substance were used:
-- C: Test substance only
-- B: Sludge only
-- A: Reference substance only
- Biodegradability of test substance determined by comparison of C and B.

TEST CONDITIONS
- Composition of medium:
Solution A:
KH2PO4 8.5 g
K2HPO4 21.75 g
Na2HPO4.2H2O 33.5 g
NH4Cl 0.5 g
dissolved in water and made up to 1L.

Solution B:
CaCl2 27.5 g
dissolved in water and made up to 1L.

Solution C:
MgSO4.7H2O 22.5 g
dissolved in water and made up to 1L.

Solution D:
FeCl3.6H2O 0.25 g
HCl Conc. One drop
dissolved in water and made up to 1L.

Mineral medium was prepared by mixing 50 mL solution A and 2000 mL deionised water , adding 5 mL of each of solutions B, C and D and making up to 5 L with deionised water. The p H is measured and if necessary adjusted to 7.4 ± 0.2 with phosphoric acid or potassium hydroxide.

-- Samples of test substance, reference substance added as required.
--- Test substance samples (5.10 mg, corresponding to 20.0 mg/L in 255 mL mineral medium) weighed in small aluminium boats.
--- Reference substance added as 1.00 mL of a 10.2 g/L solution in mineral medium (total volume: 103 mL)
-- Suspended sludge diluted to concentration of 1.53 g/L dry matter added.
--- To obtain a concentration of 30 mg/L (dry weight) suspended sludge in 103 mL of test medium (A), 2.00 mL of sludge was needed (inoculum)
--- To obtain a concentration of 30 mg/L (dry weight) suspended sludge in 255 mL of test medium (B and C), 5.00 mL of sludge was needed
- Test temperature: 22 ± 1 °C (checked daily)
- Initial pH: 7.6 (assumed to be the same as the mineral medium)
- Final pH: 7.51 to 8.02 (measured)
- pH adjusted: No

TEST SYSTEM
- Apparatus: Oxitop Control System, manufactured by Wissenschaftlich-Technische Werkstätten, Germany
- Number of culture flasks/concentration: 2
- Evolved CO₂ absorbed by NaOH pellets.

SAMPLING
- Sampling frequency: Biological oxygen demand (BOD) measured daily.
- Consumption of O₂ is measured by pressure drop in respirometer flask
- O₂ uptake was corrected to take account of small differences between measured and nominal concentrations of test and reference substances
- BOD was expressed as a % of the theoretical oxygen demand (ThOD), calculated from the elemental composition, assuming that carbon is oxidised to CO₂, hydrogen to H₂O and nitrogen to NH₄⁺, NO₂⁻ or NO₃⁻.

CONCENTRATIONS
- Nominal concentrations:
-- C: 20.0 mg/L test substance; 0 mg/L reference substance
-- B: 0 mg/L test substance; 0 mg/L reference substance
-- A: 0 mg/L test substance; 100 mg/L reference substance
- Measured concentrations:
-- C: 20.0 mg/L test substance; 0 mg/L reference substance
-- B: 0 mg/L test substance; 0 mg/L reference substance
-- A: 0 mg/L test substance; 99.0 mg/L reference substance
Reference substance:
benzoic acid, sodium salt
Test performance:
- The biodegradability of sodium benzoate exceeded 40 % after 7 d and 65 % after 14 d; the activity of the inoculum was thus verified (validity criterion).
- The repeatability validity criterion (not more than 20% difference between replicates) was fulfilled.
- Therefore the test was considered valid
Parameter:
% degradation (O2 consumption)
Value:
18
St. dev.:
1.41
Sampling time:
1 d
Remarks on result:
other: Mean value
Parameter:
% degradation (O2 consumption)
Value:
50
St. dev.:
0
Sampling time:
7 d
Remarks on result:
other: Mean value
Parameter:
% degradation (O2 consumption)
Value:
76
St. dev.:
0
Sampling time:
21 d
Remarks on result:
other: Mean value
Parameter:
% degradation (O2 consumption)
Value:
82
Sampling time:
28 d
Remarks on result:
other: Mean value
Parameter:
% degradation (O2 consumption)
Value:
83
St. dev.:
0
Sampling time:
33 d
Remarks on result:
other: Mean value
Results with reference substance:
Mean % biodegradation of reference substance (sodium benzoate) recorded as 77 % (day 5), 82 % (day 7), 92 % (day 14), 96 % (day 21), 99 % (day 28). For full results see Appendix 4 (attached).

In the conditions of the test, decanal undergoes 82 % biodegradation after 28 days. The 10-day window criterion is also fulfilled (18 % biodegradation on day and 62 % on day 11). Thus decanal is regarded as readily biodegradable.

Oxygen uptakes can be found in Appendix 1 (attached). Calculated % biodegradation curves can be found in Appendices 2, 3 and 4 (attached).

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test substance was assessed for ready biodegradation according to OECD guideline 301F. The test material was shown to be readily biodegradable.

Description of key information

Readily biodegradable, passing 10 day window (OECD 301F).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The ready biodegradability of decanal has been determined by the Manometric Respirometry Test (OECD 301 F). In the conditions of the test, decanal undergoes 82 % biodegradation after 28 days. The 10-day window criterion is also fulfilled (18 % biodegradation on day and 62 % on day 11). Thus decanal is regarded as readily biodegradable.

In an inherent biodegradation test (OECD 302) high levels of ultimate biodegradation were also achieved (78 % after 28 days). Biodegradation started immediately exceeding 40 % after only 2 days.