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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
Study period:
02 Sep - 01 Oct 2004
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
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 from the municipal wastewater treatment plant Breisgauer Bucht was used as inoculum with a concentration corresponding to 30 mg dry solids per litre. The treatment plant clarifies predominantly domestic wastewater of the region Freiburg and has a capacity of 600000 inhabitant equivalents.
- Preparation of inoculum for exposure: the activated sludge was washed twice by settling the sludge, decanting the supernatant and resuspending the sludge in aerated tap water.
- Concentration of sludge: to 1484.8 mL mineral medium 15.2 mL activated sludge was added, corresponding to 30 mg/L dry solids.
Duration of test (contact time):
28 d
Initial conc.:
20 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: Solution A: KH2PO4: 8.50 g, K2HPO4: 21.75 g, Na2HPO4 x 2H2O: 33.40 g, NH4Cl: 0.50 g; Solution B: CaCl2 x 2H2O: 36.4 g; Solution C: MgSO4 x 7H2O: 22.50 g; Solution D: FeCl3 x 6H2O: 0.25 g. For preparation of the mineral medium 10 mL of solution A is mixed with 800 mL demineralised water, 1 mL of solutions B, C and D are added and made up to 1 litre each.
- Test temperature: 21.0 °C - 22.1 °C
- Aeration of dilution water: aeration with CO2-free air at a rate of 50 - 100 mL/min
- Suspended solids concentration: dry solids of the acitvated sludge was determined as 2.96 g/L by weight measurements after 2 h drying at 105 °C (mean of triplicate measurements)



TEST SYSTEM
- Culturing apparatus: gas wash bottles (2000 mL volume) with lateral connecting pieces for butyl rubber septums were used as reactors.
- Number of culture flasks/concentration: 3
- Measuring equipment:
- Details of trap for CO2 and volatile organics if used: CO2-absorption medium: 72 g NaOH were dissolved in 9000 mL deionised water in closed recipients (0.2 M NaOH).
- Other: the CO2-free air production system consists of an air compressor, two 1000 mL gas wash bottles filled with dry soda lime, followed by one bottle filled with 0.1 M NaOH. At the end of the system was one gas wash bottle filled with demineralised water, followed by an empty one to catch any drops of condensation water. A colour range of the soda lime from white to blue indicates, that CO2 absorption capacity is depeted. The CO2-free air is passed on to an air distributer with two imput and 22 output channels and through PE-tubes.


SAMPLING
- Sampling frequency: 4, 7, 11, 14, 21 and 28 days
- Sampling method: sampling was performed through the lateral connecting pieces through the butyl rubber septum using 5 mL PE syrings.



CONTROL AND BLANK SYSTEM
- Inoculum blank: yes - 3 replicates
- Toxicity control: yes - 1 replicate containing test item and reference compound

Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
78.4 - 100.9
Sampling time:
28 d
Results with reference substance:
The reference compound reached the pass levels for ready biodegradability within 7 days

 

% of ThCO2

Day

0

4

7

11

14

21

28

28 (after acidification)

Test substance

0

59.1

74.8

89.8

99.4

98.5

95.6

100.7

Interpretation of results:
readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
04 Jun - 22 Jul 1993
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)
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): sewage plant: Marl-Ost
- Preparation of inoculum for exposure: centrifugation at 3000 rpm for 15 min. The supernatant was discarded and the sludge resuspended with mineral medium. After another centrifugation step 15 min at 3000 rpm, the sludge was resuspended.
- Concentration of sludge: 25.2 mg/L
- Water filtered: yes
Duration of test (contact time):
28 d
Initial conc.:
10.5 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
TEST CONDITIONS
- Composition of medium: solution A: 8.5 g KH2PO4, 21.75 g K2HPO4, 33.3 g NaHPO4 x 2 H2O and 20.0 g (NH4)Cl; solution B: 22.5 g MgSO4 x 7 H2O; solution C: 27.5 g CaCl2; solution D: 0.25 g FeCl3 x 6 H2O
- Test temperature: 20.0 °C - 22.2 °C
- Continuous darkness: yes


SAMPLING
- Sampling frequency: 0, 7, 14, 21, 27 and 28 days


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (DOC removal)
Value:
100
Sampling time:
28 d
Results with reference substance:
DOC removal: 100% after 28 days

 

% DOC-removal after x days

Day

0

7

14

21

27

28

Test substance

0

95

100

98

101

100

Interpretation of results:
readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to the Category Approach Justification provided in Section 13
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
yes
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
78.4 - 100.9
Sampling time:
28 d
Remarks on result:
other:
Remarks:
Source, key, 1187742-72-8, 2004
Results with reference substance:
The reference compound reached the pass levels for ready biodegradability within 7 days

 

% of ThCO2

Day

0

4

7

11

14

21

28

28 (after acidification)

Test substance

0

59.1

74.8

89.8

99.4

98.5

95.6

100.7

Interpretation of results:
readily biodegradable

Description of key information

Readily biodegradable: 78-100% (ThCO2) in 28 days (OECD 301B)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Comparing all available biodegradation studies, the members of the AES category can generally be considered as readily biodegradable.

Since no biodegradability tests are available for AES (C12-14, 1-2.5 EO) TEA (CAS 157627-94-6), a read-across approach from the two structurally similar substances AES (C12-14, 1-2.5EO) MIPA (CAS 1187742-72-8) and AES (C12-14, 1-2.5EO) Na (CAS 68891-38-3) was applied.

Both studies were conducted with non-adapted domestic sludge under GLP conditions. The test with AES (C12-14, 1-2.5EO) MIPA (CAS 1187742-72-8) was performed according to OECD guideline 301B (Sasol, 2004). After 28 days a biodegradation rate between 78 - 100% (CO2 evolution) was reported for the MIPA salt.

The test with AES (C12-14, 1-2.5EO) Na (CAS 68891-38-3) was performed according to EU-guidelines (C.4-A) (Sasol, 1993a). This test shows a biodegradation rate of 100% (DOC removal) after 28 days.