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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:
supporting study
Study period:
04 Jun - 22 Jul 1993
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
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 (according to OECD 301 ≤ 30 mg suspended solids/L≙ 10^7 - 10^8 cells/L, corresponding to 8.4 x 10^6 - 8.4 x 10^7 cells/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:
experimental study
Adequacy of study:
key study
Study period:
22 Sep - 20 Oct 1995
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: final effluent of activated sludge plant Hochdahl, Germany
- Initial cell/biomass concentration: 1 mL/L effluents corresponding to approx. 2E+04 - 2E+06 cells/L
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
act. ingr.
Initial conc.:
5 mg/L
Based on:
act. ingr.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Test temperature: 20 +/- 1 °C
- Continuous darkness: yes or diffuse lighting

TEST SYSTEM
- Culturing apparatus: conical shoulder bottles
- Test performed in closed vessels: yes
- Number of culture flasks/concentration: 2

SAMPLING
- Sampling frequency: day 0, 7, 14, 21, 28
- Sampling method: iodometric determination of oxygen concentration, analytics of nitrogen compunds

CONTROL AND BLANK SYSTEM
- Inoculum blank: 4
- Procedure control: 2

Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
>= 77
Sampling time:
28 d
Results with reference substance:
Biological degradation (% BOD/COD) after 7, 14, 21 and 28 days: 73, 80, 83 and 89%

Table 1: Degradation in percent after 7, 14, 21 and 28 days

 

% BOD/COD (ThOD) after x days

Test substance

7

14

21

28

2 mg a.i./L

61

67

77

79

5 mg a.i./L

58

65

73

77

Table 2: Validity criteria for OECD 301.

Criterion from the guideline

Outcome

Validity criterion fulfilled

Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.

 < 20%

 yes

Percentage degradation of the reference compound reached the pass level by day 14 (≥ 60%).

 80%

yes 

The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.

 80%

 yes

Oxygen depletion in the inoculum blank should not exceed 1.5 mg dissolved oxygen/L after 28 days.

 < 1.5 mg/L

 yes

The residual concentration of oxygen in the test bottles should not fall below 0.5 mg/L at any time.

 > 0.5 mg/L

 yes

Validity criteria fulfilled:
yes
Remarks:
The validity crietria according to OECD 301 are fulfilled (for details see table 3 under "any information on results")
Interpretation of results:
readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
22 Sep - 20 Oct 1995
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle 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 Hochdahl
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
act. ingr.
Initial conc.:
5 mg/L
Based on:
act. ingr.
Parameter followed for biodegradation estimation:
O2 consumption
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
76 - 81
Sampling time:
28 d
Results with reference substance:
% BSB/CSB (ThSB) after 28 days = 89%

 

% BSB/CSB (ThSB) after x days

Test substance

Concentration
[mg/L]

7

14

21

28

Texapon K 14 S "Spezial"

2 (active substance)

53

64

78

81

5 (active substance)

52

58

72

76

Sodium benzoate (Reference substance)

2

73

80

83

89

Interpretation of results:
readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
13 May - 10 Jun 1994
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Duration of test (contact time):
28 d
Initial conc.:
10 mg/L
Based on:
DOC
Parameter:
% degradation (DOC removal)
Value:
96
Sampling time:
28 d
Interpretation of results:
readily biodegradable

Description of key information

The substance is readily biodegradable in water.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Several studies on the ready biodegradability of alcohols C12 -14 ethoxysulfates are available. All studies were conducted according or equivalent to OECD or EU-guidelines and under GLP. In all tests the ready biodegradability of the test substance could be proved via O2 -consumption or determination of DOC-removal.

The key study was conducted according to OECD 301D with 1 mL effluent of a predominantly domestic sewage treatment plant corresponding to a cell concentration of approximatelly 2E+04 to 2E+06 per Litre. The pass level of 60% degradation based on BOD/ThOD was reached between day 7 and 14 for both tested concentrations (1 mg/L and 5 mg/L). The reliability criteria according to guideline were met. Therefore, the substance can be consiered as readily biodegradable.