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Environmental fate & pathways

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:
2017-09-27 to 2017-10-26
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
adopted 1992-07-17
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure):
Inoculum of the aqueous phase of non-adapted activated sludge from Municipal sewage treatment plant, 31137 Hildesheim, Germany
Receipt 2017-09-21

Pretreatment:
The activated sludge was washed twice with chlorine free tap water. After the second washing the settled sludge was resuspended in mineral salts medium and was maintained in an aerobic condition by aeration for 2:20 hours.
Thereafter the sludge was homogenized with a blender. After sedimentation the supernatant was decanted and maintained in an aerobic condition by aeration with CO2-free air for 6 days. 15 mL/L were used to initiate inoculation.
Colony forming units in the test vessels: approx. 10E7 - 10E8 CFU/L
Duration of test (contact time):
28 d
Initial conc.:
51.2 mg/L
Based on:
ThOD
Initial conc.:
26 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral salts medium according to OECD 301 F
- Additional substrate: no
- Solubilising agent (type and concentration if used): no
- Test temperature: 20.0 – 20.2 °C
- pH: 7.81
- pH adjusted: no
- CEC (meq/100 g):
- Aeration of dilution water: no
- Suspended solids concentration: no information
- Continuous darkness: Brown glass bottles

TEST SYSTEM
- Culturing apparatus: Brown glass bottles (volume 500 mL)
- Number of culture flasks/concentration:
• two for the inoculum control (C1, C2)
• one for the functional control (R1)
• two for the test item (P1, P2)
• one for the toxicity control (T1)

- Method used to create aerobic conditions:
- Measuring equipment:
OxiTop OC110 controller with software Achat OC, WTW
OxiTop measuring heads, WTW
Stirring platform, WTW
The oxygen consumption was determined in the incubation vessels by the OxiTop® measuring system during the 28 d incubation period (every 112 minutes).

CONTROL AND BLANK SYSTEM
• inoculum control
• functional control
• toxicity control

Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
replicate 1
Value:
25
Sampling time:
28 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
22
Sampling time:
28 d

Biodegradation [%] of Phosphoric acid, C12-18 alkyl esters, potassium salts in Comparison to the Functional Control and Toxicity Control:

 

Biodegradation [%]

 

Study Day [d]

 

Replicate

7

14

21

28

Test Item
26mg/L

1

11

25

28

25

2

13

24

26

22

Functional Control
45 mg/L

 

80

92

93

90

Toxicity Control
26mg/L Test Item +
45 mg/L Reference Item

 

45

53

56

55

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Phosphoric acid, C12-18 alkyl esters, potassium salts is classified as not readily biodegradable within the 28 day period of the study.
Executive summary:

The ready biodegradability of Phosphoric acid, C12-18 alkyl esters, potassium salts was determined with non-adapted activated sludge in the Manometric Respirometry Test according to OECD guideline 301 F for a period of 28 days. The test item concentration selected as appropriate was 26 mg/L, corresponding to a ThOD of 51.2 mg O2/L per test vessel. The oxygen was depleted by the respiration of bacteria and the degradation was followed by measuring the oxygen concentration. The biodegradation rate is therefore expressed as the percentage BOD (biological oxygen demand) and was calculated for each study day.

The mean oxygen depletion in the inoculum control was 15.4 mg O2/L on day 28. In order to check the activity of the test system sodium benzoate was used as functional control. The pass level > 60% was reached within 3 days. The biodegradation reached a maximum of 94% degradation on day 17. In the toxicity control containing both test and reference item 53% degradation occurred within 14 days. After 28 days the biodegradation came to 55%. The degradation of the reference item was not inhibited by the test item.

 

Both test item replicates did not reach the 60% pass level within the 28-day-period of the study. The mean biodegradation on day 28 was 24%.

Thus, Phosphoric acid, C12-18 alkyl esters, potassium saltsis classified as not readily biodegradable within the 28 day period of the study.

Description of key information

Phosphoric acid, C12-18 alkyl esters, potassium salts is classified as not readily biodegradable within the 28 day period of the study.

Key value for chemical safety assessment

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

Additional information

The ready biodegradability of Phosphoric acid, C12-18 alkyl esters, potassium salts was determined with non-adapted activated sludge in the Manometric Respirometry Test according to OECD guideline 301 F for a period of 28 days. The test item concentration selected as appropriate was 26 mg/L, corresponding to a ThOD of 51.2 mg O2/L per test vessel. The oxygen was depleted by the respiration of bacteria and the degradation was followed by measuring the oxygen concentration. The biodegradation rate is therefore expressed as the percentage BOD (biological oxygen demand) and was calculated for each study day.

 

The mean oxygen depletion in the inoculum control was 15.4 mg O2/L on day 28.In order to check the activity of the test system sodium benzoate was used as functional control. The pass level > 60% was reached within 3 days. The biodegradation reached a maximum of 94% degradation on day 17. In the toxicity control containing both test and reference item 53% degradation occurred within 14 days. After 28 days the biodegradation came to 55%. The degradation of the reference item was not inhibited by the test item.

 

Both test item replicates did not reach the 60% pass level within the 28-day-period of the study. The mean biodegradation on day 28 was 24%.

Thus, Phosphoric acid, C12-18 alkyl esters, potassium saltsis classified as not readily biodegradable within the 28 day period of the study.

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