Registration Dossier

Diss Factsheets

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From May 11, 2017 to June 15, 2017
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)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Activated sludge (domestic) was obtained from Totnes Sewage Treatment Works, Totnes, Devon, UK on 10 May 2017
- Storage conditions: Activated sludge was kept aerated at room temperature and the pH maintained at 7.0 ± 1.0
- Preparation of inoculum for exposure: Seven days prior to the exposure start the activated sludge was centrifuged, washed and re-suspended in the mineral medium and the solids concentration determined. This sludge was then diluted in mineral medium, added to test bottles and stirred until required for use
- Water filtered: No
- Volume/concentration: The seeded mineral medium had an activated sludge concentration of 40 mg/L, which, when diluted by the addition of sodium benzoate, PPG-2 myristyl ether propionate, or RO water gave an activated sludge concentration of 30 mg/L in the final volume
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: The mineral medium contained the following nutrients per litre of reverse osmosis (RO) water: 85.0 mg/L KH2PO4; 217.5 mg/L K2HPO4; 334.0 mg/L Na2HPO4.2H2O; 5.0 NH4Cl; 36.4 mg/L CaCl2.2H2O; 22.5 mg/L MgSO4.7H2O; and 0.25 mg/L FeCl3.6H2O
- Test temperature: 22 ± 1 °C maintained within an incubator
- pH: 7.4 ± 0.2
- pH adjusted: Adjusted as necessary prior to the acclimation phase and on day 0 in all treatments except for bottles containing PPG-2 myristyl ether propionate only as undissolved test substance could have adhered to the pH probe
- Continuous darkness: Each individual unit consisted of a dark glass bottle

TEST SYSTEM
- Culturing apparatus: Individual Oxitop™ respirometers that consisted of a dark glass 500 mL bottle with an Oxitop™ bottle top containing a piezoresistive electronic pressure sensor. Bottles were situated on a magnetic stirrer in a constant temperature incubator
- Number of culture flasks/concentration: Flasks contained an inoculum blank control; 100 mg/L reference substance (positive control) made up of 16.4 mL of 1000 mg/L sodium benzoate solution; 100 mg/L PPG-2 myristyl ether propionate made up of 16.4 mg of the test item; and a toxicity control containing 16.4 mg PPG-2 myristyl ether propionate and 16.4 mL of 1000 mg/L sodium benzoate. Each set of bottles was prepared in triplicate
- Method used to create aerobic conditions: Following collection from Totnes Sewage Treatment Works and prior to being added to the mineral medium, the activated sludge was kept aerated at room temperature. After being re-suspended in the mineral medium and diluted, the seeded mineral medium was added to test bottles, stirred until required for use and then pre-conditioned before the test set-up for seven days to reduce the blank oxygen uptake readings in the test
- Measuring equipment: A pH probe and an Oxitop™ controller that collected the pressure values (related to oxygen take-up) from the measuring tops and calculated the BOD (as mg/L). Cuvette tests provided by Hach Lange Ltd using a DR2800 spectrophotometer for evaluation were used to determine Chemical Oxygen Demand (COD)
- Details of trap for CO2: Carbon dioxide produced by microbial respiration was absorbed by potassium hydroxide solution (KOH) placed in a seal cup in the neck of each Oxitop™ respirometer, and the oxygen taken up was measured as a decrease in pressure
- Other: Additional single replicate PPG-2 myristyl ether propionate and toxicity control bottles were prepared for determination of pH at day 0, so undissolved test substance was not removed by the pH probe

SAMPLING
- Sampling frequency: Oxygen uptake was recorded automatically every 240 minutes during the 28-day experiment period. pH and temperature were measured on day 0 and 28
- Other: Oxygen uptake values were corrected for the inoculum blank and the biodegradation was calculated as a percentage of the chemical oxygen demand for the substance under test and as a percentage of the theoretical oxygen demand for the reference substance

CONTROL AND BLANK SYSTEM
- Inoculum blank: Contained no test or reference substance, in order to demonstrate there was no other carbon source in the medium
- Toxicity control: Contained the test and reference substances, both at 100 mg/L, and were used to show if there had been any inhibition of the inoculum by the test substance
- Other: Positive controls contained the reference substance, sodium benzoate at 100 mg/L, to demonstrate the viability of the inoculum
Reference substance:
benzoic acid, sodium salt
Test performance:
Mean oxygen uptake of the inoculum blank was below 60 mg/L, as required in the OECD guideline. The difference between replicate PPG-2 myristyl ether propionate extremes was < 20 % on day 28. Sodium benzoate reached mean 73 % biodegradation by day 14. The average of the mean oxygen consumed in the inoculum blanks was 16.6 mg/L after 28 days. Therefore, this test has satisfied all the validity criteria.
Key result
Parameter:
% degradation (O2 consumption)
Value:
64
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
63
Sampling time:
27 d
Parameter:
% degradation (O2 consumption)
Value:
61
Sampling time:
26 d
Parameter:
% degradation (O2 consumption)
Value:
60
Sampling time:
25 d
Parameter:
% degradation (O2 consumption)
Value:
59
Sampling time:
24 d
Parameter:
% degradation (O2 consumption)
Value:
59
Sampling time:
23 d
Parameter:
% degradation (O2 consumption)
Value:
57
Sampling time:
22 d
Parameter:
% degradation (O2 consumption)
Value:
55
Sampling time:
21 d
Parameter:
% degradation (O2 consumption)
Value:
54
Sampling time:
20 d
Parameter:
% degradation (O2 consumption)
Value:
53
Sampling time:
19 d
Parameter:
% degradation (O2 consumption)
Value:
52
Sampling time:
18 d
Parameter:
% degradation (O2 consumption)
Value:
51
Sampling time:
17 d
Parameter:
% degradation (O2 consumption)
Value:
49
Sampling time:
16 d
Parameter:
% degradation (O2 consumption)
Value:
47
Sampling time:
15 d
Parameter:
% degradation (O2 consumption)
Value:
45
Sampling time:
14 d
Parameter:
% degradation (O2 consumption)
Value:
44
Sampling time:
13 d
Parameter:
% degradation (O2 consumption)
Value:
42
Sampling time:
12 d
Parameter:
% degradation (O2 consumption)
Value:
39
Sampling time:
11 d
Parameter:
% degradation (O2 consumption)
Value:
37
Sampling time:
10 d
Parameter:
% degradation (O2 consumption)
Value:
35
Sampling time:
9 d
Parameter:
% degradation (O2 consumption)
Value:
33
Sampling time:
8 d
Parameter:
% degradation (O2 consumption)
Value:
30
Sampling time:
7 d
Parameter:
% degradation (O2 consumption)
Value:
27
Sampling time:
6 d
Parameter:
% degradation (O2 consumption)
Value:
24
Sampling time:
5 d
Parameter:
% degradation (O2 consumption)
Value:
19
Sampling time:
4 d
Parameter:
% degradation (O2 consumption)
Value:
13
Sampling time:
3 d
Parameter:
% degradation (O2 consumption)
Value:
4
Sampling time:
2 d
Parameter:
% degradation (O2 consumption)
Value:
1
Sampling time:
1 d
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
0 d
Key result
Parameter:
COD
Value:
2.61 g O2/g test mat.
Results with reference substance:
The ThOD of sodium benzoate was calculated as 1.67 g O2/g of substance. A maximum mean level of biodegradation (based on the BOD:ThOD ratio) of 76% was attained also, with good replication of the results. More than 60% degradation was achieved within the 10-day window as expected for a biodegradable substance, thus confirming that the activated sludge contained viable organisms. The following phases (approximate) were observed:
- Lag phase days 0 to 1
- Degradation phase days 1 to 6
- 10-day window days 1 to 11

PPG-2 Myristyl Ether Propionate

 

PPG-2 myristyl ether propionate attained a maximum mean level of biodegradation (based on the BOD:COD ratio) of 64 %, and the results showed good replication. The following phases (approximate) were observed:

- Lag phase days 0 to 2

- Degradation phase days 2 to 22

- 10-day window days 2 to 12

 

Toxicity Control

 

The mean toxicity control degradation achieved on day 14 was 42 % (based on ThOD and COD), as this is >25 % the test substance is assumed not to be inhibitory at this concentration.

 

pH and Temperature Measurements

 

At the end of the 28-day test period, the pH values ranged from 7.6 to 7.8 in the inoculum blank bottles, were 7.1 in the sodium benzoate bottles, ranged from 7.0 to 7.2 in the PPG-2 myristyl ether propionate bottles and from 6.8 to 7.0 in the toxicity control bottles. All pH values are shown in Table 5. Temperature measurements recorded in several of the test bottles on days 0 and 28 indicated the temperature was within the range 22 ± 1 °C. Continuous monitoring of the incubator temperature showed it to have remained within the range 22 ± 1 °C throughout the study.

Mean Percentage Biodegradation

Mean percentage biodegradation

Day

PPG-2 myristyl ether propionate Sodium benzoate

5

24 65

10

37 72

15

47 73

20

54 75

28

64 76
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
PPG-2 myristyl ether propionate was concluded to be readily biodegradable under the conditions of this test, with a maximum percentage biodegradation (based on the BOD:COD ratio) of 64% over a 28-day period.
Executive summary:

A 28-day test was performed to determine the ready biodegradability of PPG-2 myristyl ether propionate in line with OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test) and Good Laboratory Practise (GLP). The purpose of this test is to establish the biodegradability of an organic material in a freshwater environment. Oxygen consumption was measured in Oxitop™ respirometers (Wissenschaftlich-Technische Werkstätten, GmbH, Germany) that contained piezo-resistive electronic pressure sensors. Carbon dioxide produced by microbial respiration was absorbed by potassium hydroxide solution (KOH) placed in a seal cup in the neck of each bottle, and the oxygen taken up was measured as a decrease in pressure. All test bottles contained the prepared activated sludge inoculum in mineral medium. PPG-2 myristyl ether propionate was applied at a concentration of 100 mg/l (n= 3). A reference substance (sodium benzoate at 100 mg/l), inoculum blank control that contained no test or reference substance, and a toxicity control containing the test and reference substance were prepared in triplicate. The Chemical Oxygen Demand (COD) of the registration substance was calculated to be 2.61 g O2/g and the mean Biological Oxygen Demand (BOD) value after 28 days was 1.67 g O2/g. Percentage degradation was calculated as (BOD/COD) x 100. PPG-2 myristyl ether propionate achieved a maximum mean level of biodegradation (based on the BOD:COD ratio) of 64% and the results showed good replication. As PPG-2 myristyl ether propionate is a Substance of Unknown or Variable Composition, Complex Reaction Products and Biological Materials (UVCB), the 10-day window can be waived (OECD 2006: Guidelines for the Testing of Chemicals and ECHA 2015: Guidance on the Application of the CLP Criteria). All validity criteria of the test were satisfied. Subsequently, as >60 % biodegradation was achieved within 28 days PPG-2 myristyl ether propionate has been concluded to be readily biodegradable under the conditions of the test.

Description of key information

A test was undertaken to determine the ready biodegradation potential of PPG-2 myristyl ether propionate in freshwater over a 28-day period. A maximum percentage biodegradation (based on the BOD:COD ratio) of 64 % was obtained and, therefore, the registered substance can be considered to be readily biodegradable under the parameters of the study.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The endpoint value obtained for ready biodegradation in water has been concluded to be reliable given that it was obtained in a key study performed according to OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test) without deviation and Good Laboratory Practise (GLP). A Klimisch score of 1 (reliable without restriction) is recommended.

Categories Display