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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:
From October 19, 2017 to January 05, 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)
Deviations:
not specified
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
other: Aerobic sludge, mixed treatment plant of urban (66%) and industrial (34%)
Details on inoculum:
Method of mud sampling
For the preparation of the inoculum a sample of aerobic sludge has been selected by the mixed treatment plant of urban (about 66%) and industrial (about 34%) liquid sewage situated at San Rocco - Monza (MB), Italia. The plant of treatment is managed by "BRIANZACQUE SRL (Monza)".

Mud preparation
In the laboratory the sampled muds, have been mixed and let settle, keeping them in aerobic conditions. The mud samples, before their use, have been analysed to check its ability to form colony units. Then it has been centrifuged, washed and analyzed to quantify the suspended solids concentration for the inoculum preparation. The inoculum was prepared in order to have a concentration of suspended solid of about 4 mg/L.

Medium preparation:

Solution A
Anhydrous potassium dihydrogen phosphate (KH2P04): 8.50 g/L
Anhydrous dipotassium hydrogen phosphate (K2HP04): 21.75 g/L
Disodium hydrogen phosphate dihydrate (Na2HP04.2H20): 33.40 g/L
Ammonium chloride (NH4Cl): 0.50 g/L
pH = 7.42

Solution B
Calcium chloride dihydrate (CaCI2.2H20): 36.40 g/L

Solution C
Magnesium sulphate heptahydrate (MgSO4.7H20): 22.50 g/L

Solution D
Iron chloride (Ill) hexahydrate (FeCl3.6H20): 0.25 g/L
All solutions has been made with deionized water (MilliQ Millipore). Then for each litre of medium 10 mL of Solution A have been transferred into a 1000 mL volumetric flask and diluted with 800 mL of deionised water; 1 mL of Solution B, 1 mL of Solution C and 1 mL of Solution D have been added and the solution has been diluted to volume with deionised water. For higher volumes the medium has been prepared according to the same proportion. The preparation of the solutions has been reported in an internal laboratory logbook.
Duration of test (contact time):
ca. 56 d
Initial conc.:
ca. 32.77 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation:
inorg. C analysis
Reference substance:
benzoic acid, sodium salt
Remarks:
23.70 mg/L of TOC
Key result
Parameter:
% degradation (inorg. C analysis)
Remarks:
Test substance
Value:
ca. 2
Sampling time:
28 d
Remarks on result:
other: not readily biodegradable
Key result
Parameter:
% degradation (inorg. C analysis)
Remarks:
Test substance
Value:
ca. 7
Sampling time:
56 d
Remarks on result:
other: not readily biodegradable
Results with reference substance:
Percentage biodegradation of reference substance at 14 d was determined to be 74%, therefore the assay fulfilled the validity criteria.

Results

Quality criteria of the test were satisfied. The mean amount of TIC present in the blank controls at the end of the test was < 3 mg C/L. The trend of the inorganic carbon and related biodegradation percentages in the bottle contained both the test sample and the reference substance confirm the absence of inhibitory effect of the test sample on inoculum. The biodegradation percentage of the test substance during the test was as follow:

Check point

(d)

% of Biodegradation of reference substance

% of Biodegradation of test substance

% of Biodegradation of reference substance + test substance

0

0

0

0

1

2

0

0

7

71

4

 -

14

74

3

21

87

2

-

28

86

2

27

35

95

6

-

42

91

15

-

49

78

11

-

56

83

7

36

Conclusions

On the basis of results obtained, interpreted in accordance to OECD 310:2014, the test substance was considered not readily biodegradable in aerobic condition.

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Under the study conditions, the test substance was determined as not readily biodegradable.



Executive summary:

A study was conducted to determine the ready biodegradability of the test substance, Steardimonium hydroxypropyl hydrolysed wool (active: 18.3%), using CO2 in sealed vessels (Headspace Test) method, according to OECD Guideline 310, in compliance with GLP. In the study, 29 replicates each were included for the inoculum blanks, positive control (sodium benzoate at 23.70 mgC/L) and test substance (32.77 mgC/L) groups, whereas 11 replicates were included for the toxicity control (test substance + reference substance) group. Aerobic sludge inoculum was prepared with mixed treatment plant of urban (66%) and industrial (34%) liquid sewage and in order to have a concentration of suspended solid of about 4 mg/L. Thereafter the inoculum was added in all bottles (except the inoculum blank), closed and incubated under stirring in darkness at 20°C for 56 d. The calculation of biodegradation was based on total inorganic carbon (TIC), which was determined using TOC analyser at each sampling time points i.e., on Day 0, 1, 7, 14, 21, 28, 35, 42, 49 and 56 for the reference substance, test sample and blank groups and on Day 1, 28 and 56 for the toxicity control group. The biodegradationpercentage for the test substance was determined to be 2% after 28 d and 7% after 56 d. As less than 60% degradation was achieved within 28 d, the test substance was concluded to be not readily biodegradable under aerobic conditions. The trend of the inorganic carbon and related biodegradation percentages in the toxicity control group confirmed the absence of inhibitory effect of the test sample on inoculum. After 14 d biodegradability for reference substance was determined to be 74%. The mean amount of TIC present in the blank controls at the end of the test was <3 mg C/L. Therefore, the test had met all the validity criteria. Under the study conditions, the test substance was concluded to be not readily biodegradable (Eurofins, 2018).

Description of key information

Based on the study results, the test substance, 'Steardimonium hydroxypropyl hydrolysed wool', was determined to be not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

A study was conducted to determine the ready biodegradability of the test substance, 'Steardimonium hydroxypropyl hydrolysed wool' (active: 18.3%), using CO2 in sealed vessels (Headspace Test) method, according to OECD Guideline 310, in compliance with GLP. In the study, 29 replicates each were included for the inoculum blanks, positive control (sodium benzoate at 23.70 mgC/L) and test substance (32.77 mgC/L) groups, whereas 11 replicates were included for the toxicity control (test substance + reference substance) group. Aerobic sludge inoculum was prepared with mixed treatment plant of urban (66%) and industrial (34%) liquid sewage and in order to have a concentration of suspended solid of about 4 mg/L. Thereafter the inoculum was added in all bottles (except the inoculum blank), closed and incubated under stirring in darkness at 20°C for 56 d. The calculation of biodegradation was based on total inorganic carbon (TIC), which was determined using TOC analyser at each sampling time points i.e., on Day 0, 1, 7, 14, 21, 28, 35, 42, 49 and 56 for the reference substance, test sample and blank groups and on Day 1, 28 and 56 for the toxicity control group. The biodegradationpercentage for the test substance was determined to be 2% after 28 d and 7% after 56 d. As less than 60% degradation was achieved within 28 d, the test substance was concluded to be not readily biodegradable under aerobic conditions. The trend of the inorganic carbon and related biodegradation percentages in the toxicity control group confirmed the absence of inhibitory effect of the test sample on inoculum. After 14 d biodegradability for reference substance was determined to be 74%. The mean amount of TIC present in the blank controls at the end of the test was <3 mg C/L. Therefore, the test had met all the validity criteria. Under the study conditions, the test substance was concluded to be not readily biodegradable (Eurofins, 2018).

[Type of water: freshwater]