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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:
2015 Aug 12 to 2016 Jun 02
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)
Principles of method if other than guideline:
NA
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Sludge collection: a fresh sample of activated sludge was collected on Jan 6th, 2016 from the aeration tank ofthe Long Hua Wastewater Treatment Plant in Shanghai
which treats predominantly domestic sewage. The activated sludge was kept by aeration until used (non-aeration during transport from the wastewater treatment plant
to the laboratory was kept to a minimum). Sludge treatment: When back to the laboratory, the sludge was washed with mineral medium.
After centrifugation, the supernatant was decanted. This procedure was repeated three times (4000rpm, 4°C, centrifuge 20 minutes). Then, 1.036 g of the concentrated sludge was weighed, dried at 105°C for 1 h and then measured by moisture meter for 1 h to determine the dry weight. The dry weight of concentrated sludge was 6.85%.

Sludge suspension: According to the dry weight, 43.8 g of concentrated sludge was calculated and suspended in 1 L mineral medium to yeild a concentration of 3 g suspended solids/L. The final concentration of the activated sludge in the test medium was 30 mg/L.
Duration of test (contact time):
28 d
Initial conc.:
21.35 mg/L
Based on:
test mat.
Remarks:
final concentration was clearly above water solubility
Parameter followed for biodegradation estimation:
O2 consumption
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
6
Sampling time:
28 d
Details on results:
Under the test conditions no biodegradation of test item could be observed.
The percentage degradation did not exceed 60 % within the 10-day window and after 28 days of incubation.
The test item is considered not readily biodegradable.
The reference Item sodium sodium benzoate was sufficiently degraded to 74 % after 14 days. The percentage degradation (> 60 % after 14 days) of the reference item confirms the suitability of the used activated sludge inoculum.

The oxygen demand in the abiotic control was zero; no correction of the test item degradation rates had to be done.
Results with reference substance:
The reference Item sodium sodium benzoate was sufficiently degraded to 74 % after 14 days. The percentage degradation of the reference item confirms the suitability of the used activated sludge inoculum.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Under the test conditions no biodegradation of test item could be observed. The percentage degradation did not exceed 60 % within the 10-day window and after 28 days of incubation. The test item is considered not readily biodegradable.

Description of key information

OECD 301F: not readily biodegradable

Key value for chemical safety assessment

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

Additional information