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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 April 18, 2006 to June 26, 2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
no
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Type: Mixed population of aquatic microorganisms (activated sludge)
Origin: Aeration tank of a wastewater plant treating predominantly domestic sewage (Wupper area water authority, STP Odenthal)
Date of collection: 2006-04-18
Pretreatment: Activated sludge was washed twice with mineral medium; sludge was separated by centrifugation
Concentration of inoculum: 30 mg/L ss
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Remarks:
(The consumption of oxygen was determined by measuring the quantity of oxygen (produced electrolytically) required to maintain constant gas volume in the respirometer flask)
Details on study design:
PRETREATMENT OF THE TEST SUBSTANCE
- 25 mg test substance was weighed out on aluminium foil. This substance inclusive of the aluminium foil was added to the test vessels to give a test substance concentration of 100 mg/L.

EXPOSURE CONDITIONS
- Test volume: 250 mL
- Test apparatus: Oxi Top System (WTW)
- Mixing: One magnetic stirrer per test vessel
- Incubation time: 28 d
- Incubation temperature: 22±2°C

TREATMENT
- Control (3 replicates)
- Test substance (3 replicates)
- Reference substance (3 replicates)
- Toxicity Control (2 replicates)

CHEMICAL ANALYSIS
- Nitrate-N/Nitrite-N method: Determination of nitrite nitrogen and nitrate nitrogen and the sum of both by flow analysis (CFA and FIA) and spectrometric detection
- Standard: EN ISO 13395
- Test apparatus: Continuous Flow Analyser SKALAR SAN Plus System
Reference substance:
benzoic acid, sodium salt
Remarks:
(99% pure)
Test performance:
The test substance was not toxic effects to bacteria.
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Details on results:
pH of the test vessels: 7.3-7.4

Degradation of test substance:
0% degradation after 4 d
0% degradation after 6 d
0% degradation after 8 d
0% degradation after 12 d
0% degradation after 14 d
0% degradation after 18 d
0% degradation after 20 d
0% degradation after 22 d
0% degradation after 26 d
0% degradation after 28 d
Results with reference substance:
Degradation of reference substance:
64% degradation after 4 d
78% degradation after 6 d
82% degradation after 8 d
87% degradation after 12 d
88% degradation after 14 d
90% degradation after 18 d
91% degradation after 20 d
92% degradation after 22 d
92% degradation after 26 d
94% degradation after 28 d
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Under the study conditions, the test substance was considered to be ‘not readily biodegradable’.
Executive summary:

A study was conducted to assess the ready biodegradability of the test substance according to EU Method C.4-D (which is in most parts equivalent to OECD Guideline 301 F), in compliance with GLP.

Activated sludge was inoculated with 100 mg/L of the test substance (in triplicate) in a closed flask at a constant temperature (22±2°C) for 28 d. Degradation was assessed by the determination of Biochemical Oxygen Demand (BOD) on Days 4, 6, 8, 12, 14, 18, 20, 22, 26 and 28. A toxicity test and a control solution containing the reference substance benzoic acid, sodium salt (100 mg/L) together with inoculum were used for validation purposes. The test substance degraded 0% by Day 28. No toxicity of the test substance was observed in the toxicity control. The reference compound showed 88% degradation at Day 14.

Hence, under the study conditions, the test substance was considered to be ‘not readily biodegradable’.

Description of key information

Under the study conditions, the test substance was considered to be ‘not readily biodegradable’.

Key value for chemical safety assessment

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

Additional information

A study was conducted to assess the ready biodegradability of the test substance according to EU Method C.4-D (which is in most parts equivalent to OECD Guideline 301 F), in compliance with GLP. Activated sludge was inoculated with 100 mg/L of the test substance (in triplicate) in a closed flask at a constant temperature (22±2°C) for 28 d. Degradation was assessed by the determination of Biochemical Oxygen Demand (BOD) on Days 4, 6, 8, 12, 14, 18, 20, 22, 26 and 28. A toxicity test and a control solution containing the reference substance benzoic acid, sodium salt (100 mg/L) together with inoculum were used for validation purposes. The test substance degraded 0% by Day 28. No toxicity of the test substance was observed in the toxicity control. The reference compound showed 88% degradation at Day 14. Hence, under the study conditions, the test substance was considered to be ‘not readily biodegradable’ (Weyers, 2006a).