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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:
2003
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes
Specific details on test material used for the study:
Chemical name : 2,4,6-Trimethylbenzoylphenylphosphinsäureethylester
Substance number : 01/0673-1
Product number : 201040
CAS number : 84434-11-7
Molecular formula : C18H2103P
Molecular weight [g/mol] : 316
Aggregate state : liquid
Density [g/ml] : 1,1 at 20 °C
Water-solubility [mg/1] : c. 10 mg/I
Colour : yellow-clear
Purity of the test substance : 96,4-area % [3]
Impurities : organic By products 3,6 %
Homogeneity : homogeneous
Instability against : unknown
Special conditions for storage : storage at refrigerator and light exclusion
Storage stability : The stability of the test substance under storage conditions over the test period was guaranteed by the sponsor. The data are in the responsibility of the sponsor.
Further remarks : The data of the purity and impurities of the test substance are in the responsibility of the sponsor, and the sponsor holds this responsibility
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Inoculum: concentration of dry substance 30 mg/l.
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 principle of the Manometric Respirometry Test
The Manometric Respirometry Test is a static method for testing the ultimate aerobic biodegradability of a test substance in water . Mixtures of the test substance, a defined inorganic medium and an inoculum, which is not pre-adapted (e.g. activated sludge or effluent of a municipal or laboratory waste water treatment plant), are incubated and aerated in a respirometer (Sapromat) at room temperature up to 28 days regulary . The oxygen used for the biodegradation of the test substance (biochemical oxygen demand, BOD) is continuously produced and measured by the test apparatus .
In addition to the test substance the following investigations are required : blank values (BC), bio-degradation of a reference substance (RS), inhibition of the inoculum (IH) and abiotic elimination (PC).

Evaluation of Test Results
~ The biochemical oxygen demand gives unequivocal evidence for biodegradation . The measured BOD is compared with the calculated theoretical oxygen demand (ThOD) or the measured chemical oxygen demand (COD) of the test substance and indicated as biodegradation degree in per cent . Since the micro-organisms oxidize only part of the test substance and incorporate the rest as biomass, substances with a degree of >60 % biodegradation are considered to be sufficiently biodegradable. The relation BOD to ThOD or COD is classified as follows :

>60 % in 10 days "readily biodegradable (OECD criteria)"
>60 % "biodegradable"
20-60% "in this test moderately or partly biodegradable"
<20% "in this test poorly biodegradable"

One of the OECD criteria for ready biodegradable substances is the threshold value of 60% biodegradation within a period of 10 days during a total test period of 28 days . If a test substance is biodegradable in this test, it can be assumed that it will be biodegraded in the environment, especially in wastewater treatment plants and surface
waters. If insufficient biodegradation was measured, the test substance may nevertheless be inherently biodegradable . This has to be shown by further investigations .
Reference substance:
aniline
Parameter:
% degradation (O2 consumption)
Value:
< 10
Sampling time:
28 d
Details on results:
Kinetic of test substance (in %):
ca. 4 after 5 day(s)
ca.6 after 10 day(s)
ca.8 after 21 day(s)

Full results tables are attached.
Results with reference substance:
Kinetic of control substance (in %): ca. 70 after 12 day(s)
Reference substance : aniline
Degradation degree of the reference substance after 14 days (% BOD/ThOD) : 70-80
Degradation degree in the inhibition control after 14 days (% BOD/ThOD) : 40-50

Test temperature : 22±1 'C

Deviation of the degradation degree of the test substance in the plateau phase <20% : yes

Degradation degree of the reference substance >60% after 14 days : yes

Degradation degree in the inhibition control >25 % after 14 days : yes

Oxygen demand in the blank control < 60 mg/I at the end of the test : yes

pH values in the test assays ranged from pH 6 to 8,5 at the end of the test : yes

The test is valid : yes

Proof of ready biodegradability according to OECD criteria

Degradation degree of the test substance >60% within 28 days : no

10-day window met : no

No pre-adapted inoculum used : yes

Test substance is readily biodegradable according to OECD criteria : no

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The biodegradation of the test material was determined to be <10 at 28 days under the conditions of the test.

Description of key information

The study was conducted to recognised testing guidelines, and with GLP certification.

Key value for chemical safety assessment

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

Additional information

The substance was found to be not readily biodegradable in a standard OECD 301F respirometric test. At a test concentration of 100 mg/L the biodegradation degree (BOD of ThOD) was 0 – 10%.