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Environmental fate & pathways

Biodegradation in water: screening tests

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biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
27April 2011 to 25 May 2011
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The test was conducted according to the principles of GLP and a recognised ISO marine test guideline.

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
other: OECD guideline 306, 'Biodegradability in Seawater- Closed Bottle Method' (OECD 1992)
GLP compliance:

Test material

Study design

Oxygen conditions:
Inoculum or test system:
natural water
Details on inoculum:
Populations of bacteria which occur naturally in seawater. The raw seawater used for this study was supplied by a submersible pump situated on Sutherland’s pier on the west side of Flotta in Scapa Flow. It is pumped continuously from a depth of two metres below low water spring tide level, before passing up 1.8 kilometres of plastic pipe to a 20,000 litre storage tank. Two smaller pumps move the water to three settlement tanks situated nine metres above floor level. The
seawater temperature varies between 6 ºC in the winter and 14 ºC in the summer. The salinity is between 34‰ and 37‰. Five to seven days before test commencement, raw seawater passes by gravity through a 45 μm filter to the ageing tank stored in darkness.

The seawater used for testing was collected on 19 April 2011, the temperature at collection was 13C the seawater had a salinity of 36% and an initial population of 1.9 x10+3 CFU's per ml.

Pre-treatment prior to testing:
Filtered through 45 μm mesh
Nutrient enriched
Sedimentation and decanting
Aged in darkness for: 8 days
Aerated for: 20 minutes

The seawater had a temperature on day zero of 20.3C and a mcicrobial count of 2.13 x10+3
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
3.504 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
The study was undertaken with the Test material, test material + soluble reference (Sodium benzoate),oxygen consumption blank and soluble reference sodium benzoate. Test bottles were incubated at 20ºC ± 3ºC for 28 days. Dissolved oxygen readings were taken at 7 day intervals.
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradation
% degradation (O2 consumption)
Sampling time:
28 d

BOD5 / COD results

1.484 other: mgO2/mg
Results with reference substance:
The soluble reference material, sodium benzoate, degraded by more than 60% in the first 14 days, indicating that the seawater used in
the test contained a satisfactory population of viable bacteria..

Applicant's summary and conclusion

Validity criteria fulfilled:
Interpretation of results:
other: The test substance attained 44% degradation after 28 days but cannot be considered to be readily biodegradable in the marine environment under the terms and conditions of OECD Guideline No 306.
The test substance biodegraded by 40% over 28 days and showed an inhibition of 2% to seawater bacteria.
A maximum biodegradation of 44% on day 21 of the 28 day study.
Executive summary:

The test was conducted to OECD guideline 306, 'Biodegradability in Seawater- Closed Bottle Method' (OECD 1992) and in accordance with the study plan and met all relevant validity criteria. There were no interferences in this test.

The test substance was degraded by 40% after 28 days based on COD and measurements to account for O2 consumption.