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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:
Nov 09, 2015 - Jan 26, 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
OECD 301F protocol
HJ/T 155-2004 the Guideline ofGood Laboratory Praetices on Chemical Testing, MEP, China
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
July 17, 1992
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
EEC Publication No. L 383 A, December 1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
The Guidelines of Good Laboratory Practices on Chemical Testing (HJ/T 155-2004, MEP, China).
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
The fresh activated sludge used in the test was collected from Wuzhong district urban area
sewage treatment plant. The address of the plant is No. 1, Baodai East Road, Suzhou city. The batch
No. ofinoculum was AS-20151103-01.

The activated sludge was washed with test medium after removing the suspended solids and
coarse particles on the day of collection, the activated sludge was centrifuged at 1100 g for 5 minutes,
and the supernatant was discarded. The process was repeated for 3 times.

The dry weight content of the activated sludge was determined in triplicates after pre-treatment,
and the average value was 10.63%. 75.2453 g of the activated sludge (wet weight) was weighed and
suspended it with test medium to made up to 2 litres (the dry weight concentration was calculated tobe
4 g/L based on the dry weight content of 10.63%). After that, the suspension was aerated for 6 days at
test temperature. The d1y weight content of the activated sludge was redetermined before inoculation
and the average value oftriplicate measurements was 5.69%.
Duration of test (contact time):
28 d
Initial conc.:
32 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
1.68
Sampling time:
14 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
4.27
Sampling time:
28 d
Details on results:
The percentage biodegradation oftest substance in duplicates were 2.52% and 0.84% (mean 1.68%) on day 14, and 7.63% and 0.90% (mean 4.27%) at the end of the test (on Day 28).
Results with reference substance:
The percentage biodegradation were 81.52% in procedure control on day 14, and 40.47% in the toxicity control on day 14, indicating that the inoculum was not inhibited by the test substance and met the test requirement.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The degradation rate of the test item did not reach 60 % within the 10-day window and after 28 days of incubation. Thus, the test item is not readily biodegradable.
Executive summary:

The purpose of this study was to determine the ready biodegradability of the test item.

The information for this endpoint study record was obtained from an experimental study. The methods applied are fully compliant with OECD TG  301F.
The test item was exposed to aerobic activated sludge from the aeration tank of a domestic waste water treatment plant for 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. This type of study is recognized by the international test guidelines and should provide a rational basis to assess the ready biodegradation properties of the
test item when incubated with aerobic activated sludge.

The percentage biodegradation of the test substance in duplicates were 2.52% and 0.84% (mean 1.68%) on day 14, and 7.63% and 0.90% (mean 4.27%) at the end of the test on day 28. The percentage biodegradation were 81.52% in procedure control on day 14, and 40.47% in the toxicity control on day 14, indicating that the inoculum was not inhibited by the test substance and met the test requirement.

Under the conditions of this study the test item is considered to be 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