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Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21.5.2021-16.7.2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Version / remarks:

July 1992

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Preparation of Activated Sludge Inoculum:
The activated sludge used for this study was washed by centrifugation and the supernatant liquid
phase was decanted. The solid material was re-suspended in isotonic saline solution by shaking
and was again centrifuged. This procedure was repeated twice.
An aliquot of the final sludge suspension was weighed (5.878 g wet weight), dried and the
ratio of wet sludge to dry weight (0.6640 g dry weight) was determined. Based on this ratio,
calculated amount of wet sludge (5 g dry weight that was equivalent to 44.26 g wet sludge)
was suspended in mineral medium (Section 5.4; ad. 1000 mL) to yield a concentration
equivalent to about 5 g per litre (on dry weight basis). The prepared activated sludge
inoculum was aerated under test conditions (for 7 days) until use.
The pH of the activated sludge inoculum after preparation was 7.64, just before use the pH
was: 7.29. A pH adjustment of activated sludge inoculum was not performed.
NaCl (for isotonic saline solution): Manufacturer: lach:ner;
Batch Number: PP/2020/00452,
Retest date: 28 August 2022

Duration of test (contact time):

ca. 28 d

Initial conc.:

ca. 5 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

> 1 - < 2

St. dev.:

18

Sampling time:

28 d

Results with reference substance:

5,35

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test item, 1133-Tetrachloropropene, was considered to be not readily
biodegradable (at 5 mg/L concentration 17.1 % biodegradation was noticed on day 28).
According to the test guidelines the pass level for ready biodegradability is 60 % of
ThODNH3.

Executive summary:

The test item, 1133-Tetrachloropropene, was considered to be not readily
biodegradable (at 5 mg/L concentration 17.1 % biodegradation was noticed on day 28).
According to the test guidelines the pass level for ready biodegradability is 60 % of
ThODNH3.