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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
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)
Version / remarks:
2008
Deviations:
no
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
adopted July 1992
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
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, WWTP Odenthal)
Date of collection : 2017-06-12
Concentration of inoculum : 30 mg/L suspended solids

Pre-treatment of the inoculum
− Before use, the inoculum was stored for one day at room temperature under continuous stirring with aeration.
− The sludge was washed twice by adding mineral medium and centrifuging for 10 min at 2000 rpm and 20 °C and decanting off the supernatant.
− An aliquot of the wet sludge was dried in order to determine the wet weight / dry weight ratio of the sludge and to prepare a stock suspension (activated sludge) of 3 g dw/L.
− The calculated amount of sludge, needed to achieve 300 mL of this stock suspension, was dissolved in mineral medium and then filled up to a defined end volume.
Duration of test (contact time):
>= 0 - <= 28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Remarks:
BOD (mg O2/L)
Details on study design:
A suspension of 100 mg/L test item in a mineral medium, equalling to 50-100 mg ThOD or COD/Litre as the nominal sole source of organic carbon, was stirred in a closed flask and inoculated at a constant temperature (22 ± 1 °C) for up to 28 days under aerobic conditions in the dark.
The consumption of oxygen (BOD) was determined by measuring the drop in pressure in the automated respirometer flasks. Evolved carbon dioxide was absorbed in sodium hydroxide. The amount of oxygen taken up by the test item (corrected for uptake by blank inoculum, run in parallel) was expressed as a percentage of theoretical oxygen demand (ThOD).
The endogenous activity of the inoculum was checked running parallel blanks with inoculum but without test item. A reference compound (sodium benzoate) was run in parallel to check the operation of the procedures.
A toxicity control (test item and reference compound mixed, one replicate) was run in parallel, to ensure that the chosen concentration of the test item was not inhibitory to microorganisms.
Degradation was followed by the determination of oxygen uptake and measurements were taken at frequent intervals to allow the identification of the beginning and end of biodegradation and the slope of the biodegradation curve.
The test lasted for 28 days.
Because of the nature of biodegradation and of the mixed bacterial populations used as inoculum, determinations of test item and inoculum blank were carried out in triplicate and of reference compound in duplicate.
The oxygen uptake was calculated from the readings taken at regular and frequent intervals, using the method given by the manufacturer of the equipment. At the end of incubation, the pH was measured in the flasks.
Start of the incubation period : 2017-06-13
End of the incubation period : 2017-07-11
Reference substance:
benzoic acid, sodium salt
Remarks:
Purity : 99.9 % Batch-no. : A0357641 Expiry date : 2018-03-27
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
7 d
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
14 d
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
21 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Details on results:
Incubation temperature : 22 ± 1 °C
pH values after 28 days: 7.7 - 8.3
Parameter:
BOD5
Value:
15.7 other: mg O2/L
Remarks on result:
other: BOD values after 28 days
Parameter:
BOD5
Value:
11.4 other: mg O2/L
Remarks on result:
other: BOD values after 28 days
Parameter:
BOD5
Value:
17.1 other: mg O2/L
Remarks on result:
other: BOD values after 28 days
Results with reference substance:
The reference compound sodium benzoate showed 88 % degradation after 14 days.

All validity criteria of the test method were met.

The reference compound reached the level of ≥ 60 percent for ready biodegradability within 14 days (table 4).

The toxicity control exhibited degradation rates > 25 % within 14 days (table 5).

At the end of the test, at the plateau, or the end of the 10-d window, biodegradation in parallels with test item did not differ by more than 20 percentage points (table 3).

The oxygen uptake of the inoculum blank was ≤ 60 mg/L (table 1).

In cases where the degradation was ≤ 60 %, the pH values (table 2) were in between 6.0 and 8.5 at the end of the test.

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Within 28 days, a degradation rate of 0 % was determined for 1,4-Dichloro-5,8-dihydroxyanthraquinone. Therefore 1,4-Dichloro-5,8-dihydroxyanthraquinone is considered to be "Not Readily Biodegradable".
Executive summary:

A study was performed to assess the ready biodegradability of 1,4-Dichloro-5,8-dihydroxyanthraquinone. The study was conducted in accordance with the Council Regulation (EC) No 440/2008, Method C.4-D “Manometric Respirometry Test“. This test method is in all essential parts identical with OECD Guideline 301 F.

A suspension of 1,4-Dichloro-5,8-dihydroxyanthraquinone in a mineral medium was inoculated and incubated for 28 d under aerobic conditions. During this period, degradation was followed by continuous automated BOD determinations. 1,4-Dichloro-5,8-dihydroxyanthraquinone showed:

0 % degradation after 7 days

0 % degradation after 14 days

0 % degradation after 21 days

0 % degradation after 28 days

Therefore, 1,4-Dichloro-5,8-dihydroxyanthraquinone is considered to be “Not Readily Biodegradable“. The reference compound sodium benzoate showed 88 % degradation after 14 days.

Description of key information

A study was performed to assess the ready biodegradability of 1,4-Dichloro-5,8-dihydroxyanthraquinone. The study was conducted in accordance with the Council Regulation (EC) No 440/2008, Method C.4-D “Manometric Respirometry Test“. This test method is in all essential parts identical with OECD Guideline 301 F.

A suspension of 1,4-Dichloro-5,8-dihydroxyanthraquinone in a mineral medium was inoculated and incubated for 28 d under aerobic conditions. During this period, degradation was followed by continuous automated BOD determinations. 1,4-Dichloro-5,8-dihydroxyanthraquinone showed:

0 % degradation after 7 days

0 % degradation after 14 days

0 % degradation after 21 days

0 % degradation after 28 days

Therefore, 1,4-Dichloro-5,8-dihydroxyanthraquinone is considered to be “Not Readily Biodegradable“.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information