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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Study period:
1990
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
yes
Remarks:
: for OECD 301D secondary effluent is normally used as innoculum, whereas in this study activated sludge was used.
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Inoculum (secondary activated sludge) was sampled from an activated sludge plant (Duiven, NL) treating predominantly domestic wastewater. The activated sludge was preconditioned (by 7 day aeration of a 200 mg dry weight/L suspension) to reduce the endogenous respiration rate.
Duration of test (contact time):
98 d
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
The following test series were prepared:
(i) mineral nutrient solution without test material and without inoculum
(ii) mineral nutrient solution without test material but with inoculum (inoculum blank)
(iii) mineral nutrient solution with test material and with inoculum
(iv) mineral nutrient solution with sodium acetate and with inoculum (procedure control)
(v) mineral nutrient solution without test material but without inoculum and evaporated silica gel (inoculum blank)

Inoculum concentration in BOD bottles was 2 mg/L

Test substance (because of low water solubility) was dissolved in dichloromethane and added to 2 g silica gel. Dichloromethane was allowed to evaporate. The entire content was added to BOD bottles.
Reference substance (sodium acetated) was added at 6.7 mg/L.

The temperature was not mentioned in the report. As the GLP report claimed compliance with OECD301D, it is assumed that the experiment was performed at 22 +/- 2 °C.

Dissolved oxygen was measured at 5, 15, 28, 42, 56, 70 and 98 days. Measurements at 28, 42, 56, 70 and 98 days were performed in the same BOD vessels (opening and closing again).

Oxygen consumption (corrected for oxygen consumption in the innoculum blank) was compared with the ThOD to calculate % biodegradation.




Reference substance:
acetic acid, sodium salt
Preliminary study:
Not applicable
Test performance:
See details on study design above
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
5 d
Parameter:
% degradation (O2 consumption)
Value:
2
Sampling time:
15 d
Parameter:
% degradation (O2 consumption)
Value:
15
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
29
Sampling time:
42 d
Parameter:
% degradation (O2 consumption)
Value:
46
Sampling time:
56 d
Remarks on result:
other: 54% after 70 days and 60% after 98 days
Details on results:
pH was 7.5 at day 28
Oxygen levels were always >0.5 mg/L as required by the guideline
Oxygen depletion in inoculum blanks after 28 days was <1.5 mg/L as required by the guideline. Oxygen depletion in the inoculum blank gradually increased to 2.5 mg/L after 98 days
Results of duplicate bottles were within 25%
Reference standard met the criteria
The concentration of inoculum (2 mg dw/L) is in agreement with the principle of using a "relatively small number of micro-organisms" as required by OECD 301D.
Results with reference substance:
75% after 5 days, 85% after 15 days and 87% after 28 days
Validity criteria fulfilled:
yes
Interpretation of results:
other: ultimately biodegradable
Conclusions:
Dianol 320 is not readily biodegradable in a closed bottle biodegradation test according to OECD 301D. Ultimate biodegradation (i.e. complete mineralisation to CO2) was demonstrated (60% biodegradation after 98 days).
Executive summary:

The biodegradability of Dianol 320 was studied in a closed bottle test according to guideline OECD 301D. The incoculum was secondary activated sludge from a wastewater treatment plant receiving predominantly domestic wastewater. The inoculum concentration was 2 mg dry weight/l and the test substance concentration was 2 mg/L. The test substance (which has a low water solubility) was applied to an inert solid support (silica gel) prior to addition to the test medium. All quality criteria were fulfilled (reference standard, oxygen consumption in control, oxygen levels during the test and reproducibility). Dianol 320 was not readily biodegradable (only 15% degradation after 28 days). The study was extended, and after 98 days 60% biodegradation was observed, indicating the ultimate biodegradability of Dianol 320.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
2010
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
A sample of activated sludge was obtained from Worlingworth sewage treatment works (Suffolk, UK), which treats predominantly domestic waste. At the time of collection, the sludge was sieved (1 mm^2) then transported to the laboratory and left stand for approximately 30 minutes to allow the sewage solids to settle. A portion of the supernatant was removed and the sludge aerated until required. The concentration of suspended solids in a homogenised sample was determined before the start of the test. Aliquots (10 ml) of the sludge were filtered through dried and pre-weighed Whatman GF/C filters, which were then dried again at approximately 105°C for one hour, allowed to cool in a desiccator and reweighed. The mixed liquor suspended solids (MLSS) content of the sludge was then determined and the volume required to give a solids level of 30 mg/l in test cultures was calculated. This was added to flasks four days before test initiation to allow a period of ageing.
Duration of test (contact time):
28 d
Initial conc.:
ca. 20 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
ca. 0
Sampling time:
9 d
Remarks on result:
other: Lag period
Parameter:
% degradation (O2 consumption)
Value:
10
Sampling time:
12 d
Parameter:
% degradation (O2 consumption)
Value:
35
Sampling time:
16 d
Parameter:
% degradation (O2 consumption)
Value:
50
Sampling time:
20 d
Parameter:
% degradation (O2 consumption)
Value:
66
Sampling time:
28 d
Details on results:
Two replicates, with one showing faster initial response than the other. Final results at 28 days were 59% and 73% (mean 66%)
Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
Biodegradation started on day 9 of the test and had reached 66% after 28 days (this being the average of two replicates). The test substance was therefore considered to be inherently biodegradable, but not readily biodegradable.
Executive summary:

The ready biodegradability potential of the test substance was determined in accordance with the OECD Guideline for Testing of Chemicals 301F. The registered substance BPA 3PO has not been directly tested, but data for BPA 2PO has been generated for read-across purposes. The ready biodegradability of the test substance was determined using the manometric respirometry test. Domestic activated sludge was exposed to 20 mg/l of the test substance and oxygen consumption measured. Biodegradation started on day 9 of the test and had reached 66% after 28 days (this being the average of two replicates). The test substance was therefore considered to be inherently biodegradable, but not readily biodegradable.

Description of key information

The substance was found to be inherently or ultimately biodegradable and could not be considered readily biodegradable under the conditions of the tests conducted.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable
Type of water:
freshwater

Additional information

A key study was conducted on the read-across substance BPA 2PO according to OECD Guideline for Testing of Chemicals 301F. This study found a biodegradation of 66% of the substance after 28 days using 20 mg/l of the substance. The supporting study was conducted on BPA 2PO according to OECD Guideline for Testing of Chemicals 301D. The study found a biodegradation of 15% after 28 days and 46% after 56 days using 2 mg/l of the substance. A disregarded study has also been included in this section of the dossier. This study was conducted on BPA 5PO according to OECD Guideline for Testing of Chemicals 301B. A biodegradation of 101% was found after 28 days. This study was considered invalid as it contradicted the known biodegradability behaviour of similar substances e.g. BPA 2PO and BPA EO which are both known to have limited biodegradation potential. It should be noted that degradation products have not been identified during the degradation tests but Bisphenol A (BPA) is considered as a potential degradation product. BPA has been found to be not persistent (see information concerning the biodegradation of BPA in the European Union Risk Assessment Report: EC (2010) European Union Risk Assessment Report: 4,4’-Isopropylidenediphenol (Bisphenol A), 3rd Priority List, Volume 37, European Commission Joint Research Centre,Addendum of 2008, Final Approved Version Awaiting Publication, Italy.