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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Endpoint:
biodegradation in water: sediment simulation testing
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance is readily biodegradable
Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Biodegradation testing was initiated on 17th April 1996 and completed on 15th May 1996
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The data generated in this study are not considered suitable for determining the biodegradability of the substance in seawater. The toxicity control treatment indicates significant inhibition of micro-organism when compared to the reference compound only. The % biodegradation presented in this study are therefore not representative of the biodegradability of this substance at environmentally relevant concentrations
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 306 (Biodegradability in Seawater)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
GLP No: 40294 signature 05/06/96
Radiolabelling:
no
Oxygen conditions:
aerobic
Inoculum or test system:
natural water
Duration of test (contact time):
28 d
Initial conc.:
4.8 mg/L
Based on:
test mat.
% Degr.:
4
Parameter:
O2 consumption
Sampling time:
28 d
Transformation products:
not measured

Table 2 (attached) presents the results from the biodegradation testing of the test substance. Figure 1 (attached) shows the biodegradation curve of the test substance. The raw data are presented in Appendices 1, 2, 3 and 4 (all attached).

- Validation of Results:

The test is considered valid if the following requirements are met:

* The blank respiration has not exceeded 30% of the oxygen in the test bottle.

* Percent degradation of the reference substnace has reached the level of 50% within 5 days (the lag phase not included).

* The temperature has been in the range of 20.0°C ± 2.4°C.

In this test, the control parameters yielded the following values:

* Percent (%) degradation of the reference substance after 5 days : 68%

* The blank respiration:

- 5 days : 0.1 mg O2/l

- 15 days: 0.4 mg O2/l

- 28 days: 0.4 mg O2/l

i.e. the blank respiration is less than 30% of the oxygen in the test bottle.

* Temperature variation during the test: 18.0 - 21.0°C.

Validity criteria fulfilled:
no
Remarks:
Significant inhibition observed in toxicity control
Conclusions:
A test substance has a potential for biodegradation in the marine environment if it has been degraded ≥60% within 28 days.

The test substance was degraded by 4% after 28 days. Based on this, the test substance does not have the potential for biodegradation in the marine environment.
Executive summary:

Biodegradation testing has been performed on the test substance based on OECD guideline 306 for testing of chemicals: "Biodegradability in Seawater - Closed Bottle Test". The test substance was degraded by 4% after 28 days based on COD calculations and measurements to account for O2 consumption by nitrification. The test substance has not a potential for biodegradation in the marine environment.

Endpoint:
biodegradation in water: sewage treatment simulation testing
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
The test was carried out between 7th August and 9th October 1984
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The study was not conducted in a manner consistent with EU Method C.10 and was not suitable for assessing the biodegradability of the substance. The increasing concentrations of the test item dosed to the system suggests that inhibition due to direct toxicity was responsible for the lack of biodegradability in the test vessel.
Qualifier:
equivalent or similar to guideline
Guideline:
EU Method C.10 (Biodegradation: Activated Sludge Simulation Test)
Deviations:
yes
GLP compliance:
no
Radiolabelling:
no
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic (adaptation not specified)
Duration of test (contact time):
9 wk
Initial conc.:
5 mg/L
Based on:
test mat.
% Degr.:
15
Parameter:
DOC removal
Sampling time:
9 wk
Transformation products:
no

- Validity:

Under normal operating conditions porous pot activated sludge units will give a removal of DOC of at least 80%. Stevenage domestic sewage normally contains about 100 mg C/l. The mean effluent DOC, during the settled phase for the control unit in the present study was 10.1 to 16.7 mg C/l, which represents an 80 -90% removal of DOC. Therefore, the units can be assumed to have been performing normally under the conditions of the test.

- Calculated dosing concentrations:

The mean flow rate of test substance into the porous pot calculated from the volume of test substance stock solution used each day and the mean flow rate of sewage estimated from the quantitiy of effluent collected each day, are given in Table 1. Dosing concentrations calculated from this data, expressed as mg test substance/1 sewage and mg C/l sewage are also presented in Table 1.

- Specific analysis:

Table 2 shows the concentration of the test substance in the effluent from the test unit at each dosing concentration as determined by specific analysis along with percentage removal figures for weeks 3 to 9. During weeks 1 and 2 the concentration of the test substance was near to the detection limits of the analytical method and thus a percentage removal figure was not calculated. The results indicate that 4% of the test substance dosed to the porous pot was removed between weeks 3 and 4 (nominal dosing concentration 10 mg/l) and 47% was removed during week 5 (nominal dosing concentration 15 mg/l). The percentage removal decreased to 33% during the first week of adding nominally 20 mg/l (week 6), and had decreased further to 15% during the 'settled phase' (weeks 7 -9). The concentrations of the test substance in each sample taken for analysis have been plotted against time in Figure 1. Effluent samples from the control unit did not give a positive blank value.

- DOC analysis:

Table 3 shows differences between the DOC concentrations of the test and control effluents at nominal dosing concentrations between 9.0 and 12.0 mg C/l along with the percentage removal figures. DOC analysis was not carried out for the first part of the test (weeks 1 - 4). There was an apparent 25% removal of DOC during week 5 of the test (nominal dosing concentration 9 mg C/l). This figure decreased to 19% during week 6 (nominal dosing concentration 12 mg C/l), and had decreased further to 13% during the settled period (nominal dosing concentration 12 mg C/l). The DOC concentrations in the test and control samples taken for analysis along with the test DOC concentrations minus the control values for each sampling time have been plotted in Figure 2.

- Concentration of suspended solids:

The mean concentrations of suspended solids as determined for test and control units during each phase of the test are presented in Table 4. The concentrations were comparable in both units throughout the test.

Validity criteria fulfilled:
no
Conclusions:
The results of specific analysis and DOC analysis show that the test substance was not biodegraded or absorbed at a nominal concentration of 20 mg/l, during the settled phase of operation in this test.
Executive summary:

The biodegradability of the test substance was assessed by an activated sludge simulation test.

The test substance was added to a porous pot activated sludge unit at an initial nominal concentration of 5 mg/l (Weeks 1 and 2), increasing in stages (10 mg/l - Weeks 3 and 4; 15 mg/l - Week 5) to 20 mg/l for the final part of the test (Weeks 6 to 9). A control unit was operated without the test substance. The concentrations of test substance in the effluent of the test unit, and of dissolved organic carbon (DOC) in the test and control effluents were determined at regular intervals and from these results an estimate of bioelimination was made.

The mean removal of the test substance over the settled period of operation (7th to 9th weeks), measured by specific analysis, was found to be 15%, whereas the mean removal based on the concentration of dissolved organic carbon over the same period was 13%.

It was concluded that the test substance was not biodegraded or absorbed onto sludge solids in this test.

Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
other:

Description of key information

No reliable studies are available for simulation tests assessing biodegradation in water and sediments.

Key value for chemical safety assessment

Additional information

No information available.