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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
Reason / purpose:
data waiving: supporting information
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:
the study does not need to be conducted because the substance is readily biodegradable
Reason / purpose:
data waiving: supporting information
Endpoint:
biodegradation in water: sewage treatment simulation testing
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
From January 17, 2007 to May 16, 2007
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
KL2 due to RA
Justification for type of information:
Refer to the Quaternary ammonium salts (QAS) category or section 13 of IUCLID for details on the category justification.
Qualifier:
according to
Guideline:
OECD Guideline 303 A (Simulation Test - Aerobic Sewage Treatment. A: Activated Sludge Units)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Nature: Activated sludge
Sampling site: Duiven, the Netherlands
Preparation of inoculum for exposure: Sludge was used upon arrival
Initial cell concentration: 3 g DW/L
Duration of test (contact time):
58 d
Initial conc.:
49 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
other: Non-purgeable organic carbon concentration (NPOC)
Details on study design:
TEST SYSTEM:
- Test apparatus: The CAS test was performed in a Husmann-type units constructed of glass. The units consisted of an aeration vessel capable of holding 0.35 litre from which the liquor was passed continuously to a settler of 0.3 litre capacity. The domestic waste water liquor in a cooled vessel was supplied with a pump. The liquor passed through the aeration vessel and settler and treated effluent left the apparatus to be collected in a vessel.
Aeration was achieved through a capillary on the bottom of the aeration section at a rate of approximately 9 L/hour air.
- Number of units: Control and test unit
- Aeration device: Capillary on the bottom of the reactor
- Measuring equipment: The NPOC in acidified filtered samples were analysed in a TOC apparatus (Shimadzu, s‟Hertogenbosch, The Netherlands).
The chemical oxygen demand (COD) of the influent and effluent was determined by oxidation with an acid-dichromate mixture in which Cr6+ was reduced to Cr3+ (Hach Lange, Duesseldorf, Germany). The dissolved oxygen concentrations were determined electrochemically using an oxygen electrode (WTW Trioxmatic EO 200) and meter (WTW OXI 530) (Retsch, Ochten, The Netherlands).
The pH was measured using a Knick 765 calimatic pH meter (Elektronische Messgerate GmbH, Berlin, Germany). The temperature was measured with a Tegam thermometer Model 820 (Applikon, Schiedam, The Netherlands). The dry weight (DW) of the inoculum was determined by filtering the activated sludge over a pre weighed 12 µm Schleicher and Schüll filter. This filter was dried for 1.5 hours at 104°C and weighed after cooling. DW was calculated by subtracting the weighed filters and by dividing this difference by the filtered volume.
LC-MS/MS was used to analyse the parent compound.

- Test performed in closed vessels due to significant volatility of TS: No
- Analytical parameter: NPOC (non purgeable organic carbon) removal and LC-MS/MS

TEST CONDITIONS:
- Composition of medium: Domestic wastewater contain organic compounds
- Additional substrate: No
- Test temperature: 19-21°C
- pH: 7.0 – 8.0
- Suspended solids concentration: 2 - 3 g/L

SAMPLING:
- At least two times a week for NPOC analysis and 5 times a week during the last week of the test for LC-MS/MS analysis.

STATISTICS:
- NPOC analyses in test and control unit were treated as paired observations. With paired observations an outlier test (Dixon) was performed. t–Statistics were used to determine the significance of the carbon removal.



Test performance:
The performance of the control unit was checked (Day 14 and the last d of the test) by measuring the COD removal (Day 14 and the last d of the test) and the concentrations of ammonium and nitrite in the effluent (Day 14). At Day 14 the COD in the influent and effluent were 517 and 55 mg/L, respectively. At the last day the COD in the influent and effluent were 548 and 47 mg/L, respectively. The COD removal percentages were 89 and 91. The ammonium and nitrite concentrations in the effluent at Day 14 were <2.5 and <2.0 mg/L. These results demonstrate that the test is valid.
Key result
% Degr.:
> 99.98
Parameter:
DOC removal
Sampling time:
40 d
Remarks on result:
other: mean removal during Day 40-58
Key result
% Degr.:
0.016
Parameter:
other: via sorption
Sampling time:
57 d
Key result
% Degr.:
0.023
Parameter:
other: via sorption
Sampling time:
58 d
Key result
% Degr.:
> 99.998
Parameter:
other: Total removal
Sampling time:
58 d
Key result
% Degr.:
ca. 0.02
Parameter:
other: Emission to sludge
Sampling time:
58 d
Key result
% Degr.:
ca. 99.978
Parameter:
other: degraded
Sampling time:
58 d
Transformation products:
not measured
Evaporation of parent compound:
no
Volatile metabolites:
no
Details on results:
- From Day 40 to 58 samples were taken to assess a mean of the removal percentage with organic carbon concentrations. According to the Dixon test, there were no outliers during this period. Subsequently, all data were used in a t-statistic. The mean difference between the NPOC in the influent and effluent was 0.06 ± 1.18 mg/L (95 per cent confidence interval). The mean removal percentage calculated with this mean difference was 99.8 ± 3.5 (95 per cent confidence). This carbon removal is statistically not significant because the t-statistic (n = 15) did not exceed the critical value. The results therefore demonstrate that the continuous activated sludge system treating domestic waste water spiked with test substance removes the organic carbon of test substance (almost) completely from waste water. The high carbon removal percentages also demonstrate that recalcitrant water-soluble substances are not formed during the biodegradation process.
- During the last week of the test the parent compound in the effluent of the test unit was <10 µg/L corresponding to >99.98% removal. Analysis of the test substance present in the activated sludge demonstrated that ~99.98% of the test substance was removed by biodegradation. 
- The performance of the control unit was checked (Day 14 and the last d of the test) by measuring the COD removal (Day 14 and the last d of the test) and the concentrations of ammonium and nitrite in the effluent (Day 14). At Day 14 the COD in the influent and effluent were 517 and 55 mg/L, respectively. At the last day the COD in the influent and effluent were 548 and 47 mg/L, respectively. The COD removal percentages were 89 and 91. The ammonium and nitrite concentrations in the effluent at Day 14 were <2.5 and <2.0 mg/L. These results demonstrate that the test is valid.

For details of results and graphs, please refer to the attachment under 'Attached background material'.
Validity criteria fulfilled:
yes
Conclusions:
Based on the results of the read across study, the test substance can be expected to biodegrade almost completely in conventional biological waste water treatment plants.
Executive summary:

A continuous activated sludge (CAS) study was conducted to determine the biodegradation of the read across substance, C12-16 ADBAC (49.2% active in water), in domestic wastewater according to OECD Guideline 303A, in compliance with GLP. In this study, the domestic waste microorganisms were exposed to the read across substance, by spiking at a nominal influent concentration of 49 mg/L (36 mg/L carbon) for a period of 58 days. An additional unit fed only with the domestic wastewater was maintained as the control group. All samples were analysed for NPOC. A strong increase in the concentration of NPOC was noted on Day 2 in the test units. This was probably caused by toxicity of the read across substance. The activated sludge acclimatised to the read across substance within a few days, resulting in a decrease of the NPOC concentrations. After 3 weeks, very high carbon removal percentages were achieved. The mean removal percentage in the test unit assessed using a HLPC-MS/MS was determined to be 99.998%, indicating ultimate biodegradation. Removal of the read across substance from the influent through adsorption onto sludge was only 0.023% on Day 58, showing that the main mechanism of elimination was biodegradation. Based on the results of the study, the read across substance was removed from wastewater at a very high percentage (approximately 99.998%) in the continuous activated sludge test. Removal of the read across substance from the influent through adsorption onto sludge was only 0.016 to 0.023% at two sampling times, demonstrating that the read across substance was removed almost completely and biodegraded. This suggests that the read across substance biodegrades almost completely in conventional biological wastewater treatment plants (van Ginkel, 2007). Based on the results of the read across study, a similar complete removal of the test substance from the domestic wastewater treatment plants can be expected.

Endpoint:
biodegradation in water: sewage treatment simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From January 17, 2007 to May 16, 2007
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 303 A (Simulation Test - Aerobic Sewage Treatment. A: Activated Sludge Units)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Nature: Activated sludge
Sampling site: Duiven, the Netherlands
Preparation of inoculum for exposure: Sludge was used upon arrival
Initial cell concentration: 3 g DW/L
Duration of test (contact time):
58 d
Initial conc.:
49 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
other: non-pugeable organic carbon concentrations (NPOC)
Details on study design:
TEST SYSTEM:
- Test apparatus: The CAS test was performed in a Husmann-type units constructed of glass. The units consisted of an aeration vessel capable of holding 0.35 litre from which the liquor was passed continuously to a settler of 0.3 litre capacity. The domestic waste water liquor in a cooled vessel was supplied with a pump. The liquor passed through the aeration vessel and settler and treated effluent left the apparatus to be collected in a vessel.
Aeration was achieved through a capillary on the bottom of the aeration section at a rate of approximately 9 L/hour air.
- Number of units: Control and test unit
- Aeration device: Capillary on the bottom of the reactor
- Measuring equipment: The NPOC in acidified filtered samples were analysed in a TOC apparatus (Shimadzu, s‟Hertogenbosch, The Netherlands).
The chemical oxygen demand (COD) of the influent and effluent was determined by oxidation with an acid-dichromate mixture in which Cr6+ was reduced to Cr3+ (Hach Lange, Duesseldorf, Germany). The dissolved oxygen concentrations were determined electrochemically using an oxygen electrode (WTW Trioxmatic EO 200) and meter (WTW OXI 530) (Retsch, Ochten, The Netherlands).
The pH was measured using a Knick 765 calimatic pH meter (Elektronische Messgerate GmbH, Berlin, Germany). The temperature was measured with a Tegam thermometer Model 820 (Applikon, Schiedam, The Netherlands). The dry weight (DW) of the inoculum was determined by filtering the activated sludge over a pre weighed 12 µm Schleicher and Schüll filter. This filter was dried for 1.5 hours at 104°C and weighed after cooling. DW was calculated by subtracting the weighed filters and by dividing this difference by the filtered volume.
LC-MS/MS was used to analyse the parent compound.

- Test performed in closed vessels due to significant volatility of TS: No
- Analytical parameter: NPOC (non purgeable organic carbon) removal and LC-MS/MS

TEST CONDITIONS:
- Composition of medium: Domestic wastewater contain organic compounds
- Additional substrate: No
- Test temperature: 19-21°C
- pH: 7.0 – 8.0
- Suspended solids concentration: 2 - 3 g/L

SAMPLING:
- At least two times a week for NPOC analysis and 5 times a week during the last week of the test for LC-MS/MS analysis.

STATISTICS:
- NPOC analyses in test and control unit were treated as paired observations. With paired observations an outlier test (Dixon) was performed. t–Statistics were used to determine the significance of the carbon removal.



Test performance:
The performance of the control unit was checked (Day 14 and the last d of the test) by measuring the COD removal (Day 14 and the last d of the test) and the concentrations of ammonium and nitrite in the effluent (Day 14). At Day 14 the COD in the influent and effluent were 517 and 55 mg/L, respectively. At the last day the COD in the influent and effluent were 548 and 47 mg/L, respectively. The COD removal percentages were 89 and 91. The ammonium and nitrite concentrations in the effluent at Day 14 were <2.5 and <2.0 mg/L. These results demonstrate that the test is valid.
Key result
% Degr.:
> 99.98
Parameter:
DOC removal
Sampling time:
40 d
Remarks on result:
other: mean removal during Day 40-58
Key result
% Degr.:
0.016
Parameter:
other: via sorption
Sampling time:
57 d
Key result
% Degr.:
0.023
Parameter:
other: via sorption
Sampling time:
58 d
Key result
% Degr.:
> 99.998
Parameter:
other: Total removal
Sampling time:
58 d
Key result
% Degr.:
ca. 0.02
Parameter:
other: Emission to sludge
Sampling time:
58 d
Key result
% Degr.:
ca. 99.978
Parameter:
other: degraded
Sampling time:
58 d
Transformation products:
not measured
Evaporation of parent compound:
no
Volatile metabolites:
no
Details on results:
- From Day 40 to 58 samples were taken to assess a mean of the removal percentage with organic carbon concentrations. According to the Dixon test, there were no outliers during this period. Subsequently, all data were used in a t-statistic. The mean difference between the NPOC in the influent and effluent was 0.06 ± 1.18 mg/L (95 per cent confidence interval). The mean removal percentage calculated with this mean difference was 99.8 ± 3.5 (95 per cent confidence). This carbon removal is statistically not significant because the t-statistic (n = 15) did not exceed the critical value. The results therefore demonstrate that the continuous activated sludge system treating domestic waste water spiked with test substance removes the organic carbon of test substance (almost) completely from waste water. The high carbon removal percentages also demonstrate that recalcitrant water-soluble substances are not formed during the biodegradation process.
- During the last week of the test the parent compound in the effluent of the test unit was <10 µg/L corresponding to >99.98% removal. Analysis of the test substance present in the activated sludge demonstrated that ~99.98% of the test substance was removed by biodegradation. 
- The performance of the control unit was checked (Day 14 and the last d of the test) by measuring the COD removal (Day 14 and the last d of the test) and the concentrations of ammonium and nitrite in the effluent (Day 14). At Day 14 the COD in the influent and effluent were 517 and 55 mg/L, respectively. At the last day the COD in the influent and effluent were 548 and 47 mg/L, respectively. The COD removal percentages were 89 and 91. The ammonium and nitrite concentrations in the effluent at Day 14 were <2.5 and <2.0 mg/L. These results demonstrate that the test is valid.

For details of results and graphs, please refer to the attachment under 'Attached background material'.
Validity criteria fulfilled:
yes
Conclusions:
Under the study conditions, the test substance biodegrades almost completely in conventional biological waste water treatment plants.
Executive summary:

A continuous activated sludge (CAS) study was conducted to determine the biodegradation of the test substance, C12-16 ADBAC (49.2% active in water), in domestic waste water according to OECD Guideline 303A, in compliance with GLP. In this study, the domestic waste microorganisms were exposed to the test substance, by spiking at a nominal influent concentration of 49 mg/L (36 mg/L carbon) for a period of 58 days. An additional unit fed only with the domestic wastewater was maintained as the control group. All samples were analysed for NPOC. A strong increase in the concentration of NPOC was noted on Day 2 in the test units. This was probably caused by toxicity of the test substance. The activated sludge acclimatised to the test substance within a few days, resulting in a decrease of the NPOC concentrations. After 3 weeks, very high carbon removal percentages were achieved. The mean removal percentage in the test unit assessed using a HLPC-MS/MS was determined to be 99.998%, indicating ultimate biodegradation. Removal of the test substance from the influent through adsorption onto sludge was only 0.023% on Day 58, showing that the main mechanism of elimination was biodegradation. Based on the results of the study, the test substance was removed from wastewater at a very high percentage (approximately 99.998%) in the continuous activated sludge test. Removal of the test substance from the influent through adsorption onto sludge was only 0.016 to 0.023% at two sampling times, demonstrating that the test substance was removed almost completely and biodegraded. This suggests that the test substance biodegrades almost completely in conventional biological wastewater treatment plants (Ginkel, 2007).

Description of key information

Based on the results of the read across study, a similar complete removal of the test substance from the domestic wastewater treatment plants can be expected.

Key value for chemical safety assessment

Half-life in freshwater sediment:
87 d
at the temperature of:
20 °C

Additional information

Sewage treatment

A continuous activated sludge (CAS) study was conducted to determine the biodegradation of the read across substance, C12-16 ADBAC (49.2% active in water), in domestic wastewater according to OECD Guideline 303A, in compliance with GLP. In this study, the domestic waste microorganisms were exposed to the read across substance, by spiking at a nominal influent concentration of 49 mg/L (36 mg/L carbon) for a period of 58 days. An additional unit fed only with the domestic wastewater was maintained as the control group. All samples were analysed for NPOC. A strong increase in the concentration of NPOC was noted on Day 2 in the test units. This was probably caused by toxicity of the read across substance. The activated sludge acclimatised to the read across substance within a few days, resulting in a decrease of the NPOC concentrations. After 3 weeks, very high carbon removal percentages were achieved. The mean removal percentage in the test unit assessed using a HLPC-MS/MS was determined to be 99.998%, indicating ultimate biodegradation. Removal of the read across substance from the influent through adsorption onto sludge was only 0.023% on Day 58, showing that the main mechanism of elimination was biodegradation. Based on the results of the study, the read across substance was removed from wastewater at a very high percentage (approximately 99.998%) in the continuous activated sludge test. Removal of the read across substance from the influent through adsorption onto sludge was only 0.016 to 0.023% at two sampling times, demonstrating that the read across substance was removed almost completely and biodegraded. This suggests that the read across substance biodegrades almost completely in conventional biological wastewater treatment plants (Ginkel, 2007). Based on the results of the read across study, a similar complete removal of the test substance from the domestic wastewater treatment plants can be expected.  

Water:

The study does not need to be conducted because the substance is readily biodegradable.

Sediment:

The study does not need to be conducted because the substance is readily biodegradable.Nevertheless, as per the ECHA E.16 guidance, the half-life in the sediment compartment will be a factor 10 higher than the half-life in soil. Therefore, the sediment half-life value of 87 days has been considered further for risk assessment.