Didecyldimethylammonium chloride

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: sewage treatment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 Jan, 2007 - 16 May, 2007

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

OECD Guideline 303 A (Simulation Test - Aerobic Sewage Treatment. A: Activated Sludge Units)

Qualifier:

according to guideline

Guideline:

other: Activated sludge simulation test, ISO 11733, 1995

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.10 (Biodegradation: Activated Sludge Simulation Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on source and properties of surface water:

None

Details on source and properties of sediment:

None

Details on inoculum:

Nature: Secondary activated sludge
Source: Wastewater treatment plant
Sampling site:Nieuwgraaf, Duiven , The Netherlands
Preparation of inoculum for exposure: Sludge was used upon arrival
Initial biomass concentration: 3 g dry wt/L

Duration of test (contact time):

ca. 59 d

Initial conc.:

50 mg/L

Based on:

test mat.

Details on study design:

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 dry wt/L

-Test apparatus: The CAS test was performed in a Husmann-type unit constructed of glass. The unit consisted of an aeration vessel capable of
holding 0.35 L from which the liquor was passed continuously to a settler of 0.3 L 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 bottomof 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 of the inoculum was determined by filtering
the activated sludge over a preweighed 12 µm Schleicher and Schüll filter. This filter was dried for 1.5 hours at 104°C and weighed after cooling.
Dry weight 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

Test performance:

The performance of the test was as prescribed by the protocol and the guideline.

Key result

% Degr.:

> 99.95

Parameter:

test mat. analysis

Sampling time:

59 d

Remarks on result:

other: (assessed based on total removal percentage of >99.998% and percentage sorption to sludge of 0.032% after 58 d)

Transformation products:

not measured

Details on transformation products:

Not applicable

Evaporation of parent compound:

no

Volatile metabolites:

no

Residues:

not specified

Details on results:

TEST CONDITIONS
- Aerobicity (or anaerobicity), moisture, temperature and other experimental conditions maintained throughout the study: Yes
- Anomalies or problems encountered (if yes): No

Results with reference substance:

Not applicable

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-statistics. The mean difference between the NPOC in the influent and effluent was 0.21 ± 0.86 mg/L (95 per cent
confidence interval). The mean removal percentage calculated with this mean difference was 105 ± 4 (95 per cent
confidence). This improved carbon removal is statistically significant because the t-statistic (n = 15) did exceed the
critical value. The results therefore demonstrate that the continuous activated sludge system treating domestic
wastewater spiked with DDAC removes the organic carbon of DDAC completely from wastewater. 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 <1 µg/L corresponding with >99.998% removal. 

Analysis of the DDAC present in the activated sludge demonstrated that about 0.032% was removed via sorption which means that >99.95% of the test substance was removed by biodegradation.  

The performance of the control unit was checked (Day 14 and the last day of the test) by measuring the COD removal (Day
14 and the last day 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.

Validity criteria fulfilled:

yes

Conclusions:

Test substance removal was >99.98% in a continuous activated sludge (CAS) test.

Executive summary:

A continuous activated sludge (CAS) test was performed with the test substanceaccording to OECD Guideline 303, EU Method C.10 and ISO Method 11733, in compliance with GLP. The test substance was exposed to non-adapted microorganisms maintained by addition of domestic wastewater. The wastewater was spiked at a nominal influent concentration of ca. 50 mg/L (37 mg/L carbon) for a period of 58 days and included a control fed with domestic wastewater only. The mean removal percentage of the test substance in this test was >99.98% using specific chemical analyses (LC-MS/MS), which demonstrates a nearly complete removal of parent compound. Removal of the test substance from the influent through adsorption onto sludge was only 0.016 and 0.032%, as observed at Days 57 and 58 respectively,demonstrating that the test substance was primarily removed by biodegradation (Van Ginkel and Geerts, 2007).

Description of key information

Based on the study results, the test substance is considered to be completely mineralised.

Key value for chemical safety assessment

Half-life in freshwater sediment:

208 d

at the temperature of:

12 °C

Additional information

Sewage treatment simulation testing

A continuous activated sludge (CAS) test was performed with the test substance according to OECD Guideline 303, EU Method C.10 and ISO Method 11733, in compliance with GLP. The test substance was exposed to non-adapted microorganisms maintained by addition of domestic wastewater. The wastewater was spiked at a nominal influent concentration of ca. 50 mg/L (37 mg/L carbon) for a period of 58 days and included a control fed with domestic wastewater only. The mean removal percentage of the test substance in this test was >99.98% using specific chemical analyses (LC-MS/MS), which demonstrates a nearly complete removal of parent compound. Removal of the test substance from the influent through adsorption onto sludge was only 0.016 and 0.032%, as observed at Days 57 and 58 respectively, demonstrating that the test substance was primarily removed by biodegradation (i.e., ca. 99.95%) (Van Ginkel and Geerts, 2007). 

 

Surface water simulation testing: 

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

Sediment simulation testing :

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 208 days at 12ºC has been considered further for risk assessment.