Quaternary ammonium compounds, bis(C16-18 and C18-unsatd. alkyl)dimethyl, chlorides

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1992.06.24 - 1992.11.18

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The test was prolonged because the pass level was not reached at day 28.

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Principles of method if other than guideline:

The ready biodegradability was determined in the closed bottle test performed according to slightly modified OECD, EEC and ISO Test Guidelines. The test was prolonged because the pass level was not reached at day 28.

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

Secondary activated sludge was obtained from a plant treating predominately domestic wastewater. The sludge was pre-conditioned to reduce the endogenous respiration rates. To precondition, the sludge (200 mg Dry Weight (DW)/litre) was aerated for a period of one week. The sludge was diluted to a concentration in the BOD bottles of 2 mg DW/litre. Ammonium chloride was omitted from the medium to prevent nitrification. Due to omission the pH of the medium decreased slightly.
- Preparation of inoculum for exposure: The activated sludge was preconditioned to reduce the endogenous respiration rates.
- Pretreatment: The sludge was preconditioned to reduce the endogenous respiration rates, the sludge was diluted to a concentration of 2 mg DW/I i nthe BOD bottles.
- Concentration of sludge: 2 mg DW/litre
- Initial cell/biomass concentration:
- Water filtered: Deionized

Duration of test (contact time):

> 0 - <= 140 d

Initial conc.:

2.6 mg/L

Parameter followed for biodegradation estimation:

O2 consumption

Remarks:

ThoD ratio

Details on study design:

TEST SYSTEM
- Culturing apparatus: The test was performed in 250-300 ml BOD (Biological Oxygen Demand) bottles.

STATISTICAL METHODS:
The biodegradation was calculated as the ratio of the biochemical oxygen demand (BOD) to the theoretical oxygen demand (ThOD). The ThOD of the test compound is 2.6 g O2/g test substance. The BOD of the test substance and sodium acetate were calculated from the oxygen concentrations in the bottles without and with test substance (B, C) and the bottles without and with sodium acetate (B, D).

Reference substance:

acetic acid, sodium salt

Remarks:

Lot No. B 02099

Preliminary study:

No data supplied.

Test performance:

No data supplied.

Parameter:

% degradation (O2 consumption)

Value:

3

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

33

Sampling time:

140 d

Details on results:

Ditallowdimethylammonium chloride is not biodegraded in the closed bottle test (28 days) and this even after 140 days

Results with reference substance:

Inhibition of the degradation of a well-degradable compound, eg sodium acetate by the test compound in the closed bottle test was not determined because possible toxicity of the test substance to micro-organisms degrading acetate is not relevant; Inhibition of hte endogenous respiration of the inoculum by the test substance was not detected. Therefore, no inhibition of the biodegradation due to "high" initial concentration of the test compound is expected.

Validity criteria fulfilled:

yes

Remarks:

The validity of hte test is demonstrated by an endogenous respiration of 0.9 mg/L at day 28. Furthermore, the differences of the replicate values of the control at day 28 were less than 20%. The biodegradation percentage of the reference substance, sodium

Interpretation of results:

other: During 28d biodegradation of DTDMAC was < 20% and therefore the test substance was not readily biodegradable under the test conditions chosen and described before. Over a prolonged exposure period of 140d up to 33% biodegradation is observed under the t

Conclusions:

Under the test conditions described before Ditallowdimethylammonium chloride is not readily biodegradable (biodegradation < 20% after 28d). Nevertheless DTDAMC is biodegradable.

Executive summary:

When assessing the biodegradation behaviour of cationic surfactants like DTDMAC / DHTDMAC it is important to consider the following facts:

1. Due to the low water solubility (CMC) bioavailability of the test substance is reduced. Therefore for cationic surfactant instead of an S shape biodegradation curve a more or less straight line may be observed which can be interpreted such that biodegradation is rate limited by the dissolution of the test item.

2. Cationic surfactants may show toxicity to microorganisms at concentration levels normally used for Biodegradation screening tests e.g. the EC50 for nitrifying bacteria is 2.1 mg/L for DHTDMAC. The EC50 is lower than the test concentration in this test which is 2.6 mg/L.

Based on these fact biodegradation of cationic surfactants is often higher at lower test item concentrations which is also more environmentally relevant. Also the conditions in surface water / sediment may enhance biodegradation additionally. Adaptation of the microorganisms is another important parameter for biodegradation.

The fact that the test item DTDMAC is not readily biodegradable under the conditions of this test after 28d does not allow the conclusion that DTDMAC is recalcitrant or persistent in theSewage treatment plant (STP) or the freshwater compartment. More adequate studies like e.g. OECD 303 A (STP Simulation Test) or e.g a River die away Test have to be used in order to derive adequate biodegradation kinetics (see IUCLID Chapter 5.2.2).

Description of key information

33% biodegradation (OECD 301D; BOD; 140 d) in the prolonged closed bottle test

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

Biodegradation Screening tests

In the ECETOC Technical Report No. 53 'DHTDMAC - Aquatic and Terrestrial Hazard Assessment, CAS No. 61789 -80 -8' (ECETOC, 1993) as well as in the EU Risk Assessment 'DODMAC/DTHDMAC' (EU, 2002) the available Biodegradation Screening test results are given.

Read across from a structurally similar Quat (DHTDMAC, CAS No. 61789-80-8 ) can be applied.

When assessing the biodegradation behaviour of cationic surfactants like DTDMAC / DHTDMAC it is important to consider the following facts:

1. Bioavailability of the test substance may be reduced due to the formation of liquid crystals and vesicals. Therefore for cationic surfactant instead of an S shape biodegradation curve a more or less straight line may be observed which can be interpreted such that biodegradation is rate limited by the dissolution of the test item.

2. Cationic surfactants may show toxicity to microorganisms at concentration levels normally used for Biodegradation screening tests e.g. the EC50 for nitrifying bacteria is 2.1 mg/L for DHTDMAC. Usual test item concentrations are between 5 and 20 mg/L. Based on these facts biodegradation of cationic surfactants is often higher at lower test item concentrations which is also more environmentally relevant. Also the conditions in surface water / sediment may enhance biodegradation additionally. Adaptation of the microorganisms is another important parameter for biodegradation.

The fact that the test item DTDMAC is not readily biodegradable under the conditions of the tests listed below after 28d does not allow the conclusion that DHTDMAC/DTDMAC is recalcitrant or persistent in the Sewage treatment plant (STP) or the freshwater compartment. More adequate studies like e.g. OECD 303 A (STP Simulation Test) or e.g a River die away Test have to be used in order to derive adequate biodegradation kinetics (see IUCLID Chapter 5.2.2). Table 4.xx list the most important tests with the test setting and results.

 

Table 4.xx Biodegradation Screening tests of DHTMAC/DTDMAC

 

Test class	Test type	Guide-line	Endpoint	Exposure (d)	Test conc. (mg/L)	Adaptation	Elimination (%)	Biodegradation (%)	Year	Remark
Screening tests
	Ready	301 B	CO2 evolution	28	not given	no	n.a.	not observed	1988	Schöberl et al, 1988
	Ready	301D	BOD	180	10	no	n.a.	< 20	1991	van Ginkel & Kolvenbach, 1991
	Ready	301D	BOD	20	1	yes	n.a.	19	1991	Clancy & Tanner, 1991
				20	1	yes	n.a.	8	1991
				20	0.8	yes	n.a.	12	1991
				20	0.5	yes	n.a.	17	1991
				20	0.4	yes	n.a.	35	1991
	Ready	301D	BOD	28	2.6	no	n.a.	<20	1993	van Ginkel, 1993
			BOD	140	2.6	no	n.a.	33	1993
	Inherent	302B	DOC	15	not given	no	92	n.a.	1989	Hoechst, 1989d