cis-2-tert-butylcyclohexyl acetate

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:

12 Feb 2009 to 30 Oct 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic (adaptation not specified)

Details on inoculum:

Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (Bois-de-Bay, Satigny, Switzerland) was used. The sludge was collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day. The dry weight of suspended solids of the activated sludge was 4.6 g/L (determined by taking two 50 ml samples of the homogenised sludge, evaporating water on a steam bath, drying in an oven at 105-110 ºC for two hours and weighing the residue). To obtain a concentration of 30 mg/L (dry weight) in a 250 ml flask, 1.63 mL of sludge was needed.

The dry weight of suspended solids was 4.6 g/L, to obatin a concentration of 30 mg/L (dry weight) in a 250 mL flask, 1.63 mL sludge was added to the flasks.

Duration of test (contact time):

61 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Remarks:

as a percentage of ThOD

Details on study design:

WATER:
The water used during the study was ultrapure water, containing less than 5 ppb total organic carbon (produced by Millipore Direct-Q 3 UV purification system)

MINERAL MEDIUM:
Prepared by mixing 50 mL of solution A (8.5 g KH2PO4, 21.75 g K2HPO4, 33.4 g Na2HPO4.2H2O and 0.5 g NH4Cl per litre water) and 2000 mL deionised water, adding 5 mL of each of the solutions B (27.5 g CaCl2 per litre water), C (22.5 g MgSO4.7H2O per litre water) and D (0.25 g FeCl3.6H2O and one drop of HCl conc. per litre water) making up to 5 litres with deionised water. The pH was measured and if necessary adjusted to 7.4 ± 0.2 with phosphoric acid or patassium hydroxide.

PREPARATION OF FLASKS:
The respirometers used during this study (SAPROMAT D 12, J.M. Voith GmbH, Heidenheim, Germany) were used as the test apparaturs, test substance samples (25 mg, corresponding to 100 mg/L in a 250-mL flask) were weighed in small aluminium boats and added directly to the test flasks of the respirometers (SAPROMAT), whereas reference substance samples (sodium benzoate) were added as 1.0 mL of a 25 mg/mL solution in mineral medium.
All flasks were filled with 250 mL of mineral medium. Samples of test substance, reference substance, or both, were added. Then a volume of suspended sludge correspoding to 7.5 mg d.w. was added. Except when the test substance had an acid or alkaline character, the pH of each flask was not measured but assumed to be the same as the mineral medium, in order to not remove any floating undissolved test substance from the test medium by dipping a glass electrode in it. Neutral test substances (as well as sodium benzoate) were shown not to affect the pH of the medium by more than 0.1 pH unit. About 2 g of soda lime was placed in an attachment of the stopper, the flasks closed and placed in the water bath of the respirometer. Glass capillaries were introduced between the test flasks and the oxygen generators to limit losses of the volatile test substance. After temperature and pressure equilibration, the oxygen-meters of the instrument were set to zero (time zero of the experiment).

PERFORMANCE OF THE TEST:
Everyday the oxygen consumption of each flask was recorded and correct temperature and stirring checked. At the end of the test period, the pH of each flask was measured again.

Reference substance:

benzoic acid, sodium salt

Remarks:

purity: min. 99.0%

Test performance:

The repeatability criterion (not more than 20 % variation between replicates) is fulfilled, Therefore the test is considered valid.

Key result

Parameter:

% degradation (O2 consumption)

Value:

43

Sampling time:

28 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

62

Sampling time:

61 d

Results with reference substance:

Degradation of sodium benzoate exceeded 40% after 7 days and 65% after 14 days.

O₂uptake of test substance (mg O₂/L, adjusted to nominal concentrations).

		Days
		7	14	24	28	60	61
O2uptake sludge (inoculum blanc)	B1	10.0	19.0	25.0	27.0	43.0	43.0
	B2	15.0	19.0	28.0	30.0	47.0	47.0
	B (mean)	12.5	19.0	26.5	28.5	45.0	45.0
O2uptake test subst. + sludge	C1	33.0	46.0	131.0	144.0	198.9	200.9
	C2	34.0	46.0	121.0	143.0	216.9	218.9
O2uptake test subst.	C1-B	20.5	27.0	104.5	115.5	153.9	155.9
	C2-B	21.5	27.0	94.5	114.5	171.9	173.9
% biodegradation test subst.	D1	8	10	39	43	58	59
	D2	8	10	36	43	65	65
	D (mean)	8	10	38	43	61	62
% degradation test subst. + reference substance	Dco1	9	36	49	52	61	62
	Dco2	3	22	40	43	54	56
	Dco (mean)	6	29	45	47	57	59

O₂uptake of reference substance (mg O₂/L, adjusted to nominal concentrations).

		Days
		5	7	14	21	28	61
O2uptake sludge (inoculum blanc)	B1	7.0	10.0	19.0	23.0	27.0	43.0
	B2	13.0	15.0	19.0	25.0	30.0	47.0
	B (mean)	10.0	12.5	19.0	24.0	28.5	45.0
O2uptake reference subst. + sludge	A1	137.0	147.0	170.0	178.0	185.0	205.0
	A2	150.0	160.0	181.0	188.0	193.0	209.0
O2uptake reference subst.	A1-B	127.0	134.5	151.0	154.0	156.5	160.0
	A2-B	140.0	147.5	162.0	164.0	164.5	164.0
O2uptake reference subst. + test substance + sludge	E1	156.0	171.0	266.1	304.1	322.1	370.1
	E2	156.0	168.0	239.0	287.0	307.0	357.0
	E (mean)	156.0	169.5	252.5	295.5	314.6	363.6
% biodegradation reference subst.	D1	76	81	91	92	94	96
	D2	84	89	97	98	99	98
	D (mean)	80	85	94	95	96	97

Calculations:

B1, B2, C1, C2, A1, A2, E1, E2: experimental O₂uptake values

B = (B1 + B2) / 2

D1 = 100 * (C1 - B) / ThOD * [S]           Dco1 = 100 * (E1 – A1) / ThOD * [S]

D2 = 100 * (C2 - B) / ThOD * [S]           Dco2 = 100 * (E2 – A2) / ThOD * [S]

D = (D1 + D2) / 2                               Dco = (Dco1 + Dco2) / 2

[S]: Initial test substance concentration (mg/L).

 

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Remarks:

Substance is not persistent (62% degradation after 61 days).

Conclusions:

The test item was not ready biodegradable but not persistent under the test conditions described in the study report.

Executive summary:

A GLP-compliant OECD Guideline 301F study (Manometric Respirometry) with activated sludge from a biological waste water treatment plant treating predominantly domestic sewage is available for Verdox. The activated sludge was exposed to 100 mg/L Verdox for a total of 61 days. After 28 days exposure 43% biodegradation was observed (as O2 consumption). After 61 days degradation increased to 62%. Based on these findings the substance is not readily biodegradable but not persistent.

Description of key information

A GLP-compliant OECD Guideline 301F study (Manometric Respirometry) with activated sludge from a biological waste water treatment plant treating predominantly domestic sewage is available for Verdox. The activated sludge was exposed to 100 mg/L Verdox for a total of 61 days. After 28 days exposure 43 % biodegradation was observed (as O2 consumption). Based on these findings the substance is to be considered not readily biodegradable. The substance undergoes 61% after 60 days (62% after 61 days) and is therefore not considered persistent

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater