Styrene

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 Apr 1988 - 10 May 1988

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

ISO DIS 9408 (Ultimate Aerobic Biodegradability - Method by Determining the Oxygen Demand in a Closed Respirometer)

Deviations:

no

Principles of method if other than guideline:

Manometric respirometry of the BOD (biological oxygen demand)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: domestic, laboratory sewage treatment plant
- Concentration of sludge: 750 mg/L

Duration of test (contact time):

28 d

Initial conc.:

91 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- pH: 6.5 - 7

TEST SYSTEM
- Number of culture flasks/concentration: 7

SAMPLING
- Sampling frequency: daily

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes (2)
- Reference control: yes (1)
- Toxicity control: yes (1)
- Abiotic sterile control: yes (1)

Reference substance:

aniline

Parameter:

other: ThOD

Value:

68

Sampling time:

10 d

Remarks on result:

other: mean of 7 samples

Parameter:

other: ThOD

Value:

70.9

Sampling time:

28 d

Remarks on result:

other: mean of 7 samples

Parameter:

other: COD

Value:

100

Sampling time:

28 d

Remarks on result:

other: mean of 7 samples

Details on results:

Duration of lag-phase: 3 days
Duration of log-phase: 5 days

Results with reference substance:

ThOD of the reference substance (without nitrification): 2670 mg/g
ThOD of the reference substance (with nitrification): 3180 mg/g
% Degradation after 28 d: 73.2 % (of ThOD)

Duration of lag-phase: 3 days

Duration of log-phase: 5 days

IB1/2 = Inoculum blank

RC = Reference control

IH = Toxicity control

PC = Abiotic sterile control

1 -7 = Flasks with test substance and Inoculum

BOD (mg/L)

time [d]	IB1	IB2	RC	IH	PC	1	2	3	4	5	6	7
1	1	0	1	1	1	1	1	1	1	1	1	1
2	1	1	4	1	1	1	1	1	1	1	1	1
3	4	4	5	1	1	4	1	8	1	3	13	33
4	6	6	8	189	1	181	111	96	91	137	158	139
5	9	9	33	113	1	194	167	107	186	145	166	149
6	10	10	149	114	1	201	177	124	215	171	191	171
7	11	11	177	117	1	214	186	135	228	188	200	179
8	11	11	194	117	1	228	193	139	235	186	207	186
9	11	11	205	120	1	235	200	144	238	191	211	189
10	13	13	212	120	1	240	209	145	241	194	215	192
28	14	14	247	148	1	257	223	149	248	197	219	196

BOD (% of ThOD)

time [d]	IB1	IB2	RC	IH	PC	1	2	3	4	5	6	7
1			-4.1	0	0.3	-4.7	-4.7	-4.7	-4.7	-4.7	-4.7	-4.7
2			-3.2	-1.1	0.3	-4.7	-4.7	-4.7	-4.7	-4.7	-4.7	-4.7
3			-2.9	-1.5	0.3	-3.6	-4.7	-2.2	-4.7	-4.0	-0.4	6.7
4			-1.9	36	0.3	59.6	34.6	29.2	27.5	43.9	51.4	44.6
5			5.9	28.5	0.3	64.2	54.6	33.2	61.4	47.1	54.2	48.2
6			42.4	-12.6	0.3	66.7	58.2	39.2	71.7	56.0	63.2	56.0
7			51.2	-21.5	0.3	71.4	61.4	43.2	76.7	59.2	66.4	58.9
8			56.6	-27.6	0.3	76.4	63.9	44.6	78.8	61.4	68.9	61.4
9			60.0	-38.4	0.3	78.9	66.4	46.4	80.0	63.2	70.3	62.5
10			62.2	-32.9	0.3	80.7	69.6	46.7	82.0	64.2	71.7	63.5
28			73.2	-35.4	0.3	86.7	74.6	48.2	83.5	65.3	73.2	65.0

After 28 d (ThOD of the test substance: 3077 mg/g):

	IB1	IB2	RC	IH	PC	1	2	3	4	5	6	7
BOD [mg/g]			2330	-1088	10.9	2670	2296	1483	2571	2011	2252	2000
BOD*100/ThOD			73.2	-35.4	0.3	86.7	74.6	78.2	83.5	65.3	73.2	65.0

Specific analytic at the end of the test:

Theoretical test concentration at the beginning of the test: 91 mg/L

Measured test concentration at the end of the test: < 0.05 mg/L

Elimination: 100 %

Validity criteria fulfilled:

not specified

Interpretation of results:

readily biodegradable

Executive summary:

Styrene was tested for readily biodegradability. The biodegradation after 28 d was determined to be 100%.

Description of key information

Readily biodegradable (according to OECD criteria). According to BASF 1988 the degradation rate is 100% for COD after 28 d.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

Ready biodegradation

Several tests are available which show that styrene is readily biodegradable. Ready biodegradability test ISO DIS 9408 (Directive 79/831/EEC Annex V, Part C – manometric respirometry test, equivalent to OECD 301F) was carried out by BASF AG (Ecological laboratory, unpublished data, test no. 388576, 1988). From an initial concentration of 91 mg/l in an activated sludge of domestic origin, 68% of ThOD was reached after ten days.

The closed bottle test was carried out with an initial concentration of 3,7 and 10 mg/l with bacteria from non-adapted domestic wastewater, first in freshwater and secondly in synthetic seawater (Price et al., 1974). Biodegradation was measured as BOD as a percentage of ThOD. The results were: degradation of 65% and 87% after five days and twenty days respectively in freshwater; and 8% and 80% after five days and twenty days respectively for the synthetic seawater. The closed bottle test is an approved EC test procedure, although this study pre-dates adoption by the EC. The guidelines suggest an initial concentration between 2 mg/l and 5 mg/l, and an inoculum derived from the secondary effluent of a treatment plant or lab-scale unit receiving predominantly domestic sewage. The test as performed matches the guidelines sufficiently to be considered as a valid test.

Another test result of ready biodegradability has been found, using the standard dilution BOD method (APHA Standard Methods No 219) with added alkyl thiourea to prevent nitrification. Magnetic stirring was used for sparingly soluble chemicals including styrene. From an adapted inoculum of predominantly domestic sewage, 80% degradation was observed after five days. From a non-adapted inoculum, 42% degradation occurred in the same period (Bridié et al., 1979).

Inherent biodegradation

The modified MITI test (II) (OECD Guideline 302C) was used to determine the inherent biodegradability of styrene (CITI, 1992). From an initial concentration of 30 mg/l in activated sludge, 100% had degraded after 14 days, leading to the conclusion that styrene is at least inherently biodegradable.