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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Qualifier:
according to guideline
Guideline:
other: EC directive 84/449/EEC C.3
Principles of method if other than guideline:
Test guideline C.3, EC directive 84/449/EWG corresponds to OECD TG 301 E (Modified OECD Screening Test)
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): effluent of sewage plant Marl-West, no further data
Duration of test (contact time):
14 d
Initial conc.:
20 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
TEST CONDITIONS
- Composition of medium: no data
- Test temperature: 20 °C
- pH: no data

TEST SYSTEM
- Culturing apparatus: no data
- Number of culture flasks/concentration: 2
- Measuring equipment: carbon analyzer (Beckman)

SAMPLING
- Sampling frequency: after 0, 5, 14 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: no
Reference substance:
other: n-dodecylbenzolsulfonate (Marlon A)
Parameter:
% degradation (DOC removal)
Value:
100
Sampling time:
14 d
Parameter:
% degradation (DOC removal)
Value:
81
Sampling time:
5 d
Results with reference substance:
no data

 

DOC concentration (mg/L) after days

0

5

14

Replicate

1

2

1

2

1

2

Inoculum blanc

a

1.6

1.6

0.6

0.6

1.1

1.1

b

1.6

1.6

0.5

0.5

1.4

1.4

Mean

1.60

1.60

0.55

0.55

1.25

1.25

Test substance

a

18.2

18.2

3.6

3.8

0.6

1.5

b

18.6

18.6

3.4

4.0

1.2

1.5

Mean

18.40

18.40

3.50

3.90

0.90

1.50

 

 

Replicate

DOC removal (%) after days

0

5

14

1

0

82.44

102.08

2

0

80.06

98.51

Mean

0

81.25

100.3

 

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Butyric acid is readily biodegradable in the Modified OECD Screening Test.
Executive summary:

The ready biodegradability of butyric acid was tested in a Modified OECD Screening Test according to EU Directive 84/449/EEC C.3. The effluent of a domestic sewage treatment plant served as inoculum. The samples were incubated for 14 days at 20 °C. Two parallels were set up. DOC was analyzed after 0, 5 and 14 days. After 5 days, the test substance was degraded to 81% and after 14 days to 100 % (DOC removal). The 10-days window was met.

Butyric acid is readily biodegradable according to the pass levels of OECD TG 301 (Ready Biodegradability) (Hüls 1996).

This study is classified as acceptable. It satisfies the requirements of OECD test guideline 301 E with minor restrictions (limited reporting).

Description of key information

Butyric acid has been demonstrated to be readily biodegradable in a valid degradation test according to OECD TG 301 E (Hüls, 1996).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradability of butyric acid was tested in seven studies. In two of them anaerobic conditions were applied.

  

study record

Method

Conditions

Reliability

Result

Hüls, 1996

other guideline: EC directive 84/449/EEC C.3;

similar to OECD TG 301 E

aerobic

(14 days)

1

KS

81% within 5 days 100% at14 days readily biodegradable

Hoechst AG, 1979

Zahn-Wellens test;

similar to OECD TG 302 B

aerobic

(5 days)

2

>95% degradation

Urano 1986

MITI (I) method;

similar to OECD TG 301 C

aerobic

(250 hrs)

2

58 to 82% ThOD within 6 days;

< 90% at day 10

readily biodegradable

Dias 1971

Standard methods for the examination of water and wastewater, 1965, biochemical oxygen demand test

aerobic

(30 days)

2

48% and 58% at day 10 and 30;

ready biodegradability not met

Lutin, 1979

similar to OECD Guideline 301 F

aerobic

(72 hrs)

3

ca. 43% at 72 hrs

Chou, 1978

anaerobic degradation by acetate adapted domestic activated sludge (methanogenic culture, repeated additions of substrate))

anaerobic

3 (not suited for ready biodegradability

after a 3 day lag period, complete anaerobic degradation of butyric acid with a degradation rate of 284 mg/(L*d)

Kameya, 1995

anaerobic biodegradation test using methanogenic bacteria as inoculum

anaerobic

3 (not suited for ready biodegradability

complete anaerobic degradation of butyric acid within 7 days

 

 

The ready biodegradability of butyric acid was tested in a valid Modified OECD Screening Test according to EU Directive 84/449/EEC C.3 (similar to OECD TG 301 E; RL1). After 5 days, the test substance was degraded to 81% and after 14 days to 100% (Hüls, 1996). In several other biological degradation tests, butyric acid was demonstrated to undergo biodegradation up to 95%.

 

In one study (Dias, 1971), degradation only reached 58% within 30 days (parameter examined: oxygen consumption). This study is estimated not adequately to represent the genuine biodegradation potential of butyric acid. But reasons for the differing results are not obvious.

 

Based on the results of the key study (Hüls, 1996) and supported by the results of other studies (Urano, 1986; Hoechst AG, 1979), butyric acid is readily biodegradable.

 

In addition, butyric acid was demonstrated to undergo complete biodegradation under anaerobic conditions as well.

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