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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study with acceptable restrictions.
Qualifier:
according to guideline
Guideline:
EU Method C.4-B (Determination of the "Ready" Biodegradability - Modified OECD Screening Test)
Version / remarks:
Cited as Directive 84/449/EEC, C.3
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
other: municipal waste water treatment plant effluent
Details on inoculum:
Source of inoculum: effluent from laboratory wastewater treatment plants fed with municipal sewage
Duration of test (contact time):
21 d
Initial conc.:
20 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
Test device: 2 L Erlenmeyer flasks, liquid volume: 1000 mL
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (DOC removal)
Value:
1
Sampling time:
1 d
Parameter:
% degradation (DOC removal)
Value:
1
Sampling time:
7 d
Parameter:
% degradation (DOC removal)
Value:
4
Sampling time:
14 d
Parameter:
% degradation (DOC removal)
Value:
100
Sampling time:
21 d
Parameter:
% degradation (DOC removal)
Value:
100
Sampling time:
27 d
Details on results:
Degradation products: not measured

time

% DOC elimination

days

PC

IH

TS1

TS2

TS(mean)

0

0

0

0

0

0

1

-3

0

0

1

1

7

-3

47

0

1

1

14

-3

49

4

3

4

21

-1

99

100

99

100

27

-6

100

100

100

100

28

-8

99

99

99

99

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
100 % degradation/21 d
Executive summary:

In a OECD Screening Test (according to OECD Guideline 301-E) biodegradation of 20 mg/L test substance was investigated. Inoculum was not inhibited by the test substance at a concentration of 20 mg/L. After a lag phase (4 % degradation after 14 d), DMF was fully degraded within 21 days.

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study with acceptable restriction and basic data given.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
Principles of method if other than guideline:
experimental study, comparable to Zahn-Wellens test design (OECD Guideline 302B).
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Duration of test (contact time):
7 d
Parameter:
other: % degradation
Value:
0
Sampling time:
3 h
Parameter:
other: % degradation
Value:
92
Sampling time:
4 d
Parameter:
other: % degradation
Value:
97
Sampling time:
5 d
Parameter:
other: % degradation
Value:
99
Sampling time:
6 d
Parameter:
other: % degradation
Value:
95
Sampling time:
7 d
Details on results:
Degradation products: not measured

Year: 1976 (unclear if "Year of test guideline" or "Year of study completion".)

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
The test substance can be declared an "inherently biodegradable".
Executive summary:

A laboratory test according to Zahn-Wellens (comparable to OECD Guideline 302B) was performed. According to the results (95% degradation within 7 days) the test substance can be declared an "inherently biodegradable".

Description of key information

- Experimental study comparable to Zahn-Wellens test design (OECD Guideline 302B), non-GLP: test substance can be declared as "inherently biodegradable".

- Biodegradation in water: ready biodegradability (OECD Guideline 301-E/ EU Method C.4 -B, non-GLP): DMF was fully degraded within 21 days.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

Inherent biodegradation:

Inherent biodegradation studies (following OECD 302-B test design) confirmed the rapid elimination of DMF from water since a degradation level of 95 % was achieved after 7 days (92 % within 4 d); please refer to the report of BASF (1976) for details.

Ready biodegradability:

Under OECD 301E test conditions DMF turned out to be readily biodegradable (100 % after 21 days; BASF, 1989). A lag-phase of 14 days was observed in this study. In a MITI-test a degradation of 4.4 % after 14 days was found (CITI, 1992). However, considering the long lag-phase found in the OECD 301E study there is no discrepancy between these two studies and DMF can be classified as readily biodegradable. In a sewage treatment plant simulation test using activated sludge from a municipal sewage treatment plant as inoculum an acclimation phase of 35 days was necessary before an elimination of DMF took place. After this period DMF was almost completely removed (analysis of substance concentration) from the synthetic waste water used in the study (Dojlido, 1979).

Biodegradation of DMF (30 mg/L) in river water was also investigated (Dojlido, 1979). DMF was completely degraded in river water within 6 days.