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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Jan - Mar 1996
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: According to OECD guideline under GLP
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1996
Report Date:
1996

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
Principles of method if other than guideline:
Not relevant
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
not specified
Details on test material:
- Name of test material (as cited in study report): M-DOC
- Analytical purity: 98.2%
- Lot/batch No.: 34514021

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Duration of test (contact time):
34 d
Initial test substance concentration
Initial conc.:
10 mg/L
Based on:
DOC

Results and discussion

% Degradation
Parameter:
% degradation (CO2 evolution)
Value:
28
Sampling time:
34 d
Details on results:
Not relevant

Any other information on results incl. tables

Table 1: Biological degradation (cumulative) in percent (corrected tor blank C02 production)

Day of sampling  
Test compound    Nominal concentration of carbon   3 4 7 9 11 14 18 23 28 30 32 35 36
 ZK 9340    10 mg/I   1 1 1 5 8 12 17 23 26 27 27 28 28
 Sodium acetate    10 mg/I   15 33 58 68 73 80 84 87 89 88 88 89 90
 (reference)                                            
 ZK 9340 +    10 mg/I +   7 13 32 41 45 50 54 57 58 59 59 60 61
 sodium acetate (toxicity control)    10 mg/I                                         

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
In accordance with the OECD guideline, the test compound ZK 9340 is not readily biodegradable under the conditions of the test.
However, at the end of the test period, the test substance was partly degraded. The substance was not toxic to the microbes of activated sludge.
Executive summary:

The test substance M-DOC (ZK 9340) was incubated in aqueous solution including nutrients with microorganisms from a municipal sewage treatment plant tor 34 days (start of treatment = day 1). The experiment was extended because the plateau was not reached by day 28. The nutrient solutions were made up of phosphates, magnesium sulphate, iron chloride, ammonium chloride and calcium chloride. The test substance was incubated in a concentration of 10 mg carbon/L in triplicate. Additionally, a reference substance (sodium acetate) was tested according to the same procedure, in order to verify the viability and activity of the degrading microorganisms. One further vessel was incubated with 10 mg carbon/L sodium acetate (reference substance) plus 10 mg carbon/L test substance as a toxicity control. Furthermore, a control was tested in triplicate without any test or reference substance and used as blank. The biological degradation of the test and reference substances was evaluated by measurement of the carbon dioxide (C02) produced during the test period. CO2 production was determined on days 3,4,7,9,11,14, 18,23,28,30,32,35 and 36 and calculated as the percentage of total CO2 that the test material could theoretically have produced, based on carbon content. The blank CO2 production was subtracted tor correction.

The test compound was degraded to 28% at the end of the test, when a plateau was reached. The degradation started after a relatively long lag-phase (more than 1 week). The reference compound sodium acetate was degraded to 90% on day 36. The time required for 60% biodegradation of the reference compound was less than 9 days. In the toxicity control, the reference compound (sodium acetate) plus the test compound, was degraded to 61% on day 36, which corresponded to the degree of degradation expected on the basis of the observations with the individual compounds.