Cyanoguanidine

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:

May - November 1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)

Deviations:

yes

Remarks:

the deviations do not influence the overall study results

Principles of method if other than guideline:

OECD Test No. 301E methodology followed to GLP standards. Results are reported as a percentage degradation of DCD and concentration of Dissolved Organic Carbon in mg/l. Deviations from the protocol recorded include (i) storage of sample prior to analysis, (ii) no mention is made of pH, so it is assumed that the samples were not adjusted to pH 7.4 for the study, (iii) results are not presented graphically although 0% degradation renders a graphical ‘curve’ as slightly pointless.

GLP compliance:

yes

Remarks:

The study was conducted according to GLP and the report provides an accurate record of the results obtained.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: oxidation ditch situated on the premises of TNO, Eelft, The Netherlands; oxidation ditch is used to treat domestic sewage
- the original sludge (about 5 g of solid substance per litre) was aerated for about 24 hours to remove most of the free corbon present
- part of the sludge was used to inoculate the medium to obatin a final concentration of 30 mg dry substance per litre
- the inoculated medium was aerated before use

Duration of test (contact time):

28 d

Initial conc.:

34.2 mg/L

Based on:

test mat.

Initial conc.:

64.8 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Stock solution: 820 mg Dicyandiamide in 6000 ml water
- Composition of medium: contained buffer with higher capacity than that described in the OECD Guideline (see table 1)
- Test temperature: 20 +/- 0.2 °C
- Aeration of dilution water: yes
- Suspended solids concentration: ~ 5 g/l
- Test concentrations: 34.2 and 68.4 mg/l, theoretically corresponding to 9.9 and 19.8 mg DOC per litre
- Blank control flasks without test substance were included in the test
- Determination of inoculum activity: toxicity control flask containing 100 mg/l sodium acetate (=30 mg DOC per litre) only
- Determination of toixic effects of the test substance: toxicity control flask containing 100 mg/l sodium acetate and test substance



TEST SYSTEM
- Culturing apparatus: two-litre flasks (Schott Duran) filled with 500 ml of double-strength inoculated medium
- Number of culture flasks/concentration: 3 (blank control: 4)



SAMPLING
- Sampling frequency: weekly: one 20 ml sample was collected after 0, 1, 2, 3, 4 weeks (samples taken after 3 weeks were not analyzed)
- Sampling method: collection of 20 ml from each flask



CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes (see above)

Reference substance:

other: sodium acetate

Preliminary study:

No preliminary study

Test performance:

Not applicable

Key result

Parameter:

% degradation (DOC removal)

Value:

0

Sampling time:

28 d

Remarks on result:

other: see table 3

Details on results:

- degradation of sodium acetate: complete degradation within one week, as expected of an inoculum with sufficient activity; degradation was not influenced by Dicyandiamide
- Dicyandiamide was not degraded in the test

Results with reference substance:

The results show a complete degradation of sodium acetate within one week, as expected of an inoculum with sufficient activity. This degradation of sodium acetate was not influenced by the presence of Dicyandiamide in the medium.

Validity criteria fulfilled:

yes

Remarks:

difference of extremes of replicate values is less than 20%; percentage degradation of the reference compound has reached the pass levels by day 14; in a toxicity test more than 35% degradation occurred within 14 days

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Dicyandiamide is not regarded as readily biodegradable.

Executive summary:

The biodegradability of the product Dicyandiamide was determined by the method laid down in the OECD Guideline 301E; „Ready Biodegradability: Modified OECD Screening Test“.

Dicyandiamide was tested in two concentrations: 34 mg/l and 68 mg/l. A control test with sodium acetate showed that the activity of the inoculum was sufficient and that there was no inhibition of the inoculum activity by Dicyandiamide.

No biodegradability was found in the test bottles with Dicyandiamide; this substance is not regarded as readily biodegradable.

Description of key information

The biodegradability of the product Dicyandiamide was determined by the method laid down in the OECD Guideline 301E; „Ready Biodegradability: Modified OECD Screening Test“. 

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Dicyandiamide was tested in two concentrations: 34 mg/l and 68 mg/l. A control test with sodium acetate showed that the activity of the inoculum was sufficient and that there was no inhibition of the inoculum activity by Dicyandiamide.

No biodegradability (no DOC removal in 28 days) was found in the test bottles with Dicyandiamide; this substance is not regarded as readily biodegradable.