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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
From January 11th to February 08th, 1991
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Justification for type of information:
The read across approach is detailed into the document attached into the IUCLID section 13.
Reason / purpose:
read-across source
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Inoculum: a mixed population of activated sewage sludge microorganisms.
- Source: the aeration Stage of Severn Trent PLC Sewage Treatment Plant, Belper, Derbyshire.
- Preparation: the activated sludge was maintained at a temperature of 21 ± 1 °C for 24 hours. The sludge was washed and settled repeatedly using dilution water prior to use.
Duration of test (contact time):
28 d
Initial conc.:
30 mg/L
Based on:
test mat.
Initial conc.:
78.6 mg/L
Based on:
ThOD
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Sludge usage rate: equivalent to 100 mg dry weight/l.
- Test temperature: 25 ± 1 °C
- Agitation: by magnetic stirrers.
- Continuous darkness: yes

SAMPLING
- Sampling frequency: manometric volumes were recorded daily.

PARAMETER MEASURED
A MITI (II) test was performed due to the low solubility of the test material in water. TOC analysis on the test material was not performed for this reason.
Theoretical Oxygen Demand (ThOD) was calculated to be 78.6 mgO2/l (2.62 mgO2/mg) assuming test material to be 100 % pure using the data supplied by the Sponsor.
Reference substance:
aniline
Remarks:
100 mg/l
Parameter:
% degradation (O2 consumption)
Value:
0 - 19
Sampling time:
28 d
Details on results:
Percentage degradation values were calculated by comparison of the oxygen uptake with Chemical Oxygen Demand.
Test item attained negligible degradation within 28 days calculated from oxygen uptake and so cannot, therefore be considered as inherently biodegradable under the strict terms and consitions of the OECD guideline.

A negligible degradation was also observed from comparison of the oxygen uptake values against ThOD. The variability in the degradation valves of the test material were the result of background variation of the oxygen uptake of the control vessels.
Results with reference substance:
Aniline attained 56 % biodegradation after 7 days and 70 % after 14 days thereby confirming the suitability of the inoculum and culture conditions. Total Organic Carbon (TOC) showed that aniline attained 94 % degradation, after 28 days.

Day % biodegradation
Test item Aniline
1 4 1
2 10 4
3 6 10
4 15 21
5 0 46
6 6 52
7 0 56
8 19 58
9 0 61
10 16 66
11 13 67
12 14 70
13 15 68
14 0 70
15 7 68
16 14 71
17 0 73
18 0 72
19 0 74
20 14 76
21 7 75
22 0 70
23 0 79
24 0 82
25 0 85
26 14 85
27 0 85
28 0 79

All the biodegradability values have been corrected for blank values

Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The substance is not inherently biodegradable.
Executive summary:

A MITI (II) test was performed to investigate the biodegradability potential of the substance; the method was chosen due to the low solubility of the test material in water. TOC analysis on the test material was not performed for the same reason. Percentage degradation values were calculated by comparison of the oxygen uptake with Chemical Oxygen Demand.

Test item attained negligible degradation within 28 days (0 - 19 % over the whole experiment period) calculated from oxygen uptake, therefore, it cannot be considered as inherently biodegradable under the strict terms and consitions of the OECD guideline.

A negligible degradation was also observed from comparison of the oxygen uptake values against ThOD. The variability in the degradation valves of the test material were the result of background variation of the oxygen uptake of the control vessels.

Aniline attained 56 % biodegradation after 7 days and 70 % after 14 days thereby confirming the suitability of the inoculum and culture conditions. Total Organic Carbon (TOC) showed that aniline attained 94 % degradation, after 28 days.

Conclusion

The substance is not inherently biodegradable.

Description of key information

Neither readily nor inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The substance belongs to the class of monoazo disperse dyes, which are substantially water-insoluble nonionic dyes for application to hydrophobic fibers from aqueous dispersion. The substance is not expected to be ready biodegradable because of its chemical structure and its specific function. Commonly, dyes undergo a primary transformation, i.e. discolourization due to the interrupting the conjugation. Nevertheless, the degradation process involves more steps and take more time.

There are no experiments on the biodegradability potential of Disperse Red 054 performed following procedures in accordance with currently common scientific standards and described in sufficient detail. In a sheet of results, COD of 1667 mg/g and a BOD of 11 mg/g are reported; the

related ratio is reported to be 0.7 % (BOD/COD) (report, 1991). The mentioned data, support the expectation of a low deradability potential.

In order to further support the expected biodegradability potential and in order to better clarify the substance behavior, the available data on the structural analogous Similar Substance 01 have been taken into consideration. The read across approach can be considered as suitable and appropriate to investigate the propriety (detailed on the read across approach are given into the document attached into the IUCLID section 13).

A MITI (II) test was performed to investigate the biodegradability potential of the Similar Substance 01. Test item attained negligible degradation within 28 days (0 - 19 % over the whole experiment period) calculated from oxygen uptake, therefore, it cannot be considered as inherently biodegradable under the strict terms and consitions of the OECD guideline. A negligible degradation was also observed from comparison of the oxygen uptake values against ThOD.

REFERENCE

See attachment

[Type of water: freshwater]