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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:
2008
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2008
Report Date:
2008

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Qualifier:
according to
Guideline:
other: EEC C.4-D: Determination of ‘Ready Biodegradability (1998)
Qualifier:
according to
Guideline:
other: US EPA Harmonized Guideline 835.3110: Manometric Respirometry (1998)
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
ca. 40 mg/L
Based on:
test mat.

Results and discussion

% Degradationopen allclose all
Parameter:
% degradation (O2 consumption)
Value:
16.2
Sampling time:
28 d
Parameter:
% degradation (CO2 evolution)
Value:
14.5
St. dev.:
0.6
Sampling time:
28 d
Parameter:
% degradation (DOC removal)
Value:
85.7
St. dev.:
2.7
Sampling time:
28 d
Details on results:
The amount of DOC in solution represented less than 50% of the theoretical dose as a result of its low water solubility.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
other: not readily biodegradable
Conclusions:
The results of this study demonstrate that 6,6'-[[3,3',5,5'-tetrakis(1,1-dimethylethyl)-[1,1'- biphenyl]-2,2'-diyl] bis(oxy)]bis-dibenzo[d,f][1,3,2]-dioxaphosphepin did not meet either the pass level (> 60% DO2) or the 10-day window criteria for ready biodegradability in the Manometric Respirometry test. Degradation reached a maximum of 16.2% of THOD for the test material at the end of 28 days.
Executive summary:

6,6'-[(3,3',5,5'-tetrakis (1,1 -dimethylethyl)-(1,1'-biphenyl]-2,2'-diyl] bis(oxy)] bis-dibenzo[d,f] {1,3,2 -}-dioxaphosphepin was evaluated for ready biodegradability according to the OECD Guideline 301F: Manometric Respirometry. Biodegradation was determined at an initial concentration of approximately 40mg/L, yielding approximately 100mg/L theoretical oxygen demand (ThOD) in the test mixtures. The test chemical was added to biodegradation test mixtures coated onto silica gel as a 15.9% load to facilitate contact with the solution. The biodegradation test mixtures were composed of a defined mineral medium, which was inoculated with activated sludge (30 mg/L dry solids) from a municipal wastewater treatment facility (Midland, MI, USA). Oxygen consumption and CO2 evolution resulting from biodegradation of the test chemicals were measured over 28 days using a Columbus Instruments Micro Oxymax® Respirometer System. In addition, removal of dissolved organic carbon (DOC) from these biodegradation test mixtures was determined after 28 days. The substance achieved 16.2% of ThOD and 14.5+ 0.6% ThCO2 after 28 days of incubation. While DOC removal achieved 85.7 + 2.7%, of test substance, the amount of DOC in solution represented less than 50% of the theoretical dose as a result of its low water solubility. As a result, the substance does not meet the criteria for ready biodegradability.

The suitability of the test procedure and microbial inoculum was verified by rapid biodegradation of aniline in the Positive Control test mixtures. Biodegradation of aniline based on O2 consumption exceeded 60% after an average of 7.8 days, reaching an average of 90.25% after 28 days. The toxicity control containing a combination of 100mg/L aniline and 100 mg equivalent ThOD the substance showed no inhibition of the microbial inoculum. The observed O2 consumption and CO2 evolution in the biodegradation reactions can be attributed solely to biological activity as no net O2 consumption or CO2 evolution was observed in the abiotic control reaction containing the substance.