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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 A (old version) (Ready Biodegradability: Modified AFNOR Test)
Deviations:
yes
Remarks:
study was aborted as the measurement was technically not feasible.
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not indicated.
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, adapted
Details on inoculum:
Activated sludge from a biologic sewage treatment plant was used. The chosen plant treats mostly domestic sewage.
The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, NW-Lachen-Speyerdorf.
Date of collection: 2008-12-11
batch no: 11122008.
The sludge was filtrated through a clean cotton cloth, then washed with tap water twice, with test medium once and resuspended in test medium. It was then aerated until use in the test. Determination of dry matter gave 4860 mg suspended solids/Liter.
Duration of test (contact time):
28 d
Initial conc.:
672 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
Pre-Treatment
A stock solution containing 9975.0 mg/L in deionised water was prepared. Its TOC (total organic carbon, determined as total carbon TC minus inorganic carbon IC) and DOC (dissolved organic carbon, TOC after filtration through 0.45 μm filters) were determined in order to estimate the amount to be added to the test flasks. The TOC was 595 mg/L, the DOC 672 mg/L. The test item was added to the test flasks as an unfiltrated stock solution.
Reference substance:
aniline
Preliminary study:
Not applicable. Test was aborted.
Test performance:
Not applicable. Test was aborted.
Key result
Parameter:
% degradation (DOC removal)
Value:
0
Sampling time:
28 d
Remarks on result:
not determinable
Details on results:
DOC (dissolved organic carbon) measurement must be made for the assessment of degradation. DOC is the TOC of a filtrated solution. The content of TOC (total organic carbon) is determined by measuring the TC (total carbon) and the IC (inorganic carbon). Then the content of organic carbon is calculated as difference between TC and IC. When measuring the inorganic carbon (IC) in the carbon analyser, the CO2 is driven out by adding phosphoric acid. Under these acidic conditions, the cyanate of the test item is partly decomposed.
A determination of the biodegradation based on total carbon in the test vessels isn’t possible because the test item contains 5 % carbonate. Therefore a differentiation between carbon from cyanate and carbon from carbonate and hydrogencarbonate wasn’t possible.
Furthermore within the study, a significant reduction of the TOC was observed after three hours. Based on hydrolysis data, the reduction of TOC is due to abiotic degradation to CO2 and NH3.
Therefore a determination of the ready biodegradability isn’t possible.
Results with reference substance:
The reference substance was degraded within 28 days.
Validity criteria fulfilled:
yes
Interpretation of results:
other: not applicable, study was aborted
Conclusions:
The study was aborted as it was not technically feasible to measure the biodegradability of sodium cyanate.
Executive summary:

According to REACH Regulation Annex VII, Sect. 9.2.1.1, Column 2, a study of ready biodegradability does not need to be conducted if the substance is inorganic.

A study with sodium cyanate was conducted but It was not technically feasible to calculate the ready biodegradation parameters.

DOC (dissolved organic carbon) measurement must be made for the assessment of degradation. DOC is the TOC of a filtrated solution. The content of TOC (total organic carbon) is determined by measuring the TC (total carbon) and the IC (inorganic carbon). Then the content of organic carbon is calculated as difference between TC and IC. When measuring the inorganic carbon (IC) in the carbon analyser, the CO2 is driven out by adding phosphoric acid. Under these acidic conditions, the cyanate of the test item is partly decomposed.

A determination of the biodegradation based on total carbon in the test vessels isn’t possible because the test item contains 5 % carbonate. Therefore a differentiation between carbon from cyanate and carbon from carbonate and hydrogencarbonate wasn’t possible.

Furthermore within the study, a significant reduction of the TOC was observed after three hours. Based on hydrolysis data, the reduction of TOC is due to abiotic degradation to CO2 and NH3.

Therefore a determination of the ready biodegradability isn’t possible.

Description of key information

The study was aborted as it was not technically feasible to measure the biodegradability of sodium cyanate, a practically inorganic substance.

Key value for chemical safety assessment

Additional information

According to REACH Regulation Annex VII, Sect. 9.2.1.1, Column 2, a study of ready biodegradability does not need to be conducted if the substance is inorganic.

A study with sodium cyanate was conducted but It was not technically feasible to calculate the ready biodegradation parameters.

DOC (dissolved organic carbon) measurement must be made for the assessment of degradation. DOC is the TOC of a filtrated solution. The content of TOC (total organic carbon) is determined by measuring the TC (total carbon) and the IC (inorganic carbon). Then the content of organic carbon is calculated as difference between TC and IC. When measuring the inorganic carbon (IC) in the carbon analyser, the CO2 is driven out by adding phosphoric acid. Under these acidic conditions, the cyanate of the test item is partly decomposed.

A determination of the biodegradation based on total carbon in the test vessels isn’t possible because the test item contains 5 % carbonate. Therefore a differentiation between carbon from cyanate and carbon from carbonate and hydrogencarbonate wasn’t possible.

Furthermore within the study, a significant reduction of the TOC was observed after three hours. Based on hydrolysis data, the reduction of TOC is due to abiotic degradation to CO2 and NH3.

Therefore a determination of the ready biodegradability isn’t possible.