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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:
19 December 1986 to 1 January 1987
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: See remarks:
Remarks:
Guideline study without detailed information and with restrictions, e.g. inoculum was derived from only three sites instead of ten and the test was performed at 20 oC instead of 25 oC. In addition, no information was provided on test solution preparation, the amount of bottles used, the volume of the bottles used and limited information is presented on the results. Furthermore it should be noted that the substance is tested above the water solubility which may have affected the results. Nonetheless, the result is sufficiently acceptable for assessment.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Deviations:
yes
Remarks:
e.g. inoculum was derived from only three sites and the test was performed at 20 oC, no information was provided on test solution preparation, the amount of bottles used, the volume of the bottles used and limited information is presented on the results.
GLP compliance:
not specified
Oxygen conditions:
not specified
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
Activated sludge is prepared by mixing:
- sludge from the biological wast water treatment plant of the City of Geneva (Aire).
- sludge from the biological wate water treatment plant of Vernier-Ouest, Geneva.
- soil sampled on the bank of the Rhone river.

- Activated Sludge Concentration: 30 mg/L
Duration of test (contact time):
28 d
Initial conc.:
102 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Test temperature: 20 oC

MEASURING EQUIPMENT
- Volumetric BOD Measurement, VOITH SAPROMAT, Laborapparate AG, CH-9105 Schonengrund
- TOC DOHRMANN DC 90, Schmidlin Labor + Service AG, CH-6300 Zug

ANALYTICAL PROCEDURES
- Analytical conditions of the SAPROMAT:
Closed sytem oxygen consumption measuring apparatus.
Measurement of the oxygen consumption of microorganisms using an electro-chemical analysis process.

- Measurement of the Total Organic Carbon (TOC)
High temperature catalytic combustion, detection of the carbon dioxide formed by IR.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
Reference substance:
aniline
Remarks:
90 mg/L, purity: 99.5%
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Details on results:
Results as presented in the BOD curves, see included graph.
Biochemical Oxygen Demand of the test chemical measured on the BOD curve: 13 mg
Oxygen consumption of basal culture medium to which the inoculum is added, measured on the BOD curve: 19 mg
Theoretical Oxygen Demand required when the test chemical is completely oxidised: 301 mg
Degradation by Biochemical Oxygen Demand of the test chemical: 0%

The substance is not biodegradable under the test conditions.
According to the authors of the report the measure of the biodegradability can be stronly affected by the low solubility of the substance. The low value of the biodegradability observed for the test substance may be due to the low bioavailability of the product and/or its limited accessibility to the enzymatic sites responsible for the biodegradation.
Results with reference substance:
No biodegradation percentages for the reference substance are reported. However based on the graph presented in the report and by calculating the Theoretical Oxygen Demand of the reference sustance a rough estimate for the biodegradation percentage can be calculated of ca. 65% and 70% for day 7 and 14, respectively.
Validity criteria fulfilled:
not specified
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The substance showed no biodegradation under the conditions of the modified MITI test (OECD TG 301C) and should therefore not be classified as readily biodegradable.
Executive summary:

The ready biodegradability of the test substance was investigated in a study conducted in accordance with OECD TG 301C (modified MITI test), reported without detailed information and tested with some restrictions, Reliability 2. The concentration tested was 102 mg/L test substance, with an activated sludge concentration of 30 mg/L. No biodegradation was observed for the test substance. The substance has been tested above its water solubility. Lower concentrations, however, would not have resulted in ready biodegradability in absence of obvious biodegradable groups. Based on the results of this study the substance is considered not readily biodegradable.

Description of key information

The substance showed no biodegradation under the conditions of the modified MITI test (OECD TG 301C) and should therefore not be classified as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Key study:

The ready biodegradability of the test substance was investigated in a study conducted in accordance with OECD TG 301C (modified MITI test), reported without detailed information and tested with some restrictions, Reliability 2. The concentration tested was 102 mg/L test substance, with an activated sludge concentration of 30 mg/L. No biodegradation was observed for the test substance. The substance has been tested above its water solubility. Lower concentrations, however, would not have resulted in ready biodegradability in absence of obvious biodegradable groups. Based on the results of this study the substance is considered not readily biodegradable.

Additional available information:

Additional information is available in the RIFM database (Research Institute for Fragrance Materials) from an inherent biodegradability study (Givaudan, 1995) using the Respirometric Method (Modified MITI test II) performed in compliance with OECD TG 302C. At 30 mg/L test substance, no biodegradation was seen after 28 days. Under the conditions of this study the substance was not inherently biodegradable. Note that this study was also tested above the water solubility of the substance.