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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:
1997
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
not specified
Remarks:
Control of the sludge activity was determined by examining the biodegradation of the reference substance (ethylenglycol)
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, adapted
Details on inoculum:
Activated sludge was sampled from the waste water treatment plant of Teufen (sampling date 29.11.1997). Concentration of the inoculumn in the test was 30 mg dry matter/litre.
Duration of test (contact time):
<= 28 d
Initial conc.:
<= 31 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Key result
Parameter:
% degradation (CO2 evolution)
Value:
88
Sampling time:
28 d
Remarks on result:
other: 87 % mineralisation was achieved within 14 d
Results with reference substance:
Ethylenglycol was used as a reference substance; required mineralisation for the reference substance was fullfilled during the test performance (≥70 % in 28 d)
Validity criteria fulfilled:
yes
Remarks:
The mineralisation of the reference substance ethylenglycol was achieved during the test performance (≥70 % 28 d)
Interpretation of results:
readily biodegradable
Conclusions:
Substance is readily biodegradable and reaches 88% mineralisation after 28 d. Biodegradability was determined according to the OECD 301 B guideline method to study mineralisation of the substance by measuring the CO2 evolution. Activated sludge was adapted from the domestic waste water treatment plant. The concentration of the activated sludge was 30 mg dry matter/L.
Executive summary:

Substance is readily biodegradable and reaches 88% mineralisation after 28 d. Biodegradability was determined according to the OECD 301 B guideline method to study mineralisation of the substance by measuring the CO2 evolution. Activated sludge was adapted from the domestic waste water treatment plant. The concentration of the activated sludge was 30 mg dry matter/L.

Description of key information

Mineralisation was determined by using OECD guideline 301 B. The study was performed in the manufacturer's Corporate Research Center using best practice found. In addition, biodegradability was determined based on the BOD/COD-ratio. This ratio was calculated by using the analysed BOD-values and the theoretical COD calculations. The BOD (7) was determined in an accredited testing laboratory by using the European standard method EN-1899-1 (1998).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

This substance is readily biodegradable in water based on the screening test results (OECD 301B) and the supportive study on BOD/COD -ratio. This substance reaches 88 % mineralisation after 28 d. Biodegradability was determined according to the OECD 301 B guideline method to study mineralisation of the substance by measuring the CO2 evolution. Activated sludge was obtained from a domestic waste water treatment plant. The concentration of the activated sludge was 30 mg dry matter/l. The initial test substance concentration was 31 mg/l.

The BOD/CODTh -ratio was used as a supportive study for this endpoint. The Biological oxygen demand BOD (7) of the substance was determined by using the European standard method EN-1899-1 (1998). The BOD-values were determined after 7 days instead of 5 days. The 7-day incubation time has been applied in several Nordic countries during the past years. The BOD after 7 days incubation was 720 mg O2/g.

For biodegradation evaluation, the BOD/COD -ratio was calculated by using the analysed BOD-value and a theoretical COD value. Theoretical COD-value was used instead of measured COD-value because the COD method is not technically feasible for betaine. Chemical oxygen demand determination (i.e. methods ISO DP 6060, SFS5504) is technically feasible for organic substances that can become oxidized fully to carbon dioxide and water. In this oxidation process, nitrogen present in substances remains in the form of ammonium. This COD determination is used to describe the oxygen demand of waste water effluents at WWTP. Therefore, it is also more suitable for waste water effluents than for certain organic substances. Betaine contains trimethylamine and organic acid (COOH) functional groups that cannot become oxidized in this COD determination. Therefore, theoretical COD value was considered to be more appropriate than measured COD value to evaluate the biodegradation of this substance based on BOD:COD-ratio.

Theoretical COD -value of 710 mg/g was calculated for the substance at the test concentration of 500 mg/g. The BOD/CODTh -ratio of the test substance was 1 indicating ready biodegradability of the substance in water.