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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
March 2008
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP Guideline Study.
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Type: Activated sludge (domestic)
Source: municipal wastewater treatment plant Breisgauer Bucht
Concentration: 30 mg dry solids per litre

Dry solid of the activated sludge was determined as 535 g/L by weight measurements after 3 h drying at 105°e (mean of triplicate measurements) The activated sludge was washed twice by settling the sludge, decanting the supernatant and resuspending the sludge in aerated tap water.
Duration of test (contact time):
28 d
Parameter followed for biodegradation estimation:
CO2 evolution
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
92.7
Sampling time:
28 d
Details on results:
The mean degradation extent of the test item was 92.7% within 28 days after acidification (mean value of three test vessels). For finding the exact position of the 10-day window the degradation extents of the days without measurement were calculated by interpolation. On day 2 the calculated mean degradation extent of the test item was for the first time higher than 10% (mean value: 17.2%). Thus the end of the 10-day window was on day 12. The calculated degradation extent on day 12 was 81.6% (mean value). Therefore the test item reached the pass level for ready biodegradability (60% ThC02 and 10 d-window).
Results with reference substance:
The reference compound sodium benzoate reached the pass levels for ready biodegradability within 3 days.
The degradation in the toxicity control was 87.3% within 14 days and 99.5% within 28 days (after acidification), so there was no inhibition of the inoculum caused by the test item.
The highest mean COrevolution of the blank flasks in both test series was 22.1 mg/I within 28 days after acidification.

The biodegradability of KEU4587 exposed to microorganisms derived from activated sludge obtained from a municipal wastewater treatment plant was investigated under aerobic static exposure conditions following OECD 301B methods. After 28 days the test substance showed 92.7% degradation, after acidification, based on measured CO2. The substance degraded 81.6% by the end of the 10-day window, meeting passing requirements. The study concluded that KEU4587 can be considered to be readily biodegradable and passing the 10-day window.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The mean degradation extent of the test item was 92.7% within 28 days after acidification (mean value of three test vessels). For finding the exact position of the 10-day window the degradation extents of the days without measurement were calculated by interpolation. On day 2 the calculated mean degradation extent of the test item was for the first time higher than 10% (mean value: 17.2%). Thus the end of the 10-day window was on day 12. The calculated degradation extent on day 12 was 81.6% (mean value). Therefore the test item reached the pass level for ready biodegradability (60% ThC02 and 10 d-window) and within the 10-day window.
Executive summary:

In a reliable GLP OECD Guideline 301 B study (Ready Biodegradability: CO2 Evolution Test) the test substance KEU4587 was readily biodegradable and met the 10 -day window criterion. The mean degradation extent of the test item was 92.7% within 28 days after acidification (mean value of three test vessels).

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline Study. Not GLP however, conducted in accordance with ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories).
Qualifier:
according to
Guideline:
OECD Guideline 311 (Anaerobic Biodegradability of Organic Compounds in Digested Sludge: Measurement of Gas Production)
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
anaerobic
Inoculum or test system:
digested sludge
Details on inoculum:
Digested sludge from the digester of a municipal biological waste water treatment plant, not adapted, not pre-conditioned. 2.5 gil dry matter in the
final mixture Te
Duration of test (contact time):
68 d
Parameter followed for biodegradation estimation:
CH4 evolution
Details on study design:
Test unit: 1222 ml closed glass bottle containing a total volume of test solution of 800 ml; tightly closed with butyl rubber stoppers
Test medium: Anaerobic mineral salts medium (Table 3) prepared with double distilled water (conductivity: <1.5 ~S/cm; DOC: <03 mg/l)
Incubation: Temperature-controlled incubator (35 ± 2 °C)

Procedure:
The digested sludge was stored overnight at 35 ± 2 °C without adaptation. Prior to the test the sludge was washed twice with de-aerated tap water and once with de-aerated mineral medium. The test material was directly applied to give a final TOC concentration of about 100 mg/L.

For each test series the following number of test flasks was set up:
Test suspension (T) 3 replicates: containing digested sludge + test medium + test substance
Inoculum blank (B), 3 replicates: containing digested sludge + test medium
Procedure control (R), 2 replicates: containing digested sludge + test medium + diethyleneglycol as biodegradable reference compound known torapidly biodegrade under anaerobic conditions

The test vessels were incubated at 35 ± 2 °C for a test period of 69 days. The test vessels were not stirred, but agitated once per day (except weekends).

The biodegradation of the test material was followed by a pressure-measuring device at regular intervals.
Reference substance:
diethylene glycol
Parameter:
% degradation (CO2 evolution)
Value:
68
Sampling time:
68 d
Remarks on result:
other: A steady state (plateau) was reached after about 61 days of incubation
Parameter:
% degradation (CO2 evolution)
Value:
77
Sampling time:
68 d
Remarks on result:
other: Including the produced inorganic carbon in the liquid phase
Details on results:
Based on the data of a pressure-measuring device Servo Q 8040 reached a biodegradability of 68% after 68 days of incubation, calculated with respect to the inorganic carbon production in the headspace.

A steady state (plateau) was reached after about 61 days of incubation.

Including the produced inorganic carbon in the liquid phase, measured at the end of the incubation period, a total biodegradability of Servo Q 8040 of 77% was attained within the incubation period of 68 days.

An adaptation period (lag phase) of about 2 -3 days was observed.
Results with reference substance:
The positive control, diethylenegiycol, reached a steady state value (plateau) of 69% biodegradation after about 26 days of incubation (based on the inorganic carbon production in the headspace).
Including the produced inorganic carbon in the liquid phase, measured at the end of the incubation period, a total biodegradability of the reference compound of 78% was attained. The test was considered valid, since a plateau of more than 60% was reached within 60 days of incubation.
Validity criteria fulfilled:
yes
Interpretation of results:
other: ultimately biodegradable
Conclusions:
Servo Q 8040 reached a steady state value of 60% or more under the conditions of the OECD guideline no. 311 within 60 days and, therefore, can be termed to be ultimately biodegradable under anaerobic conditions.
Executive summary:

The ultimate biodegradability of the test substance exposed to microorganisms derived from activated sludge obtained from a municipal wastewater treatment plant was investigated under anaerobic static exposure conditions following OECD 311 methods. After 68 days the test substance showed 68% degradation, based on CO2 evolution. An adaptation period (lag phase) of about 2 -3 days was observed. The study concluded that the test substance can be considered to be ultimately biodegradable.

Description of key information

Two reliable biodegradation studies are available and both demonstrate biodegradability. The key study by Elementis Specialities (2008) determined that the test substance is readily biodegradable and meets the 10-day window criterion.

Elementis Specialities (2008) conducted a reliable (Klimisch 1) GLP compliant study according to OECD 301 B methods. The biodegradability of the substance exposed to microorganisms derived from activated sludge obtained from a municipal wastewater treatment plant was investigated under aerobic static exposure conditions. After 28 days the test substance showed 92.7% degradation, after acidification, based on measured CO2. The substance degraded 81.6% by the end of the 10-day window meeting the criterion. The study concluded that the substance can be considered to be readily biodegradable, passing the 10-day window.

 

Vendico Chemical (2010) conducted a reliable (Klimisch 1) study according to OECD 311 methods. The ultimate biodegradability of the substance exposed to microorganisms derived from activated sludge obtained from a municipal wastewater treatment plant was investigated under anaerobic static exposure conditions. After 28 days the test substance showed 68% degradation, based on CO2 evolution. An adaptation period (lag phase) of about 2 -3 days was observed. The study concluded that the substance can be considered to be ultimately biodegradable.

 

These studies demonstrate the ready and ultimate biodegradability of the substance and the key study by Elementis Specialities (2008) is taken for the biodegradation in water endpoint.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information