Pyridinium dichromate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 2010-09-07 to 2010-11-17

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)

Version / remarks:

1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-B (Determination of the "Ready" Biodegradability - Modified OECD Screening Test)

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Effluent from a sewate treatment plant, A-2451 Au am Leithagebirge, Austria
- Storage conditions: Refrigerator (2 - 8 °C)
- Preparation of inoculum for exposure: On arrival in the laboratory, the sample was aerated by means of filtered compressed air for about 4 hours before being used for the study. The inoculum was not acclimatised or adapted to the test substance before exposure to the test substance in this study.
- Pretreatment: None
- Initial cell/biomass concentration: approx. 180 000 cells per vessel.

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium as described in the guidelines
- Additional substrate: none
- Solubilising agent: not used
- Test temperature: The temperature was in the range between 20.4 and 22.0 °C.
- pH: Day 0: 7.3 - 7.6, Day 28: 7.3 - 7.6
- pH adjusted: no
- Aeration of dilution water: no
- Suspended solids concentration: not applicable
- Continuous darkness: yes.

TEST SYSTEM
- Culturing apparatus: 2 L conical flask reaction vessel filled with 1 000 mL test medium.
- Number of culture flasks/concentration: 2 negative control flasks, 2 test substance flask, 1 positive control, 1 toxicity control, 1 abiotic steril control, 1 adsorption control
- Method used to create aerobic conditions: the opening of the vessels was covered with aluminium foil in such a way that the exchang of air was guaranteed.
- Measuring equipment: Measurements were performed with a carbon analyser (TOC-Analysator multi N/C 2000, Analytik Jena).

SAMPLING
- Sampling frequency: Day 0, 2, 4, 7, 10, 14, 17, 21, 24, and 28. Abiotic steril control and adsorption control were determined only on day 28.
- Sampling method: DOC concentrations were determined from the supernatants at the beginning of the study (Day 0) and then on days 2, 4, 7, 10, 14, 17, 21, 24 and 28 from the groups A (test substance), PK (positive control), TK (Toxicity control) and NK (negative control). The DOC concentrations of the groups ASK and AK were determined at the beginning of the study and on day 28. At the scheduled terms samples of 30 mL were taken from each reaction vessel and centrifuged (4000 g, 15 min, room temperature). Measurements were performed with a carbon analyser (TOC-Analysator multi N/C 2000, Analytik Jena, D-07745 Jena, Germany). Throughout the test concentrations of DOC were determined in samples from each flask in duplicate. The samples were analysed on the same day.
- Sample storage before analysis: Refrigerator (-20 °C)

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: yes
- Toxicity control: yes
- Positive control: yes
- Adsorption control: yes

STATISTICAL METHODS: no

Reference substance:

benzoic acid, sodium salt

Preliminary study:

None

Test performance:

The validity criteria were met:
- Positive control: The plateau of biodegradation was reached on Day 4 and the degradation of the positive control substance sodium benzoate exceeded the pass level of 70 % within 14 days. The reference substance sodium benzoate was degraded by 97.3 % within 14 days.
- Toxicity control: Degradation in the toxicity control, which contained sodium benzoate and the test substance, was not indicative of an inhibition of the microbial activity by the test substance.
- Abiotic degradation: On Day 0, the DOC concentration of the abiotic sterile control was between 20.18 and 20,19 mg/L and on Day 28 between 19.67 and 19.73 mg/L, therefore no abiotic degradation to inorganic carbon occurred in the abiotic sterile control.
- Adsorption control: On Day 0, the DOC concentration was between 20.75 and 20.59 mg/L and on Day 28 between 20.02 and 20.14 mg/L, therefore no adsorption of the test substance to the inoculum occurred.
- The temperature was in the range between 20.4 and 22.0 °C.
- No major deviations were seen in the determined pH-values during the study time.

Key result

Parameter:

% degradation (DOC removal)

Value:

4.7

Sampling time:

28 d

Details on results:

Within the study period of 28 days, a degradation of 4.7 % was determined for the test substance. Therefore, the test substance is considered to be not ready biodegradable.

Results with reference substance:

The reference substance sodium benzoate was degraded by 97.3 % within 14 days. The plateau of biodegradation was reached on Day 4 and the degradation of the positive control substance sodium benzoate exceeded the pass level of 70 % within 14 days.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The ready biodegradability of the test item was determined according to OECD 301 E (1992). Within the study period of 28 days, a degradation of 4.7 % was determined for the test substance. Therefore, the test substance is considered to be not ready biodegradable.

Executive summary:

The ready biodegradability of the test item was determined according to OECD 301 E under GLP conditions.  The test substance, which provided the sole source of carbon and energy, was dissolved in buffered mineral salts medium at a nominal concentration of about 20 mg organic carbon per litre. The medium was inoculated with micro-organisms derived from a sample of a sewage effluent from the domestic waste water treatment plant "Au am Leithagebirge" in Austria not previously exposed to the test substance. The vessels were incubated in darkness within a specified temperature range for 28 days. The vessels were inserted in a shaking machine and kept there until the end of the study. DOC-determinations were performed in intervals. A positive control with sodium benzoate was performed. In addition toxicity control, abiotic control and adsorption control were carried out. The biodegradation of the positive control exceeded the pass level of 70 % within 14 days. The degradation in the toxicity control indicate no inhibition of the microbial activity by the test substance. On Day 0, the DOC concentration of the abiotic sterile control was between 20.18 and 20.19 mg/L and on Day 28 between 19.67 and 19.73 mg/L, therefore no abiotic degradation to inorganic carbon occurred in the abiotic sterile control. In addition no adsorption of the test substance occurred in the adsorption control. The validity criteria were met. Within the study period of 28 days, a degradation of 4.7 % was determined for the test substance. Therefore, the test substance is considered to be not ready biodegradable.

Description of key information

The ready biodegradability of the test item was determined according to OECD 301 E (1992) (reference 5.2.1-1). Within the study period of 28 days, a degradation of 4.7 % was determined for the test substance. Therefore, the test substance is considered to be not ready biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

The ready biodegradability of the test item was determined according to OECD 301 E under GLP conditions.  The test substance, which provided the sole source of carbon and energy, was dissolved in buffered mineral salts medium at a nominal concentration of about 20 mg organic carbon per litre. The medium was inoculated with micro-organisms derived from a sample of a sewage effluent from the domestic waste water treatment plant "Au am Leithagebirge" in Austria not previously exposed to the test substance. The vessels were incubated in darkness within a specified temperature range for 28 days. The vessels were inserted in a shaking machine and kept there until the end of the study. DOC-determinations were performed in intervals. A positive control with sodium benzoate was performed. In addition toxicity control, abiotic control and adsorption control were carried out. The biodegradation of the positive control exceeded the pass level of 70 % within 14 days. The degradation in the toxicity control indicate no inhibition of the microbial activity by the test substance. On Day 0, the DOC concentration of the abiotic sterile control was between 20.18 and 20.19 mg/L and on Day 28 between 19.67 and 19.73 mg/L, therefore no abiotic degradation to inorganic carbon occurred in the abiotic sterile control. In addition no adsorption of the test substance occurred in the adsorption control. The validity criteria were met. Within the study period of 28 days, a degradation of 4.7 % was determined for the test substance. Therefore, the test substance is considered to be not ready biodegradable.