Hydroxyl-2-pyridone

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1995-03-02 to 1995-03-31

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1995

Report date:

1995

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Hydroxyl-2-pyridone

EC Number:

212-506-0

EC Name:

Hydroxyl-2-pyridone

Cas Number:

822-89-9

Molecular formula:

C5H5NO2

IUPAC Name:

1-hydroxy-1,2-dihydropyridin-2-one

Test material form:

solid: particulate/powder

Details on test material:

- Name of test material (as cited in study reports): Oxy PYRION
- Physical state: solid (powder)
- Appearance: white speckled gold powder

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Sponsor, batch 93100020

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature
- Stability under test conditions: stable

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: none

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Pre-test (Closed bottle test (OECD 301D):
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Thorndon sewage treatment works, secondary effluent, trickling filter plant that treats predominantly domestic waste, collected at day of use.
- Storage conditions: maintained under aerobic conditions until use and vacuum filtered
- Storage length: less than a day
- Preparation of inoculum for exposure:
- Concentration of sludge: 30 mg/l total suspended solids used in test
- Water filtered: yes
- Type and size of filter used, if any: Watman GFC

Pre-test (CO2 evolution test, OECD 301B):
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Oakley STW, activated sludge, predominantly domestic waste, collected the day before the test.
- Storage conditions: aerated in the lab for four hours
- Storage length: less than a day
- Preparation of inoculum for exposure: the activated sludge was homogenized in a mechanical blender and aliquots were filtered through dried and preweighted Whatman GFC filter papers which were dried at 110 °C for at least one hour, allowed to cool in a desiccator and reweighed.
- Concentration of sludge: 30 mg/l total suspended solids used in test
- Water filtered: yes
- Type and size of filter used, if any: Watman GFC

Main test (OECD 301B):
Methods for preparing the inoculum and conducting the test are similar to those described for the OECD 301B pre-test.

Duration of test (contact time):

ca. 29 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

ca. 12 mg/L

Based on:

TOC

Initial test substance concentration 2

Initial conc.:

22.2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: Standard Mineral salts medium (MSMS)
- Test temperature: 21.3 to 23.3°C
- pH: 7.5 to 7.6 at the start of the test and 7.4 to 7.6 at the end
- pH adjusted: yes, with 5N NaOH
- Aeration of dilution water: yes
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: air flushed into vessel from inlet under the stopper; outlet contected to 3 Dreschel bottles in series containing 0.025N BaOH (100 mL); air flow 33-43 mL/min
- Test performed in closed vessels due to significant volatility of test substance: no
- Details of trap for CO2 and volatile organics if used: Dreschel bottles containing 0.025N BaOH

SAMPLING
- Sampling frequency: Day 4, 8, 12, and 29
- Sampling method: not specified
- Sample storage before analysis: not specified

CONTROL AND BLANK SYSTEM
- Inoculum blank: inoculated MSMS

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

Preliminary study:

the study was preceed by a solubility test and a 5-day bacterial inhibition assay conducted according to the conditions of the closed bottle test (OECD 301D): oxypryrion showed inhibition to the weak bacterial inoculum at a nominal concentration of 22.2 mg/L (12 mg C/L)

A second inhibition assay was conducted under the conditions of the CO2 evolution test (OECD 301B): oxypyrion did not significantly inhibit the activity of the bacterial inoculum at nominal concentrations of 6 and 12 mg C/L.

The main OECD 301B test was conducted at a nominal oxypyrion concentration of 12 mg C/L

Test performance:

The rate of degradation of sodium benzoate (60% of its TCO2 after four days and 94% after 29 days) and cumulative CO2 production in the control (84.1 and 79.1 mgCO2) fulfill the validity criteria for this test.

% Degradation

% Degradation 1

Parameter:

% degradation (CO2 evolution)

Value:

ca. 20

Sampling time:

8 d

% Degradation 2

Parameter:

% degradation (CO2 evolution)

Value:

ca. 61

Sampling time:

12 d

% Degradation 3

Key result

Parameter:

% degradation (CO2 evolution)

Value:

ca. 94

Sampling time:

29 d

Details on results:

- concentrations of oxypyrion measured by HPLC analysis of duplicate samples from each test mixture were 22.8 and 22.9 mg/L (103% of nominal value).

BOD5 / COD results

Results with reference substance:

The positive control item was biodegraded by at least 60% within 14 days (60% after 4 days), confirming suitability of the activated sludge.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

A 28-d ready biodegradability test (OECD 301B, modified Sturm test) using unadapted activated sludge from a predominantly domestic waste water treatment plant indicated that Oxypyrion is readily biodegradable under the conditions of the test (initial concentration 12 mgC/L). The test substance showed 20% after 8 days of incubation, 61% after 12 days and 94% degradation after 29 days of incubation. The results of the test can be considered reliable without restriction.