Calcium 4-[(5-chloro-4-methyl-2-sulphonatophenyl)azo]-3-hydroxy-2-naphthoate

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes

Specific details on test material used for the study:

- Storage condition of test material: At room temperature at about 20 °C, away from direct sunlight

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: aerobic activated sludge from a wastewater treatment treating predominantly domestic wastewater
- Preparation of inoculum for exposure: Sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated. Based on this ratio, calculated amounts of wet sludge were suspended in test water to obtain a concentration equivalent to 4 g (±10%) dry material per liter. During the holding period of one day prior to use, the sludge was aerated at room temperature. Prior to use, the sludge was diluted with test water to a concentration of about 1 g dry material per liter. Defined volumes of this diluted activated sludge were added to test water to obtain a final concentration of 30 mg dry material per liter.

Duration of test (contact time):

28 d

Initial conc.:

33 mg/L

Based on:

test mat.

Initial conc.:

15.3 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: One day before test start (Day-1), between 2400 and 3000 mL of untreated test medium was filled into the flasks and 90 ml activated sludge inoculum was added. Then aeration overnight with C02-free air on the following day (Day 0), defined amounts of the test item were directly added to the test flasks and made up to a volume of 3 L with test water.
- Solubilising agent: none
- Test temperature: 21-23 °C
- pH: 7.2 - 7.4
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5-liter all-glass amber bottles
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: air was led through a bottle containing about 750 mL of a 2 M NaOH solution to trap CO2. The CO2-free air was passed through the test solutions at a rate corresponding to about 30-100 mL/min.
- Details of trap for CO2 and volatile organics: two absorber flasks, the first one containing 300 mL 0.05 M NaOH and the second one containing 200 mL 0.05 M NaOH, were connected in series to the exit air line of each test flask.

SAMPLING
- Sampling frequency test item and inoculum control: day 2, 5, 7, 9, 12, 14, 19, 23, 27, 28, 29
- Sampling frequency procedure control: day 2, 7, 14, 28, 29
- Sampling frequency toxicity control: day 7, 14, 28, 29
- Sampling method: aliquot of 5.0 mL withdrawn from the absorber flask nearest to the test flask for analysis of inorganic carbon

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 replicates
- Toxicity control: 1 replicate
- Procedure control: 2 replicates

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

0

Sampling time:

28 d

Results with reference substance:

Mean degradation rate after 28 days = 77.1%

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Description of key information

Poorly biodegradable.

Additional information

In a test following OECD guideline 301B the ready biodegradability of the substance was tested. Based on the CO2 evolution a degradation rate of 0 % was determined after 28 days inoculation time (RCC Ltd, 2007).