4,5-dihydro-5-oxo-4-[[4-[[2-(sulphooxy)ethyl]sulphonyl]phenyl]azo]-1-(4-sulphophenyl)-1H-pyrazole-3-carboxylic acid, sodium salt

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:

2016-12-05 to 2017-01-04

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)

Version / remarks:

July 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: municipal wastewater treatment plant Breisgauer Bucht Germany, 600,000 inhabitant equivalents, predominantly domestic wastewater.
- Concentration of sludge: 4.6 g/L after drying at 105°C for 3h
- Initial cell/biomass concentration: 30 mg d.s./L

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

TOC

Remarks:

calculated based on molecular structure

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral medium according to guideline
- Additional substrate: no
- Solubilising agent: no
- Test temperature: room temperature - 19.4 - 22 °C
- pH: not registered
- pH adjusted: no
- Aeration of dilution water: 2.2 to 5.0 bubbles/second or 30-100 mL/min with CO2-free air
- Suspended solids concentration: 30 mg dry solids/L
- Continuous darkness: no, diffuse light


TEST SYSTEM
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: aeration with CO2-free air
- Measuring equipment: Total organic carbon analyser TOC-5050A with autosampler ASI 5000A, Shimadzu.
- Details of trap for CO2 and volatile organics if used: two 250 mL glass wash bottles in series each filled with 200 mL 0.2 M NaOH (IC = 2.39 mg/L), sampling through lateral connecting pieces, through butyl rubber septum using 5 mL PE syringes

SAMPLING
- Sampling frequency: on day 3, 7, 10, 14, 21 and 28
- Sampling method: 4 mL of NaOH sampled from 1st CO2-absorber flasks
- Sample storage before analysis: samples immediately closed with sealing film
- Final sampling: on day 28, 2mL of 4M HCl is added to the reactor to release CO2 dissolved in water. IC-analysis on day 29.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 replicates
- Abiotic sterile control: no
- Toxicity control: yes, 1 replicate at 40.0 mg/L TOC (1:1 test substance and reference substance)
- Reference substance: 3 replicates at 20 mg/L

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

3.9

St. dev.:

1.8

Sampling time:

28 d

Remarks on result:

other: as measured after acidification of the reactor flasks to release CO2 dissolved in water on day 29

Remarks:

mean of 3 replicates

Details on results:

Biodegradability remained very low. The maximum degradation reported was 5.6 % of ThCO2.

Results with reference substance:

The reference substance was rapidly biodegraded, with maximal degradation of 91.7 % ThCO2 after 28 days.

Ultimate biodegradation as % of ThCO2

Reactor	day 0	day 3	day 7	day 10	day 14	day 21	day 28	day 29
Test item, rep 1	0	2.4	5.2	5.7	6.2	5.0	4.9	5.6
Test item, rep 2	0	10.2	3.3	3.8	4	2.8	2.8	4.0
Test item, rep 3	0	0.4	2.8	2.8	2.4	1.1	1.6	2.0
Reference, rep 1	0	60.6	86.8	90.8	91.6	91.8	94.4	91.7
Reference, rep 2	0	55.4	82.9	89.8	84.8	86.7	91.4	87.5
Reference, rep 3	0	59.4	84.1	90.4	90.0	91.7	95.0	93.8
Toxicity control	0	34.1	45.7	48.1	47.7	50.3	51.5	52.3

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The biodegradability of the test item was examined in a CO2-evolution test according to OECD 301B. The test item was found to be not readily biodegradable with on average 3.9 % biodegradation after 28 days.

Executive summary:

The biodegradability of the test item was examined in a CO2-evolution test according to OECD 301B. After 28 days, the ultimate biodegradation was found to be 3.9 % (average of 3 replicates). The biodegradation never exceeded 10 % hence, the 10 -day window criteria was not met and the test item should be considered to be not readily biodegradable.

Up to 52.3 % degradation was observed in the toxicity control containing sodium benzoate and the test item. This result shows that the test item was not inhibitory to the inoculum.

Description of key information

The biodegradability of the test item was examined in a CO2-evolution test according to OECD 301B. After 28 days, the ultimate biodegradation was found to be 3.9 % (average of 3 replicates). The biodegradation never exceeded 10 % hence, the 10 -day window criteria was not met and the test item should be considered to be not readily biodegradable.

Up to 52.3 % degradation was observed in the toxicity control containing sodium benzoate and the test item. This result shows that the test item was not inhibitory to the inoculum.

Furthermore, a modified static inherent biodegradability study according to OECD 302B is available ( Pagga & Brown, 1986). This study is used as supporting study. The authors concluded that no (when considering DOC removal) to partial elimination (when considering decolourisation) is possible.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed