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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:

2020-04-23 to 2020-05-14

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:

yes

Remarks:

Use of a solid carrier (silica gel), test substance application via a solvent (dichloromethane), completely evaporated; additional replicates without ammonium; test duration prolonged to 60 d although no degradation had started until 28 d.

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Municipal wastewater treatment plant "AZV Breisgauer Bucht" (capacity of 600,000 poulation equivalents)
- Pretreatment: No
- Concentration of sludge: 30 mg dry matter/L

Duration of test (contact time):

60 d

Initial conc.:

ca. 11.8 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: 0.2 M NaOH. The inorganic carbon concentration of the 0.2 M NaOH was determined (IC = 3.163 mg/L).
- Test temperature: 21.8–22.7 °C

TEST SYSTEM
- Culturing apparatus: 2000 mL gas wash flasks with GL14 hole-caps and frit pipes (reactors). Two 250 mL gas wash bottles connected in series with GL14 hole caps for each channel and frit pipes (CO2-absorber flask).
- Number of culture flasks/concentration: 3 negative control flasks, 3 test substance flasks, 1 positive control flask, 1 toxicity control flask.
- Method used to create aerobic conditions: The CO2-free air production system consists of an air compressor, three 1000 mL gas wash bottles filled with dry soda lime in series followed by one bottle filled with 0.1 M NaOH (sodium hydroxide). At the end of the system is one gas wash bottle filled with demineralised water, followed by an empty one to catch any drops of condensation water.
- Details of trap for CO2 and volatile organics if used: The CO2 produced in the reactors was absorbed in two 250 mL gas wash bottles in series each filled with 200 mL 0.2 M NaOH.

SAMPLING
- Sampling frequency: Days 4, 8, 11, 14, 21, 28, 36, 42, 49, 56, 60 and 61
- Sampling method: Sampling was performed through the lateral connecting pieces through the butyl rubber septum using 5 mL PE syringes. 8 mL NaOH were sampled from the first of two CO2-absorber flasks connected in line.
- Sterility check if applicable: NA
- Sample storage before analysis: No

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes
- Abiotic sterile control: No
- Toxicity control: Yes
- Other: Reference substance

STATISTICAL METHODS: None. The theoretical CO2 amount of the test item (ThCO2) was calculated.

Reference substance:

benzoic acid, sodium salt

Preliminary study:

None.

Key result

Parameter:

% degradation (CO2 evolution)

Value:

< 0

Sampling time:

60 d

Details on results:

Ultimate biodegradation after 28 days was -11.2, 2.7, and -4.0 % (mean -4.2 %) of ThCO2 (mineral medium without ammonium) and -8.2, -1.1, and -7.4 % (mean -5.6 %) of ThCO2 (mineral medium with ammonium).
In the blank flasks without ammonium the CO2-evolution was 28.7 mg/L within 28 days and 44.2 mg/L within 60 days. The mean CO2-evolution of the blank flasks with ammonium was 27.4 mg/L on day 28 and 43.9 mg/L within 60 days.
The reference substance sodium benzoate was degraded by more than 80 % within 10 days in both trials (with and without ammonium).
Degradation in the toxicity control, which contained sodium benzoate and the test substance, was only prepared for the series with ammonium. No inhibitory effect on the inoculum by the test substance was observed.

Validity criteria

- The IC content in the test vessel before introducing the test item was less than 5% of the TC in the test vessels with ammonium.

- The CO2 evolution in the inoculum blank at the end of the test was below 40 mg/L within 28 days.

- The difference of extremes of replicate values of the test item at the end of the test was less than 20%.

- The biodegradation of the reference compound reached the pass level of 60 % ThCO2 by day 4.

- The degradation extent in the toxicity control was above 25 % in 14 days based on ThCO2.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

No biodegradation of the test item could be observed within the test duration of 60 days, neither in the test series with nor without ammonium in the mineral medium. The deviations from the test guideline are considered not to compromise the reliability of the study. Thus, the test item did not reach the criteria for ready biodegradability (60 % ThCO2 within a 10-d window).

Executive summary:

The ready biodegradability of N-(4-((4-(3-phenylureido)phenyl)sulfonyl)phenyl)benzenesulfonamide was determined according to OECD guideline 301 B. The carbon dioxide evolution was measured at frequent intervals. For enhanced biodegradability testing the test duration was prolonged up to 60 days. Furthermore, for observing possible support of the degradation of nitrogen-containing test substances the test was performed twice, using mineral medium with and without ammonium.

No biodegradation of the test substance could be observed. The carbon dioxide evolution from the test substance reached -5.6 % of ThCO2 (mineral medium with ammonium) and -4.2 % of ThCO2 (mineral medium without ammonium).

According to the test guideline, a substance giving a result greater than 60 % degradation within a 10-d window within 28 days is regarded as "readily biodegradable".

In conclusion, N-(4-((4-(3-phenylureido)phenyl)sulfonyl)phenyl)benzenesulfonamide cannot be classified as readily biodegradable.

Description of key information

N-(4-((4-(3-phenylureido)phenyl)sulfonyl)phenyl)benzenesulfonamide is not readilyi biodegradable when tested according to OECD guideline 301B.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater