Diphenyl sulphone

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:

22 April 2021

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:

lot nr 202011220005

Diphenyl sulphone content: 99.99 %

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.

Duration of test (contact time):

29 d

Initial conc.:

ca. 18 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium:
- Additional substrate:
- Solubilising agent (type and concentration if used):
- Test temperature: 22 +/- 2°C
- pH: 7.4 +/- 2°c
- pH adjusted: yes 1 M HCL
- CEC (meq/100 g):
- Aeration of dilution water:
- Suspended solids concentration: 12.8 mg/L
- Continuous darkness: yes
- Other:

TEST SYSTEM
- Culturing apparatus: 2 L amber glass bottles
- Number of culture flasks/concentration: Test suspension: containing test item and inoculum (2 bottles).Inoculum blank: containing only inoculum (2 bottles)
Procedural control: containing procedural control item, and inoculum (1 bottle).
Toxicity control: containing test item, procedural control item, and inoculum (1 bottle).

- Method used to create aerobic conditions:
- Method used to create anaerobic conditions:
- Measuring equipment: titration
- Test performed in closed vessels due to significant volatility of test substance:
- Test performed in open system:
- Details of trap for CO2 and volatile organics if used: Three CO2-absorbers (bottles filled with 100 mL 0.0125 M Ba(OH)2) were connected in series to the exit aeration line of each test bottle.


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes
- Other: Sodium acetate reference control

Reference substance:

acetic acid, sodium salt

Preliminary study:

Before the start of the test (Day -1) mineral components, Milli- RO water (ca. 80 % of final volume) and inoculum were added to each bottle. This mixture was aerated with synthetic air overnight to purge the system of CO2.

Key result

Parameter:

% degradation (CO2 evolution)

Value:

ca. 5

Sampling time:

28 d

Results with reference substance:

Functioning of the test system was checked by testing the procedural control item sodium acetate, which showed a normal biodegradation curve (79 % within 14 days, ).

Validity criteria fulfilled:

yes

Interpretation of results:

not inherently biodegradable

Conclusions:

Diphenyl sulphone was not readily biodegradable under the conditions of the modified Sturm test

Executive summary:

The biodegradation in water  of Diphenyl sulphone was investigated in a standard screening study OECD 301B.

 

Relative biodegradation values calculated from measurements performed during the test period revealed no biologically relevant biodegradation of Diphenyl sulphone (5 % and 0 %, based on ThCO₂).

In the toxicity control, more than 25 % biodegradation occurred within 14 days (40 %, based on ThCO₂). Therefore, the test item was considered not to inhibit microbial activity.

Functioning of the test system was checked by testing the procedural control item sodium acetate, which showed a normal biodegradation curve (79 % within 14 days ).

Description of key information

The aerobic biodegradation of diphenyl sulphone in water was determined in the OECD 301 b study.  The substance is found not to be readily biodegradable.
5% and  0% degradation  was calculated based on ThCo2 after 28 days.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

the  test results confirm the   estimated   values, and  it is   concluded that DPS was not readily biodegradable