3-Butoxy-7-ethoxy-4,6-difluoro-dibenzothiophene

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:

Jun 21 - Oct 28, 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Principles of method if other than guideline:

NA

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, adapted

Details on inoculum:

Sludge collection: a fresh sample of activated sludge was collected on Sep 08, 2016 from the aeration tank of the Long Hua Wastewater Treatment Plant in Shanghai which treats predominantly domestic sewage. The activated sludge was kept by aeration until used (non-aeration during transport from the wastewater treatment plant to the laboratory was kept to a minimum). Sludge treatment: When back to the laboratory, the sludge was washed with mineral medium.
After centrifugation, the supernatant was decanted. This procedure was repeated three times (4000rpm, 4°C, centrifuge 20 minutes). Then, 1.033g of the concentrated sludge was weighed, dried at 105°C for 1 h and then measured by moisture meter for 1 h to determine the dry weight. The dry weight of concentrated sludge was 6.78%.

Sludge suspension: According to the dry weight, 42.2 g of concentrated sludge was calculated and suspended in 1 L mineral medium to yield a concentration of 3g suspended solids/L. The final concentration of the activated sludge in the test medium was 30 mg/L.

Duration of test (contact time):

28 d

Initial conc.:

23 mg/L

Based on:

test mat.

Remarks:

final concentration was clearly above water solubility

Parameter followed for biodegradation estimation:

O2 consumption

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

3

Sampling time:

28 d

Details on results:

Under the test conditions no biodegradation of test item could be observed.
The percentage degradation did not exceed 60 % within the 10-day window and after 28 days of incubation.
The test item is considered not readily biodegradable.
The reference Item sodium sodium benzoate was sufficiently degraded to 87% after 14 days, respectively. The percentage degradation (> 60 % after 14 days) of the reference item confirms the suitability of the used activated sludge inoculum.

Results with reference substance:

The reference Item sodium sodium benzoate was sufficiently degraded to 87 % after 14 days, respectively. The percentage degradation of the reference item confirms the suitability of the used activated sludge inoculum.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Under the test conditions no biodegradation of test item could be observed. The percentage degradation did not exceed 60 % within the 10-day window and after 28 days of incubation. The test item is considered not readily biodegradable.

Executive summary:

The study was conducted according to the guidelines of "Ministry of environmental protection of the people's Republic of China, The Guidelines for the Testing of Chemicals-Degradation and Accumulation, 2013, 301 F Ready Biodegradability: Manometrie Respirometry Test" and "OECD, Guidelines for the Testing of Chemicals. Ready Biodegradability 301 F: Manometrie Respirometry Test, 1992".

Under specific experimental conditions, the ready biodegradability of the test material was determined in a 28-day dissolved oxygen depletion test using activated sludge from a domestic waste water treatment plant. The tested concentration of test substance was 23.24mg/L (i .e. 50.90mg ThOD/L). The concentration of sludge inoculum in test system was 30mg/L, and the tested concentration of sodium benzoate used as reference substance was 100mg/L (i.e.167.00mg ThOD/L). A toxicity control was also included.

During the test, the temperature was maintained at 22.0-22.2°C. The mean total oxygen uptake in the inoculum blanks at the end of the test was less than 60mg O2/L in 28 days meeting the guideline requirement. Biodegradation of the reference substance (sodium benzoate) reached the pass level of the ready biodegradation test(>60% within 14 days. Biodegradation of the reference substance (sodium benzoate) reached an average of 87% by day 14. The difference of extremes between replicate values of the removal of the test substance during the 28d test period was less than 20%. The results of the toxicity control showed that the test substance met the criteria for not being inhibitory to the microbial inoculum. Thus, the test is valid.

During the 28-day test period, compared to the blank control groups, the biochemical oxygen demand (BOD) of the test substance did not show a significant increase, and the mean biodegradation percentage of the test substance at Day 28 was 3% and there was no 10-d window.

Therefore, the test substance cannot be considered tobe readily biodegradable under the experimental conditions according to this test method.

Description of key information

OECD 301F: not readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater