STI571 F8

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes

Test material

Test material information

Constituent 1

Test material form:

solid: particulate/powder

Details on test material:

Batch number: 022401

Specific details on test material used for the study:

Purity: 79.8 %

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic, non-adapted

Details on inoculum:

Activated sludge was collected from a sewage treatment works A-2500 Baden, which waste­ water catchment is predominantly domestic. On arrival in the laboratory, the sample was aerated by means of a filtered compressed air before being used for the study.

Duration of test (contact time):

ca. 28 d

Initial test substance concentration

Initial conc.:

ca. 55 mg/L

Based on:

ThCO2

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

2400 ml mineral medium were added to each of 5-litre flask. The test substance was suspended in the medium which was free of CO2 by purging with CO2 free air, at a concentration of nominally 15 mg organic carbon per litre. The reference substance was added for groups PK and TK (15 mg organic carbon/L.). Each vessel was inoculated with micro-organisms derived from a sample of activated ludge and was filled up to a total volume of 3000 ml. The vessels were incubated in darkness until the end of the study and the medium continually supplied with CO2-free air. Barium hydroxide was used to trap the CO2 formed by the degradation of the test substance. Three absorption bottles were connected in line each containing 100 ml of 0.0125 M barium hydroxide solution, in series to each 5-litre flask. On the days of CO2 measurement, the barium hydroxide absorbers closest to the test vessels were disconnected and the barium-hydroxide solution was titrated with 0.05 M HCI using phenolphthalein as the indicator. The remaining absorbers were connected to the incubation vessels and a new absorber containing 100 ml fresh 0.0125 M barium hydroxide was placed at the far end of the series. In case a substantial precipitation was seen in the first trap, also the second bottle was analysed.
The incubation was conducted in a facility where the temperature was controlled to be within the range of 22 ± 2 °C.
Determinations were performed of samples of blank and positive control vessels at the beginning of the test. The reason for omitting the vessels which contained the test substance was the risk to remove relevant amounts of the test substance when withdrawing the possibly coated pH electrode.
The air flow was regulated for each vessel individually. Air flow was determinated volumetrically in intervals. Adjustments were made as necessary to maintain a flow rate in the range 50 to 100 ml per minute. The air used was a COrfree "control air" (Linde Gase, A-2492 Eggendorf). As an added precaution, a 0.0125 M b:trium hydroxide solution was used as CO2 absorber.

Reference substance

Reference substance:

other: sodium benzoate

Results and discussion

% Degradation

Key result

Parameter:

% degradation (CO2 evolution)

Value:

ca. 9.6

Sampling time:

28 d

Details on results:

Points of degradation plot (test substance):
9 % degradation after 10 d
9.7 % degradation after 20 d
9.6 % degradation after 28 d

BOD5 / COD results

Results with reference substance:

Points of degradation plot (reference substance):
63.4 % degradation after 10 d
72.4 % degradation after 20 d
76.4 % degradation after 28 d

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

The satisfactory response recorded for the reference substance indicates that the failure of "STl571 F8" to degrade extensively in this study cannot be attributed to the deficiencies of either the test method or the inoculum.

Interpretation of results:

not readily biodegradable

Remarks:

"STl571 F8" is not readily biodegradable as the biodegradation reached only 9.6 % after 28 days.

Conclusions:

"STl571 F8" is not readily biodegradable.