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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1994-04-28 to 1994-06-17
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Asahi Glass Co., Ltd.
- Expiration date of the lot/batch: 930817
- Purity test date: 1994-04-25

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: cold dark storage place
- Stability under test conditions: The test substance was stable during the cultivation, as shown by the finding that IR spectra of the test substance before the start and after the termination of the cultivation were identical.

FORM AS APPLIED IN THE TEST (if different from that of starting material): Colourless and Transparent Liquid
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure):

Sampling sites:
1) Fukogawa city sewage plant (Sapporo-shi Hokkaido)
2) Fukashiba industry sewage plant (Kashima-gun Ibaragi)
3) Nakahama city sewage plant (Osaka-shi Osaka)
4) Ochiai city sewage plant (Shinjuku-ku Tokyo)
5) Kitakami river (Ishinomaki-shi Miyagi)
6) Shinano river (Nishikanbara-gun Niigata)
7) Yoshino river (Tokushima-shi Tokushima)
8) Lake Biwa (Otsu-shi Shiga)
9) Hiroshima bay (Hiroshima-shi Hiroshima)
10) Dookai bay (Kitakyushu-shi Fukuoka)

Sludge sampling method:
1) City sewage: Return sludges from sewage plants were collected
2) Rivers, lake, and sea: Surface water and surface soil which are in contact with the atmosphere were collected.

Mixing of fresh and old activated sludge:
The filtrate (5L) of the supernatant of the activated sludge used at the time was mixed all together with each of the filtrate (500 mL) of the supernatant of a newly collected sludge (10 sources). The mixed filtrate (10L) was aerated (prefiltered open air used) after the pH value of the mixture was adjusted to 7.0 ± 1.0.

- Method of cultivation: In about 30 minutes after ceasing the aeration of the sludge mixture, supernatant corresponding to about 1/3 of the whole volume was removed. Then an equal volume of dechlorinated water was added to the remaining portion. This misture was aerated, and then a previously decided amount of synthetic sewage (Glucose, peptone and potassium dihydrogenphosphate were dissolved in dechlorinated water to obtain 5% (w/v) solution as to each component. The pH of the solution was adjusted to 7.0 ± 1.0 with sodium hydroxide) was added to the mixture so that the concentration of the synthetic sewage was 0.1% (w/v) in the volume of the dechlorinated water added. This procedure was repeated once every day. The cultivating was carried out at 25 ± 2°C.
- Storage conditions: Not specified
- Storage length: about 1 month from collection in March, 1994 to 1994-04-12 (date of initiation of use)
- Preparation of inoculum for exposure:
- Pretreatment: Not specified
- Concentration of sludge: The cultivated activated sludge was added to each test vessel 1) Test solution (sludge + test substance); 2) Test solution (sludge + aniline); 3) Test solution (control blank), so that the concentration of the suspended solid reached 30 mg/L.
- Water filtered: yes (Purified water (Takasugi Seiyaku Co., Ltd.))
Duration of test (contact time):
ca. 28 d
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
other: BOD
Details on study design:
Control
During cultivation, the appearance of the supernatant, setting of the sludge, formation of flock, pH, dissolved oxygen concentration in the solution and temperature were checked adjusted if necessary. Microflora in the activated sludge was microscopically observed and the sludge with no abnormal symptoms was used for the test.

Preparation for Test
1) Measurement of concentration of suspended solid: Measured in accordance with Japanese Industrial Standards (JIS) K-0102-1986-14.1.
Concentration of suspended solid in the activated sludge was 6800 mg/L.

2) Preparation of basal culture medium: Each 3 mL of solution, A, B, C and D, prescribed in JIS K 0102-1986-21, were made up of 1000 mL of purified water (Takasugi Seiyaku Co., Ltd.), and then the pH of this solution was adjusted to 7.0.

Preparation of Test Solutions
1) Addition of test substance or aniline
a) Test solution (water + test substance) (n =1, Vessel No. 6)
In one test vessel, 18 µL (30 mg) of the test substance was added into 300 mL of purified water, so that the concentration reached 100 mg/L.

b) Test solution (sludge + test substance) (n =3, Vessel No. 3, 4, and 5)
In each test vessel, 18 µL (30 mg) of the test substance was added into 300 mL of the basal culture medium, so that the concentration reached 100 mg/L.

c) Test solution (sludge + aniline) (n =1, Vessel No. 1)
In one test vessel, 29.5 µL (30.0 mg) of aniline was added into 300 mL of the basal culture medium, so that the concentration reached 100 mg/L.

d) Test solution (control blank) (n =1, Vessel No. 2)
In one test vessel, nothing was added to 300 mL of the basal culture medium.

2) Innoculation of activated sludge
The cultivated activated sludge was added to each test vessel (b), (c), and (d), so that the concentration of the suspended solid reached 30 mg/L.

Instruments and conditions of cultivation
1) Instruments for cultivation: Closed system oxygen consumption measuring apparatus:
Coulometer: Okhura Electric Co., Ltd.
Data Sampler: Asahi Instrument Industries Co., Ltd.
Vessel: 300 mL in volume (improved type for a volatile substance)
Absorbent for Carbon Dioxide: Soda Lime No. 1 (Wako Pure Chemical Industries, Ltd.)
Stirring Method: Each test solution was stirred by a magnetic stirrer.

2) Conditions of cultivation:
Cultivation temperature: 25 ± 1°C
Cultivation duration: 28 days
Room: Apparatus Room No. 511

Reference substance:
aniline
Key result
Parameter:
other: % degradation (BOD)
Value:
ca. 6
Sampling time:
28 d
Key result
Parameter:
other: % degradation (GC)
Value:
ca. 4
Sampling time:
28 d
Details on results:
Test substance is not biodegraded by microorganisms under the present test conditions.
Results with reference substance:
Percentage biodegradations of aniline calculated by the BOD values was 41% and 95% at the 7th and 14th day, respectively.

Appearance of Test Solutions

 

Test Solution

Appearance

At the initiation of cultivation

Water + Test Substance

Test substance was not dissolved

Sludge + Test Substance

Test substance was not dissolved

 

At the completion of cultivation

Water + Test Substance

Test substance was not observed by vision

Sludge + Test Substance

Test substance was not observed by vision

Growth of the sludge was not observed

Percentage Biodegradations after 28 days

 

Method

Percentage Biodegradation (%)

Vessel - 3

Vessel - 4

Vessel - 5

Average

BOD

0

15

2

6

 

GC

4

0

8

4

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Test material is not biodegraded by microorganisms under the test conditions.
Executive summary:

It was concluded that the test material is not biodegraded by microorganisms under the test conditions.

Description of key information

1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorohexane is considered to be not readily biodegradable.

Key value for chemical safety assessment

Additional information

In a GLP-compliant ready biodegradability study (equivalent to OECD Guideline 301 C), the average biodegradation of 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorohexane after 28 days was determined to be 6%.1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorohexane was not biodegraded by microorganisms under the test conditions (Kurume Research Laboratories, 1994a).

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