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Biodegradation in water: screening tests

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biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1978-07-01 to 1978-08-4
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
according to guideline
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Principles of method if other than guideline:
The test was conducted in accordance with "biodegradation test of chemical substance by microorganisms ect. stipulated in the Order Prescribing the items of the Test Relating to the New Chemical Substance (1974, Order of the Prime Minister, the Minster of Health and Welfare, the Minister of International Trade and Industry No.1). This guideline corresponds to 301C, Ready biodegradability: Modified MITI test or OECD 302C, Inherent Biodegradability: Modified MITI test, stipulated in the OECD Guidelines for testing of chemicals (May 12, 1981).
GLP compliance:
not specified
Oxygen conditions:
prefiltered open air was used for aeration
Inoculum or test system:
activated sludge, adapted
Details on inoculum:
- Preparation of activated sludge: 5L filtrated supernatant of activated sludge was mixed with 500 mL filtrated supernatant of newly collected sludge and cultured at pH 7.0 +- 1.0 and sufficient aeration (prefiltered open air = aeration)

- Source of inoculum/activated sludge: 10 places in Japan: Fukogawa city sewage plant; Fukashiba industry sewage plant, Nakahama city sewage plant; Ochiai city sewage plant, Kitakami river; Shinano river, Yoshino river, Lake Biwa, Hiroshima bay, Dookai bay.

- Method of cultivation: 30 minutes after ceasing aeration to the sludge mixture, supernatant was removed. Equal volume of dechlorination water is added and aerated again, followed by addition of synthetic sewage. This procedure was repeated once every day. The culturing was carried out at 25°C +- 2°C.

- Water filtered: yes
Duration of test (contact time):
>= 14 - <= 28 d
Initial conc.:
ca. 100 mg/L
Based on:
test mat.
Initial conc.:
ca. 30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
test mat. analysis
the test substance in the test solutions were determined
Parameter followed for biodegradation estimation:
DOC removal
the total organic carbon were determined
Details on study design:
- Test temperature: 25°C +- 1°C
- pH: 7.0
- pH adjusted: yes
- Cultivating duration: 14 or 28 days
- Aeration of dilution water:
- Continuous darkness: no

a) Water + test substance: test vessel containing 100 mg/L test item, 2 replicates
b) Sludge + test substance: test vessel containing 100 mg/L test item + 30 mg/L sludge, 2 replicates
c) Sludge + aniline (reference substance): test vessel containing 100 mg/L aniline + 30 mg/L sludge, 1 replicate
d) Control: test vessel containing 30 mg/L sludge.

Control blank: test vessel containing basal culture medium (30 mg/L) without test substance or aniline.

The activated sludge cultivated was added to each test vessel that the concentration of suspended solid reached to 30 mg/L

After the termination of cultivation, total organic carbon and the test substance in the test solutions were determined. The pH of the test solutions were measured.
Reference substance:
guaranteed reagent, Showa Chemicals Inc.
Key result
% degradation (O2 consumption)
ca. 83.4
Sampling time:
14 d
Results with reference substance:
Degradability of aniline on Day 7 = 72.4%
Validity criteria fulfilled:
Interpretation of results:
readily biodegradable
The test item is considered readily biodegradable.
Executive summary:

In the current study the ready biodegradability of the test item is assessed similar to OECD 301 C and EU C.4. The oxygen consumption was followed up and additionally DOC removal was determined. No detailed information is available on the results.

The percentage of biodegradation of the test item is 83.4% after 14 days was observed in vessels containing 100 mg/L g test item.

The results indicate that the test item is readily biodegradable according to OECD criteria.

Description of key information

83.4 % after 14 days (OECD 301C).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

One study is available in which the ready biodegradability of the test item is assessed similar to OECD 301 C.

The oxygen consumption was determined.

The percentage of biodegradation was 83.4% after 14 days.

The results indicate that the test item is readily biodegradable.