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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
according to guideline
Guideline:
other: Biodegradation test of chemical substance by mircoorganisms etc. stipulated in the order Prescribing the Items of the test relating to the new chemical substance (1974)
Principles of method if other than guideline:
This guideline corresponds to 301C, ready biodegradability: modified MITI Test (I) stipulated in the OECD Guidelines for testing of chemicals (May 12, 1981)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
mixture of sewage, soil and natural water
Details on inoculum:
Preparation of activated sludge:

Sludge sampling sites and time
Sampling were made four times in every year at ten places in Japan. Details are included in bibliographic source mentioned above

Mixing of fresh and old activated sludge
5L of the filtrate of the supernatant of an activated sludge in the present use was mixed with 500 mL of the filtrate of the supernatant of a newly collected sludge respectively and the mixture was cultured at 7.0 +- 1.0 under the sufficient aeration (prefiltered open air was used for aeration)

Culture
About 30 minutes after ceasing the aeration to the sludge mixture, supernatant corresponding to about 1/3 of the whole volume was removed. Then the equal volume of dechlorination water was added to the remaining portion and aerated again, followed by addition of synthetic sewage*, concentration of that portion was to be 0.1 (W/V)%. This procedure was repeated once every day. The culturing was carried out at 25+-2°C.
*synthetic sewage: glucose, peptone and monopotassium phosphate were dissolved in dechlorination water respectively. Each concentration of them was to be 5(W/V)% and the solution was adjusted to pH 7.0 +- 1.0 with sodium hydroxide.

Control
During the cultivation, appearance of the supernatant, precipitabiltiy, formation of flock, pH, dissolved oxygen concentration in the solution and temperature were checked and necessary adjustments were made. microflora in the activated sludge was microscopically observed and sludge with no abnormal symptom was used for the test.

Inspection of activity
Activity of the sludge was inspected to use reference substance. And the relation between new and old activated sludge was taken account.
Duration of test (contact time):
2 wk
Initial conc.:
100 mg/L
Based on:
test mat.
Reference substance:
aniline
Remarks:
guaranteed reagent, Showa Chemicals Inc.
Parameter:
% degradation (O2 consumption)
Value:
85.2
Sampling time:
14 d
Interpretation of results:
readily biodegradable
Executive summary:

In a modified MITI test comparable to OECD TG 301 C the biodegradation of phthalic anhydride was investigated (MITI, 1992). After 2 weeks 85 % degradation of the test substance was determined.

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Principles of method if other than guideline:
Method: other: "fill and draw" batch system: semi-continuous-activated sludge test (SCAS)
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, industrial, adapted
Duration of test (contact time):
24 h
Parameter:
% degradation (TOC removal)
Value:
88
Sampling time:
24 h
Parameter:
other: COD removal
Value:
33
Sampling time:
24 h
Details on results:
RS-Freetext:
Kinetic of TOC removal efficiency (%):
0 h: 0
2 h: 23
4 h: 35
24 h: 88
(detected with TOC-analyzer, Model 102 from Beckman Toshiba Ltd.)

Kinetic of test substance (in %):
0 after 0 hour(s)
22 after 2 hour(s)
22 after 4 hour(s)
33 after 24 hour(s)
RM-Freetext:
Related to COD(Mn)
Interpretation of results:
inherently biodegradable
Executive summary:

The biodegradation of phthalic anhydride was investigated with activated sludge obtained from the waste water treatment plant of the Kashima petroleum and petrochemical industrial complex in Japan. The test was performed in a "fill-and-draw" type apparatus with aeration cylinders and is regarded as a test on inherent biodegradability. TOC and COD were monitored during the test. After 24 hours, 33 % degradation was measured with COD and 88 % with TOC (Matsui, 1975, 1988).

Description of key information

Phthalic anhydride has to be classified as readily biodegradable and is regarded as inherent biodegradable. The hydrolysis product phthalic acid is also readily biodegradable (MITI, 1992; Matsui, 1975; Bayer, 1973).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

All tests found for phthalic anhydride and its hydrolysis product phthalic acid result in ready biodegradability of the substances.

In a modified MITI test comparable to OECD TG 301 C the biodegradation of phthalic anhydride was investigated (MITI, 1992). After 2 weeks 85 % degradation of the test substance was determined. Therefore, phthalic anhydride is classified as readily biodegradable. The biodegradation of phthalic anhydride was also investigated with activated sludge obtained from the waste water treatment plant of the Kashima petroleum and petrochemical industrial complex in Japan. The test was performed in a "fill-and-draw" type apparatus with aeration cylinders and is regarded as a test on inherent biodegradability. TOC and COD were monitored during the test. After 24 hours, 33 % degradation was measured with COD and 88 % with TOC (Matsui, 1975, 1988). Based on this result, phthalic anhydride is regarded as inherently biodegradable. The hydrolysis product phthalic acid shows 74% degradation after 30 days in a closed bottle test, which is comparable to the OECD TG 301 D (Bayer, 1973), indicating that the substance is readily biodegradable.