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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study conducted to GLP.
Qualifier:
according to
Guideline:
OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):Succinic anhydride has been described as insoluble or very slightly soluble in water and is inherently unstable in aqueous media, rapidly hydrolyzing to form succinic acid. This behaviour was confirmed during an attempted hydrolysis study. Therefore the behaviour of the substance succinic acid was investigated.
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Inoculum from the effluent of the sewage treatment works A-2451 Au am Leithagebirge, which waste-water catchment is predominantly domestic, was collected. On arrival in the laboratory, the sample was aerated by means of filtered compressed air for about 45 minutes before being used for the study.The inoculum was not acclimatised or adapted to "SUCCINIC ACID" before exposure to the test substance in this study.
Duration of test (contact time):
ca. 28 d
Initial conc.:
ca. 20 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
Each 2-litre conical flask reaction vessel was filled with 800 mL mineral medium. Sufficient stock solution of the test and/or the reference substance was added for groups A, PK, TK, ASK and AK. The vessel was then made up to 1 litre with deionised water. The pH value was checked (WTW Hand Held Meter, pH 340). The test media containing test substance (A3/4, TK6, ASK7 and AK8) were not within the pH range given by the guidelines of 7.4 ± 0.2. Therefore the pHs were adjusted with 0.1 M NaOH to values of 7.4 ± 0.2. Next each flask was inoculated with 0.5 mL sewage effluent with approximately 1.6 x 105 cells, (except for group ASK). The number of cells was determined with a Casy Cell Counter, Model DT (Schärfe System GmbH, Germany). The opening of the vessels was covered with aluminium foil in such a way that the exchange of air was guaranteed. The vessels were inserted in a shaking machine and kept there in darkness until the end of the study.Test duration: 28 days.
Reference substance:
benzoic acid, sodium salt
Preliminary study:
Not applicable.
Parameter:
% degradation (DOC removal)
Value:
ca. 93.57
Sampling time:
4 d
Parameter:
% degradation (DOC removal)
Value:
ca. 96.55
Sampling time:
28 d
Details on results:
Details provided below.
Results with reference substance:
Details provided below.

The degradation of the test substane, the control and toxic control are detailed below:

Table: Percentage biodegradation

Day

test substance

positive control

toxicity control

A3

A4

mean

PK5

TK6

0

0

0

0

0

0

2

-3.29

69.70

33.20

87.34

1.26

4

93.34

93.80

93.57

92.87

89.80

7

93.92

93.48

93.70

91.26

92.83

10

96.15

95.03

95.59

95.07

92.86

14

96.81

96.81

96.81

95.94

95.33

18

96.10

94.87

95.49

95.60

94.83

22

95.99

96.02

96.00

97.66

97.12

25

96.58

95.86

96.22

93.69

94.64

28

96.56

96.55

96.55

97.93

96.75

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Succinic acid is readily biodegradable.
Executive summary:

Succinic anhydride has been described as insoluble or very slightly soluble in water and is inherently unstable in aqueous media, rapidly hydrolysing to form succinic acid. This behaviour was confirmed during an attempted hydrolysis study. Therefore the behaviour of the substance succinic acid was investigated.

The ready biodegradability of succinic acid was determined by measurement of the dissolved organic carbon content (DOC) at frequesnt intervals over a period of 28 days using OECD guideline 301E. The reference substance (sodium benzoate) was degraded by 95.9% within 14 days. A toxic control containing the reference substance and succinic acid indicated no inhibition of microbial activity due to the test substance.

The test substance, Succinic acid, with a nominal starting concentration of 20 mg DOC/L was degraded by 96.6 % after 28 days of incubation at a mean temperature of 21.6°C. The "10-d window" as defined by the guidelines started at approximately Day 1. 70 % degradation was exceeded at about Day 4.

According to the guideline, succinic acid is readily biodegradable. Consequently, it can be safely assumed that succinic anhydride is also readily biodegradable.

Description of key information

Succinic acid, which is rapidly formed by hydrolysis of succinic anhydride (half-life approx. 5 min), is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Succinic anhydride has been described as insoluble or very slightly soluble in water and is inherently unstable in aqueous media, rapidly hydrolysing to form succinic acid. This behaviour was confirmed during an attempted hydrolysis study. Therefore the behaviour of the substance succinic acid was investigated.

The ready biodegradability of succinic acid was determined by measurement of the dissolved organic carbon content (DOC) at frequent intervals over a period of 28 days using OECD guideline 301E. The reference substance (sodium benzoate) was degraded by 95.9 % within 14 days. A toxic control containing the reference substance and succinic acid indicated no inhibition of microbial activity due to the test substance.

The test substance, succinic acid, with a nominal starting concentration of 20 mg DOC/L was degraded by 96.6 % after 28 days of incubation at a mean temperature of 21.6 °C. The 10-day window, as defined by the guidelines, started at day 1. Seventy percent degradation was exceeded at day 4.

According to the guideline, succinic acid is readily biodegradable. By way of read-across, it is concluded that succinic anhydride is also readily biodegradable.