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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2000-04-04 to 2000-05-02
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2000
Report Date:
2000

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
Deviations:
no
GLP compliance:
no
Remarks:
The study described in this report was conducted in accordance with SN EN 45001.

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
impurity
Test material form:
solid: bulk
Specific details on test material used for the study:
1210.9225

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Activated sludge from the aeration tank of a municipal biological waste water treatment plant, not adapted, not pre-conditioned. 0.2 g/L dry matter in the final mixture.
Prior to the test the sludge was washed twice with tap water.
Duration of test (contact time):
28 d
Initial test substance concentrationopen allclose all
Initial conc.:
50 mg/L
Based on:
DOC
Initial conc.:
343 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimationopen allclose all
Parameter followed for biodegradation estimation:
DOC removal
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
For each test series the following number of test flasks was set up:
Test suspension (T) 2 replicates: containing activated sludge + test medium + test substance
Inoculum blank (B), 2 replicas: containing activated sludge + test medium
Procedure control (R), 1 replicate: containing activated sludge + test medium + diethyleneglycol as ready biodegradable reference compound

The test vessels were stirred (100 r.p.m.) and aerated with synthetic CO2-free air for a maximum test period of 28 days.
The air leaving the individual vessels was passed through gas-absorption bottles filled with NaOH.
It was assured that during the test the oxygen concentration was > 6 mg/l.
The pHvalue was checked periodically and adjusted to pH 6.5-8.0 with NaOH or H2S04, if necessary.
The elimination of the test material was followed by DOC determinations at regular intervals.
First samples were analyzed at the beginning of and 3 h after starting the test.
The trapped CO2 was determined as inorganic carbon (IC).

Reference substance
Reference substance:
diethylene glycol

Results and discussion

Test performance:
The activated sludge was used immediately after sampling from the treatment plant without adaptation.
Prior to the test the sludge was washed twice with tap water.
The test material was diluted with mineral salts medium to give a final DOC concentration of about 50 mg/l.
% Degradationopen allclose all
Key result
Parameter:
% degradation (DOC removal)
Value:
46
Sampling time:
28 d
Key result
Parameter:
% degradation (CO2 evolution)
Value:
32
Sampling time:
28 d
Details on results:
Based on the data of the individual DOC determinations the test substance reached a biodegradation of 46 % after 28 days.

BOD5 / COD results

Results with reference substance:
The positive control, diethyleneglycol, showed 99 % biodegradation after 14 days of incubation thus confirming suitability of inoculum and test conditions.

Any other information on results incl. tables

 

Inoculum blank (B)*

Procedure control with diethylene glycon (R)

Test suspension with

test material (T)*

Time (days)

DOC

(mg/l)

DOC

(mg/l)

DOC net.

(mg/l)

Degradation(%)

DOC (mg/l)

DOC net.

(mg/l)

Degradation(%)

0

0.6

50.7

50.2

-

72.2

71.7

-

0.125

1.2

52.3

51.1

0

71.5

70.3

0

1

1.5

46.9

45.4

11

71.1

69.6

1

3

1.9

39.8

37.9

26

71.9

70.0

0

7

3.0

4.0

1.0

98

67.5

64.5

8

10

2.8

3.7

0.9

98

43.8

41.0

42

14

2.7

3.4

0.7

99

42.9

40.1

43

16

3.0

3.5

0.5

99

42.1

39.1

44

21

3.8

4.0

0.2

100

43.2

39.4

44

24

2.3

2.6

0.3

100

40.2

37.9

46

27

2.4

2.4

0.0

100

39.8

37.4

47

28

2.6

2.8

0.2

100

40.4

37.7

46

* Mean of two replicates

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable, fulfilling specific criteria
Conclusions:
Based on the results Guanidinium Thiocyanate can be termed as inherently biodegradable under the conditions of the OECD guideline no. 302, since more than 20 %, but less than 70 % degradation was attained after 28 days of contact time.
Executive summary:

The biodegradability of Guanidinium Thiocyanate exposed to activated sludge of a municipal sewage treatment plant was investigated under aerobic static conditions, according to OECD guideline 302B.

 

Based on the data of the individual DOC determinations the test substance reached a biodegradation of 46 % after 28 days.

The main degradation process occurred during the first 10 days, when more than 40 % of the initial DOC was removed.

Maximum biodegradation was attained after 24 days of incubation. An adaptation period (lag phase) of 3 days was observed.

 

No significant elimination of the test substance due to adsorption to the activated sludge, on the glass surface or other physico-chemical processes was found as determined by means of DOC measurements 3 h after the start of the test.

 

The positive control, diethyleneglycol, showed 99 % biodegradation after 14 days of incubation thus confirming suitability of inoculum and test conditions.

 

The test was considered valid, since the degradation of the reference compound reached more than 70 % within 14 days of incubation.

 

The biodegradation of Guanidinium Thiocyanate based on CO2 evolution and calculated as %

ThCO2 reached 32 % after 28 days of incubation, showing that part of the organic carbon of the test material was transformed into CO2.

The extent of mineralization of the procedure control with diethyleneglycol was 81 % based on ThCO2 .

 

Based on the results Guanidinium Thiocyanate can be termed as inherently biodegradable under the conditions of the OECD guideline no. 302, since more than 20 %, but less than 70 % degradation was attained after 28 days of contact time.