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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:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Remarks:
Filtrate of homogenised activated sludge from the waste water treatment plant at Taunusstein-Bleidenstadt
Details on inoculum:
Filtrate of homogenised activated sludge from the waste-water treatment plant at Taunusstein-Bleidenstadt; Lot-no : 10-Aug-2016
Duration of test (contact time):
28 d
Initial conc.:
>= 38.03 - <= 38.34 mg/L
Based on:
test mat.
Initial conc.:
>= 37.2 - <= 37.5 mg/L
Based on:
ThCO2
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
The test item and the polyvalent inoculum from an activated sewage plant dealing predominantly with domestic sewage are incubated together in a mineral nutrient medium at a temperature range of 19 to 25°C. The test item is the sole carbon and energy source. The test solutions are aerated with CO2-free compressed air and are stirred on a magnetic stirrer. When the test material is mineralised it is converted to CO2 which is trapped in a system of gas washing bottles into bariumhydroxide. The CO2 is quantified by titration of the remaining bariumhydroxide with HCl. Comparing the amount of CO2 produced upon degradation of the test item with the theroretical amount of CO2 (ThCO2) the percentage of degradation is calculated. Two blank controls with inoculum but without any test item are run in parallel in order to determine the amount of CO2 derived from the inoculum. The mean of these values have to be subtracted from those values determined for the test solutions with the test item. At the end of the test the reaction in the test solutions is stopped by addition of 1 mL HCl conc. to each of the test solutions and inorganic carbonates are made volatile. Aeration with CO2-free compressed air is continued for another day in order to purge the remaining CO2 off the test solutions. Two test solutions with the test item are tested in parallel at 10 mg/L TOC. The test duration normally is 28 days (+1 day purging of f the dissolved CO2 from the test solutions after acidification of the test solutions.)
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Remarks:
Test solution 1
Value:
1
Sampling time:
4 d
Parameter:
% degradation (CO2 evolution)
Remarks:
Test solution 1
Value:
7
Sampling time:
8 d
Parameter:
% degradation (CO2 evolution)
Remarks:
Test solution 1
Value:
11
Sampling time:
12 d
Parameter:
% degradation (CO2 evolution)
Remarks:
Test solution 1
Value:
15
Sampling time:
18 d
Parameter:
% degradation (CO2 evolution)
Remarks:
Test solution 1
Value:
19
Sampling time:
25 d
Parameter:
% degradation (CO2 evolution)
Remarks:
Test solution 1
Value:
24
Sampling time:
28 d
Parameter:
% degradation (CO2 evolution)
Remarks:
Test solution 1
Value:
33
Sampling time:
29 d
Parameter:
% degradation (CO2 evolution)
Remarks:
Test solution 2
Value:
2
Sampling time:
4 d
Parameter:
% degradation (CO2 evolution)
Remarks:
Test solution 2
Value:
7
Sampling time:
8 d
Parameter:
% degradation (CO2 evolution)
Remarks:
Test solution 2
Value:
10
Sampling time:
12 d
Parameter:
% degradation (CO2 evolution)
Remarks:
Test solution 2
Value:
12
Sampling time:
18 d
Parameter:
% degradation (CO2 evolution)
Remarks:
Test solution 2
Value:
14
Sampling time:
25 d
Parameter:
% degradation (CO2 evolution)
Value:
19
Sampling time:
28 d
Parameter:
% degradation (CO2 evolution)
Value:
24
Sampling time:
29 d
Details on results:
The threshold of "ready biodegradability" of >= 60% was not met within both test solutions. The mean value of 29% is lower than the pass value of the OECD Guideline 301B. The 10-Days-Window as indicated in the OECD test guideline 301B was not met within bith treatmens with the test item. Thus the test item can be termed "not readily biodegradable". According to the results of the toxicity control, a toxic effect towards microorganisms at the concentration tested can be excluded.
Results with reference substance:
The control was degraded 76% within 28 days. The threshold of "ready biodegradability" of >= 60% was passed within 8 days (63%) and thus within the "10-days window" as requested by the OECD test guideline 301B.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test item and the polyvalent inoculum from an activated sewage plant dealing predominantly with domestic sewage are incubated together in a mineral nutrient medium at a temperature range of 19 to 25°C. The test item is the sole carbon and energy source. The conversion into CO2 was quantified by titration of the remaining bariumhydroxide with HCl. Comparing the amount of CO2 produced upon degradation of the test item with the theroretical amount of CO2 (ThCO2) the percentage of degradation is calculated.
The threshold of "ready biodegradability" of >= 60% was not met within both test solutions. The mean value of 29% is lower than the pass value of the OECD Guideline 301B. The 10-Days-Window as indicated in the OECD test guideline 301B was not met within bith treatmens with the test item. Thus the test item can be termed "not readily biodegradable".  According to the results of the toxicity control, a toxic effect towards microorganisms at the concentration tested can be excluded.
Executive summary:

The test item and the polyvalent inoculum from an activated sewage plant dealing predominantly with domestic sewage are incubated together in a mineral nutrient medium at a temperature range of 19 to 25°C. The test item is the sole carbon and energy source. The conversion into CO2 was quantified by titration of the remaining bariumhydroxide with HCl. Comparing the amount of CO2 produced upon degradation of the test item with the theroretical amount of CO2 (ThCO2) the percentage of degradation is calculated.

The threshold of "ready biodegradability" of >= 60% was not met within both test solutions. The mean value of 29% is lower than the pass value of the OECD Guideline 301B. The 10-Days-Window as indicated in the OECD test guideline 301B was not met within bith treatmens with the test item. Thus the test item can be termed "not readily biodegradable".  According to the results of the toxicity control, a toxic effect towards microorganisms at the concentration tested can be excluded.

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
Activated sludge from the waste water treatment plant at Taunusstein-Bleidenstadt, Lot-No: 09-Dec-2013
Duration of test (contact time):
28 d
Initial conc.:
1 665 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
0.2 g to 1 g of dry matter of acticated sludge is mixed together with a mineral nutrient solution and the test item in a 2 litre glass vessel, equipped with stirrer and aerator. The test item is the sole carbon source. Its concentration is chosen in a way to provide an initial DOC-value of 50 to 400 mg/L or 100 to 1000 mg COD/L. The ratio between inoculum and test item should be in the range of 2.5:1 to 4:1.

Duration of the test is normally 28 days, but was stopped after 14 days as a result >> 90% had been measured twice. The reaction mixture is kept at 20-25°C. At fixed intervals, samples are taken from the reaction vessels and examined for DOC-content. The decrease in DOC is a measure for the biodegradability of the test item. If a degradation value of >= 95% has been measured before the test duration has reached 28d of incubation, the test may be stopped.
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (DOC removal)
Value:
0
Sampling time:
1 d
Parameter:
% degradation (DOC removal)
Value:
0
Sampling time:
3 d
Parameter:
% degradation (DOC removal)
Value:
20.5
Sampling time:
7 d
Parameter:
% degradation (DOC removal)
Value:
27.5
Sampling time:
10 d
Parameter:
% degradation (DOC removal)
Value:
29.5
Sampling time:
14 d
Parameter:
% degradation (DOC removal)
Value:
35.5
Sampling time:
18 d
Parameter:
% degradation (DOC removal)
Value:
30.7
Sampling time:
24 d
Parameter:
% degradation (DOC removal)
Value:
52.6
Sampling time:
28 d
Details on results:
The test item was degraded 53% in 28 days. Therefore, it must be considered "inherently degradable" according to OECD 302B. The test is considered valid because the control item sodium benzoate was degraded > 99.9% within 7 days. The toxicity control run in parallel indicates that the test item does not exhibit any toxic effect towards the bacteria in the test treatment at the concentration used in the test.
Results with reference substance:
The control item sodium benzoate was degraded > 99.9% within 7 days.
Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
The test item was degraded 53% in 28 days. Therefore, it must be considered "inherently degradable" according to OECD 302B. The test is considered valid because the control item sodium benzoate was degraded > 99.9% within 7 days. The toxicity control run in parallel indicates that the test item does not exhibit any toxic effect towards the bacteria in the test treatment at the concentration used in the test.
Executive summary:

A test for Inherently Biodegradability according to OECD 302B was performed on the test item. The test item was degraded 53% in 28 days. Therefore, it must be considered "inherently degradable" according to OECD 302B. The test is considered valid because the control item sodium benzoate was degraded > 99.9% within 7 days. The toxicity control run in parallel indicates that the test item does not exhibit any toxic effect towards the bacteria in the test treatment at the concentration used in the test.

Description of key information

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable
Type of water:
freshwater

Additional information