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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
Study period:
2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)
Version / remarks:
1992
Qualifier:
according to guideline
Guideline:
other: Real Decreto 363/1995 (BOE núm. 133 de Junio de 1995)
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic (adaptation not specified)
Details on inoculum:
100 mL secondary effluent of an urban treatment plant / L
Duration of test (contact time):
28 d
Initial conc.:
10 mg/L
Based on:
TOC
Initial conc.:
30 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation:
TOC removal
Details on study design:
TEST CONDITIONS
Trial duration: 28 days
Test temperature: 22 ± 2 ºC
Photoperiod: diffuse light
Test containers: 2 L conical flasks
Test volume used: 1 Liter.
Number of test vessels per concentration: 2
Composition of medium:
Solution 1:
MnSO4.4H2O 39.9 mg/L H2O
K2HPO4 57.2 mg/L H2O
Na2HPO4 7H2O 42.8 mg/L H2O
NH4Cl 34.7 mg/L H2O
FeCl3 ac.ethylenediaminetetraacetic 100 mg/L H2O
Solution 2:
yeast extract 15.0 mg/100 mL H2O
Add to 1000 mL of deionized water: 1 mL solution 1 and 1 mL solution 2


Reference substance:
acetic acid, sodium salt
Key result
Parameter:
% degradation (TOC removal)
Remarks:
10 ppm initial TOC
Value:
12.5
Sampling time:
28 d
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
30 ppm initial TOC
Value:
8
Sampling time:
28 d
Details on results:
The test item presents a percentage of Biodegradation of 12.5% (10 ppm initial TOC) and 8.0% (30 ppm initial TOC) after 28 days of testing.
Results with reference substance:
100% of degradation after 28 days

Table 1. Percentages of biodegradation of the test item in the course of time

time         % biodegradation
    test item    
    sodium acetate  10 ppm TOC  30 ppm TOC
 0h  0  0  0
 day 2  67,2  0,2  0,2
 day 5  81,3  2,4  1,0
 day 7  84,2  3,6  1,3
day 9  88,6  6,8  3,5
 day 12  90,5  11,7  6,9
 day 14  94,3  12,0  7,2
 day 16  97,6  12,1  7,4
 day 19  98,8  12,3  7,6
 day 21  100  12,3  7,8
 day 23  100  12,4  7,9
 day 26  100  12,5  7,9
 day 28  100  12,5  8,0
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test item presents a percentage of biodegradation of 12.5% (10 ppm initial TOC) and 8.0% (30 ppm Initial TOC) after 28 days of testing.
Executive summary:
The determination of the biodegradability of the dye Direct Black 155 RBK (97.87% active matter) (batch: 12337-d) has been carried out after 28 days . For the determination of biodegradability, the operating method OECD 301E (1992) and Royal Decree 363/1995 (BOE no. 133 of June 1995) have been followed. Biodegradation is defined as the decomposition of an organic compound by the biological action of microorganisms, which results in the disappearance of the original molecular structure and the formation of smaller organic molecules. The results are expressed as a percentage of biodegradation after 28 days. The result obtained in this test indicates that the dye Direct Black 155 RBK has biodegradation percentages of 12.5% (10 ppm initial TOC) and 8% (30 ppm of initial TOC) at 28 days of testing.
Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
Version / remarks:
1992
Qualifier:
according to guideline
Guideline:
other: Real Decreto 363/1995 (BOE núm. 133 de Junio de 1995)
GLP compliance:
no
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
1g dry material / activated sludge of an urban treatment plant / L
Duration of test (contact time):
28 d
Initial conc.:
50 mg/L
Based on:
TOC
Initial conc.:
100 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation:
TOC removal
Details on study design:
DESCRIPTION OF THE TEST DESIGN:
Test temperature: 22 ± 2 ºC
Photoperiod: diffuse light
 Test containers: 5 L conical flasks
 Test volume used: 2 Liters.
 Number of test vessels per concentration: 2
 Composition Culture medium:
- Solution 1:
KH2PO4 8.5 g / L H2O
K2HPO4 21.75 g / L H2O
Na2HPO4 2H2O 33.4 g / L H2O
NH4Cl 0.5 g / L H2O
- Solution 2: CaCl2 2H2O 36.4 g / L H2O
- Solution 3: MgSO4 7H2O 22.5 g / L H2O
- Solution 4: FeCl3 6H2O 0.25 g / L H2O
To 1000 mL of deionized water, add: 10 mL of solution 1; 1 mL of solution 2; 1 mL of solution 3; 1mL of solution 2
Reference substance:
diethylene glycol
Key result
Parameter:
% degradation (TOC removal)
Remarks:
50 ppm initial TOC
Value:
74.8
Sampling time:
28 d
Key result
Parameter:
% degradation (DOC removal)
Remarks:
100 ppm initial TOC
Value:
47.3
Sampling time:
28 d
Details on results:
The percentage of biodegradation at 28 days of the test item is:
50 ppm initial TOC: Bio28 days (%) = 74.8%
100 ppm initial TOC: Bio28 days (%) = 47.3%

Table 1. Percentages of biodegradation of the test time over the time

 time        % of biodegradation
   diethylene glycol     test item
     50 ppm TOC  100 ppm TOC
 0h  0,0  0,0  0,0
3h  0,0  11,4  9,9
 day 2  2,8  17,6  11,7
 day 5  11,8  18,9  14,9
 day 7  24,5  39,8  16,5
 day 9  51,0  45,2  26,7
 day 12  68,9  52,0  30,5
 day 14  71,4  54,0  36,6
 day 16  80,5  60,9  38,8
 day 19  94,7  65,0  40,2
 day 21  99,4  68,3  42,0
 day 23  100  71,0  43,4
 day 26  100  73,2  45,6
 day 28  100  74,8  47,3
Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
The test item presents a percentage of biodegradation of 74.8% (50 ppm initial TOC) and 47.3% (100 initial TOC ppm) after 28 days of testing
Executive summary:






The determination of the biodegradability of the dye Direct Black 155 RBK dye (97.87% active matter) (batch: 12337-d) has been carried out after 28 days. For the determination of biodegradability, the operating method OECD 302B (1992) and Royal Decree 363/1995 (BOE no. 133 of June 1995) have been followed. Biodegradation is defined as the decomposition of an organic compound by the biological action of microorganisms, which results in the disappearance of the original molecular structure and the formation of smaller organic molecules. The results are expressed as a percentage of biodegradation at 28 days. The result obtained in this test indicates that the dye Direct Black 155 RBK has biodegradation percentages of 74.8% (50 ppm initial TOC) and 47.3% (100 ppm of initial TOC) at 28 days of testing.






Description of key information

One study has been conducted according to the OECD 301A. The results show a degradation of the substance after 28 days of 12.5% (10 ppm Initial TOC) and 8.0% (30 ppm Initial TOC). In view of the results, we can conclude that the colorant Direct Black RBK does not have a rapid biodegradation in the specific conditions of the 301A guideline.
Another study has been conducted according to the OECD 302B (Zahn-Wellens). The results show a degradation of the substance after 28 days of 74.8% (50 ppm of initial TOC) and of 47.3% (100 ppm of initial TOC). It is to say that at concentrations of ca. 50 ppm of initial TOC this substance has an inherent biodegradability of 75%.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable
Type of water:
freshwater

Additional information