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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:
other: GLP Guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
A mixed population of sewage treatment micro-organisms was obtained on
17 December 2009 from the final effluent stage of the Severn Trent Water Pic sewage
treatment plant at Loughborough, Leicestershire, UK, which treats predominantly
domestic sewage.
A mixed population of sewage treatment micro-organisms was obtained on 17 December 2009 from the final effluent stage of the Severn Trent Water Pic sewage treatment plant at Loughborough, Leicestershire, UK, which treats predominantly domestic sewage.
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
DOC removal
Key result
Parameter:
% degradation (O2 consumption)
Value:
87
Sampling time:
28 d
Remarks on result:
other: The 10-Day window validation criterion is satisfied, whereby 60% degradation must be attained with 10 days of the degradation exceeding 10%

Biodegradation Values

Sample

ThOD/COD

(mg O2/l)

Day 7

Day 14

Day 28

BOD

(mg O2/l)

Degradation (%)

BOD

(mg O2/l)

Degradation (%)

BOD

(mg O2/l)

Degradation

(%)

Mean biodegradation

(%)

Control     R1

                R2

-

5.84

-

10.20

-

19.16

-

 

-

6.00

-

10.70

-

19.82

-

 

Aniline

309

6.54

0

200.0

61

277.52

84

 

Test          R1

Material   R2

248

81.38

30

152.56

57

230.82

85

87

248

83.14

31

171.64

65

239.12

89

Toxicity control

557

72.34

12

275.68

48

353.94

60

 

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test material is considered readily biodegradable under the strict terms and conditions of OECD Guideline No 301 F.
Executive summary:

The study was performed to assess the ready biodegradability of the test material in an aerobic aqueous media. The method followed that described in the OECD GuidelineNo 301F, "Ready Biodegradability; Manometric Respirometry Test" The test material at a concentration of 100 mg/I was exposed to sewage treatment micro-organisms with culture medium in sealed culture vessels in diffuse light at 21 + 1 C for 28 days. The test material was adsorbed onto granular silica gel prior to dispersion in the test medium to aid dispersion of the test material in the test medium and to increase the surface area of the test material exposed to the test organisms. The degradation of the test material was assessed by the measurement of daily oxygen consumption values on Days 0 to 28. Control solutions with inoculum and the standard material, aniline, together with a toxicity control were used for validation purposes.

Based on the chemical oxygen demand for the test material, the test material attained 87% degradation after 28 days, calculated from the oxygen consumption values, and satisfied the 10-Day window validation criterion, whereby 60% degradation must be attained with 10 days of the degradation exceeding 10%. The test material can therefore be considered readily biodegradable under the strict terms and conditions of OECD Guideline No 301 F.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study performed according to OECD guideline
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
other: Brazos River water; Bacteriological analysis was not performed
Details on inoculum:
Identification: Brazos River water; Bacteriological analysis was not performed
Lot No.: Q50480.01
Source: Brazos River, Texas, USA
Collection Method: Grab
Collection Date: 28 Nov 2005
Duration of test (contact time):
28 d
Initial conc.:
ca. 2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
DOC removal
Reference substance:
acetic acid, sodium salt
Preliminary study:
none
Parameter:
% degradation (DOC removal)
Value:
10
Sampling time:
7 d
Parameter:
% degradation (DOC removal)
Value:
10.5
Sampling time:
14 d
Parameter:
% degradation (DOC removal)
Value:
21.7
Sampling time:
21 d
Parameter:
% degradation (DOC removal)
Value:
34.7
Sampling time:
28 d
Details on results:
For the test substance, 10 to 10.50% degradation was observed between day 7 and 14, 21.70% after day 21 and a maximum of 34.70% was obtained on day 28 of the study.


Parameter:
COD
Value:
2.09 mg O2/g test mat.
Results with reference substance:
The reference substance used was Sodium Acetate and Theoriticval Oxygen Demand was calculated to be 0.4703 mg O2/mg.
59.60% degradation was obtained on day 7 and a maximum of 88.20% was reached on day 14.

Table 1: Test substance readings and percent biodegradation
Reading (mg/L of O2) Average reading (mg/L of O2) Net O2depletion (mg/L of O2) % biodegradation
Day 0 8.85 8.83 Not applicable Not applicable
8.80
Day 7 7.65 7.78 0.42 10.00
7.90
Day 14 7.50 7.50 0.43 10.50
7.50
Day 21 6.80 6.95 1.03 21.70
7.10
Day 28 6.05 6.28 1.58 34.70
6.50
Table 2: Reference substance readings and percent biodegradation
Reading (mg/L of O2) Average reading (mg/L of O2) Net O2depletion (mg/L of O2) % biodegradation
Day 0 8.85 8.83 Not applicable Not applicable
8.80
Day 7 7.60 7.65 0.55 59.60
7.70
Day 14 7.15 7.10 0.83 88.20
7.05
Day 21 7.40 7.15 0.82 88.20
6.90
Day 28 7.50 7.45 0.40 44.10
7.40
Table 3: Blank readings and O2 depletion
Reading (mg/L of O2) Average reading (mg/L of O2) Net O2depletion (mg/L of O2)  
Day 0 8.80 8.80 Not applicable  
8.80
Day 7 8.20 8.20 0.60  
8.20
Day 14 8.05 7.93 0.88  
7.80
Day 21 7.85 7.98 0.83  
8.10
Day 28 7.60 7.85 0.95  
8.10
Validity criteria fulfilled:
yes
Remarks:
59.6% for sodium acetate after 7 days and 88.2% after 14 days. All extremes of the measured dissolved Oxygen in each replicate were less than 20% of the two values recorded for each test group at each time point. DO decrease < 1.5 mg/l in 28 d
Interpretation of results:
inherently biodegradable, not fulfilling specific criteria
Conclusions:
34.7% biodegradation was obtained on day 28, the substance is therefore not considered to be readily biodegradable however as degradation started after 14 days and reached a certain level after 28 days, it can be reasonably anticipated that the substance will be inherently biodegradable.
Executive summary:

As the percentage of degradation did not reached the threshold of 60%, the test substance is not considered to be readily biodegradable. However, a maximum of 34.7% biodegradation was obtained within 28 days suggesting that the substance is inherently biodegradable.

Reference material (sodium acetate) was observed with 59.6% degradation after 7 days and 88.2% after 14 days.

Description of key information

Based on the chemical oxygen demand for the test material, the test material attained 87% degradation after 28 days, calculated from the oxygen consumption values, and satisfied the 10-Day window validation criterion, whereby 60% degradation must be attained with 10 days of the degradation exceeding 10%. The test material can therefore be considered readily biodegradable under the strict terms and conditions of OECD Guideline No 301 F.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information