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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
From 12 December, 1986 to 4 February, 1987
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Justification for type of information:
Refer to the Quaternary ammonium salts (QAS) category or section 13 of IUCLID for details on the category justification. The study with the read across substance is considered sufficient to fulfil the information requirements as further explained in the provided endpoint summary.
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Version / remarks:
The method was modified acording to the recommendations of ECETOC (1985) or Blok et al. (1985).
Deviations:
not specified
Principles of method if other than guideline:
The solution of the test substance in mineral medium, usually at 2-5 mg/l, was inoculated with a relatively small number of micro-organisms from a mixed population and kept in completely full, closed bottles in the dark at constant temperature. Degradation was followed by analysis of dissolved oxygen over a 28-d period. The amount of oxygen taken up by the microbial population during biodegradation of the test substance, corrected for uptake by the blank inoculum run in parallel, was expressed as a percentage of ThOD or, less satisfactorily COD.
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
The inoculum was taken from an activated sludge plant, the water treatment plant in Duiven (NL). The sludge was preconditioned during a week: a sludge suspension of 1 g s.s./l was aerated in the dilution water. This modification was introduced to reduce high residual respiration rates. The density of the inoculum in the test was 3 mg s.s./l. On day 0, 14, 28 and 42 the concentration of oxygen was measured. On day 28, nitrite and nitrate concentrations were measured. The dilution water was the medium as prescribed by the test guideline without ammonia. This modification was introduced to minimize the consumption of oxygen for the nitrification process.
Duration of test (contact time):
ca. 2 - ca. 6 wk
Initial conc.:
6.1 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Biodegradability test
The biodegradability test was carried out according to OECD Test Guideline 301D: Closed Bottle Test. The method was modified according to the recommendations of ECETOC (1985) or Blok et al. (1985). Modifications concern the inoculum, the composition of the dilution water and the analyses. The inoculum was taken from an activated sludge plant, the water treatment plant in Duiven (NL). The sludge was preconditioned during a week: a sludge suspension of 1 g s.s./L was aerated in the dilution water. This modification was introduced to reduce high residual respiration rates. The density of the inoculum in the test was 3 mg s.s./L. On Day 0, 14, 28 and 42 the concentration of oxygen was measured. On Day 28, nitrite and nitrate concentrations were measured. The dilution water was the medium as prescribed by the test guideline without ammonia. This modification was introduced to minimize the consumption of oxygen for the nitrification process. Dark glass bottles of about 280 mL with glass stoppers were filled completely with a suspension of preconditioned activated sludge (3 mg s.s/L) in dilution water and a concentration of the test substance equivalent to about 6 mg ThOD/L (Theoretical Oxygen Demand). The test was carried out in triplicate and at every observation time measurements of oxygen and pH were carried out in a new series of three bottles.
According to the OECD expert group on degradation accumulation (1981), a substance may be regarded as readily biodegradable if within 28 days the biodegradation, measured as BOD/ThOD has passed 60%. In this study, measured COD was used for the calculations.
Reference substance:
acetic acid, sodium salt
Parameter:
other: Percentage degradation based on BOD5/COD ratios
Value:
ca. 90 - ca. 97
Sampling time:
28 d
Remarks on result:
other:
Remarks:
readily biodegradable
Details on results:
ThOD = 0.97 mg o2/mg
COD = 0.68 mg o2 / mg
Theconcentration in the test= 6.1 mg Arquad/l,
therefore, the COD test suspension = 4.15 mg o2/l.
 
Toxicity
The oxygen consumption caused by the biodegradation of NaAc during one week was 8.68-3.92 =4.8 mg o2/l. The consumption of oxygen for the biodegradation of NaAc was not inhibited by concentrations of 6.1 and 18.3 mg/I.
 
Biodegradation
The extra consumption of oxygen as compared to the blank (Biochemical Oxygen Demand, BOD) can be attributed to the biodegradation of the test substance. The extent of biodegradation, calculated as the BOD related the COD for test substance was 90% or more after 2, 4 and 6 weeks.
Key result
Parameter:
BOD5*100/COD
Value:
ca. 90 - ca. 97

Table 1: Measurements of oxygen concentration, pH and calculated percentage of degradation

Week

Blank

Test

substance

Extra

O2 consumption

BOD/COD =

% Biodegradation

2

 

8.40

4.70

 

3.73

 

3.73/4.15 = 90 %

8.42

4.49

8.41

4.85

Mean

8.41

4.68

pH

7.1

6.9

4

 

8.15

4.25

4.01

 

4.01/4.15 = 97 %

 

8.21

4.02

8.05

4.12

Mean

8.14

4.13

pH

7.1

7

6

 

 

7.66

4.04

 

 

4.04/4.15 = 97 %

 

 

7.62

4

8.22

4.05

8

3.45

Mean

7.88

3.83

pH

6.9

6.7

After 4 weeks, the nitrite concentration was <0.1 mg/l and the nitrate concentration was <1.5 mg/l.

Table 2: Concentration of oxygen after 7 days

 

 

 

 

 

Blank

NaAc

Test substance

14.6 mg/l

6.1 mg/l

18.3 mg/l

mg O2/l

8.65

4.09

0.83

1.70

8.72

3.87

0.82

*

8.68

3.79

1.97

3.75

mean

8.68

3.92

1.21

2.73

pH

6.9

6.8

6.7

6.7

*Leaking bottle

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Based on the results of the read across study, the test substance, C12-14 TMAC, can also be considered to be readily biodegradable.
Executive summary:

A study was conducted to determine the biodegradability of the read across substance, Coco TMAC (34% Coco TMAC in water), according to OECD Guideline 310D (closed bottle test), in an aerobic activated sludge test system. The method was modified according to the recommendations of ECETOC (1985) or Bloket al.(1985). In the experiment, dark glass bottles of about 280 mL with glass stoppers were filled completely with a suspension of preconditioned activated sludge (3 mg s.s/L) in dilution water and a concentration of the test substance equivalent to about 6 mg ThOD (Theoretical Oxygen Demand)/L. The test was carried out in triplicate and, at every observation time, measurements of oxygen and pH were carried out in a new series of three bottles. The percentage degradation calculated based on measured BOD/COD values at 2, 4 and 6 weeks, were found to be 90%, 97% and 97% respectively. Based on the results, it was concluded that test substance passed the OECD criteria of 60% to classify it as readily biodegradable (Balk, 1987). Based on the results of the read across study, the test substance, C12-14 TMAC, can also be considered to be readily biodegradable.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
From 26 November, 1988 to 29 December, 1988
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Justification for type of information:
Refer to the Quaternary ammonium salts (QAS) category or section 13 of IUCLID for details on the category justification. The study with the read across substance is considered sufficient to fulfil the information requirements as further explained in the provided endpoint summary.
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
yes
Remarks:
Deviations: -Instead of an effluent/extract/mixture, activated sludge was used as an inoculums -ammonium chloride was omitted from the medium to prevent nitrification -the course of the oxygen decrease was measured in one bottle using a special funnel
Qualifier:
according to
Guideline:
other: EEC, 1984: “Official Journal of the European communities” L251, 1984.09.19. Part C. Methods for the determination of ecotoxicity, C Degradation biotic degradation: Closed bottle test.
GLP compliance:
no
Remarks:
No, although the study was not performed under GLP it was performed in a GLP lab by the same people with the GLP experience and equipment under the same circumstances as the GLP studies
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Secondary activated sludge was obtained from the RZWI Nieuwgraaf at duiven (1988.11.26). The RZWI Nieuwgraaf is an activated sludge plant treating predominantly domestic waste water.
Duration of test (contact time):
ca. 28 d
Initial conc.:
3 mg/L
Based on:
act. ingr.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
The test was performed in 250 to 300 mL BOD bottles. The test substance was added to an aqueous solution of mineral salts and exposed to relatively low number of microorganisms under aerobic conditions for a period of 28 days.The dissolved oxygen concentration were determined electrochemically using an oxygen electrode and meter.
Reference substance:
acetic acid, sodium salt
Remarks:
at 5 mg/L
Parameter:
% degradation (O2 consumption)
Value:
59
Sampling time:
5 d
Parameter:
% degradation (O2 consumption)
Value:
74
Sampling time:
17 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
75
Sampling time:
28 d
Details on results:
As evident from the biodegradation of 59% at Day 5 and 74% at Day 17, the plateau for ready biodegradability of the test substance was reached within 14 d of time point when 10 % degradation occurred. The 14 d window was therefore achieved.
Results with reference substance:
For the reference substance, the biodegradation was 82% after 28 d.

Oxygen consumption in the presence of the test substance and sodium acetate:

Time (days)

5

15

28

Test substance (mg O2/L)

4.9

6.1

6.2

Sodium acetate (mg O2/L)

3

3.2

3.2

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Based on the results of the read across study, the test substance, C12-14 TMAC, can also be considered to be readily biodegradable.
Executive summary:

A study was conducted to determine the ready biodegradability of the read across substance, Coco TMAC, according to OECD Guideline 301D and EEC Guidelines using a closed bottle test. The test substance at 3 mg/L was incubated with sludge from activated sludge plant treating predominantly domestic waste and O2 consumption was determined over a period of 28 d. The biodegradation was calculated as the ratio of the biochemical oxygen demand to the theoretical oxygen demand. The test substance reached a biodegradation of 75% at Day 28. As evident from the biodegradation of 59% at Day 5 and 74% at Day 17, the plateau for ready biodegradability of the test substance was reached within 14 d of time point when 10% degradation occurred. Under the test conditions, the test substance was readily biodegradable (van Ginkel, 1989). Based on the results of the read across study, the test substance, C12-14 TMAC, can be considered to be readily biodegradable.

Description of key information

Based on the results of the two guideline compliant read across biodegradation studies, the test substance, C12-14 TMAC, can be considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Study 1:

A study was conducted to determine the biodegradability of the read across substance, Coco TMAC (34% Coco TMAC in water), according to OECD Guideline 310D (closed bottle test), in an aerobic activated sludge test system. The method was modified according to the recommendations of ECETOC (1985) or Bloket al.(1985). In the experiment, dark glass bottles of about 280 mL with glass stoppers were filled completely with a suspension of preconditioned activated sludge (3 mg s.s/L) in dilution water and a concentration of the test substance equivalent to about 6 mg ThOD (Theoretical Oxygen Demand)/L. The test was carried out in triplicate and, at every observation time, measurements of oxygen and pH were carried out in a new series of three bottles. The percentage degradation calculated based on measured BOD/COD values at 2, 4 and 6 weeks, were found to be 90%, 97% and 97% respectively. Based on the results, it was concluded that test substance passed the OECD criteria of 60% to classify it as readily biodegradable (Balk, 1987). Based on the results of the read across study, the test substance, C12-14 TMAC, can be considered to be readily biodegradable.

 

Study 2:

A study was conducted to determine the ready biodegradability of the read across substance, Coco TMAC, according to OECD Guideline 301D and EEC Guidelines using a closed bottle test. The test substance at 3 mg/L was incubated with sludge from activated sludge plant treating predominantly domestic waste and O2 consumption was determined over a period of 28 d. The biodegradation was calculated as the ratio of the biochemical oxygen demand to the theoretical oxygen demand. The test substance reached a biodegradation of 75% at Day 28. As evident from the biodegradation of 59% at Day 5 and 74% at Day 17, the plateau for ready biodegradability of the test substance was reached within 14 d of time point when 10% degradation occurred. Under the test conditions, the test substance was readily biodegradable (van Ginkel, 1989). Based on the results of the read across study, the test substance, C12-14 TMAC, can be considered to be readily biodegradable.