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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:
2nd - 30th June 1995
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was performed in accordance with GLP and to relevant guidelines.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1995

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
Version / remarks:
The test solutions were not analysed on the last two consecutive days of the test as stated in the guideline.

The guideline also states that the Zahn-Wellen units should be topped up with water to replace that lost through evaporation but that account should be taken of the reduction in volume due to the removal of samples. In this study the volume was made up to the original volume of 1.5 litres, resulting in a gradual dilution of the unit contents over the course of the study. As a result the unit contents will be 89% of the starting concentrations. Given the results of the functional control (100% biodegradation in 5 days) this was considered not to adversely affect the results of the study.
Deviations:
yes
Principles of method if other than guideline:
The test solutions were not analysed on the last two consecutive days of the test as stated in the guideline.
This was considered not to have adversely affected the results of the study.

The guideline also states that the Zahn-Wellen units should be topped up with water to replace that lost through evaporation but that account should be taken of the reduction in volume due to the removal of samples. In this study the volume was made up to the original volume of 1.5 litres, resulting in a gradual dilution of the unit contents over the course of the study. As a result the unit contents will be 89% of the starting concentrations. Given the results of the functional control (100% biodegradation in 5 days) this was considered not to adversely affect the results of the study.
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): L-2-Chloropropionic acid, referred to as AB0350 throughout the study.
- Physical state: Liquid
- Analytical purity: 92.7% w/w
- Purity test date: 18th April 1995
- Lot/batch No.: Bx 19
- Expiration date of the lot/batch: Not specified
- Storage condition of test material: ambient temperature

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Buckland Sewage Treatment Works, (Newton Abbot , Devon)
- Storage conditions: Aerated at room temperature, pH maintained at pH 7.
- Preparation of inoculum for exposure: On the day of the test the activated sludge was washed twice by allowing the sludge to settle, removing the supernatant liquid and making up to the original volume by the addition of water.
- Initial cell/biomass concentration: solids concentration of 2477 mg/L
- Water filtered: no data
Duration of test (contact time):
ca. 28 d
Initial test substance concentration
Initial conc.:
ca. 1 000 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
other: Dissolved non-purgeable organic carbon analysis (DNPOC)
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral nutrient solution was prepared according to the 'Official Jounal of C, L133, Volume 31 Part C. Methods for determination of ecotoxicity. 30 May 1988. The composition was as follows, per litre of deionised water.
Ammonium chloride: 38.5g
Sodium dihydrogen phosphate: 33.4g
potassium dihydrogen phosphate: 8.5g
dipotassium hydrogen phosphate: 21.75g

- Solubilising agent : Not required
- Test temperature: 20 +/- 3oC
- pH: pH 7.0 - 7.6
- pH adjusted: yes if required
- Aeration of dilution water: Not specified
- Suspended solids concentration: Not specified
- Continuous darkness:Not specified

TEST SYSTEM
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: Not specified
- Test performed in open system: yes

SAMPLING
- Sampling frequency: 3 hours, days 5, 7, 11, 14, 21, 28.
- Sampling method: 25ml aliquots were removed from the test vessel.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes
Reference substance
Reference substance:
aniline

Results and discussion

% Degradation
Parameter:
other: Dissolved Non Purgeable Organic Carbon
Value:
ca. 100
Sampling time:
21 d

Any other information on results incl. tables

The resuts are summarised in the table below.

Dissolved Non Purgeable Organic Carbon Results

 

Test time

Blank DNPOC

(mg/L)

AB0350

(LCPA)

Aniline

 

 

DNPOC (mg/L)

Net DNPOC (mg/L)

Biodegradation

*(%)

DNPOC (mg/L)

Net DNPOC (mg/L)

Biodegradation

*(%)

3 hours

5.7

42

36

<1

79

73

<1

5 days

19

52

33

9

9

<1

100

7 days

24

67

43

<1

15

<1

100

11 days

18

20

2

94

11

<1

100

14 days

19

20

2

96

15

<1

100

21 days

16

15

<1

100

10

<1

100

28 days

17

16

<1

100

15

<1

100

 

The DNPOC results are the mean of duplicate analyses.

Where the calculation of % biodegradation resolves as zero or as a negative figure this is reported as <1.

Where the calculation of net DNPOC resolves as a negative, this is reported as <1.

Where the calculation of % biodegradation resolves as more than 100% this is reported as 100% biodegradation.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
The results for AB0350 (LCPA) show that there was an adaptation period phase of at least 7 days and that by day 11 of the test 90% degradation was observed. Complete biodegradation was obserevd by day 21. Therefore the conclusion is that the substance is inherently biodegradable.
Executive summary:

A guideline GLP study was conducted to assess the inherent biodegradability of L-2-Chloropropionc acid using a Zahn-Wellens test over a 28 day period. Activated sludge obtained from the local sewage works was the inoculum.

The concentration of dissolved non purgeable organic carbon was used to assess the ultimate biodegradation over the test period; the concentration of L-2-chloropropionic acid was determined by HPLC at the end of the test period to assess any primary biodegradation that may have occurred.

An aqueous mixture of activated sludge, mineral nutrients and test material was placed in a cylindrical vessel with stirring and aeration for 28 days. A reference substance (aniline) and blank solutions were also tested concurrently. All tests were performed in duplicate.

The nominal concentration for the test substance and reference substance was 1000 mg/L.

Samples were removed from the test solutions at 3 hours and days 5, 7, 11, 14, 21 and 28.

A 25 ml sample was removed, centrifuged and the supernatant liquid analysed for DNPOC. The pH of each test vessel was monitored daily and adjusted if outside the specified limits of pH 7.0 -7.6. Any loss in volume due to evaporation was made up by the addition of water.

The results showed there was an adaptation phase of at least 7 days and that by day 11 of the test there was > 90% degradation. Complete biodegradation had taken place by day 21. The conclusion is that L-2-chloropropionic acid is inherently biodegradable.