Registration Dossier

Diss Factsheets

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1999-02-05 to 1999-03-05
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to OECD 301 F test guideline and in compliance with GLP
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): The activated sludge was obtained from the municipal sewage treatment plant in Reutlingen.

- Preparation of inoculum for exposure: The innoculum was washed 2 times with dechlorinated tap water and centrifuged at 3000 rpm for 1 minute, 1 g of the wet centrifugate corresponded to approx. 60 mg suspended solids. 0.1 g of the centrifugate were introduced per flask of volume 250 mL.

- Concentration of sludge: 24 mg/L suspended solids

- Water filtered: no
Duration of test (contact time):
28 d
Initial conc.:
102.2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: The following stock solution were prepared, see table 1

- Solubilising agent (type and concentration if used): No

- Test temperature: 22 ± 2 °C

- pH: 7.7

- pH adjusted: no

- Aeration of dilution water: Demineralised water was aerated for 1 day with oil-free compressed air. Before usage, the water was allowed to stand for 0.5 hours at 20 °C.

- Suspended solids concentration: 24 mg/L

- Continuous darkness: no


TEST SYSTEM
- Culturing apparatus: Closed bottles

- Number of culture flasks/concentration: 6 Flasks: 1. Test article in mineral medium + inoculum; 2: Test article in mineral medium + inoculum; 3: Mineral medium + inoculum (blank); 4: Mineral medium + inoculum (blank); 5: Reference article in mineral medium + inoculum; 6: Test article in dilution water, sterilised with 6 mL HgCl2/L medium (C HgCl2 = 10 g/L; abiotic control).

- Method used to create aerobic conditions: Electrolytic oxygen supply and automatic data registration

- Measuring equipment: BOD-digi (J. Otto-GmbH), electrolytic oxygen supply with automatic data registration

- Test performed in closed vessels: Yes

- Details of trap for CO2 and volatile organics if used: Respirometric BOD-determination with CO2 absorption on soda lime

SAMPLING
- Sampling frequency: Continuous BOD measurement

- Sampling method: Automatic data registration



CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes: mineral medium + inoculum.

- Abiotic sterile control: Yes: test article in dilution water, sterilised with 6 mL HgCl2/L medium (C HgCl2 = 10 g/L; abiotic control).

- Toxicity control: No


STATISTICAL METHODS: None
Reference substance:
benzoic acid, sodium salt
Test performance:
The measurements concerning the innoculum blank, the reference substance and the test article comply with the criteria for validity in the OECD Guideline 301 F.
Key result
Parameter:
% degradation (O2 consumption)
Value:
73.2
Sampling time:
28 d
Results with reference substance:
Test concentration: 102.2 mg/L

- Theoretical Oxygen demand (ThOD): 1,67 mg O2/mg substance
- ThOD in flask 5: 165 mg O2/L

- BOD in flask 5 after 28 days: 1.691 mgO2/mg substance or 166.6 mg O2/L (including blank)

- Biodegradation after 14 days: 91.5 %

- Biodegradation after 28 days: 97.2 %

Table 2: BOD removal from the test flasks during the 28 day exposure

Flask

O2 uptake (mg O2/L)

Remarks

ThODTest substance

264.6 

 

 

 

 

 

 

BOD Test substance

200.7 

 

 

 

 

 

 

BOD Blank

6.9 

 

 

 

 

 

 

BODAbioticdegradation

 

 

 

 

 

 

BOD Reference article

166.6 

 

 

 

 

 

 

BOD Removal

193.8 

 

 

 

 

 

 

 BOD removal = BODtestsubstance -BODblank-BODabiotic= 193.8 mg O2/L or 1.896 mg O2/mg test substance. 

 

Validity criteria fulfilled:
yes
Interpretation of results:
other: Readily biodegradable; no information on degradation in 10 day window
Conclusions:
A biodegradation value of 73 % after 28 days in a Manometric Respirometry test was determined in a reliable study conducted according to OECD 301 F, and in compliance with GLP. The test substance was considered readily biodegradable.

Description of key information

Ready Biodegradation: 73.2% in 28 days (OECD 301F)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradation of DTO as a whole substance is required for the purposes of hazard classification. However, for risk characterisation, it is necessary to consider the properties of the individual constituents and determine their environmental fate. As a consequence, in this section, data describing the biodegradation in water of the whole substance and its constituents are considered separately.
DTO biodegradation as a whole substance

A ready biodegradation value of 73.2% (measured as percentage of theoretical oxygen demand) was achieved in 28 days using a method consistent with OECD Guideline 301 F (manometric respirometer) for Distilled Tall Oil (DTO). Although, information about the 10-day window was not available, the degradation rate is very rapid for a very poorly soluble substance. The reference substance attained 92% degradation by Day 14 and percentage degradation between replicate test samples was ± 20%, satisfying the validity criteria of the test.

In other supporting studies, DTO was readily biodegradable in a GLP test conducted according to OECD 301D (Closed Bottle Test) using an equal volume mixture of three commercially available products. The substance achieved significant levels of biodegradation (60% in 28 days) but failed to meet the 10-day window. The biodegradability of a commercial grade of DTO was measured in a GLP test according to OECD Guideline 301E (Modified OECD Screening Test). The test medium comprised an aqueous extract of the product, prepared by loading culture medium with 10 g/l test substance and stirring for 23 hours, standing for 1 hours and removing the aqueous extract by siphoning. The aqueous extract attained 64% degradation in 28 days.

However, the assessment of biodegradability of the test substance is based on the test conducted in accordance to OECD 301F because this is more applicable to a poorly soluble substance like DTO. As a whole, it can be concluded that DTO is readily biodegradable for purposes of classification and labelling.

The biodegradation of the individual constituents of the substance are discussed below.

Biodegradation of constituents of DTO: Estimated data
For environmental risk assessment it is necessary to consider the biodegradability of the constituent blocks of DTO. The method used for modelling the biodegradation of the individual constituents is detailed in PFA (2010b).

Table 4.3 shows the summary from BIOWIN Ultimate model for the constituent blocks of DTO, and the resulting biodegradation rating used for modelling degradation in the waste water treatment plant. The ratings are:

RB10   Readily Biodegradable meeting the ’10-day window’

RBN     Readily biodegradable not meeting the ’10-day window’

INHY    Inherently biodegradable fulfilling criteria

INHN    Inherently biodegradable not fulfilling criteria

NB Not biodegradable.

However the predicted biodegradation rating for the resin acids constituents in Block 4 – 6 were overwritten based on available reliable measured ready biodegradation data for these groups of constituents. A ready biodegradation of 64% in 28 days using OECD 301B has been determined for the resin acid constituents of DTO (Schaefer EC and Haberlein D (1998)).

Table 4.3: Biodegradation class for the constituents of DTO

Block

Constituents

Biodegradation class

1

Low boiling fatty acids

RB10

2

C16 saturated - C18.3 unsaturated fatty acids

RBN

3

C18 saturated - C24 saturated and unsaturated fatty acids

RBN

4

Abietic acid

RBN

5

Palustric acid

RBN

6

Pimaric acid

RBN

7

Sesquiterpene

INHN

8

Abietol

INHN

9

Tetracosanol and dehydrated sterol

INHY

10

Aldehydes

NB

11

Dimethoxystilbene

INHN

12

Sitosterols and analoque

NB

13

Polymeric acids

NB

14

Polymeric neutrals

NB

Categories Display