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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:
weight of evidence
Study period:
2003
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other:
Remarks:
Oxygen demand in blank controls (1.67 mg/L) slightly exceeded the recommended value of 1.5 mg/L. This was regarded as neglegible for reliability and overall outcome of the study. Test substance concentration in the test was inhibitory to microorganisms.
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
yes
Remarks:
test substance concentrations were in the toxic range for microorganisms
GLP compliance:
yes
Test material information:
Composition 1
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: 1046638
- Purity: 98.9%
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge: STP Breisgauer Bucht, Germany
- Laboratory culture: No
- Method of cultivation: Not applicable
- Preparation of inoculum for exposure: No data
- Pretreatment: Preincubation for 48 hours in darkness under aeration at 20 – 21°C
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
TEST CONDITIONS
- Composition of medium: According to guideline OECD 301 D “closed bottle test”
- Additional substrate: No
- Test temperature: 20.5 – 21.5 °C
- pH: 6.9 – 7.3
- Aeration of dilution water: For 48 hrs prior to the test
- Suspended solids concentration: No data; sewage effluent was diluted 2500-fold (0.4 mL/L)

TEST SYSTEM
- Culturing apparatus: BOD flasks, 250 – 300 mL
- Number of culture flasks/concentration: At least duplicate measurements at each time point
- Measuring equipment: Oxygen electrode and meter: WTWOxi 330, pH electrode and meter: WTW pH330
- Test performed in closed vessels due to significant volatility of test substance: test substance is not volatile

SAMPLING
- Sampling frequency: On days 0, 4, 7, 10, 14, 21, 28

CONTROL AND BLANK SYSTEM
- Procedure control: reference substance
- Inoculum blank: mineral medium + inoculum
- Toxicity control: 2 mg Octenidine dihydrochloride/L + 4 mg sodium acetate/L

STATISTICAL METHODS: Arithmetic means and %-deviation from duplicate and triplicate measurements
Reference substance:
acetic acid, sodium salt
Key result
Parameter:
% degradation (DOC removal)
Value:
-16.51
Sampling time:
28 d
Details on results:
In the toxicity control containing test and reference substance no degradation occurred, which demonstrated that octenidine dihydrochloride at 2 mg/L was toxic to the inoculated microorganisms
Results with reference substance:
78.4 % at Day 3
Validity criteria fulfilled:
no
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Octenidine dihydrochloride did not reach the pass levels for ready biodegradability, which was due to its antimicrobial activity, as demonstrated by the toxicity control. From the test results, no conclusions on the biodegradability of octenidine dihydrochloride can be drawn.
Executive summary:

The test was performed in accordance with guideline OECD 301D (Closed bottle test). Octenidine dihydrochloride (2 mg/L) was incubated with an inoculum from a sewage effluent of a STP that received predominantly domestic sewage water.

In the test substance incubations no decrease in O2 content was measured after 28 days, indicating that no biodegradation had occurred. A negative value (- 16.5%) results because the %-degradation is calculated on the basis of the results from the blank vessels. In these, oxygen consumption exceeded that of the test vessles, probably due to bactericidal properties of octenidine dihydochloride. This is supported by the results from the inhibition test containing both, test and reference substance. Here, no degradation could be demonstrated, while in the procedure controls containing only sodium acetate ~75% degradation was achieved.

All relevant criteria for test validity were met.Oxygen demand in the blank vessels slightly exceeded the value of 1.5 mg/L, which is recommended in the guideline OECD 301D. Measured oxygen demand was 1.67 mg/L. This deviation was considered as not having any influence on the validity of the study. The results indicate that Octenidine dihydrochloride provoked microbial toxicity at the tested concentration (2 mg/L). This is in accordance with the findings of a study on aerobic sludge respiration inhibition according to OECD 209, where an EC50(3 h) of 2.77 mg/L was found .

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
disregarded due to major methodological deficiencies
Study period:
1995
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: The investigations were not reported in full detail. The low test concentration makes the result unreliable.
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
yes
Remarks:
The test concentration was lowered to 0.1 mg/L in order to avoid microbicidal effects. This is below the range recommended by the guideline (2 – 10 mg/L).
GLP compliance:
no
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic (adaptation not specified)
Duration of test (contact time):
28 d
Initial conc.:
0.1 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
DOC removal
Remarks:
determined by the Winckler method (iodometric titration)
Details on study design:
TEST CONDITIONS
- Composition of medium: According to guideline OECD 301 D “closed bottle test”

SAMPLING
- Sampling frequency: On days 5 and 28
Reference substance:
acetic acid, sodium salt
Remarks:
0.1 mg/L
Key result
Parameter:
% degradation (DOC removal)
Value:
100
Sampling time:
5 d
Key result
Parameter:
% degradation (DOC removal)
Value:
100
Sampling time:
28 d
Results with reference substance:
No data, but test on reference substance (sodium benzoate) was included

Intermediates/degradation products: No data. However, a screening for possible cytotoxic effects of degradation products was performed by cytotoxicity tests with Fogh-Lund cells.

Interpretation of results:
readily biodegradable
Conclusions:
Octenidine dihydrochloride can be classified as “readily biodegradable”. However, the authors stated that the low test concentration led to considerable scatter in the test results. Therefore, the test outcome cannot be regarded as fully reliable.
Executive summary:

The test was performed in accordance with guideline OECD 301D (Closed bottle test). Octenidine dihydrochloride (0.1 mg/L) was incubated with an inoculum from a sewage effluent of a STP that received predominantly domestic sewage water.

From the above results, octenidine dihydrochloride can be classified as “readily biodegradable”. However, the authors stated that the low test concentration led to considerable scatter in the test results. Therefore, the test outcome cannot be regarded as fully reliable.

Description of key information

Two tests on ready biodegradability are available, but no clear conclusion on the biodegradability of octenidine dihydrochloride can be drawn from the existing studies as both results are not reliable and contradictory. No further studies are available in which rate and route of degradation in aquatic systems (incl. sewage treatment plants) is investigated.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information