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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1998
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Test performed according guidelines according to GLP; no deviations.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1998
Report date:
1998

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): PDTN
- Physical state: white crystalline solid
- Organic purtiy 99.2 +/- 1.0 m/m%
- Impurities (identity and concentrations): 0.5 +/-0.1 m/m% water
- Purity test date: 21-april-1998
- Lot/batch No.: JNN98038
- Test substance storage: at room temperature in the dark
- Stability under test conditions: stable
- Stability in water: not indicated
- expiry date: 01 June 2000

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): activated sludge freshly obtained from a
municipal sewage treatment platn: waterschap de Maaskant, s-Hertogenbosch, the Netherlands
- Pretreatment: The sludge was kept under continuous aeration until further treatment. Before use, the sludge was allowed to settle for at least 30 minutes and the liquid decanted for use as inoculum at the amount of 10ml/l of mineral medium

Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
21 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: The nutrient medium of the closed bottle test contained per litre of deionized water: 85 mg KH2PO4, 217.5 mg K2HPO4, 672.0 mg Na2HPO4.12H2O, 5 mg/l NH4Cl, 22.5 mg MgSO4.7H2O, 36.4 mg CaCl2.2H2O, 0.25 mg FeCl3.6H2O.
- pH adjusted: no
-Temperature: 20-22 °C
- pH 7.6 -7.8
- Aeration of mineral medium: no
- Continuous darkness: yes


TEST SYSTEM
2 litre all-glass brown coloured bottles
CO2 free air (21% oxygen; 79% nitrogen) was first led through the test bottle and then to three CO2 absorbers connected in serie (filled with 100 ml Ba(OH)2)
Test suspension: containing test substance and inoculum (2 bottles)
Inoculum blank: containing only inoculum (2 bottles)
Positive control: containing reference substance , sodium acetate (TOC = 12 mg/l) (1 bottle)
Toxicity control: containing test substance reference substance and inoculum (1 bottle)

SAMPLING
titrations were made every second or third day during the first 10days and thereafter at least every fifth day until day 28. Each time the CO2-absorber nearest tot the test bottle was removed for titration; each of the remaining two absorbers was moved one position in the direction of the test bottle. A new CO2-absorber was placed at the far en of the series.
At day 28 the pH of the test suspension was measured and 1 ml of concentrated HCL was added to each bottle to drive of the CO2 present in the suspension. THe final CO2 titration of all the bottles was done on day 29.


CALCULATIONS:
ThCO2 PDTN = 2.1 mg CO2/mg; concentration PDTN (test material) = 21 mg/l
ThCO2 sodiumacetate = 1.07 mg/mg; concentration sodium aceatete = 40.5 mg/l

CO2 production (mg/l) = mean CO2 production (mg/l) test (or reference)mean - mean CO2 production (mg/l) inoculum blank
Biodegradation (%) = CO2 production/ThCO2 *100



Results and discussion

% Degradation
Parameter:
% degradation (CO2 evolution)
Value:
0.5
Sampling time:
28 d
Details on results:
reference control = at least 60% biodegradation at day 14
CO2 release in the blank = 13 mg CO2/ litres of medium
Differences between duplicates < 20%
All quality criteria were met therefore the study is considered to be valid

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
PDTN was not readily biodegradable under the conditions of the modified Sturm test.
The test was performed according the guidelines under GLP, all quality criteria were met.
Because of the stringency of the method, low values do not necessarily mean that the test substance is not biodegradable under environmental conditions, but indicates more work will be necessary to establish biodegradability.
Executive summary:

PDTN was tested for its ready biodegradabiltiy in the carbon dioxide (CO2) evolution test (modified sturm test) at 42 mg per 2 litres, corresponding to 12 mg TOC/L.

The study procedure was based on EEC directive 92/69, C.4-C, December 1992, and OECD guideline No. 301 B July 17, 1992. The Theoretical CO2 production (ThCO2) of PDTN was calculated to be 2.10 mg CO2/mg. The relative degradation values calculated from the measurements performed during the test period revealed no significant degradation of PDTN. In the toxicity control PDTN was found to be not inhibitory. Since all acceptability criteria prescribed by the protocol were met, this study was considered to be valid. In conclusion, PDTN was not readily biodegradable under the conditions of the modified Sturm test presently performed.