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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:
2009.10.27-2009.11.24
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study performed in accordance with OECD principles of GLP with no deviations. Furthermore, the study fulfilled the validity criteria described in the OECD guideline.
Cross-referenceopen allclose all
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report date:
2010

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Principles of method if other than guideline:
NA
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Reference substance name:
PC2414
IUPAC Name:
PC2414
Details on test material:
- Name of test material (as cited in study report): PC2414
- Lot/batch No.: 0932L004
- Expiration date of the lot/batch: 18 months from manufacturing date (september 2009)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
NA

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, adapted
Details on inoculum:
The inoculum used was collected from a municipal wastewater treatment plant in Usserød, Denmark. Activated sludge was stabilized under continuous aeration for a period of 4 days in order to reduce the content of easily degradable carbon in the inoculum. The mineral medium used was prepared in accordance with the OECD test guideline 301F and inoculated with activated sludge to obtain a concentration of 29.3 mg suspended solids (dry weight) per litre in the test medium. The concentration of suspended solids was determined in accordance with the Danish Standard DS/EN 872. Deionised water was used for all preparations.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
18 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
The respirometer has 20 available test bottles, individually connected to independent sensor heads, each containing a sensitive pressure transducer. The microorganisms use O2 for converting the degradable carbon in solution into CO2, which is then absorbed in a trap containing KOH. This causes a decrease in the pressure equal to the amount of consumed O2. The change in pressure is detected by a pressure transducer, and an electrolytic
process is initiated, which supplies O2 and restores the pressure in the test bottle. The respirometer automatically determines the oxygen consumption in the test bottles.

PC2414 was added from a stock solution of 180 mg/L to a concentration of 18 mg/L in the test medium. This test concentration corresponds to 35.5 mg ThOD/L based on the result from the COD analysis. The reference substance was added from a concentrated aqueous stock solution to a concentration of 20 mg/L in the test medium. Deionised water was used for all preparations.

The test mixtures used in this study were:
1) Inoculated medium (inoculum control)
2) Inoculated medium and test product at 18 mg/L (test suspension)
3) Inoculated medium and reference substance at 20 mg/L (activity control)
4) Inoculated medium, test product and reference substance, 18 mg/L and 20 mg/L, respectively (toxicity control)

Triplicate bottles were prepared for the mixtures 1 to 4 above.




Reference substance
Reference substance:
benzoic acid, sodium salt
Remarks:
(Sigma 71295; lot and filing code: 1373379 44708139

Results and discussion

Preliminary study:
NA
Test performance:
The test was performed in accordance with guideline and the following criteria was fulfilled:

The BOD of the reference substance reached 86% of ThOD after 14 days, which is higher than the required 60% after 14 days.

The initial inhibition of the inoculum by PC2414 was within the limits accepted in the OECD Test Guideline No. 301F as 84% degradation (based on total ThOD) was seen after 14 days in the toxicity controls, which is higher than the required 25% after 14 days.

The total oxygen uptake in the inoculum control after 28 days was 27 mg O2/L (including nitrification), which is acceptable, and at a level comparable to the typical respiration (20-30 mg/L) specified by the OECD Test Guideline No 301F.

The deviation between BOD of the replicates at the plateau is below 20% and therefore acceptable according to the validation criteria specified by the OECD Test Guideline No 301F.
% Degradation
Parameter:
% degradation (O2 consumption)
Value:
86
St. dev.:
3
Sampling time:
28 d
Details on results:
Chemical analyses of nitrite- and nitrate-nitrogen (NOx-N) showed a NOx-N-production due to nitrification in the test suspensions of 2.58 mg N/L and in the inoculum controls of 1.96 mg N/L, respectively. The nitrification corresponded to 33% of the total oxygen consumption in the inoculum controls, 20% of the total oxygen consumption in the test suspensions, 15% of the total oxygen consumption in the activity controls and 12% of the total oxygen consumption in the toxicity controls.

The oxygen consumption of the activity controls showed that the activity of the inoculum was satisfactory. After 14 days, the bottles with sodium benzoate had reached a BOD of 86±3% of ThOD. At the end of the test, the BOD in the activity control was 94±3% of ThOD.

In the toxicity controls, the oxygen consumption in the test bottles, to which both PC2414 and sodium benzoate were added, indicated that PC2414 did not inhibit the inoculum at the applied test concentration. The oxygen consumption in the bottles containing both PC2414 and sodium benzoate was higher than the sum of the oxygen demands when the test product and the reference substance were tested individually (showing a deviation of 1-5%) (Table xx).

The stock solution of PC2414 (180 mg/L) was analysed for COD in duplicate and the average content was 355 mg O2/L. Thus, the ThOD of PC2414 was
calculated to be 1.97 mg O2/mg PC2414. The total ThOD for each test bottle with test suspension was therefore 31.9 mg O2 (18.0 mg/L, 900 mL).

The BOD of PC2414 attained 77±3% at the end of the 10-day window (day 2 to day 12) and 86±3% of ThOD was reached during the test period of 28 days. Thus, PC2414 is considered as readily biodegradable on the basis of the results of the present study as the 60% pass level and the 10-day window requirement for ready biodegradability were fulfilled.

BOD5 / COD results

BOD5 / COD
Parameter:
COD
Value:
mg O2/g test mat.
Results with reference substance:
The BOD of reference substance (sodium benzoate) reached 86% of ThOD after 14 days.

Any other information on results incl. tables

The data collection stopped at day 24 due to an electrical fall out. The monitoring stopped with lack of data for the period from day 24 to day 28. The mixing and temperature control was still intact. As the oxygen consumption had almost reached the plateau in bottles with PC2414 and in bottles with the reference substance at the time for the stop, the stop had only little influence on the results. The oxygen consumption at day 28 was calculated by extrapolation from day 24 using the slope of the oxygen consumption from day 19 to 24.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
The validity criteria described in the OECD test guideline was fulfilled
Interpretation of results:
readily biodegradable
Conclusions:
The ready biodegradability of PC2414 was examined by use of manometric respiration in accordance with OECD guideline 301F. The pass level for ready biodegradability (60% of ThOD) was accomplished at the end of the test (28 days) and within the 10-day window. Hence, PC2414 was found to be readily biodegradable.
Executive summary:

The ready biodegradability of PC2414 was examined using manometric respiration in accordance with OECD guideline 301F. The ready biodegradability of PC2414 was determined by continuous measurement of the oxygen consumption, the biochemical oxygen demand (BOD), during the test period. The measured oxygen consumption was compared to the theoretical oxygen demand (ThOD) for a complete oxidation of PC2414. The ThOD of PC2414 was expressed as the chemical oxygen demand (COD), which was measured according to the ISO standard 15705.

PC2414 is known to hydrolyse and hydrolysis was therefore expected during preparation of stock solution. The test was performed on test solutions prepared from stock solution indicating that BOD represent both PC2414 and hydrolysis products. As the ThOD is measured on subsamples from the stock solution it is also anticipated that ThOD represent both PC2414 and hydrolysis products. Thus the measured BOD and ThOD are comparable.

The pass level for ready biodegradability (60% of ThOD) was accomplished at the end of the test (28 days) and within the 10-day window. All validity criteria were fulfilled, hence PC2414 was found to be readily biodegradable.