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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2016-11-09 to 2016-12-09
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2016
Report Date:
2018

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Version / remarks:
July 1992
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Details on test material:
- Appearance: solid yellow powder

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: municipal wastewater treatment plant Breisgauer Bucht Germany, 600,000 inhabitant equivalents, predominantly domestic wastewater.
- Concentration of sludge: 4.2 g/L after drying at 105°C
- Initial cell/biomass concentration: 30 mg/L
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
20.1 mg/L
Based on:
TOC
Remarks:
calculated based on molecular structure
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: mineral medium according to guideline
- Additional substrate: no
- Solubilising agent: no
- Test temperature: 20.5 - 23.1°C
- pH: not registered
- pH adjusted: no
- Aeration of dilution water: 2.5 to 4.3 bubbles/second or 30-100 mL/min with CO2-free air
- Suspended solids concentration: 30 mg dry solids/L
- Continuous darkness: no, diffuse light


TEST SYSTEM
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: aeration with CO2-free air
- Measuring equipment: Total organic carbon analyser TOC-5050A with autosampler ASI 5000A, Shimadzu.
- Details of trap for CO2 and volatile organics if used: two 250 mL glass wash bottles in series each filled with 200 mL 0.2 M NaOH, sampling through lateral connecting pieces, through butyl rubber septum using 5 mL PE syringes

SAMPLING
- Sampling frequency: on day 4, 7, 11, 14, 21 and 28
- Sampling method: 4 mL of NaOH sampled from 1st CO2-absorber flasks
- Sample storage before analysis: samples immediately closed with sealing film
- Final sampling: on day 28, 2mL of 4M HCl is added to the reactor to release CO2 dissolved in water. IC-analysis on day 29.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 replicates
- Abiotic sterile control: no
- Toxicity control: yes, 1 replicate at 40.1 mg/L TOC
- Reference substance: 3 replicates at 30 mg/L

Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradation
Key result
Parameter:
% degradation (CO2 evolution)
Value:
19.57
St. dev.:
2.66
Sampling time:
29 d
Remarks on result:
other: as measured after acidification of the reactor flasks to release CO2 dissolved in water.
Remarks:
Mean of 3 replicates
Details on results:
The 10-day window started around day 16. The maximal degradation observed was 22.1 %, hence, the 10-day window criteria was not met. See below for details on results.

BOD5 / COD results

Results with reference substance:
The reference substance was rapidly biodegraded, with maximal degradation of 87.1 %.

Any other information on results incl. tables

Reactor day 0 day 4 day 7 day 11 day 14 day 21 day 28 day 29
Test item, rep 1 0 -3.5 -5.1 -6.7 2.9 15.0 18.6 22.1
Test item, rep 2 0 -3.9 -6.5 -1.6 8.1 15.7 19.8 19.8
Test item, rep 3 0 -3.3 -5.2 -5.7 -8.7 11.5 15.4 16.8
Reference, rep 1 0 71.0 80.9 79.2 83.0 77.1 82.4 84.0
Reference, rep 2 0 77.6 79.1 80.5 85.0 80.1 86.0 87.1
Reference, rep 3 0 68.5 77.6 77.1 84.1 76.7 82.6 84.6
Toxicity control 0 29.5 30.9 35.7 39.2 41.2 45.4 46.7

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The biodegradability of the test item was examined in a CO2-evolution test according to OECD 301B. The test item was found to be not readily biodegradable with on average 19.6 % biodegradation after 28 days.
Executive summary:

The biodegradability of the test item was examined in a CO2-evolution test according to OECD 301B. After 28 days, the ultimate biodegradation was found to be 19.6% (average of 3 replicates). The 10 -day window criteria was not met and the test item should be considered to be not readily biodegradable.

Up to 46.7 % degradation was observed in the toxicity control containing sodium benzoate and the test item. This result shows that the test item was not inhibitory to the inoculum.