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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:
April - June 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report date:
2018

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes

Test material

Constituent 1
Reference substance name:
Cassava, ext.
EC Number:
296-251-0
EC Name:
Cassava, ext.
Cas Number:
92456-72-9
IUPAC Name:
Cassava, ext.
Test material form:
solid: particulate/powder

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge: The inoculum was a fresh sample of activated sludge and was collected from the aeration tank of a sewage treatment plant receiving predominantly domestic sewage.
- Sample site: Water treatment plant "STEP de Lille", 33290 Blanquefort (France) - Tank 2.
- Laboratory culture: A filtration through a fine sieve (about 1 mm) was performed in order to remove coarse particles. After removal of any coarse particles, the sludge was washed by recantation in a mineral medium until sludge was considered free from excess substrate or inhibitor.
- Inoculum preconditioning: Pre-conditioning consisted in aerating sludge (in mineral medium) for 5-7 days before the test and at the test temperature.
Duration of test (contact time):
ca. 28 d
Initial test substance concentration
Initial conc.:
ca. 100 g/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST ITEM PREPARATION
The test item is soluble in water; it was diluted with mineral medium at 1g/L and directly introduced with sludge into each test vessels.
The test item was tested at 100 mg/L in mineral medium.
The test medium was the mineral medium, a weakly saline aqueous medium.

TEST CONDITIONS
Composition of medium: Mineral medium according to OECD 301F guideline
- Test temperature: The test was performed in darkness between 21.3 to 21.9°C (constant temperature +/- 1°C).
- Mineral medium - pH: 7.6
- Inoculum : pH: 6.9, Dissolved oxygen: 8.8 mg/L, Suspended solids concentration: 3.11 g/L
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus:WTW Oxitop (FCBA reference: ACQU 1030)
- Number of culture flasks/concentration: 3 flasks (test item and inoculum)
- Test performed in closed vessels: Yes
- A measured volume of inoculated medium containing a known concentration of the test item (100 mg/L) as the nominal sole source of Carbon, was stirred in a closed vessel at a constant temperature up to 28 days.
- Details of trap for CO2: Microbial respiration consumes O2 and releases CO2 which were absorbed by soda lime pellets present in the headspace of flasks. This produced a decrease in pressure in the flask proportional to the amount of oxygen taken up by the microbial population during biodegradation
, which was expressed as a percentage of ThOD (Theoretical Oxygen Demand).
- Allowance was made for the endogenous activity of the inoculum by running parallel blanks withinoculum but without the test item. Furthermore, in order to check the procedure, a reference item control (sodium benzoate 60.2 mg/L + inoculum) and toxicity control (sodium benzoate + inoculum +test item) were run in parallel.
SAMPLING
- Sampling frequency: 0 to 28 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 flasks (inoculum only)
- Reference item: 2 flasks (Sodium benzoate and inoculum)
- Toxicity control: 2 flasks (test item, sodium benzoate and inoculum)
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Preliminary study:
none
% Degradation
Key result
Parameter:
% degradation (O2 consumption)
Value:
ca. 61.17
St. dev.:
2.73
Sampling time:
28 d
Details on results:
Based on ThODNH4, the degradation rate of the test item do not reach 60% within the 10-Day window but after 28 days of incubation the biodegradation was 61.17% (for information 58.11% to 63.36%)
The results obtained show that the test item is considered to be readily biodegradable following the ThODNH4, after 28 days of incubation.
Under conditions of OECD Guideline 301F, the test item, is considered to be readily biodegradable, but failing the 10-day window.

BOD5 / COD results

Results with reference substance:
The reference item “Sodium benzoate” was degraded up to 87.86% after 14 days.
Therefore, it confirms the suitability of the used aerobic sludge inoculum.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
Based on ThODNH4, the degradation rate of the test item do not reach 60% within the 10-Day window but after 28 days of incubation the biodegradation was 61.17% (for information 58.11% to 63.36%)
The results obtained show that the test item is considered to be readily biodegradable following the ThODNH4, after 28 days of incubation.
Under conditions of OECD Guideline 301F, the test item, is considered to be readily biodegradable, but failing the 10-day window.
Executive summary:

The aim of this study was to determine the ready biodegradability of the test item, according to the OECD 301F guideline, within an experimental period of 28 days by respirometric method. 

The amount of oxygen taken up by the microbial population during the biodegradation of the test item (corrected by blank inoculum, run in parallel) was determined from the change in pressure in apparatus and will be expressed as percentage of theoretical Oxygen Demand (ThOD). 

The test item contains no nitrogen so, Oxygen consumption was studied without nitrification (ThODNH4).

Based on ThODNH4, the degradation rate of the test item do not reach 60% within the 10-Day window but after 28 days of incubation the biodegradation was 61.17% (for information 58.11% to 63.36%)

The results obtained show that the test item is considered to be readily biodegradable following the ThODNH4, after 28 days of incubation.

Under conditions of OECD Guideline 301F, the test item, is considered to be readily biodegradable, but failing the 10-day window.