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Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 2018-01-16 to 2018-03-01

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Deviations:

no

Principles of method if other than guideline:

Not relevant.

GLP compliance:

yes (incl. QA statement)

Remarks:

Signed on 2017-11-22

Specific details on test material used for the study:

ThODNH4 = 1.290 mg O2/ mg test item

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

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 1
Date of sampling: January 11, 2018
Inoculum:
- physico-chemical characteristic
Suspended solid: 4.99 g/L
pH: 5.9
Dissolved oxygen: 9.2 mg/L

- Activated sludge preparation
1: Filtration through a 1 mm sieve
2: 3 Successive decantations into mineral medium
3: Activated sludge aeration during 5 days

Laboratory preparation: 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 decantation in a mineral medium until sludge was considered free from excess substrate or inhibitor.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST ITEM PREPARATION:
A solution 1g test item /L was prepared at the start of the test, this solution was cloudy,so the test item was weighed directly in the replicates “test item” and “toxicity control” in order to obtain 100 mg test item /L in mineral medium as compliant with OECD 301F.
The test item “SOCOGEL PART I P14133” was tested at 100 mg/L in mineral medium.
The test medium was the mineral medium, a weakly saline aqueous medium,


TEST CONDITIONS
- Test duration: 28 days
- Light intensity: Darkness
- Temperature: 21.9 to 22.3°C, (constant temperature ± 1°C)
- Incubation conditions: Closed test flasks incubated in environmental simulation chamber under continuous stirring
- Mineral medium
Batch number: 7/09011801 7/09011802
pH: 7.4

TEST SYSTEM
- Culturing apparatus: WTW Oxitop (FCBA reference: ACQU 1011)
- Number of culture flasks/concentration: 3
- Test performed in closed vessels: yes

SAMPLING
Oxygen consumption measured daily.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 flasks
- Refernce item: 2 flasks
- Toxicity control: 2 flasks

Reference substance:

benzoic acid, sodium salt

Remarks:

Purity: ≥ 99.5%

Preliminary study:

An elementary analysis was performed by an external laboratory to calculate the Theoretical Oxygen Demand (ThOD).
The evaluation of biodegradation has to be based on the ThODNH4 as The test item “SOCOGEL PART I P14133” contains no nitrogen.

Test performance:

No data.

Parameter:

% degradation (O2 consumption)

Value:

25.6

Sampling time:

1 d

Parameter:

% degradation (O2 consumption)

Value:

66.63

Sampling time:

4 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

88.63

St. dev.:

2.19

Sampling time:

28 d

Details on results:

The test item “SOCOGEL PART I P14133” contains no nitrogen according to the elementary analysis (see Appendix 6: Study plan, Appendix 1-2), the evaluation of biodegradation has to be based in the following based on the ThODNH4.
The degradation for the 10-day window beginning was reached on Day 1 (25.66%), before the end of the 10-day window on Day 4 the mean degradation was 66.63%, therefore the D-day window was reached.
The degradation rate of the test item “SOCOGEL PART I P14133” reached 88.63% (87.08% to 90.18%), based on the ThODNH4, after 28 days of incubation.

Results with reference substance:

The reference item “Sodium benzoate” was degraded up to 84.30% and 96.97% after 14 days.
Therefore, it confirms the suitability of the used aerobic sludge inoculum.

Biodegradation results of test item at 28 days

Treatment	% Biodegradation at 28 days	pH at the end of the test (28 days)
	(with ThODNH4)
Test item “SOCOGEL PART I P14133”	90.18	7.3
	87.08
Average (± SD)	88.63% (± 2.19)

Biodegradation of the Toxicity Control

A biodegradation of 85.50% and 86.81% after 14 days of incubation was noted in the Toxicity control (containing both of the test item and the reference item) based on the ThOD_NH4.

At the end on the test, 28 days of incubation, the result was 88.27% and 91.32% respectively for both replicates.

Therefore, the test item was not inhibitory at the tested concentration on the aerobic activated sludge micro-organism because degradation was superior to 25% within 14 days (validity criterion).

 Validity criteria conformity

Criteria	Validity for OECD 301F	Validity for the test
Variation between the test item replicates at 28 days	< 20%	Yes (2.47%)
Biodegradability of the toxicity control within 14 days	> 25%	Yes(85.50% and 86.81%)
Oxygen uptake of the inoculum control in 28 days	< 60 mg/L	Yes(2.8 to 7.0 mg/L)
Biodegradability of the reference item within 14 days	> 60%	Yes(84.30 to 96.97%)
pH of the inoculum control at 28 days	6 to 8.5	Yes(7.3)

SD: Standard deviation

 

All the validity criteria were successful.

Deviation:

Two deviations to the study plan 17/1353F/a was observed in this Study:

 1/ A solution 1g test item /L was prepared at the start of the test, this solution was cloudy,so the test item was weighed directly in the flasks replicates “test item” and “toxicity control” in order to obtain 100 mg test item /L in mineral medium as compliant with OECD 301F.

 2/At the end of the test, an unexpected value (pH=8.8) was recorded for the pH of one of the test item replicates (no.24).

This is out of the acceptability range for pH. Therefore, the pressure measurements measured in this replicate were not taken into consideration for the caculation of the biodegradability, although they were similar to those from the other “test item” replicates.

According to OECD 301F, the monitoring of two replicates for the test item must be done. The data corresponding to the flasks 23 and 18 were used for the calculation.

 

These two deviations has no incidence on study results.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Under conditions of OECD Guideline 301F, the test item “SOCOGEL PART I P14133SS0416”, is readily biodegradable.

Executive summary:

The aim of this study was to determine the biodegradability of the test item “SOCOGEL PART I P14133”, according to the OECD 301F guideline, ready biodegradability 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 is expressed as percentage of the theoretical Oxygen Demand (ThOD).

Based on ThOD_NH4, the degradation rate ofthe test item “SOCOGEL PART I P14133” reached 60% within the 10-Day window on Day 4 (66.63%) and after 28 days of incubation the biodegradation was 88.63% (87.08% to 90.18%).

The results obtained show that the test itemis readily biodegradable based on the ThOD_NH4,after 28 days of incubation.

Under conditions of OECD Guideline 301F, the test item “SOCOGEL PART I P14133SS0416”, is readily biodegradable.

Description of key information

Under conditions of OECD Guideline 301F, the resgistered substance , is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

The aim of this study was to determine the biodegradability of the test item “SOCOGEL PART I P14133”, according to the OECD 301F guideline, ready biodegradability 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 is expressed as percentage of the theoretical Oxygen Demand (ThOD).

Based on ThOD_NH4, the degradation rate ofthe test item “SOCOGEL PART I P14133” reached 60% within the 10-Day window on Day 4 (66.63%) and after 28 days of incubation the biodegradation was 88.63% (87.08% to 90.18%).

The results obtained show that the test itemis readily biodegradable based on the ThOD_NH4,after 28 days of incubation.

Under conditions of OECD Guideline 301F, the test item “SOCOGEL PART I P14133SS0416”, is readily biodegradable.