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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:

January 2021 to October 2021

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

The maximum deviation in temperature of vessels should be 1 oC. One of the vessels containing only water was recorded at 22.5 oC. As the test was conducted at 21 oC the maximum deviation was exceeded. This should not effect the overall result.

GLP compliance:

yes

Specific details on test material used for the study:

Test material is a solid (deliquescent) and has a purity of approximately 94.5%. The test material has an expiry date of 3rd December 2021 and should be stored at room temperature in the dark under nitrogen.

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic (adaptation not specified)

Details on inoculum:

The sample of effluent was filtered through course filter paper (first approximate 200 mL discarded) and maintained on aeration in a temperature controlled room at measured temperatures of approximately 21 oC prior to use.

Duration of test (contact time):

60 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS

The mineral medium used in the study is the one recommended by OECD guidelines. Solution A contained KH2PO4 (8.50 g/L), K2HPO4 (21.75 g/L), Na2HPO4.2H2O (33.40 g/L) and NH4Cl (0.5 g/L) with a final pH of 7.4. Solution B contained CaCl2.2H2O (36/40 g/L). Solution C contained MgSO4.7H2O (2.50 g/L) and solution D contained FeCL3.6H2O (0.25 g/L). The mineral media was then prepared by adding solution A (10 mL), solution B (1 mL), solution C (1 mL) and solution D (1 mL) to purified water to generate a 1 L solution. The pH of the mineral media was measured to be pH 7.7 and and adjusted to pH 7.5 using diluted hydrochloric acid.

Prior to the start of the test, the purified water was aerated for approximately 20 hours at the test temperature to give a dissolved oxygen concentration of approximately 8.9 O2/L.

TEST SYSTEM


The following test preparations were prepared and inoculated in 500 mL glass bottles:

a) Three replicate bottles containing inoculated mineral medium to act as the inoculate control.
b) Two replicate bottles containing inoculated mineral medium and the reference item, aniline, at a concentration of 100 mg/L to act as a procedural control.
c) Three replicate bottles containing the test item and inoculated mineral medium at 100 mg/L
d) Two replicate bottles containing the test item at a concentration of 100 mg/L in inoculated mineral medium and the reference item aniline, at a concentration of 100 mg/L to act as a toxicity control.

All vessels were inoculated wit the prepared inoculum at a rate of 1% v/v.

On day 0, the test and reference items were added to the mineral medium and the pH measured. All vessels were placed in a CES Multi-Channel Aerobic Respirometer. The system consists of a sample flask sealed by a sensor head/CO2 trap immersed in a temperature cold water bath. The samples were stirred for the duration of the test with a magnetically coupled stirrer.

The test was conducted in diffuse light at temperatures between 21 and 23 oC.

Reference substance:

aniline

Parameter:

% degradation (O2 consumption)

Value:

62

Sampling time:

60 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

47

Sampling time:

28 d

Details on results:

The test item obtained 47% biodegradation after 28 days and 62% biodegradation after 60 days. Despite attaining excess of 60% biodegradation the test item failed to satisfy the 10-day window validation criterion, whereby 60% biodegradation must be attained within the 10 days of biodegradation exceeding 10% by 28 days, and therefore cannot be considered readily biodegradable.

Results with reference substance:

Aniline attained 74% biodegradation after 14 days with greater than 60% degradation being obtained in a 10-day window. After 28 and 60 days 80% and 106% biodegradation was obtained.

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

The test item obtained 47% biodegradation after 28 days and 62% biodegradation after 60 days. Despite attaining excess of 60% biodegradation the test item failed to satisfy the 10-day window validation criterion, whereby 60% biodegradation must be attained within the 10 days of biodegradation exceeding 10% by 28 days, and therefore cannot be considered readily biodegradable. However, the test item has exhibited the potential for rapid biodegradation.

Executive summary:

The ready biodegradability of the test substance was determined during a GLP compliant study performed in accordance with OECD Test Guideline 301F.

Aniline was used as a reference substance and the activated sludge was taken from a domestic sewege treatment plate.  All validation criteria were met.

The test item obtained 47% biodegradation after 28 days and 62% biodegradation after 60 days. Despite attaining excess of 60% biodegradation the test item failed to satisfy the 10-day window validation criterion, whereby 60% biodegradation must be attained within the 10 days of biodegradation exceeding 10% by 28 days, and therefore cannot be considered readily biodegradable. However, the test item has exhibited the potential for rapid biodegradation.

Description of key information

The ready biodegradability of the test substance was determined during a GLP compliant study performed in accordance with OECD Test Guideline 301F.

Aniline was used as a reference substance and the activated sludge was taken from a domestic sewege treatment plate.  All validation criteria were met.

The test item obtained 47% biodegradation after 28 days and 62% biodegradation after 60 days. Despite attaining excess of 60% biodegradation the test item failed to satisfy the 10-day window validation criterion, whereby 60% biodegradation must be attained within the 10 days of biodegradation exceeding 10% by 28 days, and therefore cannot be considered readily biodegradable. However, the test item has exhibited the potential for rapid biodegradation.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater