Bos taurus, milk, pasteurized, homogenized, skimmed, fermented, spray-dried

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:

21 December 2017 - 18 January 2018

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)

Version / remarks:

2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Version / remarks:

Regulation (EC) No 440/2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Total carbon content (TOC) and chemical oxygen demand (COD) were determined by an external laboratory following DIN guideline under the quality system management ISO/IEC 17025 and are therefore excluded from the statement of GLP compliance.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source: Sludge from the aeration tank of the ARA Werdhölzli (CH-8048 Zürich), a municipal biological waste water treatment plant.
- Preparation of inoculum for exposure: The sludge was pre-conditioned for 7 days (aerated but not fed) to reduce the amount of O2 consumed by the blank controls. Therefore, the sludge was washed twice with tap water and once with test medium.
- Pretreatment: The activated sludge was used after sampling from the treatment plant without adaptation.
- Concentration of sludge: 30 mg/L dry matter in the final mixture.

Duration of test (contact time):

28 d

Initial conc.:

86.3 mg/L

Based on:

other: nominal test item concentration based on 100 mg COD/L

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of test medium: Aerobic mineral salts medium prepared with ultrapure water (conductivity: <1.5 µS/cm; DOC: <0.5 mg/L)
* mineral stock solution A (10mL/L): 8.5 g/L KH2PO4, 28.49 g/L K2HPO4.3H2O, 33.4 g/L Na2HPO4.2H2O, 0.5 g/L NH4Cl, pH 7.4
* mineral stock solution B (1 mL/L): 36.4 g/L CaCl2.2H2O
* mineral stock solution C (1 mL/L): 22.5 g/L MgSO4.7H2O
* mineral stock solution D (1 mL/L): 0.25 g/L FeCl3.6H2O
* Final test medium: 10 mL of solution A and 1 mL of solutions B, C and D per L of test medium

- Test temperature: 22±2°C, controlled at ± 1°C, in a thermostat cabinet
- pH: 7.4±0.2°C (measured prior to testing and if necessary adjusted with NaOH or HCl (except in flask C).
- Continuous darkness: yes, test bottles were in a thermostat cabinet.

TEST SYSTEM
- Test flasks: 510 mL glass bottles (tightly closed with manometric BOD measuring devices) containing a total volume of test solution of 200 mL. The bottles were equipped with stirring rods and butylrubber quivers which contain 2 pellets of sodium hydroxide each to absorb the produced CO2 from the head space.
- Test performed in duplicate (two test flasks)

After centrifugation, the sludge was suspended in test medium, at 2.5 g/L dry matter. Before the test, this suspension was diluted down to 60 mg/L dry matter, i.e. twice the final concentration, since this suspension was diluted 1:1 (v:v) afterwards. The test item was applied by direct addition into the test vessels to give a final test concentration as COD of about 100 mg O2/L.

CONTROL AND BLANK SYSTEM
B: Inoculum blank (two replicates)
R: Procedure control (two replicates): 60.0 mg/L Sodium benzoate (99.9 mg ThOD/L)
C: Abiotic sterile control (one replicate): 86.0 mg/L test item (99.8 mg COD/L)
X: Toxicity control (one replicate): 86.5 mg/L test item and 60.0 mg/L reference item (total 200 mg oxygen demand/L)

SAMPLING
The test vessels were stirred by an inductive stirring system for a maximum test period of 28 days. During the test the O2 uptake was continuously measured with a manometric BOD measuring device. Temperature was recorded with a data logger.
At the end of the test, the pH was measured in all flasks, and the DOC content was determined in the flasks of the test suspension, inoculum blank and procedure control.

STATISTICAL METHODS:
Values of % degradation were calculated for each test flask and day. The arithmetic mean of % degradation in each test flask on each day was calculated.

Reference substance:

other: Sodium benzoate

Remarks:

CAS 532-32-1

Key result

Parameter:

% degradation (O2 consumption)

Value:

> 100

Sampling time:

28 d

Remarks on result:

other: test flask 1 after 28 d: 104.9% test flask 2 after 28 d: 110.2%

Details on results:

The biodegradability of Yoghurt powder based on O2 consumption (mineralisation) was calculated to be >100% after 28 days as compared to the chemical oxygen demand (COD). The biodegradation reached 97% at the end of the 10-d window (i.e. within 10 days after attainment of 10% degradation). Biodegradation of the test item started without any significant lag-phase.
The respective concentrations of organic carbon at the beginning (theoretical value, as mg TOC/L) and at the end of the test (mean measured value of the two replicates, as mg DOC/L) were respectively:
- 32.8* and 1.54 for the test units (mean of two replicates)
- <0.5 and 1.17 for the blank control (mean of two replicates)
- 35.0 and 1.08 for the procedure control (mean of two replicates)
* Theoretical value calculated based on the carbon content and the test concentration.

The total elimination calculated based on the determination of the dissolved organic carbon (DOC) at the end of the test reached 99% for Yoghurt powder and 100% for sodium benzoate, respectively. This data is in line with the degradation calculated based on O2 consumption.
Yoghurt powder (EC no. 917-734-0) reached the pass level of 60% mineralisation in the Manometric Respirometry Test within the 10-d window and, therefore, can be termed as readily biodegradable.

Further remarks:
The biodegradation based on O2 consumption (mineralisation) was calculated to be >100% after 28 days as compared to the chemical oxygen demand (COD). The reason for the biodegradation being greater than 100% are not known however, one reason could be the COD being too low. But this was excluded since the COD measurement was repeated and the results were confirmed. Evidently, the biodegradation reached 97% at the end of the 10-d window, which is distinctly greater than 60%, and therefore, the test item can be termed as readily biodegradable.
The temperature was in the required range (22±2 °C, controlled at ±1 °C) during the whole incubation period (in °C: Maximum: 21.9; Minimum: 21.3; Mean: 21.5; Delta Mean - Max.: 0.4; Delta Mean - Min.: 0.2).

Procedure control:

The procedure control sodium benzoate reached a biodegradation of 81% (mineralisation) after 14 days, thus confirming suitability of inoculum and test conditions.

Toxicity control:

At the applied initial test concentration of 86.5 mg/L the test item was not judged to have any inhibitory effect on the microbial population, since the biodegradation of the mixture (test item + reference item sodium benzoate) exceeded 25% within 14 days.

Abiotic steril control:

Yoghurt powder was not abiotically degraded (by processes using O2) during the whole test period of 28 days in the absence of microorganisms as confirmed by the lack of oxygen consumption in the abiotic sterile control.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

A 28-d ready biodegradability test (OECD 301F, Manometric Respirometry Test) using activated sludge of a municipal sewage treatment plant indicated that Yoghurt powder (EC no.917-734 -0) reached a biodegradation of >100% based on O2 consumption. The substance reached the pass level of 60% for ready biodegradability in the Manometric Respirometry Test within the 10-d window and, therefore, can be termed as readily biodegradable. All validity criteria were fulfilled.

Executive summary:

The biodegradability of Yoghurt powder (EC no.917-734 -0) exposed to microorganisms derived from activated sludge of a municipal sewage treatment plant was investigated under aerobic static exposure conditions, following the test guideline OECD 301 F.
Both the mineralisation over the course of the test (based on O₂consumption) and the total elimination at the end of the test (based on the determination of the dissolved organic carbon, DOC) were assessed.

The biodegradability of Yoghurt powder based on O₂consumption (mineralisation) was calculated to be >100% after 28 days as compared to the chemical oxygen demand (COD).

The biodegradation reached 97% at the end of the 10-d window (i.e. within 10 days after attainment of 10% degradation).

Biodegradation of the test item started without any significant lag-phase.

The procedure control sodium benzoate reached a biodegradation of 81% (mineralisation) after 14 days, thus confirming suitability of inoculum and test conditions.

The total elimination calculated based on the determination of the dissolved organic carbon (DOC) at the end of the test reached 99% for Yoghurt powder and 100% for sodium benzoate, respectively. This data is in line with the degradation calculated based on O₂consumption.

Yoghurt powder (EC no.917-734-0) reached the pass level of 60% mineralisation in the Manometric Respirometry Test within the 10-d window and, therefore, can be termed as readily biodegradable.

All validity criteria were fulfilled.

Description of key information

The biodegradability of Yoghurt powder (EC no.917-734 -0) exposed to microorganisms derived from activated sludge of a municipal sewage treatment plant was investigated under aerobic static exposure conditions, following the test guideline OECD 301 F.

The biodegradability of Yoghurt powder based on O₂consumption (mineralisation) was calculated to be >100% after 28 days as compared to the chemical oxygen demand (COD).

The biodegradation reached 97% at the end of the 10-d window (i.e. within 10 days after attainment of 10% degradation).

The total elimination calculated based on the determination of the dissolved organic carbon (DOC) at the end of the test reached 99% for Yoghurt powder and 100% for sodium benzoate, respectively.

Yoghurt powder (EC no.917-734-0) reached the pass level of 60% mineralisation in the Manometric Respirometry Test within the 10-d window and, therefore, can be termed as readily biodegradable. All validity criteria were fulfilled.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater