Plum, ext.

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:

11 January 2018 - 15 February 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

17 July 1992

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: ISO International Standard 10634. "Water Quality - Guidance for the preparation and treatment of poorly water-soluble organic compounds for the subsequent evaluation of their biodegradability in an aqueous medium"

Version / remarks:

1995

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Plum, ext.

EC Number:

290-179-3

EC Name:

Plum, ext.

Cas Number:

90082-87-4

Molecular formula:

not applicable

IUPAC Name:

Extract obtained from fruits of Prunus domestica L. Rosaceae

Test material form:

liquid

Details on test material:

- Physical appearance: Blackish brown to dark brown liquid
- Storage conditions: At room temperature

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Municipal sewage treatment plant 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
- Storage conditions: Freshly obtained sludge was kept under continuous aeration until further treatment.
- Concentration of suspended solids: 3.0 g/L in the concentrated sludge.
- Preparation of inoculum for exposure: The sludge was coarsely sieved (1 mm) and washed with mineral medium.
- Pretreatment: The day before the start of the test (day -1) mineral components, Milli-RO water (ca. 80% of final volume) and inoculum (1% of final volume) were added to each bottle. This mixture was aerated with synthetic air overnight to purge the system of CO2.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

12 mg/L

Based on:

TOC

Initial test substance concentration 2

Initial conc.:

38 mg/L

Based on:

test mat.

Initial test substance concentration 3

Initial conc.:

1.17 other: mg CO2/mg

Based on:

ThCO2

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONCENTRATIONS:
- Test solutions: bottle A: 38.26 mg test item per litre; bottle B: 37.83 mg test item per litre

CONTROLS:
- Inoculum blank: containing only inoculum (2 bottles)
- Positive control: containing reference item and inoculum (1 bottle).
- Toxicity control: containing test item, reference item and inoculum (1 bottle).

PREPARATION OF TEST SOLUTIONS:
The test item was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 1 g/L. TOC content of the test item was determined by TOC analysis to be 31.78%. On the day of testing weighed amounts of the test item were added to the 2-litres test bottles containing medium with microbial organisms and mineral components small watch glasses were used to add weighed amounts to the 2-litres test bottles containing medium with microbial organisms and mineral components. 10 mL of Milli- RO water was added to each bottle and after vigorous mixing (vortex) the resulting suspension was added to the test medium. The test solutions were continuously stirred during the test, to ensure optimal contact between the test item and the test organisms.

TEST CONDITIONS
- Composition of medium: According to OECD 301B
- Test temperature: 22-23 °C
- pH: at start: 7.6; t=14d: 7.7 (positive and toxicity control); t=28d: 7.5-7.6 (blank controls and test solutions)
- pH adjusted: yes, the pH was adjusted using 1 M HCl to 7.6 in all test vessels, except for the toxicity control which was adjusted to 7.5.
- Suspended solids concentration: 15 mg/L
- Test media were excluded from light and the test vessels were brown coloured glass bottles.
- Test media were aerated and stirred continuously.

TEST SYSTEM
- Number of culture flasks/concentration: 2 for test suspension, 2 for inoculum blank, 1 for positive control, 1 for toxicity control.
- Method used to create aerobic conditions: synthetic air (CO2 < 1 ppm) sparged through scrubbing solutions at a rate of approximately 1-2 bubbles per second (ca. 30-100 mL/min).
- Details of trap for CO2 and volatile organics: Three CO2-absorbers (bottles filled with 100 mL 0.0125 M Ba(OH)2) were connected in series to the exit air line of each test bottle. Each time the CO2-absorber nearest to the test bottle was removed for titration; each of the remaining two absorbers was moved one position in the direction of the test bottle. A new CO2-absorber was placed at the far end of the series.
- Phenolphthalein (1% solution in ethanol, Merck) was used as pH-indicator.

SAMPLING
- Sampling frequency: Titrations were made on day 2, 5, 8, 12, 15, 19, 23 and 29. Titrations for the positive and toxicity control were made over a period of at least 14 days.
- Sampling method: Titration of Ba(OH)2 in the gas scrubbing bottles.

Reference substance

Reference substance:

acetic acid, sodium salt

Remarks:

Purity: 99.5%; ThCO2: 1.07 mg CO2/mg

Results and discussion

% Degradation

% Degradation 1

Key result

Parameter:

% degradation (CO2 evolution)

Value:

85

Sampling time:

28 d

Remarks on result:

other: Bottle A

% Degradation 2

Key result

Parameter:

% degradation (CO2 evolution)

Value:

79

Sampling time:

28 d

Remarks on result:

other: Bottle B

Details on results:

- The ThCO2 of Plum concentrate was calculated to be 1.17 mg CO2/mg.
- Biodegradation: The relative biodegradation revealed 85% and 79% biodegradation of the test item (based on ThCO2), for the duplicate bottles tested. The criterion for ready biodegradability (at least 60% biodegradation within a 10-day window) was met.
- Toxicity control: More than 25% biodegradation occurred within 14 days (77%, based on ThCO2). Therefore, the test item was assumed not to inhibit microbial activity.
- Functioning of the test system was checked by testing the reference item sodium acetate, which showed a normal biodegradation curve.

BOD5 / COD results

Results with reference substance:

The positive control, sodium acetate, showed a normal biodegradation curve and reached 90% biodegradation after 14 days, which passes the validity criterium of at least 60% biodegradation within 14 days.

Any other information on results incl. tables

Acceptability of the test

1. The positive control item was biodegraded by at least 60% (90%) within 14 days.

2. The difference of duplicate values for %-degradation of the test item was always less than 20% (≤ 9%).

3. The total CO2 release in the blank at the end of the test did not exceed 40 mg/L (61.5 mg CO2 per 2 litres of medium, corresponding to 30.8 mg CO2/L).

4. The Inorganic Carbon content (IC) of the test item (suspension) in the mineral medium at the beginning of the test was less than 5% of the Total Carbon content (TC). Since the test medium was prepared in tap-water purified by reverse osmosis, IC was less than 5% of TC (mainly coming from the test item, 12 mg TOC/L).

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

See 'overall remarks'

Interpretation of results:

readily biodegradable

Conclusions:

In a biodegradability test (Modified Sturm Test), performed according to OECD 301B and GLP principles, Plum concentrate was readily biodegradable (85% and 79% biodegradation in duplicate bottles tested).