Bis(pentane-2,4-dionato-O,O')zinc

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Bis(pentane-2,4-dionato-O,O')zinc

EC Number:

237-860-3

EC Name:

Bis(pentane-2,4-dionato-O,O')zinc

Cas Number:

14024-63-6

Molecular formula:

C10H14O4Zn

IUPAC Name:

zinc bis(4-oxopent-2-en-2-olate)

Test material form:

solid: particulate/powder

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, adapted

Details on inoculum:

Activated sludge (27-01-2012) was obtained from the wastewater treatment plant Nieuwgraaf in Duiven, The Netherlands. This activated sludge plant treats predominantly domestic wastewater. The activated sludge was preconditioned to reduce the endogenous respiration rates. To this end, 400 mg Dry Weight (DW)/L of activated sludge was aerated for one week. The sludge was diluted in the BOD bottles (van Ginkel and Stroo, 1992).

Duration of test (contact time):

28 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

2 mg/L

Based on:

test mat.

Initial test substance concentration 2

Initial conc.:

6.7 mg/L

Based on:

test mat.

Details on study design:

Use was made of 10 bottles containing only inoculum, 10 bottles containing inoculum and test substance, and 6 bottles containing sodium acetate and inoculum. The concentrations of the test substance and sodium acetate in the bottles were 2.0 and 6.7 mg/L, respectively. Each of the prepared solutions was dispensed into the respective group of BOD bottles so that all bottles were completely filled without air bubbles. The zero time bottles were immediately analyzed for dissolved oxygen using an oxygen electrode. The remaining bottles were closed and incubated in the dark. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21, and 28.
The pH of the media was 7.1 at the start of the test. The pH of the medium at day 28 was 7.1 (control and test). Temperatures were within the prescribed temperature range of 22 to 24°C.

Reference substance

Reference substance:

acetic acid, sodium salt

Results and discussion

% Degradation

% Degradation 1

Key result

Parameter:

% degradation (O2 consumption)

Value:

64

Sampling time:

7 d

% Degradation 2

Key result

Parameter:

% degradation (O2 consumption)

Value:

82

Sampling time:

14 d

% Degradation 3

Key result

Parameter:

% degradation (O2 consumption)

Value:

82

Sampling time:

21 d

% Degradation 4

Key result

Parameter:

% degradation (O2 consumption)

Value:

82

Sampling time:

28 d

Details on results:

Inhibition of the degradation of a well-degradable compound, e.g. sodium acetate by the test substance in the Closed Bottle test was not determined because possible toxicity of bis(pentane-2,4-dionato) zinc to microorganisms degrading acetate is not relevant. Inhibition of the endogenous respiration of the inoculum by the test substance was not detected. Therefore, no inhibition of the biodegradation due to the "high" initial concentration of the test substance is expected.

BOD5 / COD results

Results with reference substance:

The calculated theoretical oxygen demand (ThOD) of bis(pentane-2,4-dionato) zinc is 1.4 mg/mg. The ThOD of sodium acetate is 0.8 mg/mg.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Bis(pentane-2,4-dionato) zinc is biodegraded by 82% at day 28 in the Closed Bottle test. Over 60% biodegradation was achieved in a period of 6 days immediately following the attainment of 10% biodegradation. The window criterion was therefore met. Bis(pentane-2,4-dionato) zinc should therefore be classified as readily biodegradable.