SDBR

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:

26 May to 23 June 1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)

Version / remarks:

1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Storage conditions: room temperature

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

A sample of activated sludge was taken from an oxidation ditch situated in the municipality of Berkel and Roodenrijs, The Netherlands. The oxidation ditch was used to treat domestic waste water. The activated sludge was transported in a plastic bottle and aerated until use.

The sludge was used at the same day it was collected.
Settling time of the sludge: 30 minutes
Used supernatant for inoculation: 30.8 mL/ L
Total volume inoculated mineral medium: 26 L

The mineral medium was prepared from concentrated stock solutions in ultrapure water and was aerated vigorously before use.

Duration of test (contact time):

28 d

Initial conc.:

1.2 mg/L

Based on:

test mat.

Remarks:

corresponds to a ThOD of 2.5 mg O2/L

Initial conc.:

2.4 mg/L

Based on:

test mat.

Remarks:

corresponds to a ThOD of 5.0 mg O2/L

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Test temperature: 19.1 - 20.0
- pH: 6.9 - 7.4
- pH adjusted: no
- Aeration of dilution water: yes

The following test series were included:
- Test substance
Concentrations: 0, 1.20 and 2.40 mg/L
Number of replicate bottles/ time-point: 4
Oxygen concentration determined after: 0, 7, 14, 21, 28 and 56 days

- Microbial activity control
Concentration of the reference substance: 4.0 mg/L
Number of replicate bottles/ time-point: 4
Oxygen concentration determined after: 0, 7 and 14 days

- Toxicity control
Concentration of reference substance: 4.0 mg/L
Concentration of test substance: 2.40 mg/L
Number of replicate bottles/ time-point: 4
Oxygen concentration determined after: 0, 7 and 14 days

The oxygen depletion in each test bottle after 7, 14, 21 and 28 days was calculated by subtracting each measured oxygen concentration from the mean oxygen concentration measured at the start of the test. The oxygen depletion due to the test or control substance at each time was calculated (in mg O2/L) by subtracting the oxygen concentration in the relevant inoculum control or other control bottle from that in the bottle under consideration. These values were then converted to values per mg substance (BOD). The percentage biodegradation of the test substance was calculated as BOD/ThODNH3 x 100.

Reference substance:

acetic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Remarks:

2.4 mg/L

Value:

4

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Remarks:

1.2 mg/L

Value:

5

Sampling time:

7 d

Details on results:

The mean biochemical oxygen demand (BOD) values and the percentage biodegradation calculated from the ThOD of SDBR are given in tabular from below.
The maximum (mean) biodegradability (corrected for the inoculum control) of 5% was reached with 1.20 mg/L after 7 days and 4% with 2.40 mg/L after 14 days. Due to the small difference between the control and the treatment at these low biodegradation values, a considerable variation was observed between individual bottles.

Results with reference substance:

Degradation (reference substance): 79 % degradation after 7 d and 77 % degradation after 14 d.

The validity criteria were met as follows:
1. The replicate degradation at 1.20 mg/L varied between 2% and 6% degradation after 28 days, and at 2.40 mg/L between 1% and 7% degradation after 28 days. At both concentrations the extreme replicate values differ by less than 20%.
2. The reference substance was degraded for 79% (ThODNH3) within 14 days.
3. No inhibition was observed in the toxicity control with the high test substance concentration.
4. With 2.99 mg O2/L, the inoculum control oxygen consumption was higher than the validity limit after 28 days. However the inoculum activity is not considered to have influenced the result of the test.
5. The residual oxygen concentration in the test bottles was >>0.5 mg O2/L at any time.

SDBR at 1.20 mg/L

Time (days)	BOD (mg O2/mg)	% biodegradation ThODNH3
7	0.1	5
14	0.07	4
21	0.05	2
28	0.01	0

 

SDBR at 2.40 mg/L

Time (days)	BOD (mg O2/mg)	% biodegradation ThODNH3
7	-0.04	-2
14	0.08	4
21	0.04	2
28	0.03	2

 

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

In a reliable biodegradation study, performed according to OECD/EC guidelines and GLP, SDBR was considered not to have exceeded the pass level of 60% ThOD removal within 28 days, classifying it as not readily degradable.

Description of key information

Based on the results of a reliable biodegradation study, performed according to OECD/EC guidelines and GLP, SDBR was considered to be not readily degradable.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater