Salicylonitrile

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:

03 May - 01 June 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): - Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Sourced from predominatly domestic wastewater treatment plant (ARA Ergolz II, Fullinsdorf / Switzerland)
- Storage conditions: Room temperature. Aeration.
- Storage length: 1 day
- Preparation of inoculum for exposure: Washed twice with tap water by centrifugation, supernatant liquid phase decanted.
- Concentration of sludge: 30 mg dry material per litre.

Duration of test (contact time):

28 d

Initial conc.:

41.8 - 42.3 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: Purified water with dissolved analytical grade salts
- Test temperature: 22 - 24 °C
- pH: start: 7.3-7.4, end: 7.3 - 7.8
- pH adjusted: yes
- Aeration of dilution water: Test media was constantly stirred, flasks were prepared as to allow for exchange of air between flasks and surrounding atmosphere.
- Suspended solids concentration: 30 mg dry material per litre.
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 2000 mL Erlenmeyer flasks, 1000 mL test medium per flask. Flasks loosely covered with aluminium foil.
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: Test media was constantly stirred, flasks were prepared as to allow for exchange of air between flasks and surrounding atmosphere.
- Measuring equipment: Samples analysed for DOC by means of a TOC-analyser with automatic sampler [combustion/non-dispersive IR gas analysis method]
- At each sampling point water evapouration losses were determined and compensated for and deposits on the test vessels resuspended

SAMPLING
- Sampling frequency: Test item and inncoulum control: 0, 3 , 7, 10 , 14, 16, 21 and 28 days. Procedure control: 0, 3, 7, 14 amd 28 days. Toxicity control: 0, 7, 14 and 28 days.
- Sampling method: 10 mL samples taken. Samples filtered through 0.45 µm filter (first 3-4 mL of filtrate discarded)

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes.
- Abiotic sterile control: No
- Toxicity control: Yes (test substance 42mg/L, plus reference (sodium benzoate) 50mg/L)
- Procedure control: Yes (reference item)

Degradation was calculated by comparing DOC removal in the test flasks to that in the inoculum controls.

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (DOC removal)

Value:

0

Sampling time:

10 d

Parameter:

% degradation (DOC removal)

Value:

99

Sampling time:

28 d

Details on results:

Results are given as the average of the degradation in the two replicates.

Results with reference substance:

100% degradation of the reference item within 7 days was observed in the procedure control

Table 1. Percentage degradation in the Test Flasks

Time (days)	Percentage biodegradation (corrected for the innoculum controls)
	Test Item			Procedure Control			Toxicity Control
	Replicate No.			Replicate No.			Replicate No.
	1	2	mean	1	2	mean	1
0	0	0	0	0	0	0	0
3	-2	-3	-2	99	98	98	n.d.
7	-1	-2	-1	100	99	100	50
10	1	-1	0	n.d.	n.d.	n.d.	n.d.
14	53	8	31	99	100	99	51
16	99	61	80	n.d.	n.d.	n.d.	n.d.
21	99	99	99	n.d.	n.d.	n.d.	n.d.
28	99	99	99	98	100	99	100

n.d. = not determined

Validity criteria fulfilled:

yes

Remarks:

The suitability of the activated sludge was confirmed as the reference substance degraded by 100% within 7 days.

Interpretation of results:

readily biodegradable

Conclusions:

The substance is readily biodegradable.

Executive summary:

In a GLP compliant, OECD guideline test, the substance degraded sufficiently that it can be considered readily biodegradable. The 10 -day window was met with degradation going from 0 to 80% between days 10 and 16. The results from the toxicity control show that the substance is not inhibitory to activated sludge.

Description of key information

Readily biodegradable, OECD 301A, Eisner 2010

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

The study by Urushigawa(1984) did not quantify degradation and was discarded. In a GLP compliant, OECD guideline test the substance degraded sufficiently that it can be considered readily biodegradable (Eisner, 2010). The 10-day window was met with degradation going from 0 to 80% between days 10 and 16. The results from the toxicity control showed that the substance is not inhibitory to activated sludge. The study was considered to be reliable and suitable for use in classification, labelling and risk assessment.