[No public or meaningful name is available]

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:

29 June 2017 to 04 September 2017

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)

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Totnes Sewage Treatment Works, Totnes, Devon, UK
- Storage conditions: aerated at room temperature at pH 7.0 ± 1.0.
- Storage length: 1 day
- Preparation of inoculum for exposure: Seven days prior to the exposure start the activated sludge was centrifuged, washed and re suspended in the mineral medium and the solids concentration determined. This sludge was then diluted in medium, added to test bottles and stirred until required for use. The seeded mineral medium was pre-conditioned for seven days to reduce the blank oxygen uptake readings in the test.
- Concentration of sludge: SS 2806 mg/L

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Remarks:

calculated as BOD/COD

Details on study design:

TEST CONDITIONS
- Composition of medium: according to the guideline
- Additional substrate: none
- Solubilising agent (type and concentration if used): none
- Test temperature: 22 ± 1 °C
- pH: 7.4 ± 0.2 (actual 7.26)
- pH adjusted: no
- Sludge concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: dark glass 500 mL bottle placed in incubator
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: continuously stirred
- Measuring equipment: Oxitop respirometer
- Details of trap for CO2 and volatile organics if used: KOH

Examiniations
- Frequency: daily
- Method: measurement of decrease in pressure over 240 min period

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes (3 replicates)
- Abiotic sterile control: none
- Toxicity control: yes (3 replicates)

STATISTICAL METHODS: NA

Reference substance:

benzoic acid, sodium salt

Parameter:

other: % degradation BOD/COD

Value:

13

Sampling time:

3 d

Remarks on result:

other: start of degradation

Parameter:

other: % degradation BOD/COD

Value:

47

Sampling time:

13 d

Remarks on result:

other: end of 10 day window

Parameter:

other: % degradation BOD/COD

Value:

72

Sampling time:

28 d

Details on results:

The substance is UVCB, according to OECD and ECHA guidance documents, the 10-day window can be waived. Therefore, as > 60% biodegradation was achieved within 28 days the substance is readily biodegradable.
Initial pH 7.26, at 28 days 6.7 for substance
Initial pH 7.2, at 60 days 7.1-7.2 for inoculum blank (60 day due to perallel testing)

Day	Sodium benzoate Biodegradation(%)	Test substance Biodegradation (%)	Toxicity control Biodegradation (%)
1	3	1	3
2	39	7	22
3	47	13	26
4	55	19	30
5	59	23	33
6	61	26	35
7	63	31	38
8	65	34	39
9	66	37	41
10	66	39	42
11	66	42	44
12	67	44	45
13	67	47	47
14	68	49	47
15	68	51	49
16	68	53	50
17	69	56	51
18	70	57	52
19	70	59	52
20	70	61	54
21	69	62	54
22	69	63	55
23	70	65	56
24	70	66	57
25	70	68	57
26	70	69	58
27	71	71	59
28	70	72	59

Biodegradation (%) =       Biological Oxygen Demand (g O₂/g)× 100 / ThOD (1.67 g O₂/g) and/or COD (1.94 g O₂/g)

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

The substance is a UVCB and although not meeting the 10-day window is considered readily biodegradable (see OECD and ECHA guidance)

Executive summary:

Subject	Determination of Ready Biodegradability
Guideline	OECD 301F: Manometric respirometry
Test concentration	Control and 100 mg/L
Length of test	28 days
Nominal test temperature	22 ± 1°C
Mean degradation after 28 days	72%
Classification	Readily biodegradable
Reference substance	Sodium benzoate
Experimental values	Substance		Reference substance
	Day	Mean percentage biodegradation	Day	Mean percentage biodegradation
	5	23	5	59
	10	39	10	66
	15	51	15	68
	20	61	20	70
	28	72	28	70
Comments	The CODof the test substance was measured as1.94 g O2/g and the mean BOD value after 28 days was 1.40 g O2/g. The percentage degradation was calculated as (BOD/COD)´100
Conclusions	The substance attained a maximum mean level of biodegradation (based on the BOD:COD ratio) of 72% and the results showed good replication. The substance exhibited the potential for rapid degradation and can be classified as inherently biodegradable. As the substance is UVCB, according to OECD and ECHA guidance documents (references 3 and 4), the 10-day window can be waived. Therefore, as > 60% biodegradation was achieved within 28 days The substance is readily biodegradable.

Description of key information

In a study according to OECD 301F, the substance attained a maximum mean level of biodegradation (based on the BOD:COD ratio) of 72% over a 28 day period and the results showed good replication. As the substance is UVCB, according to OECD and ECHA guidance documents, the 10-day window can be waived. Therefore, as > 60% biodegradation was achieved within 28 days The substance is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater