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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:

10 Nov - 12 Dec 2017

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)

Version / remarks:

adopted 17 Jul. 1992

Deviations:

yes

Remarks:

See section "Any other information on material and methods incl tables"

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted 30 May 2008

Deviations:

yes

Remarks:

See section "Any other information on material and methods incl tables"

GLP compliance:

yes (incl. QA statement)

Remarks:

Landesamt für Umwelt Rheinland-Pfalz, Mainz, Germany

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, NW-Lachen-Speyerdorf. Date of collection: 14. Nov. 2017, batch no: 20171114
- Preparation of inoculum for exposure: The sludge was filtrated through a clean cotton cloth, then washed with medium 2x, and resuspended in test medium. It was then aerated until use in the test.
- Preparations: The inoculum was taken from its source, washed, aerated and the dry matter was determined
- Concentration of sludge: Determination of dry matter gave 4760 mg suspended solids/L.
- Initial cell/biomass concentration: 24.9 mg/L (Inoculum concentration)

Duration of test (contact time):

28 d

Initial conc.:

40 mg/L

Based on:

other: organic carbon of test item

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: medium was used which is recommended in the guideline
- Test temperature: 19.7 – 21.3 °C
- pH: 7.4
- pH adjusted: no
- Aeration of dilution water: yes
- Suspended solids concentration: 4760 mg suspended solids/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 500 mL-ERLENMEYER-flasks were used as test vessels, all glassware was cleaned with the laboratory cleaning agent and then rinsed with tap water (3x), diluted HCL (1x), tap water (3x) and diluted water (3x).
- Number of culture flasks/concentration: Control (2), Positive control (2), Test item (2), Abiotic control (1), Adsorption control (1), Toxicity control (1),
- Measuring equipment: DOC was determined as difference between TC (total carbon) and IC (inorganic carbon) using the carbon analyser TOC multi N/C 2100S, Analytik Jena. Each filtrated sample was measured in duplicate or triplicate, respectively (depending on the variation between the
measured values). The carbon analyser was calibrated with freshly prepared reference solutions (C8H5KO4 for TC, Na2CO3 and NaHCO3 for IC) once per month.

SAMPLING
- Sampling frequency: after 3 hours and on days 2, 7, 10, 14, 17, 22 and 28
- Sampling method: From each replicate, 8 samples were taken in order to determine the DOC. The sample volume was 2 mL. The samples were filtrated (0.45 μm Nylon filters).

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2
- Abiotic sterile control: 1
- Adsorption control: 1
- Toxicity control: 1
- Positive control: 1

Reference substance:

aniline

Remarks:

Phenylamine, C6H5NH2, CAS-No. 62-53-3

Parameter:

% degradation (DOC removal)

Value:

96.7

Sampling time:

28 d

Results for the Test item

- The pass level was reached at day 14 with  88.4 %

- The degree of biodegradation reached 97 % after 28 days.

- The test item can be considered as „readily biodegradable"

Table 1: DOC Values in mg/L

Day	Control 1	Control 2	Positive Control 1	Positive Control 2	Test 1	Test 2	Abiotic Control	Adsorption Control	Toxicity Control
0.125	1.72	1.10	41.74	43.78	40.80	40.19	39.36	39.78	79.58
2	1.23	1.37	41.40	41.87	23.44	24.84	41.13	40.43	65.18
7	0.71	0.65	1.51	1.69	17.08	17.20	41.75	41.19	16.86
10	0.00	0.00	0.89	1.02	14.78	13.90	42.72	44.43	9.37
14	0.00	0.00	0.63	0.60	1.80	7.21	41.17	42.40	5.69
17	0.05	0.00	0.21	0.54	1.38	2.10	41.01	44.02	1.98
22	0.16	0.00	0.19	0.28	0.82	1.15	42.90	44.03	1.16
28	0.00	0.05	0.60	0.56	1.34	1.29	45.14	46.87	1.39

 

Table 2: Degradation values in %

Day	Positive Control 1	Positive Control 2	Positive Control Mean	Test 1	Test 2	Test Mean	Abiotic Control	Adsorption Control	Toxicity Control
2	0.6	4.2	2.4	43.8	39.3	41.6	-4.5	-2.0	18.3
7	97.9	97.6	97.8	58.4	57.4	57.9	-6.1	-5.6	79.3
10	97.8	97.6	97.7	62.5	64.2	63.4	-8.5	-15.8	88.0
14	98.4	98.6	98.5	95.4	81.4	88.4	-4.6	-10.5	92.7
17	99.5	98.8	99.2	96.6	94.6	95.6	-4.2	-14.7	97.5
22	99.7	99.5	99.6	98.1	97.2	97.7	-9.0	-14.5	98.6
28	98.6	98.7	98.7	96.7	96.7	96.7	-14.7	-22.1	98.3

Table 3: Validity criteria for OECD 301.

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	0%	Yes
Percentage degradation of the reference compound reached the pass level by day 14 (≥ 60%).	pass level of 70 % on day 5	Yes
The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.	93 %	Yes

 

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Interpretation of results:

readily biodegradable

Conclusions:

The pass level was reached at day 14 with  88.4 %. Therefore, test item Reaction mass of potassium sodium phosphotartrate and potassium sodium tartrate and potassium sodium orthophosphate (aqueous solution) is readily biodegradable following OECD 301A and EU C.4-A respectively.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater