NO. 701 BASE

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

6 May 1998 - 4 June 1998

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study has been performed according to OECD and EC guidelines and in compliance with GLP principles.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

yes

Remarks:

1. total CO2 evolution in control vessels exceeds 40 mg/l medium (although below max allowed 70 mgl medium) 2. validity criterium IC/TC ratio < 5% not evaluated

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

yes

Remarks:

see deviations OECD 301B

Test guideline 3

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Details on test material:

Description: yellow/green powder
Batch number: 6090

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

A mixed population of activated sewage sludge micro-organisms sampled from Severn Trent Water Plc sewage treatment plant at Belper, Derbyshire, UK (treats predominantely domestic sewage). Three times washed by settlement and resuspension in culture medium and maintained under continuous aeration.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

16.1 mg/L

Based on:

test mat.

Initial test substance concentration 2

Initial conc.:

10 other: mg C/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of culture medium: according to OECD 301
- Additional substrate: No
- Solubilising agent (type and concentration if used): None used
- Test temperature: 21 +/- 1°C
- pH: not reported
- pH adjusted: Not reported
- Aeration of dilution water: Yes
- Suspended solids concentration: 30 mg/L
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: 5L vessels (3L medium)
- Number of culture flasks/concentration: 2/10 mg C/l
- Method used to create aerobic conditions: continuous magnetic stirring, continuous aeration with CO2 free air at a rate of approx 40 ml/minute
- Measuring equipment: TOC analyser
- Details of trap for CO2 and volatile organics if used: 2 traps (500 ml Dreschel bottles), 0.05 M NaOH

SAMPLING
- Sampling frequency:
CO2 traps: 0, 1, 2, 3 (not analysed), 5, 7, 9, 11 (not analysed), 13, 15, 17 (not analysed), 20, 22, 27, 28 and 29 days;
- Sample storage before analysis: None

CONTROL AND BLANK SYSTEM
- Inoculum blank (control): Yes, duplicate
- Reference (sodium benzoate): Yes, duplicate, 10 mg C/l
- Abiotic sterile control: No
- Toxicity control: Yes, single

STATISTICAL METHODS: not reported

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

Preliminary study:

not performed

Test performance:

CO2 evolution in control vessel was 55 mg/L after 28 days. This satisfies the OECD 301B validity criterion.
IC/TC ratio: see 'overall remarks'
Difference between replicates was <20%. This satisfies the OECD 301B validity criterion.

% Degradation

Parameter:

% degradation (CO2 evolution)

Value:

17

Sampling time:

28 d

Details on results:

The total CO2 evolution in the control vessels on day 28 was 55 mg/l (= 201 mg/ 3 l). Although the CO2 evolution was in excess of 40 mg/l at the end of the test, this was considered not to affect the integrity of the study as the upper level of 70 mg/l given in the OECD guideline was not exceeded.

toxicity control: >25% after 14 days, 54% after 28 days
standard material: degradation > 60% by day 14 (80% after 15 days)
IC/TC ratio: not reported
pH of the test solutions: not reported

BOD5 / COD results

Results with reference substance:

Based on CO2 evolution:
Day 0: 0%
Day 1: 8%
Day 2: 32%
Day 3: 55%
Day 5: 64%
Day 7: 75%
Day 9: 75%
Day 13: 77%
Day 15: 80%
Day 20: 90%
Day 22: 92%
Day 27: 96%
Day 28: 92%
Day 29: 89%

Any other information on results incl. tables

Theoretical carbon content of the test material was calculated to be 61.99%.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

other: not readily biodegradable

Conclusions:

Under the conditions of the CO2 evolution test was the test material shown to be not readily biodegradable (17% degradation after 28 days).

Executive summary:

The ready biodegradability of the test material was assessed according to OECD 301B CO2 evolution test (Modified Sturm Test). The test was performed in agreement with the OECD 301B guideline and fulfilled the validity criteria. No biodegradation of the test material was observed (based on CO2 evolution). The test substance is therefore not ready biodegradable.