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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
The definitive study was conducted between 29 April 2003 and 28 May 2003 and data was last acquired for the study on 30 May 2003. The final report was issued 14th July 2003.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Meets the criteria for classification as Reliable without restriction according to Klimisch et al (1997)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2003
Report Date:
2003

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid

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 was obtained on 28 April 2003 from the aeration stage of the Sevem Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK, which treats predominantly domestic sewage.The sample of activated sewage sludge was maintained on continuous aeration upon receipt. A sample of the activated sewage sludge was washed three times by settlement and resuspension in culture medium to remove any excessive amounts of dissolved organic carbon (DOC) that may have been present. Determination of the suspended solids level of the activated sewage sludge was camed out by filtering a sample (100 ml) of the activated sewage sludge by suction through a piece of pre-weighed GFIA filter paper using a Buchner funnel. The piece of GFIA filter paper was then dried in an oven at approximately 110°C for 1 hour and allowed to cool before reweighing. The suspended solids was equal to 3.4 g/l prior to use.
Duration of test (contact time):
28 d
Details on study design:
The test material, at a concentration of 10 mg Carbon/litre, was exposed to activated sewage sludge micro-organisms with culture medium in sealed culture vessels in the dark at 21°C for 28 days.The degradation of the test material was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the standard material, sodium benzoate, together with a toxicity control were used for validation purposes.The following test preparations were prepared and inoculated in 5 litre glass culture vessels each containing 3 litres of solution:a) A control, in duplicate, consisting of inoculated culture medium.b) The standard material (sodium benzoate), in duplicate, in inoculated culture medium to give a final concentration of 10 mg carbon/litre.c) The test material, in duplicate, in inoculated culture medium to give a final concentration of 10 mg carbon/litre.d) The test material plus the standard material in inoculated culture medium to give a final concentration of 20 mg carbon/litre to act as a toxicity control (one vessel only).Each test vessel was inoculated with the prepared inoculum at a final concentration of 30 mg suspended solids (ss)/l. The study was carried out in a temperature controlled room at 21°C, in darkness.Approximately 24 hours prior to addition of the test and standard materials the vessels were filled with 2400 ml of culture medium and 26.5 ml of inoculum and aerated overnight. On Day 0 the test and standard materials were added and the volume in all the vessels adjusted to 3 litres by the addition of culture medium. The culture vessels were sealed and C02-free air bubbled through the solution at a rate of approximately 40 dminute and stirred continuously by magnetic stirrer. The C02-free air was produced by passing compressed air through a glass column containing self indicating soda lime (carbosorb granules). The CO2 produced by degradation was collected in two 500 ml Dreschel bottles containing 350 ml of 0.05 M NaOH. The C02 absorbing solutions were prepared using purified de-gassed water.Samples (2 ml) were taken from the first C02 absorber vessel on Days 0, 1,2, 3, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 27, 28 and 29. The second absorber vessel was sampled on Days 0 and 29. The samples taken on Days 0, 1, 2 ,3, 6, 8, 10, 14, 16, 20, 22, 24, 27, 28 and 29 were analysed for CO2 immediately. The samples taken on days 12 and 18 were stored at approximately -20oC. However, these samples were not analysed for C02 as the results obtained from previous and subsequent analyses showed that the level of degradation of the test material did not significantly increase during this time and therefore additional analyses were considered to be unnecessary.On Days 0 and 28 samples (20 ml) were removed from all culture vessels and filtered through Gelman 0.45 pm Acrocap filters (approximately 5 ml discarded) prior to DOC analysis. The samples were analysed for DOC using a Shimadzu TOC-5050A TOC analyser and an Ionics 1555B TOC analyser.The pH of the test preparations was determined on Day 28, prior to acidification with hydrochloric acid, using a pH meter.
Reference substance
Reference substance:
other: Sodium Benzoate

Results and discussion

% Degradation
Key result
Parameter:
% degradation (CO2 evolution)
Value:
24
Sampling time:
28 d
Details on results:
Points of degradation plot (test substance):1 % degradation after 1 d0 % degradation after 2 d10 % degradation after 3 d10 % degradation after 6 d10 % degradation after 8 d15 % degradation after 10 d16 % degradation after 14 d18 % degradation after 16 d16 % degradation after 20 d17 % degradation after 22 d21 % degradation after 24 d27 % degradation after 27 d24 % degradation after 28 dOn day 28 the pH of the test solutions and controls raged from 7.8-8.0

BOD5 / COD results

Results with reference substance:
Points of degradation plot (reference substance):20 % degradation after 1 d37 % degradation after 2 d46 % degradation after 3 d52 % degradation after 6 d66 % degradation after 8 d74 % degradation after 10 d86 % degradation after 14 d89 % degradation after 16 d87 % degradation after 20 d90 % degradation after 22 d92 % degradation after 24 d99 % degradation after 27 d100 % degradation after 28 d

Any other information on results incl. tables

The total C02 evolution in the control vessels on Day 28 was 19.68 mg/l and therefore satisfied the validation criterion given in the OECD Test Guidelines.

The IC/TC ratio of the test material suspension in the mineral medium at the start of the test was below 5% and hence satisfied the validation criterion given in the OECD Test Guidelines.

The difference between the values for C02 production at the end of the test for the replicate vessels was <20% and hence satisfied the validation criterion given in the OECD Test Guidelines.

At the end of the 28 day test period, the pH values in the test preparations ranged from 7.8 to 8.0

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test substance is considered to be not readily biodegradable.
Executive summary:

Introduction.

A study was performed to assess the ready biodegradability of the test material in an aerobic aqueous medium. The method followed that described in the OECD Guidelines for Testing of Chemicals (1992) No 301B, "Ready Biodegradability; C02 Evolution Test" referenced as Method C.4-C of Commission Directive 92/69/EEC (which constitutes Annex V of Council Directive 67/548/EEC), and US EPA Fate, Transport, and Transformation Test Guidelines OPPTS 835.3110 Paragraph (m).

Methods.

The test material, at a concentration of 10 mg Cl!, was exposed to activated sewage sludge micro-organisms with culture medium in sealed culture vessels in the dark at 21°C for 28 days. The degradation of the test material was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the standard material, sodium benzoate, together with a toxicity control were used for validation purposes.

Results and Conclusion

The test material attained 24% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301B.