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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Follows a recognised guideline and performed to GLP standards.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2008
Report Date:
2008

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Mixed population of activated sewage sludge micro-organisms obtained from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, UK, which predominantly treats domestic sludge.
- Preparation of inoculum for exposure: washed three times by settlement and resuspension in culture medium to remove any excessive amounts of dissolved organic carbon (DOC) that may be present. The washed sample was then maintained on continuous aeration in the laboratory at a temperature of approximately 21 C and used on the day of collection.
- Suspended solids concentration: 1.9 g/L
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
10 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: Solution A: KH2PO4 8.50 g/l, K2HPO4 21.75 g/l, Na2HPO4.2H2O 33.40 g/l. NH4Cl 0.50 g/l; Solution B: CaCl2 27.50 g/l; Solution C: MgSO4.7H2O; Solution D: FeCl3.6H2O 0.25 g/l.
- Test temperature: 21 C
- pH: 7.4
- pH adjusted: no
- Suspended solids concentration: 30 mg (ss)/l
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5 litre culture vessels.
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: CO2-free air bubbled through the solution at a rate of approximately 40 ml/minute stirred continuously by magnetic stirrer.
- Measuring equipment: CO2 analyser - Tekmar-Dohrmann Apollo 9000 TOC analyser and a Shimadzu TOC-V(CSH) TOC analyser. DOC analyser - Shimadzu TOC-5050A TOC analyser.
- Details of trap for CO2 and volatile organics if used: CO2 produced by degradation was collected in 2 500ml Dreschel bottles containing 350 ml of 0.05 M NaOH.

SAMPLING
- Sampling frequency: Samples were taken from the first CO2 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.
- Other: CO2 analysis: The samples taken on day 0, 1, 2, 3, 6, 8, 10, 14, 16, 20, 24, 28 and 29 were analysed for CO2 immediately. The samples taken on days 12, 18, 22 and 27 were stored at approximately -20 C. On day 28, 1 ml of concentrated HCl was added to each absorber vessel to drive off any inorganic carbonates formed. These vessels were resealed, aerated overnight and the final samples taken from absorber vessels on day 29. DOC analysis: On day 0 and 28, samples were removed from all culture vessels and filtered through filters prior to DOC analysis.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Preliminary study:
Results show that trisodium 6,6',6"-(1,3,5-triazine-2,4,6-triyltriimino)trihexanoate did not absorb to filter matrices or to activated sewage sludge. Therefore samples taken for DOC analysis were filtered to remove the suspended solids present without the loss of any test material.
Test performance:
The total CO2 evolution in the control vessels on day 28 was 15.70 mg/l and the IC content of the test material suspension in the mineral medium at the start of the test was below 5% of the TC content; both satisfied the validation criterion given in the OECD test guidelines.
% Degradation
Parameter:
% degradation (CO2 evolution)
Value:
108
Sampling time:
29 d
Details on results:
Results of the main study are in table 1. Trisodium 6,6',6"-(1,3,5-triazine-2,4,6-triyltriimino)trihexanoate attained 108% degradation after 29 days and satisfied the 10-day window validation criterion, whereby 60% degradation must be attained within 10 days of the degradation exceeding 10%.
The toxicity control attained 96% degradation after 14 days and 106% degradation after 28 days thereby confirming the suitability of the inoculum and test conditions. Analysis of the test media from the test material culture vessels on day 0 and 28 for DOC can be seen in table 2.

BOD5 / COD results

Results with reference substance:
Sodium benzoate attained 103% degradation after 14 days and 105% degradation after 28 days thereby confirming the suitability of the inoculum and test conditions (see table 1).

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Trisodium 6,6',6"-(1,3,5-triazine-2,4,6-triyltriimino)trihexanoate attained 108% degradation after 29 days and satisfied the 10-day window validation criterion, whereby 60% degradation must be attained within 10 days of the degradation exceeding 10%. Therefore trisodium 6,6',6"-(1,3,5-triazine-2,4,6-triyltriimino)trihexanoate can be considered to be readily biodegradable under the conditions of OECD guideline 301B.