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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2002-03-07 to 2002-06-19
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)
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): activated sludge from a wastewater treatment plant (ARA Ergolz II, Fullinsdorf, Switzerland) treating predominantly domestic wastewater.

- Preparation of inoculum for exposure: washed once with tap water

- Concentration of sludge: 30 mg dry material per litre
Duration of test (contact time):
28 d
Initial conc.:
102 mg/L
Based on:
test mat.
Initial conc.:
101 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS

- Test temperature: 22°C

- pH: 7.3-8.1

- pH adjusted: no

- Continuous darkness: yes


TEST SYSTEM

- Culturing apparatus: 500 mL Erlenmeyer flasks,

- Number of culture flasks/concentration: two test substance flasks, two inoculum control flasks, two reference substance flasks, one abiotic control flask, one toxicity control flask.

SAMPLING

- Sampling frequency: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 19, 20, 21, 22, 23, 24, 26, 27, 28 days

- Sampling method: Electro-chemical analysis: as dissolved oxygen consumed CO2 is generated. The CO2 is absorbed by soda lime and the total pressure decreases in the airtight flasks. The pressure drop is detected by electrode type manometer. The consumed oxygen is replaced by electrolytically generated oxygen from a copper sulphate solution.

CONTROL AND BLANK SYSTEM

- Inoculum blank: yes

- Abiotic sterile control: yes

- Toxicity control: yes
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
69
Sampling time:
28 d
Details on results:
A biodegradation rate for the test substance of 60% of the ThOD in a 10-day window within the 28-day test period was not reached.

The biodegradation of the reference substance was 82% after 14 days (84% after 28 days). This fulfils the validity criteria of the guideline.

The biodegradation of the toxicity control was 60% after 14 days. This fulfils the validity criteria of the guideline (> 25% within 14 days for test substance with no inhibitory effect).

No degradation of the test item occurred in the abiotic control under the test conditions.

Table 1: Cumulative biochemical oxygen demand (BOD mg O2/L) and Percentage Biodegradation


































































































































































































































































































































































































































































































































Days



Test Suspension



Inoculum Blank



Reference Control



Toxicity Control



Abiotic Control



BOD (mg O2/L)



% Degradation



BOD (mg O2/L)



BOD (mg O2/L)



% Degradation



BOD (mg O2/L)



% Degradation



BOD (mg O2/L)



R1



R2



R1



R2



R1



R2



R1



R2



R1



R2



R1



R1



R1



0



0



0



0



0



0



0



0



0



0



0



0



0



0



1



2



2



1



1



1



0



11



9



6



5



6



2



0



2



7



7



3



3



2



1



78



81



46



48



86



25



0



3



17



19



6



7



7



6



95



97



53



54



105



29



1



4



44



44



21



21



7



6



108



107



61



60



135



38



1



5



49



49



24



24



7



6



119



115



67



65



147



41



1



6



52



52



26



26



7



6



124



121



70



69



155



43



1



7



56



56



28



28



7



6



130



127



74



72



171



48



1



8



59



60



29



30



8



7



135



133



76



75



191



54



1



9



61



64



30



32



9



8



138



137



78



77



195



54



1



10



64



70



31



35



10



8



141



141



79



79



199



55



1



11



68



82



33



41



10



9



143



145



80



81



203



57



1



12



-



-



-



-



-



-



-



-



-



-



-



-



-



13



93



102



46



52



12



11



146



147



81



81



211



58



1



14



99



107



49



54



12



11



147



149



81



82



217



60



1



15



106



114



52



57



15



14



150



153



81



83



227



62



1



16



111



118



55



59



15



14



150



153



81



83



235



64



1



17



115



123



57



62



15



14



151



155



82



84



245



67



1



18



-



-



-



-



-



-



-



-



-



-



-



-



-



19



125



133



62



67



16



15



152



157



82



85



259



71



1



20



127



134



63



68



16



15



152



157



82



85



263



72



1



21



129



136



64



68



17



16



152



159



81



85



265



73



1



22



130



138



64



69



18



17



153



159



81



85



269



73



1



23



131



139



64



69



18



17



153



159



81



85



271



74



1



24



132



140



65



70



18



17



153



160



81



85



273



75



1



25



-



-



-



-



-



-



-



-



-



-



-



-



-



26



133



142



65



71



18



17



153



161



81



86



283



78



1



27



133



142



65



71



18



17



153



163



81



87



283



78



1



28



136



145



66



72



20



19



154



165



81



87



287



78



1



Mean (Day 28)



-



69



-



-



84



-



-



-


Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
A biodegradation rate of 69% within 28 days was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. The 10 day window was not met.

Description of key information

Biodegradation in water screening tests: Readily biodegradable but failing the 10-day window. Once the biodegradation of the alkoxy groups is taken into account there is evidence that the methacrylate side-chain is biodegrading to some extent, but it is unlikely that the silanol hydrolysis product would meet the criteria for rapid biodegradability.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable but failing 10-day window
Type of water:
freshwater

Additional information

Two reliable studies are available. A study conducted according to OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test) gave a result of 69% biodegradation in 28 days (not passing the 10-day window) (Grutzner 2002). This is selected as the key study as it was the study conducted most recently.


 


A study conducted according to EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test) gave a result of 74% biodegradation in 28 days (not passing the 10-day window) (Enste-Diefenback 1995). This is used as a supporting study.


 


Based on these two studies it is concluded that the substance is readily biodegradable but failing the 10-day window.


 


3-Trimethoxysilylpropyl methacrylate hydrolyses within the timescale of the ready biodegradation study (1.87 h at pH 7 and 20ºC to form 3-(trihydroxysilyl)propyl methacrylate and methanol. The biodegradation observed in the study is largely attributable to the biodegradation of the methanol hydrolysis product.


 


Methanol is readily biodegradable (OECD 2004a). Once the biodegradation of the methanol is taken into account there is evidence that the methacrylate side-chain is biodegrading to some extent, but it is unlikely that the silanol hydrolysis product would meet the criteria for rapid biodegradability. 


 


Reference:


OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1.